Milky Way demographics with the VVV survey. I. The 84-million star colour-magnitude diagram of the Galactic bulge

NASA Astrophysics Data System (ADS)

Saito, R. K.; Minniti, D.; Dias, B.; Hempel, M.; Rejkuba, M.; Alonso-García, J.; Barbuy, B.; Catelan, M.; Emerson, J. P.; Gonzalez, O. A.; Lucas, P. W.; Zoccali, M.

2012-08-01

Context. The Milky Way (MW) bulge is a fundamental Galactic component for understanding the formation and evolution of galaxies, in particular our own. The ESO Public Survey VISTA Variables in the Vía Láctea is a deep near-IR survey mapping the Galactic bulge and southern plane. Particularly for the bulge area, VVV is covering ~315 deg2. Data taken during 2010 and 2011 covered the entire bulge area in the JHKs bands. Aims: We used VVV data for the whole bulge area as a single and homogeneous data set to build for the first time a single colour - magnitude diagram (CMD) for the entire Galactic bulge. Methods: Photometric data in the JHKs bands were combined to produce a single and huge data set containing 173 150 467 sources in the three bands, for the ~315 deg2 covered by VVV in the bulge. Selecting only the data points flagged as stellar, the total number of sources is 84 095 284. Results: We built the largest colour-magnitude diagrams published up to date, containing 173.1+ million sources for all data points, and more than 84.0 million sources accounting for the stellar sources only. The CMD has a complex shape, mostly owing to the complexity of the stellar population and the effects of extinction and reddening towards the Galactic centre. The red clump (RC) giants are seen double in magnitude at b ~ -8° -10°, while in the inner part (b ~ -3°) they appear to be spreading in colour, or even splitting into a secondary peak. Stellar population models show the predominance of main-sequence and giant stars. The analysis of the outermost bulge area reveals a well-defined sequence of late K and M dwarfs, seen at (J - Ks) ~ 0.7-0.9 mag and Ks ≳ 14 mag. Conclusions: The interpretation of the CMD yields important information about the MW bulge, showing the fingerprint of its structure and content. We report a well-defined red dwarf sequence in the outermost bulge, which is important for the planetary transit searches of VVV. The double RC in magnitude seen in the outer bulge is the signature of the X-shaped MW bulge, while the spreading of the RC in colour, and even its splitting into a secondary peak, are caused by reddening effects. The region around the Galactic centre is harder to interpret because it is strongly affected by reddening and extinction. Based on observations taken within the ESO VISTA Public Survey VVV, Programme ID 179.B-2002.The VVV survey data are available through the ESO archive http://www.eso.org/sci/archive.html

Searches for point sources in the Galactic Center region

NASA Astrophysics Data System (ADS)

di Mauro, Mattia; Fermi-LAT Collaboration

2017-01-01

Several groups have demonstrated the existence of an excess in the gamma-ray emission around the Galactic Center (GC) with respect to the predictions from a variety of Galactic Interstellar Emission Models (GIEMs) and point source catalogs. The origin of this excess, peaked at a few GeV, is still under debate. A possible interpretation is that it comes from a population of unresolved Millisecond Pulsars (MSPs) in the Galactic bulge. We investigate the detection of point sources in the GC region using new tools which the Fermi-LAT Collaboration is developing in the context of searches for Dark Matter (DM) signals. These new tools perform very fast scans iteratively testing for additional point sources at each of the pixels of the region of interest. We show also how to discriminate between point sources and structural residuals from the GIEM. We apply these methods to the GC region considering different GIEMs and testing the DM and MSPs intepretations for the GC excess. Additionally, we create a list of promising MSP candidates that could represent the brightest sources of a MSP bulge population.

JASMINE: constructor of the dynamical structure of the Galactic bulge

NASA Astrophysics Data System (ADS)

Gouda, N.; Kobayashi, Y.; Yamada, Y.; Yano, T.; Tsujimoto, T.; Suganuma, M.; Niwa, Y.; Yamauchi, M.

2008-07-01

We introduce a Japanese space astrometry project which is called JASMINE. JASMINE (Japan Astrometry Satellite Mission for INfrared Exploration) will measure distances and tangential motions of stars in the Galactic bulge with yet unprecedented precision. JASMINE will operate in z-band whose central wavelength is 0.9 micron. It will measure parallaxes, positions with accuracy of about 10 micro-arcsec and proper motions with accuracy of about 10 micro- arcsec/year for the stars brighter than z=14 mag. The number of stars observed by JASMINE with high accuracy of parallaxes in the Galactic bulge is much larger than that observed in other space astrometry projects operating in optical bands. With the completely new “map of the Galactic bulge” including motions of bulge stars, we expect that many new exciting scientific results will be obtained in studies of the Galactic bulge. One of them is the construction of the dynamical structure of the Galactic bulge. Kinematics and distance data given by JASMINE are the closest approach to a view of the exact dynamical structure of the Galactic bulge. Presently, JASMINE is in a development phase, with a target launch date around 2016. We comment on the outline of JASMINE mission, scientific targets and a preliminary design of JASMINE in this paper.

VizieR Online Data Catalog: Galactic bulge eclipsing & ellipsoidal binaries (Soszynski+, 2016)

NASA Astrophysics Data System (ADS)

Soszynski, I.; Pawlak, M.; Pietrukowicz, P.; Udalski, A.; Szymanski, M. K.; Wyrzykowski, L.; Ulaczyk, K.; Poleski, R.; Kozlowski, S.; Skowron, D. M.; Skowron, J.; Mroz, P.; Hamanowicz, A.

2018-04-01

Our collection of binary systems in the Galactic bulge is based on the photometric data collected by the OGLE survey between 1997 and 2015 at Las Campanas Observatory, Chile, with the 1.3-m Warsaw Telescope. The observatory is operated by the Carnegie Institution for Science. In 1997-2000, during the OGLE-II stage, about 30 million stars in the area of 11 square degrees in the central parts of the Milky Way were constantly monitored. In 2001, with the beginning of the OGLE-III survey, the sky coverage was extended to nearly 69 square degrees and the number of monitored stars increased to 200 million. Finally, from 2010 until today the OGLE-IV project regularly observes about 400 million stars in 182 square degrees of the densest regions of the Galactic bulge. Our search for eclipsing variables was based primarily on the OGLE-IV data. (4 data files).

New VVV Survey Globular Cluster Candidates in the Milky Way Bulge

NASA Astrophysics Data System (ADS)

Minniti, Dante; Geisler, Douglas; Alonso-García, Javier; Palma, Tali; Beamín, Juan Carlos; Borissova, Jura; Catelan, Marcio; Clariá, Juan J.; Cohen, Roger E.; Contreras Ramos, Rodrigo; Dias, Bruno; Fernández-Trincado, Jose G.; Gómez, Matías; Hempel, Maren; Ivanov, Valentin D.; Kurtev, Radostin; Lucas, Phillip W.; Moni-Bidin, Christian; Pullen, Joyce; Ramírez Alegría, Sebastian; Saito, Roberto K.; Valenti, Elena

2017-11-01

It is likely that a number of Galactic globular clusters remain to be discovered, especially toward the Galactic bulge. High stellar density combined with high and differential interstellar reddening are the two major problems for finding globular clusters located toward the bulge. We use the deep near-IR photometry of the VISTA Variables in the Vía Láctea (VVV) Survey to search for globular clusters projected toward the Galactic bulge, and hereby report the discovery of 22 new candidate globular clusters. These objects, detected as high density regions in our maps of bulge red giants, are confirmed as globular cluster candidates by their color-magnitude diagrams. We provide their coordinates as well as their near-IR color-magnitude diagrams, from which some basic parameters are derived, such as reddenings and heliocentric distances. The color-magnitude diagrams reveal well defined red giant branches in all cases, often including a prominent red clump. The new globular cluster candidates exhibit a variety of extinctions (0.06 < A Ks < 2.77) and distances (5.3 < D < 9.5 kpc). We also classify the globular cluster candidates into 10 metal-poor and 12 metal-rich clusters, based on the comparison of their color-magnitude diagrams with those of known globular clusters also observed by the VVV Survey. Finally, we argue that the census for Galactic globular clusters still remains incomplete, and that many more candidate globular clusters (particularly the low luminosity ones) await to be found and studied in detail in the central regions of the Milky Way. Based on observations taken within the ESO programs 179.B-2002 and 298.D-5048.

Microlensing optical depth towards the Galactic Bulge using bright sources from OGLE-II

NASA Astrophysics Data System (ADS)

Sumi, T.; Woźniak, P.; Udalski, A.; Szymański, M.; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Zebruń, K.; Szewczyk, O.; Wyrzykowski, L.

2004-12-01

We present a measurement of the microlensing optical depth towards the Galactic Bulge by using bright stars as sources from the central 20 OGLE-II Galactic bulge fields covering a range of 0o

THE VERTICAL X-SHAPED STRUCTURE IN THE MILKY WAY: EVIDENCE FROM A SIMPLE BOXY BULGE MODEL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Zhaoyu; Shen Juntai, E-mail: jshen@shao.ac.cn

2012-09-20

A vertical X-shaped structure in the Galactic bulge was recently reported. Here, we present evidence of a similar X-shaped structure in the Shen et al. 2010 bar/boxy bulge model that simultaneously matches the stellar kinematics successfully. The X-shaped structure is found in the central region of our bar/boxy bulge model and is qualitatively consistent with the observed one in many aspects. End-to-end separations of the X-shaped structure in the radial and vertical directions are roughly 3 kpc and 1.8 kpc, respectively. The X-shaped structure contains about 7% of light in the boxy bulge region, but it is significant enough tomore » be identified in observations. An X-shaped structure naturally arises in the formation of bar/boxy bulges and is mainly associated with orbits trapped around the vertically extended x{sub 1} family. Like the bar in our model, the X-shaped structure tilts away from the Sun-Galactic center line by 20 Degree-Sign . The X-shaped structure becomes increasingly symmetric about the disk plane, so the observed symmetry may indicate that it formed at least a few billion years ago. The existence of the vertical X-shaped structure suggests that the formation of the Milky Way bulge is shaped mainly by internal disk dynamical instabilities.« less

A New Population of Galactic Bulge Planetary Nebulas

NASA Astrophysics Data System (ADS)

Stenborg, T. N.

A new population of Galactic bulge planetary nebulas is presented. Nebula candidates were discovered by systematically reviewing archival [OIII] on/off band survey imaging of the central -5° ≤ l ≤ 5°, -5° ≤ b ≤ 5° region around the Galactic centre. An image segmentation and interleaving scheme was developed to facilitate this review. The resultant candidates (> 200) were then double checked against complementary archival Hα sky survey data to screen for obvious planetary nebula (PN) mimics or spurious image artefacts. Confirmatory spectroscopy of the PN candidates was pursued with thin slit, fibre multiobject and wide field spectrographs. Custom software was built to streamline interfacing with third-party spectroscopic management tools and a parallel greedy set cover algorithm implemented for efficient field selection in constrained multi-object observations. The combined imaging and spectroscopic evidence yielded true (4), probable (31) and possible (83) PNs toward the bulge. Secondary discoveries such as new PN mimics and late type stars were by-products of the confirmatory spectroscopy. Instances of literature PN duplication encountered during the investigation were noticed and documented. Spectral analysis of new PNs, including those obtained with a new optimised sky subtraction technique devised and demonstrated here, provided diagnostic data allowing radial velocity and Balmer decrement determination. Using a combined diameter and radial velocity criterion, bona fide bulge PNs were distinguished from new foreground PNs. Where Balmer decrements were available for new bulge PNs, differential aperture photometry was used to provide a modest data increment to Galactic bulge planetary nebula luminosity function (PNLF). The PNLF was revised with data from some new bulge PNs, but more significantly, by a series of corrections to the data derived from previously known bulge PNs (~225), such as improved filter transmission effects, statistically justified binning and application of a uniform bulge-relevant extinction law. The result was the most rigorous bulge PNLF to date. An improvement on the legacy PNLF, the revised PNLF exhibited a form inconsistent with typical extragalactic examples, an expected result of the unusual extinction correction method used to address bulge-specific observational limitations. Issues restricting the accuracy of the bulge PNLF were identified. Until those restrictions are ameliorated, the utility of the PNLF in aiding physical understanding of its constituent members or their progenitors cannot be realised.

JASMINE: Infrared Space Astrometry Mission

NASA Astrophysics Data System (ADS)

Gouda, Naoteru; Working Group, Jasmine

JASMINE is an astrometry satellite mission that measures in an infrared band annual parallaxes, positions on the celestial sphere, and proper motions of stars in the bulge of the Milky Way (the Galaxy) with high accuracies. These measurements give us 3-dimensional positions and 2-dimensional velocities (tangential velocities) of many stars in the Galactic bulge. A completely new “map” of the Galactic bulge given by JASMINE will bring us many exciting scientific results. A target launch date is the first half of the 2020s. Before the launch of JASMINE, we are planning two other missions; Nano-JASMINE and Small-JASMINE. Nano-JASMINE uses a very small nano-satellite and it is determined to be launched in 2011. Small-JASMINE is a downsized version of JASMINE satellite which observes toward restricted small regions of the Galactic bulge. These satellite missions need severe stability of the pointing of telescopes and furthermore high stability of telescope structures to measure stellar positions with high accuracies. This fact requires severe control of the pointing of telescopes and thermal control in payload modules. The control systems are very important keys for success of space astrometry missions including the series of JASMINE missions.

Determining the Absolute Magnitudes of Galactic-Bulge Red Clump Giants in the Z and Y Filters of the Vista Sky Surveys and the IRAC Filters of the Spitzer Sky Surveys

NASA Astrophysics Data System (ADS)

Karasev, D. I.; Lutovinov, A. A.

2018-04-01

The properties of red clump giants in the central regions of the Galactic bulge are investigated in the photometric Z and Y bands of the infrared VVV (VISTA/ESO) survey and the [3.6], [4.5], [5.8], and [8.0] μm bands of the GLIMPSE (Spitzer/IRAC) Galactic plane survey. The absolute magnitudes for objects of this class have been determined in these bands for the first time: M Z = -0.20 ± 0.04, M Y = -0.470 ± 0.045, M [3.6] = -1.70 ± 0.03, M [4.5] = -1.60 ± 0.03, M [5.8] = -1.67 ± 0.03, and M [8.0] = -1.70 ± 0.03. A comparison of the measured magnitudes with the predictions of theoretical models for the spectra of the objects under study has demonstrated good mutual agreement and has allowed some important constraints to be obtained for the properties of bulge red clump giants. In particular, a comparison with evolutionary tracks has shown that we are dealing predominantly with the high-metallicity subgroup of bulge red clump giants. Their metallicity is slightly higher than has been thought previously, [ M/H] ≃ 0.40 ( Z ≃ 0.038) with an error of [ M/H] ≃ 0.1 dex, while the effective temperature is 4250± 150 K. Stars with an age of 9-10 Gyr are shown to dominate among the red clump giants, although some number of younger objects with an age of 8 Gyr can also be present. In addition, the distances to several Galactic bulge regions have been measured, as D = 8200-8500 pc, and the extinction law in these directions is shown to differ noticeably from the standard one.

Two Populations of SiO Masers in the Galactic Bulge

NASA Astrophysics Data System (ADS)

Trapp, Adam; Rich, Robert Michael; Morris, Mark; Pihlstrom, Ylva; Sjouwerman, Lorant; Claussen, Mark J.; Stroh, Michael

2017-01-01

We present a summary of the kinematics of stellar SiO masers observed in the direction of the galactic bulge with ALMA (885 sources), and the JVLA (2,479 sources). These objects are selected by color from the MSX point source catalog, which has given an SiO detection rate of ~70%. The presented sample, along with the ~24,000 sources still being observed and reduced, enable radial velocity measurements even in regions with extreme optical extinction. These maser stars are compared to the known bulge surveys: APOGEE (~25,000 sources), BRAVA (~8000 sources), and GIBS (~6,400 sources). We have found that BAaDE stars in the direction of the bulge exist in two subpopulations: (1) A kinematically hot population exhibiting cylindrical rotation consistent with the other bulge surveys, and (2) a kinematically cold population more consistent with a disk population. In the ALMA data, we find evidence for a -200 km/s feature at (l,b) = (-9,0), possibly the symmetric complement to a previously proposed +200 km/s feature (Nidever 2012), that we do not confirm with our data.

Finding evolved stars in the inner Galactic disk with Gaia

NASA Astrophysics Data System (ADS)

Quiroga-Nuñez, L. H.; van Langevelde, H. J.; Pihlström, Y. M.; Sjouwerman, L. O.; Brown, A. G. A.

2018-04-01

The Bulge Asymmetries and Dynamical Evolution (BAaDE) survey will provide positions and line-of-sight velocities of ~20, 000 evolved, maser bearing stars in the Galactic plane. Although this Galactic region is affected by optical extinction, BAaDE targets may have Gaia cross-matches, eventually providing additional stellar information. In an initial attempt to cross-match BAaDE targets with Gaia, we have found more than 5,000 candidates. Of these, we may expect half to show SiO emission, which will allow us to obtain velocity information. The cross-match is being refined to avoid false positives using different criteria based on distance analysis, flux variability, and color assessment in the mid- and near-IR. Once the cross-matches can be confirmed, we will have a unique sample to characterize the stellar population of evolved stars in the Galactic bulge, which can be considered fossils of the Milky Way formation.

The Optical Gravitational Lensing Experiment Catalog of stellar proper motions in the OGLE-II Galactic bulge fields

NASA Astrophysics Data System (ADS)

Sumi, T.; Wu, X.; Udalski, A.; Szymański, M.; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Woźniak, P.; Zebruń, K.; Szewczyk, O.; Wyrzykowski, L.

2003-12-01

We present proper motion (μ ) catalogue of 5,078,188 stars in 49 Optical Gravitational Lensing Experiment II (OGLE-II) Galactic bulge fields, with the total area close to 11 square degrees. The proper motion measurements are based on 138 - 555 I-band images taken during four observing seasons: 1997-2000. The catalogue stars are in the magnitude range 11 < I < 18 mag. In particular, the catalogue includes Red Clump Giants (RCGs) and Red Giants in the Galactic Bulge, and main sequence stars in the Galactic disc. The proper motions up to μ = 500 mas yr -1 were measured with the mean accuracy of 0.8 ˜ 3.5 mas yr-1, depending on the brightness of a star. This catalogue may be useful for studying the kinematic of stars in the Galactic Bulge and the Galactic disk with Extinction maps in these fields which are construncted by using two-band photometry of RCGs.

Comment on “Characterizing the population of pulsars in the Galactic bulge with the Fermi large area telescope” [arXiv:1705.00009v1

DOE PAGES

Bartels, Richard

2018-04-24

Here, themore » $$\\textit{Fermi}$$-LAT Collaboration recently presented a new catalog of gamma-ray sources located within the $$40^{\\circ} \\times 40^{\\circ}$$ region around the Galactic Center~(Ajello et al. 2017) -- the Second Fermi Inner Galaxy (2FIG) catalog. Utilizing this catalog, they analyzed models for the spatial distribution and luminosity function of sources with a pulsar-like gamma-ray spectrum. Ajello et al. 2017 v1 also claimed to detect, in addition to a disk-like population of pulsar-like sources, an approximately 7$$\\sigma$$ preference for an additional centrally concentrated population of pulsar-like sources, which they referred to as a "Galactic Bulge" population. Such a population would be of great interest, as it would support a pulsar interpretation of the gamma-ray excess that has long been observed in this region. In an effort to further explore the implications of this new source catalog, we attempted to reproduce the results presented by the $$\\textit{Fermi}$$-LAT Collaboration, but failed to do so. Mimicking as closely as possible the analysis techniques undertaken in Ajello et al. 2017, we instead find that our likelihood analysis favors a very different spatial distribution and luminosity function for these sources. Most notably, our results do not exhibit a strong preference for a "Galactic Bulge" population of pulsars. Furthermore, we find that masking the regions immediately surrounding each of the 2FIG pulsar candidates does $$\\textit{not}$$ significantly impact the spectrum or intensity of the Galactic Center gamma-ray excess. Although these results refute the claim of strong evidence for a centrally concentrated pulsar population presented in Ajello et al. 2017, they neither rule out nor provide support for the possibility that the Galactic Center excess is generated by a population of low-luminosity and currently largely unobserved pulsars.« less

Comment on “Characterizing the population of pulsars in the Galactic bulge with the Fermi large area telescope” [arXiv:1705.00009v1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bartels, Richard

Here, themore » $$\\textit{Fermi}$$-LAT Collaboration recently presented a new catalog of gamma-ray sources located within the $$40^{\\circ} \\times 40^{\\circ}$$ region around the Galactic Center~(Ajello et al. 2017) -- the Second Fermi Inner Galaxy (2FIG) catalog. Utilizing this catalog, they analyzed models for the spatial distribution and luminosity function of sources with a pulsar-like gamma-ray spectrum. Ajello et al. 2017 v1 also claimed to detect, in addition to a disk-like population of pulsar-like sources, an approximately 7$$\\sigma$$ preference for an additional centrally concentrated population of pulsar-like sources, which they referred to as a "Galactic Bulge" population. Such a population would be of great interest, as it would support a pulsar interpretation of the gamma-ray excess that has long been observed in this region. In an effort to further explore the implications of this new source catalog, we attempted to reproduce the results presented by the $$\\textit{Fermi}$$-LAT Collaboration, but failed to do so. Mimicking as closely as possible the analysis techniques undertaken in Ajello et al. 2017, we instead find that our likelihood analysis favors a very different spatial distribution and luminosity function for these sources. Most notably, our results do not exhibit a strong preference for a "Galactic Bulge" population of pulsars. Furthermore, we find that masking the regions immediately surrounding each of the 2FIG pulsar candidates does $$\\textit{not}$$ significantly impact the spectrum or intensity of the Galactic Center gamma-ray excess. Although these results refute the claim of strong evidence for a centrally concentrated pulsar population presented in Ajello et al. 2017, they neither rule out nor provide support for the possibility that the Galactic Center excess is generated by a population of low-luminosity and currently largely unobserved pulsars.« less

Comment on "Characterizing the population of pulsars in the Galactic bulge with the Fermi large area telescope" [arXiv:1705.00009v1

NASA Astrophysics Data System (ADS)

Bartels, Richard; Hooper, Dan; Linden, Tim; Mishra-Sharma, Siddharth; Rodd, Nicholas L.; Safdi, Benjamin R.; Slatyer, Tracy R.

2018-06-01

The Fermi-LAT Collaboration recently presented a new catalog of gamma-ray sources located within the 40 ° × 40 ° region around the Galactic Center Ajello et al. (2017) - the Second Fermi Inner Galaxy (2FIG) catalog. Utilizing this catalog, they analyzed models for the spatial distribution and luminosity function of sources with a pulsar-like gamma-ray spectrum. Ajello et al. (2017) v1 also claimed to detect, in addition to a disk-like population of pulsar-like sources, an approximately 7 σ preference for an additional centrally concentrated population of pulsar-like sources, which they referred to as a "Galactic Bulge" population. Such a population would be of great interest, as it would support a pulsar interpretation of the gamma-ray excess that has long been observed in this region. In an effort to further explore the implications of this new source catalog, we attempted to reproduce the results presented by the Fermi-LAT Collaboration, but failed to do so. Mimicking as closely as possible the analysis techniques undertaken in Ajello et al. (2017), we instead find that our likelihood analysis favors a very different spatial distribution and luminosity function for these sources. Most notably, our results do not exhibit a strong preference for a "Galactic Bulge" population of pulsars. Furthermore, we find that masking the regions immediately surrounding each of the 2FIG pulsar candidates does not significantly impact the spectrum or intensity of the Galactic Center gamma-ray excess. Although these results refute the claim of strong evidence for a centrally concentrated pulsar population presented in Ajello et al. (2017), they neither rule out nor provide support for the possibility that the Galactic Center excess is generated by a population of low-luminosity and currently largely unobserved pulsars. In a spirit of maximal openness and transparency, we have made our analysis code available at https://github.com/bsafdi/GCE-2FIG.

Elucidation of kinematical and dynamical structure of the Galactic bulge

NASA Astrophysics Data System (ADS)

Yano, T.; Gouda, N.; Ueda, H.; Koyama, H.; Kan-ya, Y.; Taruya, A.

2008-07-01

Future space mission of astrometric satellite, GAIA and JASMINE (Japan Astrometry Satellite Mission for Infrared Exploration), will produce astrometric parameter, such as positions, parallaxes, and proper motions of stars in the Galactic bulge. Then kinematical information will be obtained in the future. Accordingly it is expected that our understanding of the dynamical structure will be greatly improved. Therefore it is important to make a method to construct a kinematical and dynamical structure of the Galactic bulge immediately.

JASMINE design and method of data reduction

NASA Astrophysics Data System (ADS)

Yamada, Yoshiyuki; Gouda, Naoteru; Yano, Taihei; Kobayashi, Yukiyasu; Niwa, Yoshito

2008-07-01

Japan Astrometry Satellite Mission for Infrared Exploration (JASMINE) aims to construct a map of the Galactic bulge with 10 μ arc sec accuracy. We use z-band CCD for avoiding dust absorption, and observe about 10 × 20 degrees area around the Galactic bulge region. Because the stellar density is very high, each FOVs can be combined with high accuracy. With 5 years observation, we will construct 10 μ arc sec accurate map. In this poster, I will show the observation strategy, design of JASMINE hardware, reduction scheme, and error budget. We also construct simulation software named JASMINE Simulator. We also show the simulation results and design of software.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryde, N.; Schultheis, M.; Grieco, V.

The structure, formation, and evolution of the Milky Way bulge is a matter of debate. Important diagnostics for discriminating between models of bulge formation and evolution include α-abundance trends with metallicity, and spatial abundance and metallicity gradients. Due to the severe optical extinction in the inner Bulge region, only a few detailed investigations of this region have been performed. Here we aim at investigating the inner 2 degrees of the Bulge (projected galactocentric distance of approximately 300 pc), rarely investigated before, by observing the [α/Fe] element trends versus metallicity, and by trying to derive the metallicity gradient in the bmore » < 2° region. [α/Fe] and metallicities have been determined by spectral synthesis of 2 μm spectra of 28 M-giants in the Bulge, lying along the southern minor axis at (l, b) = (0, 0), (0, −1°), and (0, −2°). These were observed with the CRIRES spectrometer at the Very Large Telescope, (VLT) at high spectral resolution. Low-resolution K-band spectra, observed with the ISAAC spectrometer at the VLT, are used to determine the effective temperature of the stars. We present the first connection between the Galactic center (GC) and the Bulge using similar stars, high spectral resolution, and analysis techniques. The [α/Fe] trends in all our three fields show a large similarity among each other and with trends further out in the Bulge. All point to a rapid star formation episode in the Bulge. We find that there is a lack of an [α/Fe] gradient in the Bulge all the way into the center, suggesting a homogeneous Bulge when it comes to the enrichment process and star formation history. We find a large range of metallicities from −1.2 < [Fe/H] < +0.3, with a lower dispersion in the GC: −0.2 < [Fe/H] < +0.3. The derived metallicities of the stars in the three fields get, in the mean, progressively higher the closer to the Galactic plane they lie. We could interpret this as a continuation of the metallicity gradient established further out in the Bulge, but due to the low number of stars and possible selection effects, more data of the same sort as presented here is necessary to conclude on the inner metallicity gradient from our data alone. Our results firmly argue for the center being in the context of the Bulge rather than very distinct.« less

Series of JASMINE missions

NASA Astrophysics Data System (ADS)

Gouda, N.

We are planning three space astrometry missions as a series of JASMINE missions; Nano-JASMINE, Small-JASMINE and (Medium-sized)JASMINE. JASMINE is an abbreviation of Japan Astrometry Satellite Mission of INfrared Exploration. The JASMINE mission will measure in an infrared band annual parallaxes, positions on the celestial sphere, and proper motions of many stars in the bulge of the Milky Way (the Galaxy) with high accuracies. A target launch date is the first half of the 2020s. Before the launch of JASMINE, we are planning Nano-JASMINE and Small-JASMINE. Nano-JASMINE uses a very small nano-satellite and it is determined to be launched in 2011. Small-JASMINE is a downsized version of the JASMINE satellite, which observes toward restricted small regions of the Galactic bulge. A target launch date is around 2016. A completely new "map" of the Galactic bulge given by Small-JASMINE and JASMINE will bring us many exciting scientific results.

Tracing the evolution of the Galactic bulge with chemodynamical modelling of alpha-elements

NASA Astrophysics Data System (ADS)

Friaça, A. C. S.; Barbuy, B.

2017-02-01

Context. Galactic bulge abundances can be best understood as indicators of bulge formation and nucleosynthesis processes by comparing them with chemo-dynamical evolution models. Aims: The aim of this work is to study the abundances of alpha-elements in the Galactic bulge, including a revision of the oxygen abundance in a sample of 56 bulge red giants. Methods: Literature abundances for O, Mg, Si, Ca and Ti in Galactic bulge stars are compared with chemical evolution models. For oxygen in particular, we reanalysed high-resolution spectra obtained using FLAMES+UVES on the Very Large Telescope, now taking each star's carbon abundances, derived from CI and C2 lines, into account simultaneously. Results: We present a chemical evolution model of alpha-element enrichment in a massive spheroid that represents a typical classical bulge evolution. The code includes multi-zone chemical evolution coupled with hydrodynamics of the gas. Comparisons between the model predictions and the abundance data suggest a typical bulge formation timescale of 1-2 Gyr. The main constraint on the bulge evolution is provided by the O data from analyses that have taken the C abundance and dissociative equilibrium into account. Mg, Si, Ca and Ti trends are well reproduced, whereas the level of overabundance critically depends on the adopted nucleosynthesis prescriptions. Observations collected both at the European Southern Observatory, Paranal, Chile (ESO programmes 71.B-0617A, 73.B0074A, and GTO 71.B-0196)

The Galactic Bulge Radial Velocity/Abundance Assay

NASA Astrophysics Data System (ADS)

Rich, R. M.

2012-08-01

The Bulge Radial Velocity Assay (BRAVA) measured radial velocities for ˜ 9500 late-type giants in the Galactic bulge, predominantly from -10° < l < +10° and -2° < b < -10°. The project has discovered that the bulge exhibits cylindrical rotation characteristic of bars, and two studies of dynamics (Shen et al. 2010; Wang et al. 2012 MNRAS sub.) find that bar models- either N-body formed from an instability in a preexisting disk, or a self-consistent model- can account for the observed kinematics. Studies of the Plaut field at (l,b) = 0°, -8° show that alpha enhancement is found in bulge giants even 1 kpc from the nucleus. New infrared studies extending to within 0.25° = 35 pc of the Galactic Center find no iron or alpha gradient from Baade's Window (l,b) = 0.9°, -3.9° to our innermost field, in contrast to the marked gradient observed in the outer bulge. We consider the case of the remarkable globular cluster Terzan 5, which has a strongly bimodal iron and rm [α/Fe] within its members, and we consider evidence pro and con that the bulge was assembled from dissolved clusters. The Subaru telescope has the potential to contribute to study of the Galactic bulge, especially using the Hyper Superime-Cam and planned spectroscopic modes, as well as the high resolution spectrograph. The planned Jasmine satellite series may deliver a comprehensive survey of distances and proper motions of bulge stars, and insight into the origin and importance of the X-shaped bulge.

A HIGH-VELOCITY BULGE RR LYRAE VARIABLE ON A HALO-LIKE ORBIT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kunder, Andrea; Storm, J.; Rich, R. M.

2015-07-20

We report on the RR Lyrae variable star, MACHO 176.18833.411, located toward the Galactic bulge and observed within the data from the ongoing Bulge RR Lyrae Radial Velocity Assay, which has the unusual radial velocity of −372 ± 8 km s{sup −1} and true space velocity of −482 ± 22 km s{sup −1} relative to the Galactic rest frame. Located less than 1 kpc from the Galactic center and toward a field at (l, b) = (3, −2.5), this pulsating star has properties suggesting it belongs to the bulge RR Lyrae star population, yet a velocity indicating it is abnormal,more » at least with respect to bulge giants and red clump stars. We show that this star is most likely a halo interloper and therefore suggest that halo contamination is not insignificant when studying metal-poor stars found within the bulge area, even for stars within 1 kpc of the Galactic center. We discuss the possibility that MACHO 176.18833.411 is on the extreme edge of the bulge RR Lyrae radial velocity distribution, and also consider a more exotic scenario in which it is a runaway star moving through the Galaxy.« less

Discovery of carbon-rich Miras in the Galactic bulge

NASA Astrophysics Data System (ADS)

Matsunaga, Noriyuki; Menzies, John W.; Feast, Michael W.; Whitelock, Patricia A.; Onozato, Hiroki; Barway, Sudhanshu; Aydi, Elias

2017-08-01

Only one carbon-rich (C-rich, hereinafter) Mira variable has so far been suggested as a member of the Galactic bulge and this is in a symbiotic system. Here we describe a method for selecting C-rich candidates from an infrared colour-colour diagram, (J - Ks) versus ([9] - [18]). Follow-up low-resolution spectroscopy resulted in the detection of eight C-rich Mira variables from a sample of 36 candidates towards the Galactic bulge. Our near-infrared photometry indicates that two of these, including the known symbiotic, are closer than the main body of the bulge while a third is a known foreground object. Of the five bulge members, one shows He I and [O II] emission and is possibly another symbiotic star. Our method is useful for identifying rare C-rich stars in the Galactic bulge and elsewhere. The age of these C-rich stars and the evolutionary process which produced them remain uncertain. They could be old and the products of either binary mass transfer or mergers, I.e. the descendants of blue stragglers, but we cannot rule out the possibility that they belong to a small in situ population of metal-poor intermediate age (<5 Gyr) stars in the bulge or that they have been accreted from a dwarf galaxy.

Estrellas variables en campos de cúmulos abiertos galácticos detectadas en el relevamiento VVV

NASA Astrophysics Data System (ADS)

Palma, T.; Dékany, I.; Clariá, J. J.; Minniti, D.; Alonso-García, J. A.; Ramírez Alegría, S.; Bonatto, C.

2016-08-01

The present project constitutes a massive search for variable stars in the field of open clusters projected on highly reddened regions of the galactic disk and bulge. This search is being performed using -, - and -band observations of the near-infrared variability Survey Vista variables in the Via Lactea. We present the first results obtained in four open clusters projected on the Galactic bulge. The new variables discovered in the current work, 182 in total, are classified on the basis of their light curves and their locations in the corresponding color-magnitude diagrams. Among the newly discovered variable stars, Cepheids, RR Lyrae, Scuti, eclipsing binaries and other types have been found.

Mass Loss at Higher Metallicity: Quantifying the Mass Return from Evolved Stars in the Galactic

NASA Astrophysics Data System (ADS)

Sargent, Benjamin

Bulge Mass-losing evolved stars, and in particular asymptotic giant branch (AGB) stars and red supergiant (RSG) stars, are expected to be the major producers of dust in galaxies. This dust will help form planetary systems around future generations of stars. Our ADAP program to measure the mass loss from the AGB and RSG stars in the Magellanic Clouds is nearing completion, and we wish to extend this successful study to the Galactic bulge of the Milky Way Galaxy. Metallicity should determine the amount of elements available to condense dust in the star's outflow, so evolved stars of differing metallicities should have differing mass-loss rates. Building upon our work on evolved stars in the Magellanic Clouds, we will compare the mass-loss rates from AGB and RSG stars in the older and potentially more metal-rich Bulge to the mass-loss rates of AGB and RSG stars in the Magellanic Clouds, which have lower metallicity, making for an interesting contrast. In addition, the Galactic bulge, like the Clouds, is located at a well-determined distance ( 8 kpc), thereby removing the distance ambiguities that present a major uncertainty in determining mass-loss rates and luminosities for evolved stars. To model photometric observations of outflowing dust shells around evolved stars, we have constructed the Grid of Red supergiant and Asymptotic giant branch ModelS (GRAMS; Sargent et al 2011; Srinivasan et al 2011) using the radiative transfer code 2Dust (Ueta and Meixner 2003). Our study will apply these models to the large photometric database of sources identified in the Spitzer Space Telescope GLIMPSE survey of the Milky Way and also to the various infrared spectra of Bulge AGB and RSG stars from Spitzer, ISO, etc. We have already modeled a few Galactic bulge evolved stars with GRAMS, and we will use these results as the foundation for modeling a large and representative sample of Galactic bulge evolved stars identified and measured photometrically by GLIMPSE. We will use our GRAMS grid, expanding as necessary to enable modeling of the higher metallicity evolved stars of the Galactic bulge, along with models of other types of stars, such as YSOs (Robitaille et al 2006), to identify the evolved stars in the GLIMPSE sample of the Galactic bulge. We will use these well-tested GRAMS models, which we have already extensively applied to study populations of mass losing evolved stars in the Magellanic Clouds, to fit the Spectral Energy Distributions (SEDs; plots of emitted power versus wavelength) of GLIMPSE Galactic bulge sources identified as RSG stars and oxygen-rich (O-rich), carbon-rich (C-rich), and extreme AGB stars. This modeling will yield stellar luminosities and mass-loss rates, as well as general dust chemistry (Orich versus C-rich) and other essential characteristics of the dust produced by evolved stars in the galactic plane. Our ongoing Magellanic Cloud and proposed Milky Way Galactic bulge evolved star studies will lay the groundwork for future studies of evolved stars in other nearby galaxies using data from the James Webb Space Telescope and other planned missions.

METALLICITY GRADIENTS THROUGH DISK INSTABILITY: A SIMPLE MODEL FOR THE MILKY WAY'S BOXY BULGE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martinez-Valpuesta, Inma; Gerhard, Ortwin, E-mail: imv@mpe.mpg.de, E-mail: gerhard@mpe.mpg.de

2013-03-20

Observations show a clear vertical metallicity gradient in the Galactic bulge, which is often taken as a signature of dissipative processes in the formation of a classical bulge. Various evidence shows, however, that the Milky Way is a barred galaxy with a boxy bulge representing the inner three-dimensional part of the bar. Here we show with a secular evolution N-body model that a boxy bulge formed through bar and buckling instabilities can show vertical metallicity gradients similar to the observed gradient if the initial axisymmetric disk had a comparable radial metallicity gradient. In this framework, the range of metallicities inmore » bulge fields constrains the chemical structure of the Galactic disk at early times before bar formation. Our secular evolution model was previously shown to reproduce inner Galaxy star counts and we show here that it also has cylindrical rotation. We use it to predict a full mean metallicity map across the Galactic bulge from a simple metallicity model for the initial disk. This map shows a general outward gradient on the sky as well as longitudinal perspective asymmetries. We also briefly comment on interpreting metallicity gradient observations in external boxy bulges.« less

The Optical Gravitational Lensing Experiment: Analysis of the Bulge RR Lyrae Population from the OGLE-III Data

NASA Astrophysics Data System (ADS)

Pietrukowicz, P.; Udalski, A.; Soszyński, I.; Nataf, D. M.; Wyrzykowski, Ł.; Poleski, R.; Kozłowski, S.; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Ulaczyk, K.

2012-05-01

We have analyzed the data on 16,836 RR Lyrae (RR Lyr) variables observed toward the Galactic bulge during the third phase of the Optical Gravitational Lensing Experiment (OGLE-III), which took place in 2001-2009. Using these standard candles, we show that the ratio of total-to-selective extinction toward the bulge is given by RI = AI /E(V - I) = 1.080 ± 0.007 and is independent of color. We demonstrate that the bulge RR Lyr stars form a metal-uniform population, slightly elongated in its inner part. The photometrically derived metallicity distribution is sharply peaked at [Fe/H] = -1.02 ± 0.18, with a dispersion of 0.25 dex. In the inner regions (|l| < 3°, |b| < 4°) the RR Lyr tend to follow the barred distribution of the bulge red clump giants. The distance to the Milky Way center inferred from the bulge RR Lyr is R 0 = 8.54 ± 0.42 kpc. We report a break in the mean density distribution at a distance of ~0.5 kpc from the center indicating its likely flattening. Using the OGLE-III data, we assess that (4-7) × 104 type ab RR Lyr variables should be detected toward the bulge area of the ongoing near-IR VISTA Variables in the Via Lactea (VVV) survey, where the uncertainty partially results from the unknown RR Lyr spatial density distribution within 0.2 kpc from the Galactic center.

The missing bulge globular clusters in M31 - New optical candidates

NASA Technical Reports Server (NTRS)

Wirth, A.; Smarr, L. L.; Bruno, T. L.

1985-01-01

A new method to attack the question of the 'missing' globular clusters in the bulge of M31 is used. Image-processing techniques were used on 13 videocamera fields to obtain an accurate photometric census of stellar objects in M31's bulge down to a limiting B magnitude of 21. This luminosity distribution is compared with the Bahcall-Soneira model of galactic foreground stars. A statistically significant excess of bright images in the luminosity range of globular clusters at M31's distance is found. If the optical candidates considered prove to be globular clusters, they would double the number of known globular clusters in the surveyed region. The colors of a subsample of the candidates are the same as those of the known globular clusters. It is concluded that the previously observed flattening away from a de Vaucouleurs law in the radial distribution of M31 may be an observational selection effect. As an offshoot of this analysis, no evidence is found for very luminous stars in the inner bulge of M31. The lack of such stars indicates that there has not been active star formation (with a normal IMF) in the recent past. Coupled with the existence of many planetary nebulae in the bulge, this may strengthen the case for a galactic wind in M31's bulge.

Mapping the X-shaped Milky Way Bulge

NASA Astrophysics Data System (ADS)

Saito, R. K.; Zoccali, M.; McWilliam, A.; Minniti, D.; Gonzalez, O. A.; Hill, V.

2011-09-01

We analyzed the distribution of the red clump (RC) stars throughout the Galactic bulge using Two Micron All Sky Survey data. We mapped the position of the RC in 1 deg2 fields within the area |l| <= 8fdg5 and 3fdg5 <= |b| <= 8fdg5, for a total of 170 deg2. The single RC seen in the central area splits into two components at high Galactic longitudes in both hemispheres, produced by two structures at different distances along the same line of sight. The X-shape is clearly visible in the Z-X plane for longitudes close to the l = 0° axis. Crude measurements of the space densities of RC stars in the bright and faint RC populations are consistent with the adopted RC distances, providing further supporting evidence that the X-structure is real, and that there is approximate front-back symmetry in our bulge fields. We conclude that the Milky Way bulge has an X-shaped structure within |l| <~ 2°, seen almost edge-on with respect to the line of sight. Additional deep near-infrared photometry extending into the innermost bulge regions combined with spectroscopic data is needed in order to discriminate among the different possibilities that can cause the observed X-shaped structure.

Galactic bulge population II Cepheids in the VVV survey: period-luminosity relations and a distance to the Galactic centre

NASA Astrophysics Data System (ADS)

Bhardwaj, A.; Rejkuba, M.; Minniti, D.; Surot, F.; Valenti, E.; Zoccali, M.; Gonzalez, O. A.; Romaniello, M.; Kanbur, S. M.; Singh, H. P.

2017-09-01

Context. Multiple stellar populations of different ages and metallicities reside in the Galactic bulge that trace its structure and provide clues to its formation and evolution. Aims: We present the near-infrared observations of population II Cepheids in the Galactic bulge from VISTA Variables in the Vía Láctea (VVV) survey. The JHKs photometry together with optical data from Optical Gravitational Lensing Experiment (OGLE) survey provide an independent estimate of the distance to the Galactic centre. The old, metal-poor and low-mass population II Cepheids are also investigated as useful tracers for the structure of the Galactic bulge. Methods: We identify 340 population II Cepheids in the VVV survey Galactic bulge catalogue based on their match with the OGLE-III Catalogue. The single-epoch JH and multi-epoch Ks observations complement the accurate periods and optical (VI) mean-magnitudes from OGLE. The sample consisting of BL Herculis and W Virginis subtypes is used to derive period-luminosity relations after correcting mean-magnitudes for the extinction. Our Ks-band period-luminosity relation, Ks = -2.189(0.056) [log (P)-1] + 11.187(0.032), is consistent with published work for BL Herculis and W Virginis variables in the Large Magellanic Cloud. Results: We present a combined OGLE-III and VVV catalogue with periods, classification, mean magnitudes, and extinction for 264 Galactic bulge population II Cepheids that have good-quality Ks-band light curves. The absolute magnitudes for population II Cepheids and RR Lyraes calibrated using Gaia and Hubble Space Telescope parallaxes, together with calibrated magnitudes for Large Magellanic Cloud population II Cepheids, are used to obtain a distance to the Galactic centre, R0 = 8.34 ± 0.03(stat.) ± 0.41(syst.), which changes by with different extinction laws. While noting the limitation of small number statistics, we find that the present sample of population II Cepheids in the Galactic bulge shows a nearly spheroidal spatial distribution, similar to metal-poor RR Lyrae variables. We do not find evidence of the inclined bar as traced by the metal-rich red-clump stars. Conclusions: Population II Cepheid and RR Lyrae variables follow similar period-luminosity relations and trace the same metal-poor old population in the Galactic bulge. The number density for population II Cepheids is more limited as compared to abundant RR Lyraes but they are bright and exhibit a wide range in period that provides a robust period-luminosity relation for an accurate estimate of the distance to the Galactic centre. The full Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/605/A100

THE VVV SURVEY REVEALS CLASSICAL CEPHEIDS TRACING A YOUNG AND THIN STELLAR DISK ACROSS THE GALAXY’S BULGE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dékány, I.; Minniti, D.; Majaess, D.

2015-10-20

Solid insight into the physics of the inner Milky Way is key to understanding our Galaxy’s evolution, but extreme dust obscuration has historically hindered efforts to map the area along the Galactic mid-plane. New comprehensive near-infrared time-series photometry from the VVV Survey has revealed 35 classical Cepheids, tracing a previously unobserved component of the inner Galaxy, namely a ubiquitous inner thin disk of young stars along the Galactic mid-plane, traversing across the bulge. The discovered period (age) spread of these classical Cepheids implies a continuous supply of newly formed stars in the central region of the Galaxy over the lastmore » 100 million years.« less

VERY METAL-POOR STARS IN THE OUTER GALACTIC BULGE FOUND BY THE APOGEE SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garcia Perez, Ana E.; Majewski, Steven R.; Hearty, Fred R.

2013-04-10

Despite its importance for understanding the nature of early stellar generations and for constraining Galactic bulge formation models, at present little is known about the metal-poor stellar content of the central Milky Way. This is a consequence of the great distances involved and intervening dust obscuration, which challenge optical studies. However, the Apache Point Observatory Galactic Evolution Experiment (APOGEE), a wide-area, multifiber, high-resolution spectroscopic survey within Sloan Digital Sky Survey III, is exploring the chemistry of all Galactic stellar populations at infrared wavelengths, with particular emphasis on the disk and the bulge. An automated spectral analysis of data on 2403more » giant stars in 12 fields in the bulge obtained during APOGEE commissioning yielded five stars with low metallicity ([Fe/H] {<=} -1.7), including two that are very metal-poor [Fe/H] {approx} -2.1 by bulge standards. Luminosity-based distance estimates place the 5 stars within the outer bulge, where 1246 of the other analyzed stars may reside. A manual reanalysis of the spectra verifies the low metallicities, and finds these stars to be enhanced in the {alpha}-elements O, Mg, and Si without significant {alpha}-pattern differences with other local halo or metal-weak thick-disk stars of similar metallicity, or even with other more metal-rich bulge stars. While neither the kinematics nor chemistry of these stars can yet definitively determine which, if any, are truly bulge members, rather than denizens of other populations co-located with the bulge, the newly identified stars reveal that the chemistry of metal-poor stars in the central Galaxy resembles that of metal-weak thick-disk stars at similar metallicity.« less

THE BULGE RADIAL VELOCITY ASSAY (BRAVA). II. COMPLETE SAMPLE AND DATA RELEASE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kunder, Andrea; De Propris, Roberto; Stubbs, Scott A.

2012-03-15

We present new radial velocity measurements from the Bulge Radial Velocity Assay, a large-scale spectroscopic survey of M-type giants in the Galactic bulge/bar region. The sample of {approx}4500 new radial velocities, mostly in the region -10 Degree-Sign < l < +10 Degree-Sign and b Almost-Equal-To -6 Degree-Sign , more than doubles the existent published data set. Our new data extend our rotation curve and velocity dispersion profile to +20 Degree-Sign , which is {approx}2.8 kpc from the Galactic center. The new data confirm the cylindrical rotation observed at -6 Degree-Sign and -8 Degree-Sign and are an excellent fit to themore » Shen et al. N-body bar model. We measure the strength of the TiO{epsilon} molecular band as a first step toward a metallicity ranking of the stellar sample, from which we confirm the presence of a vertical abundance gradient. Our survey finds no strong evidence of previously unknown kinematic streams. We also publish our complete catalog of radial velocities, photometry, TiO band strengths, and spectra, which is available at the Infrared Science Archive as well as at UCLA.« less

Galactic Bulge Giants: Probing Stellar and Galactic Evolution. 1. Catalogue of Spitzer IRAC and MIPS Sources (PREPRINT)

NASA Technical Reports Server (NTRS)

Uttenthaler, Stefan; Stute, Matthias; Sahai, Raghvendra; Blommaert, Joris A.; Schultheis, Mathias; Kraemer, Kathleen E.; Groenewegen, Martin A.; Price, Stephan D.

2010-01-01

Aims. We aim at measuring mass-loss rates and the luminosities of a statistically large sample of Galactic bulge stars at several galactocentric radii. The sensitivity of previous infrared surveys of the bulge has been rather limited, thus fundamental questions for late stellar evolution, such as the stage at which substantial mass-loss begins on the red giant branch and its dependence on fundamental stellar properties, remain unanswered. We aim at providing evidence and answers to these questions. Methods. To this end, we observed seven 15 15 arcmin2 fields in the nuclear bulge and its vicinity with unprecedented sensitivity using the IRAC and MIPS imaging instruments on-board the Spitzer Space Telescope. In each of the fields, tens of thousands of point sources were detected. Results. In the first paper based on this data set, we present the observations, data reduction, the final catalogue of sources, and a detailed comparison to previous mid-IR surveys of the Galactic bulge, as well as to theoretical isochrones. We find in general good agreement with other surveys and the isochrones, supporting the high quality of our catalogue.

The Extinction Toward the Galactic Bulge from RR Lyrae Stars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kunder, A; Popowski, P; Cook, K

2007-11-07

The authors present mean reddenings toward 3525 RR0 Lyrae stars from the Galactic bulge fields of the MACHO Survey. These reddenings are determined using the color at minimum V-band light of the RR0 Lyrae stars themselves and are found to be in general agreement with extinction estimates at the same location obtained from other methods. Using 3256 stars located in the Galactic Bulge, they derive the selective extinction coefficient R{sub V,VR} = A{sub V}/E(V-R) = 4.2 {+-} 0.2. this value is what is expected for a standard extinction law with R{sub V,BV} = 3.1 {+-} 0.3

Space Astrometry JASMINE

NASA Astrophysics Data System (ADS)

Yano, T.; Gouda, N.; Kobayashi, Y.; Yamada, Y.; Tsujimoto, T.; Suganuma, M.; Niwa, Y.; Yamauchi, M.

2008-07-01

JASMINE is the acronym of the Japan Astrometry Satellite Mission for INfrared (z-band: 0.9 micron) Exploration, and is planned to be launched around 2017. The main objective of JASMINE is to study the fundamental structure and evolution of the Milky Way bulge components. In order to accomplish these objectives, JASMINE will measure trigonometric parallaxes, positions and proper motions of about ten million stars in the Galactic bulge with a precision of 10 microarcsec at z = 14mag. The primary mirror for the telescope has a diameter of 75cm with a focal length of 22.5m. The back-illuminated CCD is fabricated on a 300 micron thick substrate which is fully depleted. These thick devices have extended near infrared response. The size of the detector for z-band is 3cm×3cm with 2048×2048 pixels. The size of the field of view is about 0.6deg×0.6deg by using 64 detectors on the focal plane. The telescope is designed to have only one field of view, which is different from the designs of other astrometric satellites. JASMINE will observe overlapping fields without gaps to survey a total area of about 20deg×10 deg around the Galactic bulge. Accordingly we make a “large frame” of 20deg×10 deg by linking the small frames using stars in overlapping regions. JASMINE will observe the Galactic bulge repeatedly during the mission life of about 5 years.

A parametric description of the 3D structure of the Galactic bar/bulge using the VVV survey

NASA Astrophysics Data System (ADS)

Simion, I. T.; Belokurov, V.; Irwin, M.; Koposov, S. E.; Gonzalez-Fernandez, C.; Robin, A. C.; Shen, J.; Li, Z.-Y.

2017-11-01

We study the structure of the inner Milky Way using the latest data release of the VISTA Variables in the Via Lactea (VVV) survey. The VVV is a deep near-infrared, multi-colour photometric survey with a coverage of 300 square degrees towards the bulge/bar. We use red clump (RC) stars to produce a high-resolution dust map of the VVV's field of view. From de-reddened colour-magnitude diagrams, we select red giant branch stars to investigate their 3D density distribution within the central 4 kpc. We demonstrate that our best-fitting parametric model of the bulge density provides a good description of the VVV data, with a median percentage residual of 5 per cent over the fitted region. The strongest of the otherwise low-level residuals are overdensities associated with a low-latitude structure as well as the so-called X-shape previously identified using the split RC. These additional components contribute only ˜5 per cent and ˜7 per cent respectively to the bulge mass budget. The best-fitting bulge is `boxy' with an axial ratio of [1:0.44:0.31] and is rotated with respect to the Sun-Galactic Centre line by at least 20°. We provide an estimate of the total, full sky, mass of the bulge of M_bulge^{Chabrier} = 2.36 × 10^{10} M_{⊙} for a Chabrier initial mass function. We show that there exists a strong degeneracy between the viewing angle and the dispersion of the RC absolute magnitude distribution. The value of the latter is strongly dependent on the assumptions made about the intrinsic luminosity function of the bulge.

Does the Galactic Bulge Have Fewer Planets?

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-12-01

The Milky Ways dense central bulge is a very different environment than the surrounding galactic disk in which we live. Do the differences affect the ability of planets to form in the bulge?Exploring Galactic PlanetsSchematic illustrating how gravitational microlensing by an extrasolar planet works. [NASA]Planet formation is a complex process with many aspects that we dont yet understand. Do environmental properties like host star metallicity, the density of nearby stars, or the intensity of the ambient radiation field affect the ability of planets to form? To answer these questions, we will ultimately need to search for planets around stars in a large variety of different environments in our galaxy.One way to detect recently formed, distant planets is by gravitational microlensing. In this process, light from a distant source star is bent by a lens star that is briefly located between us and the source. As the Earth moves, this momentary alignment causes a blip in the sources light curve that we can detect and planets hosted by the lens star can cause an additional observable bump.Artists impression of the Milky Way galaxy. The central bulge is much denserthan the surroundingdisk. [ESO/NASA/JPL-Caltech/M. Kornmesser/R. Hurt]Relative AbundancesMost source stars reside in the galactic bulge, so microlensing events can probe planetary systems at any distance between the Earth and the galactic bulge. This means that planet detections from microlensing could potentially be used to measure the relative abundances of exoplanets in different parts of our galaxy.A team of scientists led by Matthew Penny, a Sagan postdoctoral fellow at Ohio State University, set out to do just that. The group considered a sample of 31 exoplanetary systems detected by microlensing and asked the following question: are the planet abundances in the galactic bulge and the galactic disk the same?A Paucity of PlanetsTo answer this question, Penny and collaborators derived the expected distribution of host distances from a simulated microlensing survey, correcting for dominant selection effects. They then compared the distribution of distances in this model sample to the distribution of distances measured for the actual, observed systems.Histogram and cumulative distribution (black lines) of distance estimates for microlensing planet hosts. Red lines show the distributions predicted by the model if the disk and bulge abundances were the same. [Penny et al. 2016]Intriguingly, the two distributions dont match when you assume that the planet abundances in the disk and the bulge are the same. The relative abundances appear to be higher in the disk than in the bulge, according to the teams results: the observations agree with a model in which the bulge/disk abundance ratio is less than 0.54.Whats to Blame?There are a few ways to interpret this result: 1) distance measurements for the sample of planets discovered by microlensing have errors, 2) the model is too simplified; it needs to also include dependence of planet abundance and detection sensitivity on properties like host mass and metallicity, or 3) the galactic bulge actually has fewer planets than the disk.Penny and collaboratorssuspect some combination of the first two interpretations is most likely, but an actual paucity of planets in the galactic bulge cant be ruled out. Performing similar analysis on a larger sample of microlensing planets expected from upcoming, second-generation microlensing searches and obtaining more accurate distance measurements will help us to address this puzzlemore definitively in the future.CitationMatthew T. Penny et al 2016 ApJ 830 150. doi:10.3847/0004-637X/830/2/150

COSMIC-LAB: unveling the true nature of Terzan 5, a pristine fragment of the Galactic bulge

NASA Astrophysics Data System (ADS)

Ferraro, Francesco

2012-10-01

We have discovered that Terzan5, a stellar system in the Galactic bulge, harbors two stellar populations with different iron content {Delta[Fe/H] 0.5 dex} and possibly different ages {Ferraro et al. 2009, Nature 462, 483}. Moreover, the observed chemical patterns {Origlia et al. 2011, ApJ 726, L20} significantly differ from those observed in any known genuine GC. These evidences demonstrate that, similarly to omega Centauri in the halo, Terzan5 is NOT a genuine globular cluster {GC}, but a stellar system that was able to retain the gas ejected by violent supernova {SN} explosions.Indeed the striking chemical similarity with the bulge stars suggests that Terzan5 and the Galactic bulge shared the same star formation and chemical enrichment processes, driven by an exceptional amount of SNeII explosions {this is also the key to understand the origin of the extraordinary population of millisecond pulsars in Terzan5}. A quite intriguing scenario is emerging from these observations: Terzan5 could be the relic of one of the massive clumps that contributed {through strong dynamical interactions with other pre-formed and internally-evolved sub-structures} to the formation of the Galactic bulge.Here we propose to use the WFC3 to accurately measure the age of the two populations directly from the main sequence turn-off luminosities. Precisely dating the first and second burst of star formation is a crucial step for the correct reconstruction of the evolutionary history of Terzan5, with a significant impact on our comprehension of the formation processes of the Milky Way bulge and, more in general, of galactic spheroids.

Thousands of Stellar SiO masers in the Galactic center: The Bulge Asymmetries and Dynamic Evolution (BAaDE) survey

NASA Astrophysics Data System (ADS)

Sjouwerman, Loránt O.; Pihlström, Ylva M.; Rich, R. Michael; Morris, Mark R.; Claussen, Mark J.

2017-01-01

A radio survey of red giant SiO sources in the inner Galaxy and bulge is not hindered by extinction. Accurate stellar velocities (<1 km/s) are obtained with minimal observing time (<1 min) per source. Detecting over 20,000 SiO maser sources yields data comparable to optical surveys with the additional strength of a much more thorough coverage of the highly obscured inner Galaxy. Modeling of such a large sample would reveal dynamical structures and minority populations; the velocity structure can be compared to kinematic structures seen in molecular gas, complex orbit structure in the bar, or stellar streams resulting from recently infallen systems. Our Bulge Asymmetries and Dynamic Evolution (BAaDE) survey yields bright SiO masers suitable for follow-up Galactic orbit and parallax determination using VLBI. Here we outline our early VLA observations at 43 GHz in the northern bulge and Galactic plane (0

CXOGBS J173620.2-293338: A candidate symbiotic X-ray binary associated with a bulge carbon star

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hynes, Robert I.; Britt, C. T.; Johnson, C. B.

2014-01-01

The Galactic Bulge Survey (GBS) is a wide but shallow X-ray survey of regions above and below the Plane in the Galactic Bulge. It was performed using the Chandra X-ray Observatory's ACIS camera. The survey is primarily designed to find and classify low luminosity X-ray binaries. The combination of the X-ray depth of the survey and the accessibility of optical and infrared counterparts makes this survey ideally suited to identification of new symbiotic X-ray binaries (SyXBs) in the Bulge. We consider the specific case of the X-ray source CXOGBS J173620.2-293338. It is coincident to within 1 arcsec with a verymore » red star, showing a carbon star spectrum and irregular variability in the Optical Gravitational Lensing Experiment data. We classify the star as a late C-R type carbon star based on its spectral features, photometric properties, and variability characteristics, although a low-luminosity C-N type cannot be ruled out. The brightness of the star implies it is located in the Bulge, and its photometric properties are overall consistent with the Bulge carbon star population. Given the rarity of carbon stars in the Bulge, we estimate the probability of such a close chance alignment of any GBS source with a carbon star to be ≲ 10{sup –3}, suggesting that this is likely to be a real match. If the X-ray source is indeed associated with the carbon star, then the X-ray luminosity is around 9 × 10{sup 32} erg s{sup –1}. Its characteristics are consistent with a low luminosity SyXB, or possibly a low accretion rate white dwarf symbiotic.« less

Chemically Dissected Rotation Curves of the Galactic Bulge from Main-sequence Proper Motions

NASA Astrophysics Data System (ADS)

Clarkson, William I.; Calamida, Annalisa; Sahu, Kailash C.; Brown, Thomas M.; Gennaro, Mario; Avila, Roberto J.; Valenti, Jeff; Debattista, Victor P.; Rich, R. Michael; Minniti, Dante; Zoccali, Manuela; Aufdemberge, Emily R.

2018-05-01

We report results from an exploratory study implementing a new probe of Galactic evolution using archival Hubble Space Telescope imaging observations. Precise proper motions are combined with photometric relative metallicity and temperature indices, to produce the proper-motion rotation curves of the Galactic bulge separately for metal-poor and metal-rich main-sequence samples. This provides a “pencil-beam” complement to large-scale wide-field surveys, which to date have focused on the more traditional bright giant branch tracers. We find strong evidence that the Galactic bulge rotation curves drawn from “metal-rich” and “metal-poor” samples are indeed discrepant. The “metal-rich” sample shows greater rotation amplitude and a steeper gradient against line-of-sight distance, as well as possibly a stronger central concentration along the line of sight. This may represent a new detection of differing orbital anisotropy between metal-rich and metal-poor bulge objects. We also investigate selection effects that would be implied for the longitudinal proper-motion cut often used to isolate a “pure-bulge” sample. Extensive investigation of synthetic stellar populations suggests that instrumental and observational artifacts are unlikely to account for the observed rotation curve differences. Thus, proper-motion-based rotation curves can be used to probe chemodynamical correlations for main-sequence tracer stars, which are orders of magnitude more numerous in the Galactic bulge than the bright giant branch tracers. We discuss briefly the prospect of using this new tool to constrain detailed models of Galactic formation and evolution. Based on observations made with the NASA/ESA Hubble Space Telescope and obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Two Red Clumps and the X-shaped Milky Way Bulge

NASA Astrophysics Data System (ADS)

McWilliam, Andrew; Zoccali, Manuela

2010-12-01

From Two Micron All Sky Survey infrared photometry, we find two red clump (RC) populations coexisting in fields toward the Galactic bulge at latitudes |b|>5fdg5, ranging over ~13° in longitude and 20° in latitude. These RC peaks indicate two stellar populations separated by ~2.3 kpc at (l, b) = (+1, - 8) the two RCs are located at 6.5 and 8.8 ± 0.2 kpc. The double-peaked RC is inconsistent with a tilted bar morphology. Most of our fields show the two RCs at roughly constant distance with longitude, also inconsistent with a tilted bar; however, an underlying bar may be present. Stellar densities in the two RCs change dramatically with longitude: on the positive longitude side the foreground RC is dominant, while the background RC dominates negative longitudes. A line connecting the maxima of the foreground and background populations is tilted to the line of sight by ~20°±4°, similar to claims for the tilt of a Galactic bar. The distance between the two RCs decreases toward the Galactic plane; seen edge-on the bulge is X-shaped, resembling some extragalactic bulges and the results of N-body simulations. The center of this X is consistent with the distance to the Galactic center, although better agreement would occur if the bulge is 2-3 Gyr younger than 47 Tuc. Our observations may be understood if the two RC populations emanate, nearly tangentially, from the Galactic bar ends, in a funnel shape. Alternatively, the X, or double funnel, may continue to the Galactic center. From the Sun, this would appear peanut/box shaped, but X-shaped when viewed tangentially.

Reddening and Extinction toward the Galactic Bulge from OGLE-III: The Inner Milky Way's RV ~ 2.5 Extinction Curve

NASA Astrophysics Data System (ADS)

Nataf, David M.; Gould, Andrew; Fouqué, Pascal; Gonzalez, Oscar A.; Johnson, Jennifer A.; Skowron, Jan; Udalski, Andrzej; Szymański, Michał K.; Kubiak, Marcin; Pietrzyński, Grzegorz; Soszyński, Igor; Ulaczyk, Krzysztof; Wyrzykowski, Łukasz; Poleski, Radosław

2013-06-01

We combine VI photometry from OGLE-III with VISTA Variables in The Via Lactea survey and Two Micron All Sky Survey measurements of E(J - Ks ) to resolve the longstanding problem of the non-standard optical extinction toward the Galactic bulge. We show that the extinction is well fit by the relation AI = 0.7465 × E(V - I) + 1.3700 × E(J - Ks ), or, equivalently, AI = 1.217 × E(V - I)(1 + 1.126 × (E(J - Ks )/E(V - I) - 0.3433)). The optical and near-IR reddening law toward the inner Galaxy approximately follows an RV ≈ 2.5 extinction curve with a dispersion {\\sigma }_{R_{V}} \\approx 0.2, consistent with extragalactic investigations of the hosts of Type Ia SNe. Differential reddening is shown to be significant on scales as small as our mean field size of 6'. The intrinsic luminosity parameters of the Galactic bulge red clump (RC) are derived to be (M_{I,RC}, \\sigma _{I,RC,0}, (V-I)_{RC,0}, \\sigma _{(V-I)_{RC}}, (J-K_{s})_{RC,0}) = (-0.12, 0.09, 1.06, 0.121, 0.66). Our measurements of the RC brightness, brightness dispersion, and number counts allow us to estimate several Galactic bulge structural parameters. We estimate a distance to the Galactic center of 8.20 kpc. We measure an upper bound on the tilt α ≈ 40° between the bulge's major axis and the Sun-Galactic center line of sight, though our brightness peaks are consistent with predictions of an N-body model oriented at α ≈ 25°. The number of RC stars suggests a total stellar mass for the Galactic bulge of ~2.3 × 1010 M ⊙ if one assumes a canonical Salpeter initial mass function (IMF), or ~1.6 × 1010 M ⊙ if one assumes a bottom-light Zoccali IMF. Based on observations obtained with the 1.3 m Warsaw telescope at the Las Campanas Observatory of the Carnegie Institution for Science.

Galactic-scale Feedback Observed in the 3C 298 Quasar Host Galaxy

NASA Astrophysics Data System (ADS)

Vayner, Andrey; Wright, Shelley A.; Murray, Norman; Armus, Lee; Larkin, James E.; Mieda, Etsuko

2017-12-01

We present high angular resolution multiwavelength data of the 3C 298 radio-loud quasar host galaxy (z = 1.439) taken using the W.M. Keck Observatory OSIRIS integral field spectrograph (IFS) with adaptive optics, the Atacama Large Millimeter/submillimeter Array (ALMA), the Hubble Space Telescope (HST) WFC3, and the Very Large Array (VLA). Extended emission is detected in the rest-frame optical nebular emission lines Hβ, [O III], Hα, [N II], and [S II], as well as in the molecular lines CO (J = 3‑2) and (J = 5‑4). Along the path of the relativistic jets of 3C 298, we detect conical outflows in ionized gas emission with velocities of up to 1700 {km} {{{s}}}-1 and an outflow rate of 450–1500 {M}ȯ {{yr}}-1 extended over 12 kpc. Near the spatial center of the conical outflow, CO (J = 3‑2) emission shows a molecular gas disk with a rotational velocity of ±150 {km} {{{s}}}-1 and total molecular mass ({M}{{{H}}2}) of 6.6+/- 0.36× {10}9 {M}ȯ . On the blueshifted side of the molecular disk, we observe broad extended emission that is due to a molecular outflow with a rate of 2300 {M}ȯ {{yr}}-1 and depletion timescale of 3 Myr. We detect no narrow Hα emission in the outflow regions, suggesting a limit on star formation of 0.3 {M}ȯ {{yr}}-1 {{kpc}}-2. Quasar-driven winds are evacuating the molecular gas reservoir, thereby directly impacting star formation in the host galaxy. The observed mass of the supermassive black hole is {10}9.37{--9.56} {M}ȯ , and we determine a dynamical bulge mass of {M}{bulge}=1{--}1.7× {10}10\\tfrac{R}{1.6 {kpc}} {M}ȯ . The bulge mass of 3C 298 lies 2–2.5 orders of magnitude below the expected value from the local galactic bulge—supermassive black hole mass ({M}{bulge}{--}{M}{BH}) relationship. A second galactic disk observed in nebular emission is offset from the quasar by 9 kpc, suggesting that the system is an intermediate-stage merger. These results show that galactic-scale negative feedback is occurring early in the merger phase of 3C 298, well before the coalescence of the galactic nuclei and assembly on the local {M}{bulge}{--}{M}{BH} relationship.

The Barred Inner Region of the Milky Way

NASA Astrophysics Data System (ADS)

Gerhard, Ortwin

2018-04-01

The central few kpc of our Galaxy, the Milky Way, are dominated by thegravitational field of the Galactic bar. This talk describes dynamicalmodels of the bar and box/peanut bulge, and what we have learnt fromthem about the dynamical structure, the distribution of stellar anddark matter mass, and the spatial and orbital distributions of theGalactic stellar populations. Finally I discuss models for theformation of galaxies like ours, and how Milky Way studies enlightengalaxy formation theories in general.

REVIEWS OF TOPICAL PROBLEMS: Gravitational microlensing

NASA Astrophysics Data System (ADS)

Zakharov, Aleksandr F.; Sazhin, Mikhail V.

1998-10-01

The foundations of standard microlensing theory are discussed as applied to stars in the Galactic bulge, Magellanic Clouds or other nearby galaxies and gravitational microlenses assumed to lie in-between these stars and the terrestrial observer. In contrast to the review article by Gurevich et al. [48], microlensing by compact objects is mainly considered. Criteria for the identification of microlensing events are discussed as also are microlensing events not satisfying these criteria, such as non-symmetrical light curves and chromatic and polarization effects. The Large Magellanic Cloud (LMC) and Galactic bulge microlensing data of the MACHO group are discussed in detail and also the LMC data of EROS and the Galactic bulge data of OGLE are presented. A detailed comparison of theoretical predictions and observations is given.

Why is the rapid burster different from all other galactic-bulge X-ray sources?

NASA Astrophysics Data System (ADS)

Milgrom, M.

1987-01-01

It is suggested that the rapid X-ray burster exhibits unique behavior because it contains a neutron star whose stellar radius is smaller than the minimum radius of a circular orbit that is stable according to general relativity. The star accretes from a disk that extends down to the last stable orbit. In this state, the disk is unstable against a rapid fall and accretion of its innermost part onto the star. The sudden dumping of mass gives rise to a burst of X-rays. The disk then heals, refilling the inner region at a pace that is dictated mainly by the global accretion rate, in order to ready itself for the next burst. In all other galactic-bulge-type sources, the neutron star is larger than the last stable orbit.

Sigma observations of the low mass X-ray binaries of the galactic bulge

NASA Technical Reports Server (NTRS)

Goldwurm, A.; Denis, M.; Paul, J.; Faisse, S.; Roques, J. P.; Bouchet, L.; Vedrenne, G.; Mandrou, P.; Sunyaev, R.; Churazov, E.

1995-01-01

The soft gamma-ray telescope (35-1300 keV) SIGMA aboard the high energy GRANAT space observatory has been monitoring the Galactic Bulge region for more than 2000 h of effective time since March 1990. In the resulting average 35-75 keV image we detected ten sources at a level of greater than 5 standard deviations, 6 of which can be identified with low mass X-ray binaries (LMXB). Among them, one is the 1993 X-ray nova in Ophiuchus (GRS 1726-249), one is an X-ray pulsar (GX 1+4), two are associated with X-ray bursters (GX 354-0 and A 1742-294) and two with bursting X-ray binaries in the globular clusters Terzan 2 and Terzan 1. Their spectral and long term variability behavior as measured by SIGMMA are presented and discussed.

The Apache Point Observatory Galactic Evolution Experiment (APOGEE) and its successor, APOGEE-2

NASA Astrophysics Data System (ADS)

Majewski, S. R.; APOGEE Team; APOGEE-2 Team

2016-09-01

The Apache Point Observatory Galactic Evolution Experiment (APOGEE) of Sloan Digital Sky Survey III (SDSS-III) has produced a large catalog of high resolution ({R = 22 500}), high quality (S/N > 100), infrared (H-band) spectra for stars throughout all stellar populations of the Milky Way, including in regions veiled by significant dust opacity. APOGEE's half million spectra collected on > 163 000 unique stars, with time series information via repeat visits to each star, are being applied to numerous problems in stellar populations, Galactic astronomy, and stellar astrophysics. From among the early results of the APOGEE project - which span from measurements of Galactic dynamics, to multi-element chemical maps of the disk and bulge, new views of the interstellar medium, explorations of stellar companions, the chemistry of star clusters, and the discovery of rare stellar species - I highlight a few results that demonstrate APOGEE's unique ability to sample and characterize the Galactic disk and bulge. Plans are now under way for an even more ambitious successor to APOGEE: the six-year, dual-hemisphere APOGEE-2 project. Both phases of APOGEE feature a strong focus on targets having asteroseismological measurements from either Kepler or {CoRoT}, from which it is possible to derive relatively precise stellar ages. The combined APOGEE and APOGEE-2 databases of stellar chemistry, dynamics and ages constitute an unusually comprehensive, systematic and homogeneous resource for constraining models of Galactic evolution.

Chemical Characterization of the Inner Galactic bulge: North-South Symmetry

NASA Astrophysics Data System (ADS)

Nandakumar, G.; Ryde, N.; Schultheis, M.; Thorsbro, B.; Jönsson, H.; Barklem, P. S.; Rich, R. M.; Fragkoudi, F.

2018-05-01

While the number of stars in the Galactic bulge with detailed chemical abundance measurements is increasing rapidly, the inner Galactic bulge (|b| < 2°) remains poorly studied, due to heavy interstellar absorption and photometric crowding. We have carried out a high-resolution IR spectroscopic study of 72 M giants in the inner bulge using the CRIRES (ESO/VLT) facility. Our spectra cover the wavelength range of 2.0818 - 2.1444 μm with the resolution of R˜50,000 and have signal-to-noise ratio of 50-100. Our stars are located along the bulge minor axis at l = 0°, b = ±0°, ±1°, ±2°and +3°. Our sample was analysed in a homogeneous way using the most current K-band line list. We clearly detect a bimodal MDF with a metal-rich peak at ˜ +0.3 dex and a metal-poor peak at ˜ -0.5 dex, and no stars with [Fe/H] > +0.6 dex. The Galactic Center field reveals in contrast a mainly metal-rich population with a mean metallicity of +0.3 dex. We derived [Mg/Fe] and [Si/Fe] abundances which are consistent with trends from the outer bulge. We confirm for the supersolar metallicity stars the decreasing trend in [Mg/Fe] and [Si/Fe] as expected from chemical evolution models. With the caveat of a relatively small sample, we do not find significant differences in the chemical abundances between the Northern and the Southern fields, hence the evidence is consistent with symmetry in chemistry between North and South.

Opening the Window on Galaxy Assembly: Ages and Structural Parameters of Globular Clusters Towards the Galactic Bulge

NASA Astrophysics Data System (ADS)

Cohen, Roger

2015-10-01

The primary aim of this program is to undertake a systematic investigation of highly reddened Galactic globular clusters (GGCs) located towards the Galactic bulge. These clusters have been excluded from deep space-based photometric surveys due to their severe total and differential extinction. We will exploit the photometric depth and homogeneity of two existing Treasury programs (the ACS GGC Treasury Survey and the WFC3 Bulge Treasury Program) along with the unique optical+IR parallel imaging capabilities of HST to finally place the bulge GGCs in the context of their optically well-studied counterparts. Specifically, by leveraging ACS/WFC together with WFC3/IR, we first exploit the reddening sensitivity at optical wavelengths to map severe, small-scale differential reddening in the cluster cores. Corrected two-color WFC3/IR photometry will then be used to measure cluster ages to better than 1 Gyr relative precision, finally completing the age-metallicity relation of the Milky Way GGC system. Ages are obtained using a demonstrated procedure which is strictly differential, and therefore insensitive to total distance, reddening, reddening law, or photometric calibration uncertainties. At the same time, deep archival Treasury survey imaging of the Galactic bulge will be used to decontaminate cluster luminosity functions, yielding measurements of bulge GGC mass functions and mass segregation on par with results from the ACS GGC Treasury survey. Finally, the imaging which we propose will be combined with existing wide-field near-IR PSF photometry, yielding complete radial number density profiles, structural and morphological parameters.

Extremely metal-poor stars from the cosmic dawn in the bulge of the Milky Way.

PubMed

Howes, L M; Casey, A R; Asplund, M; Keller, S C; Yong, D; Nataf, D M; Poleski, R; Lind, K; Kobayashi, C; Owen, C I; Ness, M; Bessell, M S; Da Costa, G S; Schmidt, B P; Tisserand, P; Udalski, A; Szymański, M K; Soszyński, I; Pietrzyński, G; Ulaczyk, K; Wyrzykowski, Ł; Pietrukowicz, P; Skowron, J; Kozłowski, S; Mróz, P

2015-11-26

The first stars are predicted to have formed within 200 million years after the Big Bang, initiating the cosmic dawn. A true first star has not yet been discovered, although stars with tiny amounts of elements heavier than helium ('metals') have been found in the outer regions ('halo') of the Milky Way. The first stars and their immediate successors should, however, preferentially be found today in the central regions ('bulges') of galaxies, because they formed in the largest over-densities that grew gravitationally with time. The Milky Way bulge underwent a rapid chemical enrichment during the first 1-2 billion years, leading to a dearth of early, metal-poor stars. Here we report observations of extremely metal-poor stars in the Milky Way bulge, including one star with an iron abundance about 10,000 times lower than the solar value without noticeable carbon enhancement. We confirm that most of the metal-poor bulge stars are on tight orbits around the Galactic Centre, rather than being halo stars passing through the bulge, as expected for stars formed at redshifts greater than 15. Their chemical compositions are in general similar to typical halo stars of the same metallicity although intriguing differences exist, including lower abundances of carbon.

The Globular Clusters of the Galactic Bulge: Results from Multiwavelength Follow-up Imaging

NASA Astrophysics Data System (ADS)

Cohen, Roger; Geisler, Doug; Mauro, Francesco; Alonso Garcia, Javier; Hempel, Maren; Sarajedini, Ata

2018-01-01

The Galactic globular clusters (GGCs) located towards the bulge of the Milky Way suffer from severe total and differential extinction and high field star densities. They have therefore been systematically excluded from deep, large-scale homogenous GGC surveys, and will present a challenge for Gaia. Meanwhile, existing observations of bulge GGCs have revealed tantalizing hints that they hold clues to Galactic formation and evolution not found elsewhere. Therefore, in order to better characterize these poorly studied stellar systems and place them in the context of their optically well-studied counterparts, we have undertaken imaging programs at optical and near-infrared wavelengths. We describe these programs and present a variety of results, including self-consistent measurement of bulge GGC ages and structural parameters. The limitations imposed by spatially variable extinction and extinction law are highlighted, along with the complimentary nature of forthcoming facilities, allowing us to finally complete our picture of the Milky Way GGC system.

Bulge Growth Through Disc Instabilities in High-Redshift Galaxies

NASA Astrophysics Data System (ADS)

Bournaud, Frédéric

The role of disc instabilities, such as bars and spiral arms, and the associated resonances, in growing bulges in the inner regions of disc galaxies have long been studied in the low-redshift nearby Universe. There it has long been probed observationally, in particular through peanut-shaped bulges (Chap. 14 10.1007/978-3-319-19378-6_14"). This secular growth of bulges in modern disc galaxies is driven by weak, non-axisymmetric instabilities: it mostly produces pseudobulges at slow rates and with long star-formation timescales. Disc instabilities at high redshift (z > 1) in moderate-mass to massive galaxies (1010 to a few 1011 M⊙ of stars) are very different from those found in modern spiral galaxies. High-redshift discs are globally unstable and fragment into giant clumps containing 108-9 M⊙ of gas and stars each, which results in highly irregular galaxy morphologies. The clumps and other features associated to the violent instability drive disc evolution and bulge growth through various mechanisms on short timescales. The giant clumps can migrate inward and coalesce into the bulge in a few 108 years. The instability in the very turbulent media drives intense gas inflows toward the bulge and nuclear region. Thick discs and supermassive black holes can grow concurrently as a result of the violent instability. This chapter reviews the properties of high-redshift disc instabilities, the evolution of giant clumps and other features associated to the instability, and the resulting growth of bulges and associated sub-galactic components.

Peanuts, brezels and bananas: food for thought on the orbital structure of the Galactic bulge

NASA Astrophysics Data System (ADS)

Portail, Matthieu; Wegg, Christopher; Gerhard, Ortwin

2015-06-01

Recent observations have discovered the presence of a box/peanut or X-shape structure in the Galactic bulge. Such box/peanut structures are common in external disc galaxies, and are well known in N-body simulations where they form following the buckling instability of a bar. From studies of analytical potentials and N-body models, it has been claimed in the past that box/peanut bulges are supported by `bananas', or x1v1 orbits. We present here a set of N-body models where instead the peanut bulge is mainly supported by brezel-like orbits, allowing strong peanuts to form with short extent relative to the bar length. This shows that stars in the X-shape do not necessarily stream along banana orbits which follow the arms of the X-shape. The brezel orbits are also found to be the main orbital component supporting the peanut shape in our recent made-to-measure dynamical models of the Galactic bulge. We also show that in these models the fraction of stellar orbits that contribute to the X-structure account for 40-45 per cent of the stellar mass.

VizieR Online Data Catalog: Frequency of snowline-region planets (Shvartzvald+, 2016)

NASA Astrophysics Data System (ADS)

Shvartzvald, Y.; Maoz, D.; Udalski, A.; Sumi, T.; Friedmann, M.; Kaspi, S.; Poleski, R.; Szymanski, M. K.; Skowron, J.; Kozlowski, S.; Wyrzykowski, L.; Mroz, P.; Pietrukowicz, P.; Pietrzynski, G.; Soszynski, I.; Ulaczyk, K.; Abe, F.; Barry, R. K.; Bennett, D. P.; Bhattacharya, A.; Bond, I. A.; Freeman, M.; Inayama, K.; Itow, Y.; Koshimoto, N.; Ling, C. H.; Masuda, K.; Fukui, A.; Matsubara, Y.; Muraki, Y.; Ohnishi, K.; Rattenbury, N. J.; Saito, T.; Sullivan, D. J.; Suzuki, D.; Tristram, P. J.; Wakiyama, Y.; Yonehara, A.

2017-06-01

Our genII survey network is a collaboration between three groups: OGLE, MOA, and Wise. The OGLE and MOA groups regularly monitor a large region of the Galactic bulge, and routinely identify and monitor microlensing events. The Wise group monitors a field of 8 deg2, within the observational footprints of both OGLE and MOA, having the highest event rates based on previous years' observations (see Shvartzvald & Maoz, 2012MNRAS.419.3631S). The sample of microlensing events analysed here consists of 224 events from the 2011-2014 bulge seasons, observed by all three groups, and with each group having data near the peak of the event. (1 data file).

Quasiperiodic oscillations in bright galactic-bulge X-ray sources

NASA Technical Reports Server (NTRS)

Lamb, F. K.; Shibazaki, N.; Alpar, M. A.; Shaham, J.

1985-01-01

Quasiperiodic oscillations with frequencies in the range 5-50 Hz have recently been discovered in X-rays from two bright galactic-bulge sources and Sco X-1. These sources are weakly magnetic neutron stars accreting from disks which the plasma is clumped. The interaction of the magnetosphere with clumps in the inner disk causes oscillations in the X-ray flux with many of the properties observed.

REDDENING AND EXTINCTION TOWARD THE GALACTIC BULGE FROM OGLE-III: THE INNER MILKY WAY'S R{sub V} {approx} 2.5 EXTINCTION CURVE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nataf, David M.; Gould, Andrew; Johnson, Jennifer A.

We combine VI photometry from OGLE-III with VISTA Variables in The Via Lactea survey and Two Micron All Sky Survey measurements of E(J - K{sub s} ) to resolve the longstanding problem of the non-standard optical extinction toward the Galactic bulge. We show that the extinction is well fit by the relation A{sub I} = 0.7465 Multiplication-Sign E(V - I) + 1.3700 Multiplication-Sign E(J - K{sub s} ), or, equivalently, A{sub I} = 1.217 Multiplication-Sign E(V - I)(1 + 1.126 Multiplication-Sign (E(J - K{sub s} )/E(V - I) - 0.3433)). The optical and near-IR reddening law toward the inner Galaxymore » approximately follows an R{sub V} Almost-Equal-To 2.5 extinction curve with a dispersion {sigma}{sub R{sub V}}{approx}0.2, consistent with extragalactic investigations of the hosts of Type Ia SNe. Differential reddening is shown to be significant on scales as small as our mean field size of 6'. The intrinsic luminosity parameters of the Galactic bulge red clump (RC) are derived to be (M{sub I,RC},{sigma}{sub I,RC,0}, (V-I){sub RC,0},{sigma}{sub (V-I){sub R{sub C}}}, (J-K{sub s}){sub RC,0}) = (-0.12, 0.09, 1.06, 0.121, 0.66). Our measurements of the RC brightness, brightness dispersion, and number counts allow us to estimate several Galactic bulge structural parameters. We estimate a distance to the Galactic center of 8.20 kpc. We measure an upper bound on the tilt {alpha} Almost-Equal-To 40 Degree-Sign between the bulge's major axis and the Sun-Galactic center line of sight, though our brightness peaks are consistent with predictions of an N-body model oriented at {alpha} Almost-Equal-To 25 Degree-Sign . The number of RC stars suggests a total stellar mass for the Galactic bulge of {approx}2.3 Multiplication-Sign 10{sup 10} M{sub Sun} if one assumes a canonical Salpeter initial mass function (IMF), or {approx}1.6 Multiplication-Sign 10{sup 10} M{sub Sun} if one assumes a bottom-light Zoccali IMF.« less

A Spectroscopic and Photometric Study of Gravitational Microlensing Events

NASA Astrophysics Data System (ADS)

Kane, Stephen R.

2000-08-01

Gravitational microlensing has generated a great deal of scientific interest over recent years. This has been largely due to the realization of its wide-reaching applications, such as the search for dark matter, the detection of planets, and the study of Galactic structure. A significant observational advance has been that most microlensing events can be identified in real-time while the source is still being lensed. More than 400 microlensing events have now been detected towards the Galactic bulge and Magellanic Clouds by the microlensing survey teams EROS, MACHO, OGLE, DUO, and MOA. The real-time detection of these events allows detailed follow-up observations with much denser sampling, both photometrically and spectroscopically. The research undertaken in this project on photometric studies of gravitational microlensing events has been performed as a member of the PLANET (Probing Lensing Anomalies NETwork) collaboration. This is a worldwide collaboration formed in the early part of 1995 to study microlensing anomalies - departures from an achromatic point source, point lens light curve - through rapidly-sampled, multi-band, photometry. PLANET has demonstrated that it can achieve 1% photometry under ideal circumstances, making PLANET observations sensitive to detection of Earth-mass planets which require characterization of 1%--2% deviations from a standard microlensing light curve. The photometric work in this project involved over 5 months using the 1.0 m telescope at Canopus Observatory in Australia, and 3 separate observing runs using the 0.9 m telescope at the Cerro Tololo Inter-American Observatory (CTIO) in Chile. Methods were developed to reduce the vast amount of photometric data using the image analysis software MIDAS and the photometry package DoPHOT. Modelling routines were then written to analyse a selection of the resulting light curves in order to detect any deviation from an achromatic point source - point lens light curve. The photometric results presented in this thesis are from observations of 34 microlensing events over three consecutive bulge seasons. These results are presented along with a discussion of the observations and the data reduction procedures. The colour-magnitude diagrams indicate that the microlensed sources are main sequence and red clump giant stars. Most of the events appear to exhibit standard Paczynski point source - point lens curves whilst a few deviate significantly from the standard model. Various microlensing models that include anomalous structure are fitted to a selection of the observed events resulting in the discovery of a possible binary source event. These fitted events are used to estimate the sensitivity to extra-solar planets and it is found that the sampling rate for these events was insufficient by about a factor of 7.5 for detecting a Jupiter-mass planet. This result assumes that deviations of 5% can be reliably detected. If microlensing is caused predominantly by bulge stars, as has been suggested by Kiraga and Paczynski, the lensed stars should have larger extinction than other observed stars since they would preferentially be located at the far side of the Galactic bulge. Hence, spectroscopy of Galactic microlensing events may be used as a tool for studying the kinematics and extinction effects in the Galactic bulge. The spectroscopic work in this project involved using Kurucz model spectra to create theoretical extinction effects for various spectral classes towards the Galactic centre. These extinction effects are then used to interpret spectroscopic data taken with the 3.6 m ESO telescope. These data consist of a sample of microlensed stars towards the Galactic bulge and are used to derive the extinction offsets of the lensed source with respect to the average population and a measurement of the fraction of bulge-bulge lensing is made. Hence, it is shown statistically that the microlensed sources are generally located on the far side of the Galactic bulge. Measurements of the radial velocities of these sources are used to determine the kinematic properties of the far side of the Galactic bulge.

The Split Red Clump of the Galactic Bulge from OGLE-III

NASA Astrophysics Data System (ADS)

Nataf, D. M.; Udalski, A.; Gould, A.; Fouqué, P.; Stanek, K. Z.

2010-09-01

The red clump (RC) is found to be split into two components along several sightlines toward the Galactic bulge. This split is detected with high significance toward the areas (-3.5 < l < 1, b < -5) and (l, b) = (0, + 5.2), i.e., along the bulge minor axis and at least 5 deg off the plane. The fainter (hereafter "main") component is the one that more closely follows the distance-longitude relation of the bulge RC. The main component is ~0.5 mag fainter than the secondary component and with an overall approximately equal population. For sightlines further from the plane, the difference in brightness increases, and more stars are found in the secondary component than in the main component. The two components have very nearly equal (V - I) color.

The Galactic Nova Rate Revisited

NASA Astrophysics Data System (ADS)

Shafter, A. W.

2017-01-01

Despite its fundamental importance, a reliable estimate of the Galactic nova rate has remained elusive. Here, the overall Galactic nova rate is estimated by extrapolating the observed rate for novae reaching m≤slant 2 to include the entire Galaxy using a two component disk plus bulge model for the distribution of stars in the Milky Way. The present analysis improves on previous work by considering important corrections for incompleteness in the observed rate of bright novae and by employing a Monte Carlo analysis to better estimate the uncertainty in the derived nova rates. Several models are considered to account for differences in the assumed properties of bulge and disk nova populations and in the absolute magnitude distribution. The simplest models, which assume uniform properties between bulge and disk novae, predict Galactic nova rates of ˜50 to in excess of 100 per year, depending on the assumed incompleteness at bright magnitudes. Models where the disk novae are assumed to be more luminous than bulge novae are explored, and predict nova rates up to 30% lower, in the range of ˜35 to ˜75 per year. An average of the most plausible models yields a rate of {50}-23+31 yr-1, which is arguably the best estimate currently available for the nova rate in the Galaxy. Virtually all models produce rates that represent significant increases over recent estimates, and bring the Galactic nova rate into better agreement with that expected based on comparison with the latest results from extragalactic surveys.

Shaping the relation between the mass of supermassive black holes and the velocity dispersion of galactic bulges

NASA Astrophysics Data System (ADS)

Chan, M. H.

2013-05-01

I use the fact that the radiation emitted by the accretion disk of supermassive black hole can heat up the surrounding gas in the protogalaxy to achieve hydrostatic equilibrium during the galaxy formation. The correlation between the black hole mass M BH and velocity dispersion σ thus naturally arises. The result generally agrees with empirical fittings from observational data, even with M BH ≤106 M ⊙. This model provides a clear picture on how the properties of the galactic supermassive black holes are connected with the kinetic properties of the galactic bulges.

VizieR Online Data Catalog: APOGEE kinematics. I. Galactic bulge overview (Ness+, 2016)

NASA Astrophysics Data System (ADS)

Ness, M.; Zasowski, G.; Johnson, J. A.; Athanassoula, E.; Majewski, S. R.; Garcia Perez, A. E.; Bird, J.; Nidever, D.; Schneider, D. P.; Sobeck, J.; Frinchaboy, P.; Pan, K.; Bizyaev, D.; Oravetz, D.; Simmons, A.

2016-05-01

We use the APOGEE spectra (R=22500) from the SDSS-III Data Release 12 (DR12; Ahn et al. 2014ApJS..211...17A) for about 20000 stars toward the Galactic bulge and surrounding disk. The APOGEE survey, part of the SDSS-III project (Eisenstein et al. 2011AJ....142...72E), operates at the 2.5m telescope of the Apache Point Observatory. (1 data file).

Gauging the Helium Abundance of the Galactic Bulge RR Lyrae Stars

NASA Astrophysics Data System (ADS)

Marconi, Marcella; Minniti, Dante

2018-02-01

We report the first estimate of the He abundance of the population of RR Lyrae stars in the Galactic bulge. This is done by comparing the recent observational data with the latest models. We use the large samples of ab-type RR Lyrae stars found by OGLE IV in the inner bulge and by the VVV survey in the outer bulge. We present the result from the new models computed by Marconi et al., showing that the minimum period for fundamental RR Lyrae pulsators depends on the He content. By comparing these models with the observations in a period versus effective temperature plane, we find that the bulk of the bulge ab-type RR Lyrae are consistent with primordial He abundance Y = 0.245, ruling out a significant He-enriched population. This work demonstrates that the He content of the bulge RR Lyrae is different from that of the bulk of the bulge population as traced by the red clump giants that appear to be significantly more He-rich. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 179.B-2002 and 298.D-5048.

The Gaia-ESO Survey: Exploring the complex nature and origins of the Galactic bulge populations

NASA Astrophysics Data System (ADS)

Rojas-Arriagada, A.; Recio-Blanco, A.; de Laverny, P.; Mikolaitis, Š.; Matteucci, F.; Spitoni, E.; Schultheis, M.; Hayden, M.; Hill, V.; Zoccali, M.; Minniti, D.; Gonzalez, O. A.; Gilmore, G.; Randich, S.; Feltzing, S.; Alfaro, E. J.; Babusiaux, C.; Bensby, T.; Bragaglia, A.; Flaccomio, E.; Koposov, S. E.; Pancino, E.; Bayo, A.; Carraro, G.; Casey, A. R.; Costado, M. T.; Damiani, F.; Donati, P.; Franciosini, E.; Hourihane, A.; Jofré, P.; Lardo, C.; Lewis, J.; Lind, K.; Magrini, L.; Morbidelli, L.; Sacco, G. G.; Worley, C. C.; Zaggia, S.

2017-05-01

Context. As observational evidence steadily accumulates, the nature of the Galactic bulge has proven to be rather complex: the structural, kinematic, and chemical analyses often lead to contradictory conclusions. The nature of the metal-rich bulge - and especially of the metal-poor bulge - and their relation with other Galactic components, still need to be firmly defined on the basis of statistically significant high-quality data samples. Aims: We used the fourth internal data release of the Gaia-ESO survey to characterize the bulge metallicity distribution function (MDF), magnesium abundance, spatial distribution, and correlation of these properties with kinematics. Moreover, the homogeneous sampling of the different Galactic populations provided by the Gaia-ESO survey allowed us to perform a comparison between the bulge, thin disk, and thick disk sequences in the [Mg/Fe] vs. [Fe/H] plane in order to constrain the extent of their eventual chemical similarities. Methods: We obtained spectroscopic data for 2500 red clump stars in 11 bulge fields, sampling the area -10° ≤ l ≤ + 8° and -10° ≤ b ≤ -4° from the fourth internal data release of the Gaia-ESO survey. A sample of 6300 disk stars was also selected for comparison. Spectrophotometric distances computed via isochrone fitting allowed us to define a sample of stars likely located in the bulge region. Results: From a Gaussian mixture models (GMM) analysis, the bulge MDF is confirmed to be bimodal across the whole sampled area. The relative ratio between the two modes of the MDF changes as a function of b, with metal-poor stars dominating at high latitudes. The metal-rich stars exhibit bar-like kinematics and display a bimodality in their magnitude distribution, a feature which is tightly associated with the X-shape bulge. They overlap with the metal-rich end of the thin disk sequence in the [Mg/Fe] vs. [Fe/H] plane. On the other hand, metal-poor bulge stars have a more isotropic hot kinematics and do not participate in the X-shape bulge. Their Mg enhancement level and general shape in the [Mg/Fe] vs. [Fe/H] plane is comparable to that of the thick disk sequence. The position at which [Mg/Fe] starts to decrease with [Fe/H], called the "knee", is observed in the metal-poor bulge at [Fe/H] knee = -0.37 ± 0.09, being 0.06 dex higher than that of the thick disk. Although this difference is inside the error bars, it suggest a higher star formation rate (SFR) for the bulge than for the thick disk. We estimate an upper limit for this difference of Δ [Fe/H] knee = 0.24 dex. Finally, we present a chemical evolution model that suitably fits the whole bulge sequence by assuming a fast (<1 Gyr) intense burst of stellar formation that takes place at early epochs. Conclusions: We associate metal-rich stars with the bar boxy/peanut bulge formed as the product of secular evolution of the early thin disk. On the other hand, the metal-poor subpopulation might be the product of an early prompt dissipative collapse dominated by massive stars. Nevertheless, our results do not allow us to firmly rule out the possibility that these stars come from the secular evolution of the early thick disk. This is the first time that an analysis of the bulge MDF and α-abundances has been performed in a large area on the basis of a homogeneous, fully spectroscopic analysis of high-resolution, high S/N data. Based on data products from observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 188.B-3002. These data products have been processed by the Cambridge Astronomy Survey Unit (CASU) at the Institute of Astronomy, University of Cambridge, and by the FLAMES/UVES reduction team at INAF/Osservatorio Astrofisico di Arcetri. These data have been obtained from the Gaia-ESO Survey Data Archive, prepared and hosted by the Wide Field Astronomy Unit, Institute for Astronomy, University of Edinburgh, which is funded by the UK Science and Technology Facilities Council.

Ultraviolet Imaging Telescope ultraviolet images - Large-scale structure, H II regions, and extinction in M81

NASA Technical Reports Server (NTRS)

Hill, Jesse K.; Bohlin, Ralph C.; Cheng, Kwang-Ping; Hintzen, Paul M. N.; Landsman, Wayne B.; Neff, Susan G.; O'Connell, Robert W.; Roberts, Morton S.; Smith, Andrew M.; Smith, Eric P.

1992-01-01

The study employs UV images of M81 obtained by the Ultraviolet Imaging Telescope (UIT) during the December 1990 Astro-1 spacelab mission to determine 2490- and 1520-A fluxes from 46 H II regions and global surface brightness profiles. Comparison photometry in the V band is obtained from a ground-based CCD image. UV radial profiles show bulge and exponential disk components, with a local decrease in disk surface brightness inside the inner Lindblad Resonance about 4 arcmin from the nucleus. The V profile shows typical bulge plus exponential disk structure, with no local maximum in the disk. There is little change of UV color across the disk, although there is a strong gradient in the bulge. Observed m152-V colors of the H II regions are consistent with model spectra for young clusters, after dereddening using Av determined from m249-V and the Galactic extinction curve. The value of Av, so determined, is 0.4 mag greater on the average than Av derived from radio continuum and H-alpha fluxes.

EMISSION-LINE OBJECTS PROJECTED UPON THE GALACTIC BULGE*

PubMed Central

Herbig, G. H.

1969-01-01

Low-dispersion slit spectrograms have been obtained of 34 faint objects that lie in the direction of the galactic bulge and have the Hα line in emission upon a detectable continuum. Eleven of these are certain or probable symbiotic stars. A rough comparison with R CrB stars in the same area suggests that these brightest symbiotics in the bulge have in the mean Mv ≈ -3 to -4, which suggest Population II red giants rather than conventional Population I M-type objects. The sample also contains a number of hot stars having H and [O II] or [O III] in emission, as well as four conventional Be stars, and six certain or possible planetary nebulae. Images PMID:16578699

Emission-line objects projected upon the galactic bulge.

PubMed

Herbig, G H

1969-08-01

Low-dispersion slit spectrograms have been obtained of 34 faint objects that lie in the direction of the galactic bulge and have the Halpha line in emission upon a detectable continuum. Eleven of these are certain or probable symbiotic stars. A rough comparison with R CrB stars in the same area suggests that these brightest symbiotics in the bulge have in the mean M(v) approximately -3 to -4, which suggest Population II red giants rather than conventional Population I M-type objects. The sample also contains a number of hot stars having H and [O II] or [O III] in emission, as well as four conventional Be stars, and six certain or possible planetary nebulae.

The scientific goal of the Japanese small astrometric satellite, Small-JASMINE

NASA Astrophysics Data System (ADS)

Yano, Taihei; Gouda, Naoteru; Kobayashi, Yukiyasu; Tsujimoto, Takuji; Niwa, Yoshito; Yamada, Yoshiyuki

2013-02-01

Small-JASMINE is a small Japanese astrometric satellite, developed mainly at the National Astronomical Observatory of Japan. The target launch date of Small-JASMINE is around 2017. The satellite will be equipped with a telescope with an aperture size of 30 cm and a focal length of approximately 3.9 m. The operational wavelength will be centered on the infrared Hw band, between 1.1 and 1.7 μm, using a HgCdTe detector with 4k × 4k pixels. This will enable us to observe the central regions of our Galaxy and clarify the dynamical structure of the bulge region. A restricted region of the Galactic bulge will be observed using a frame-linking method, which is different from the approach taken by both Hipparcos and Gaia, both developed at ESA. The target accuracy of the annual parallax and proper motion is approximately 10 μas and 10 μas yr-1, respectively, in the central region of the survey area of 0.3 × 0.3 deg2. The target accuracy of the annual parallax, ~ 50 μas, and that of the proper motion, ~ 50 μas yr-1, will be obtained within a region of 2 × 2 deg2. The observing region covers a field of approximately 3 × 3 deg2. The mission is required to continue for around three years to obtain reliable measurements. In the winter season, the angular distance between the Sun and the Galactic bulge region is small. Accordingly, we may have the chance to observe different regions which contain scientifically interesting targets, such as Cygnus X-1. If we are successful in observing the object over the course of a few weeks, the orbital elements of the star accompanying Cygnus X-1 can be resolved by Small-JASMINE.

K-band observations of boxy bulges - I. Morphology and surface brightness profiles

NASA Astrophysics Data System (ADS)

Bureau, M.; Aronica, G.; Athanassoula, E.; Dettmar, R.-J.; Bosma, A.; Freeman, K. C.

2006-08-01

In this first paper of a series on the structure of boxy and peanut-shaped (B/PS) bulges, Kn-band observations of a sample of 30 edge-on spiral galaxies are described and discussed. Kn-band observations best trace the dominant luminous galactic mass and are minimally affected by dust. Images, unsharp-masked images, as well as major-axis and vertically summed surface brightness profiles are presented and discussed. Galaxies with a B/PS bulge tend to have a more complex morphology than galaxies with other bulge types, more often showing centred or off-centred X structures, secondary maxima along the major-axis and spiral-like structures. While probably not uniquely related to bars, those features are observed in three-dimensional N-body simulations of barred discs and may trace the main bar orbit families. The surface brightness profiles of galaxies with a B/PS bulge are also more complex, typically containing three or more clearly separated regions, including a shallow or flat intermediate region (Freeman Type II profiles). The breaks in the profiles offer evidence for bar-driven transfer of angular momentum and radial redistribution of material. The profiles further suggest a rapid variation of the scaleheight of the disc material, contrary to conventional wisdom but again as expected from the vertical resonances and instabilities present in barred discs. Interestingly, the steep inner region of the surface brightness profiles is often shorter than the isophotally thick part of the galaxies, itself always shorter than the flat intermediate region of the profiles. The steep inner region is also much more prominent along the major-axis than in the vertically summed profiles. Similarly to other recent work but contrary to the standard `bulge + disc' model (where the bulge is both thick and steep), we thus propose that galaxies with a B/PS bulge are composed of a thin concentrated disc (a disc-like bulge) contained within a partially thick bar (the B/PS bulge), itself contained within a thin outer disc. The inner disc likely formed secularly through bar-driven processes and is responsible for the steep inner region of the surface brightness profiles, traditionally associated with a classic bulge, while the bar is responsible for the flat intermediate region of the surface brightness profiles and the thick complex morphological structures observed. Those components are strongly coupled dynamically and are formed mostly of the same (disc) material, shaped by the weak but relentless action of the bar resonances. Any competing formation scenario for galaxies with a B/PS bulge, which represent at least 45 per cent of the local disc galaxy population, must explain equally well and self-consistently the above morphological and photometric properties, the complex gas and stellar kinematics observed, and the correlations between them.

Tracing the Chemical Evolution of Metal-rich Galactic Bulge Globular Clusters

NASA Astrophysics Data System (ADS)

Munoz Gonzalez, Cesar; Saviane, Ivo; Geisler, Doug; Villanova, Sandro

2018-01-01

We present in this poster the metallicity characterization of the four metal rich Bulge Galactic Gobular Clusters, which have controversial metallicities. We analyzed our high-resolution spectra (using UVES-580nm and GIRAFFE-HR13 setups) for a large sample of RGB/AGB targets in each cluster in order to measure their metallicity and prove or discard the iron spread hypothesis. We have also characterized chemically stars with potentially different iron content by measuring light (O, Na, Mg, Al), alpha (Si, Ca, Ti), iron–peak (V, Cr, Ni, Mn) and s and r process (Y, Zr, Ba, Eu) elements. We have identified possible channels responsible for the chemical heterogeneity of the cluster populations, like AGB or massive fast-rotating stars contamination, or SN explosion. Also, we have analyzed the origin and evolution of these bulge GCs and their connection with the bulge itself.

The imprints of bars on the vertical stellar population gradients of galactic bulges

NASA Astrophysics Data System (ADS)

Molaeinezhad, A.; Falcón-Barroso, J.; Martínez-Valpuesta, I.; Khosroshahi, H. G.; Vazdekis, A.; La Barbera, F.; Peletier, R. F.; Balcells, M.

2017-05-01

This is the second paper of a series aimed to study the stellar kinematics and population properties of bulges in highly inclined barred galaxies. In this work, we carry out a detailed analysis of the stellar age, metallicity and [Mg/Fe] of 28 highly inclined (I > 65°) disc galaxies, from S0 to S(B)c, observed with the SAURON integral-field spectrograph. The sample is divided into two clean samples of barred and unbarred galaxies, on the basis of the correlation between the stellar velocity and h3 profiles, as well as the level of cylindrical rotation within the bulge region. We find that while the mean stellar age, metallicity and [Mg/Fe] in the bulges of barred and unbarred galaxies are not statistically distinct, the [Mg/Fe] gradients along the minor axis (away from the disc) of barred galaxies are significantly different than those without bars. For barred galaxies, stars that are vertically further away from the mid-plane are in general more [Mg/Fe]-enhanced and thus the vertical gradients in [Mg/Fe] for barred galaxies are mostly positive, while for unbarred bulges the [Mg/Fe] profiles are typically negative or flat. This result, together with the old populations observed in the barred sample, indicates that bars are long-lasting structures, and therefore are not easily destroyed. The marked [Mg/Fe] differences with the bulges of unbarred galaxies indicate that different formation/evolution scenarios are required to explain their build-up, and emphasizes the role of bars in redistributing stellar material in the bulge-dominated regions.

The Age of the Young Bulge-like Population in the Stellar System Terzan 5: Linking the Galactic Bulge to the High-z Universe

NASA Astrophysics Data System (ADS)

Ferraro, F. R.; Massari, D.; Dalessandro, E.; Lanzoni, B.; Origlia, L.; Rich, R. M.; Mucciarelli, A.

2016-09-01

The Galactic bulge is dominated by an old, metal-rich stellar population. The possible presence and the amount of a young (a few gigayears old) minor component is one of the major issues debated in the literature. Recently, the bulge stellar system Terzan 5 was found to harbor three sub-populations with iron content varying by more than one order of magnitude (from 0.2 up to two times the solar value), with chemical abundance patterns strikingly similar to those observed in bulge field stars. Here we report on the detection of two distinct main-sequence turnoff points in Terzan 5, providing the age of the two main stellar populations: 12 Gyr for the (dominant) sub-solar component and 4.5 Gyr for the component at super-solar metallicity. This discovery classifies Terzan 5 as a site in the Galactic bulge where multiple bursts of star formation occurred, thus suggesting a quite massive progenitor possibly resembling the giant clumps observed in star-forming galaxies at high redshifts. This connection opens a new route of investigation into the formation process and evolution of spheroids and their stellar content. Based on data obtained with (1) the ESA/NASA HST, under programs GO-14061, GO-12933, GO-10845, (2) the Very Large Telescope of the European Southern Observatory during the Science Verification of the camera MAD; (3) the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and NASA.

THE GALACTIC POSITRON ANNIHILATION RADIATION AND THE PROPAGATION OF POSITRONS IN THE INTERSTELLAR MEDIUM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Higdon, J. C.; Lingenfelter, R. E.; Rothschild, R. E.

2009-06-10

The ratio of the luminosity of diffuse 511 keV positron annihilation radiation, measured by INTEGRAL in its four years, from a Galactic 'positron bulge' (<1.5 kpc) compared to that of the disk is {approx}1.4. This ratio is roughly 4 times larger than that expected simply from the stellar bulge-to-disk ratio of {approx}0.33 of the Galactic supernovae (SNe), which are thought to be the principal source of the annihilating positrons through the decay of radionuclei made by explosive nucleosynthesis in the SNe. This large discrepancy has prompted a search for new sources. Here, however, we show that the measured 511 keVmore » luminosity ratio can be fully understood in the context of a Galactic SN origin when the differential propagation of these {approx} MeV positrons in the various phases of the interstellar medium is taken into consideration, since these relativistic positrons must first slow down to energies {<=}10 eV before they can annihilate. Moreover, without propagation, none of the proposed positron sources, new or old, can explain the two basic properties on the Galactic annihilation radiation: the fraction of the annihilation that occurs through positronium formation and the ratio of the broad/narrow components of the 511 keV line. In particular, we show that in the neutral phases of the interstellar medium, which fill most of the disk (>3.5 kpc), the cascade of the magnetic turbulence, which scatters the positrons, is damped by ion-neutral friction, allowing positrons to stream along magnetic flux tubes. We find that nearly 1/2 of the positrons produced in the disk escape from it into the halo. On the other hand, we show that within the extended, or interstellar, bulge (<3.5 kpc), essentially all of the positrons are born in the hot plasmas which fill that volume. We find that the diffusion mean free path is long enough that only a negligible fraction annihilate there and {approx}80% of them escape down into the H II and H I envelopes of molecular clouds that lie within 1.5 kpc before they slow down and annihilate, while the remaining {approx}20% escape out into the halo and the disk beyond. This propagation accounts for the low observed annihilation radiation luminosity of the disk compared to the bulge. In addition, we show that the primary annihilation sites of the propagating positrons in both the bulge and the disk are in the warm ionized phases of the interstellar medium. Such annihilation can also account for those two basic properties of the emission, the fraction ({approx}93% {+-} 7%) of annihilation via positronium and the ratio ({approx}0.5) of broad ({approx}5.4 keV) to narrow ({approx}1.3 keV) components of the bulge 511 keV line emission. Moreover, we expect that the bulk of this broad line emission comes from the tilted disk region (0.5 < R < 1.5 kpc) with a very large broad/narrow flux ratio of {approx}6, while much of the narrow line emission comes from the inner bulge (R < 0.5 kpc) with a negligible broad/narrow flux ratio. Separate spectral analyses of the 511 keV line emission from these two regions should be able to test this prediction, and further probe the structure of the interstellar medium. Lastly, we show that the asymmetry in the inner disk annihilation line flux, which has been suggested as added evidence for new sources, can also be fully understood from positron propagation and the asymmetry in the inner spiral arms as viewed from our solar perspective without any additional sources.« less

Entire Sky

NASA Image and Video Library

1999-12-01

Aitoff projection of the three-color composite JHKs source count map of the entire sky, based on 95,851,173 stars with Ks 13.5. What appears most prominently are the Galactic plane and the Galactic bulge.

The population of single and binary white dwarfs of the Galactic bulge

NASA Astrophysics Data System (ADS)

Torres, S.; García-Berro, E.; Cojocaru, R.; Calamida, A.

2018-05-01

Recent Hubble Space Telescope observations have unveiled the white dwarf cooling sequence of the Galactic bulge. Although the degenerate sequence can be well fitted employing the most up-to-date theoretical cooling sequences, observations show a systematic excess of red objects that cannot be explained by the theoretical models of single carbon-oxygen white dwarfs of the appropriate masses. Here, we present a population synthesis study of the white dwarf cooling sequence of the Galactic bulge that takes into account the populations of both single white dwarfs and binary systems containing at least one white dwarf. These calculations incorporate state-of-the-art cooling sequences for white dwarfs with hydrogen-rich and hydrogen-deficient atmospheres, for both white dwarfs with carbon-oxygen and helium cores, and also take into account detailed prescriptions of the evolutionary history of binary systems. Our Monte Carlo simulator also incorporates all the known observational biases. This allows us to model with a high degree of realism the white dwarf population of the Galactic bulge. We find that the observed excess of red stars can be partially attributed to white dwarf plus main sequence binaries, and to cataclysmic variables or dwarf novae. Our best fit is obtained with a higher binary fraction and an initial mass function slope steeper than standard values, as well as with the inclusion of differential reddening and blending. Our results also show that the possible contribution of double degenerate systems or young and thick-discbulge stars is negligible.

DISCOVERY OF A PAIR OF CLASSICAL CEPHEIDS IN AN INVISIBLE CLUSTER BEYOND THE GALACTIC BULGE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dékány, I.; Palma, T.; Minniti, D.

2015-01-20

We report the discovery of a pair of extremely reddened classical Cepheid variable stars located in the Galactic plane behind the bulge, using near-infrared (NIR) time-series photometry from the VISTA Variables in the Vía Láctea Survey. This is the first time that such objects have ever been found in the opposite side of the Galactic plane. The Cepheids have almost identical periods, apparent brightnesses, and colors. From the NIR Leavitt law, we determine their distances with ∼1.5% precision and ∼8% accuracy. We find that they have a same total extinction of A(V)≃32 mag, and are located at the same heliocentricmore » distance of 〈d〉=11.4±0.9 kpc, and less than 1 pc from the true Galactic plane. Their similar periods indicate that the Cepheids are also coeval, with an age of ∼48±3 Myr, according to theoretical models. They are separated by an angular distance of only 18.″3, corresponding to a projected separation of ∼1 pc. Their position coincides with the expected location of the Far 3 kpc Arm behind the bulge. Such a tight pair of similar classical Cepheids indicates the presence of an underlying young open cluster that is both hidden behind heavy extinction and disguised by the dense stellar field of the bulge. All our attempts to directly detect this “invisible cluster” have failed, and deeper observations are needed. (letters)« less

OGLE-III Microlensing Events and the Structure of the Galactic Bulge

NASA Astrophysics Data System (ADS)

Wyrzykowski, Łukasz; Rynkiewicz, Alicja E.; Skowron, Jan; Kozłowski, Szymon; Udalski, Andrzej; Szymański, Michał K.; Kubiak, Marcin; Soszyński, Igor; Pietrzyński, Grzegorz; Poleski, Radosław; Pietrukowicz, Paweł; Pawlak, Michał

2015-01-01

We present and study the largest and most comprehensive catalog of microlensing events ever constructed. The sample of standard microlensing events comprises 3718 unique events from 2001-2009 with 1409 events that had not been detected before in real-time by the Early Warning System of the Optical Gravitational Lensing Experiment. The search pipeline uses machine learning algorithms to help find rare phenomena among 150 million objects and to derive the detection efficiency. Applications of the catalog can be numerous, from analyzing individual events to large statistical studies of the Galactic mass, kinematics distributions, and planetary abundances. We derive maps of the mean Einstein ring crossing time of events spanning 31 deg2 toward the Galactic center and compare the observed distributions with the most recent models. We find good agreement within the observed region and we see the signature of the tilt of the bar in the microlensing data. However, the asymmetry of the mean timescales seems to rise more steeply than predicted, indicating either a somewhat different orientation of the bar or a larger bar width. The map of events with sources in the Galactic bulge shows a dependence of the mean timescale on the Galactic latitude, signaling an increasing contribution from disk lenses closer to the plane relative to the height of the disk. Our data present a perfect set for comparing and enhancing new models of the central parts of the Milky Way and creating a three-dimensional picture of the Galaxy. Based on observations obtained with the 1.3 m Warsaw telescope at the Las Campanas Observatory of the Carnegie Institution for Science.

The panchromatic Hubble Andromeda treasury. VII. The steep mid-ultraviolet to near-infrared extinction curve in the central 200 pc of the M31 Bulge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, Hui; Lauer, Tod R.; Olsen, Knut

We measure the extinction curve in the central 200 pc of M31 at mid-ultraviolet to near-infrared wavelengths (from 1928 Å to 1.5 μm), using Swift/UVOT and Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3)/Advanced Camera for Surveys (ACS) observations in 13 bands. Taking advantage of the high angular resolution of the HST/WFC3 and ACS detectors, we develop a method to simultaneously determine the relative extinction and the fraction of obscured starlight for five dusty complexes located in the circumnuclear region. The extinction curves of these clumps (R{sub V} = 2.4-2.5) are steeper than the average Galactic one (R{sub V}more » = 3.1), but are similar to optical and near-infrared curves recently measured toward the Galactic bulge (R{sub V} ∼ 2.5). This similarity suggests that steep extinction curves may be common in the inner bulge of galaxies. In the ultraviolet, the extinction curves of these clumps are also unusual. We find that one dusty clump (size < 2 pc) exhibits a strong UV bump (extinction at 2175 Å), more than three standard deviation higher than that predicted by common models. Although the high stellar metallicity of the M31 bulge indicates that there are sufficient carbon and silicon to produce large dust grains, the grains may have been destroyed by supernova explosions or past activity of the central supermassive black hole, resulting in the observed steepened extinction curve.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gould, A.; Yee, J. C.; Pinsonneault, M. H.

The Galactic bulge source MOA-2010-BLG-523S exhibited short-term deviations from a standard microlensing light curve near the peak of an A {sub max} {approx} 265 high-magnification microlensing event. The deviations originally seemed consistent with expectations for a planetary companion to the principal lens. We combine long-term photometric monitoring with a previously published high-resolution spectrum taken near peak to demonstrate that this is an RS CVn variable, so that planetary microlensing is not required to explain the light-curve deviations. This is the first spectroscopically confirmed RS CVn star discovered in the Galactic bulge.

First detection of the white dwarf cooling sequence of the galactic bulge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Calamida, A.; Sahu, K. C.; Anderson, J.

2014-08-01

We present Hubble Space Telescope data of the low-reddening Sagittarius window in the Galactic bulge. The Sagittarius Window Eclipsing Extrasolar Planet Search field (∼3'× 3'), together with three more Advanced Camera for Surveys and eight Wide-Field Camera 3 fields, were observed in the F606W and F814W filters, approximately every two weeks for 2 yr, with the principal aim of detecting a hidden population of isolated black holes and neutron stars through astrometric microlensing. Proper motions were measured with an accuracy of ≈0.1 mas yr{sup –1} (≈4 km s{sup –1}) at F606W ≈ 25.5 mag, and better than ≈0.5 mas yr{supmore » –1} (≈20 km s{sup –1}) at F606W ≈ 28 mag, in both axes. Proper-motion measurements allowed us to separate disk and bulge stars and obtain a clean bulge color-magnitude diagram. We then identified for the first time a white dwarf (WD) cooling sequence in the Galactic bulge, together with a dozen candidate extreme horizontal branch stars. The comparison between theory and observations shows that a substantial fraction of the WDs (≈30%) are systematically redder than the cooling tracks for CO-core H-rich and He-rich envelope WDs. This evidence would suggest the presence of a significant number of low-mass WDs and WD-main-sequence binaries in the bulge. This hypothesis is further supported by the finding of two dwarf novae in outburst, two short-period (P ≲ 1 day) ellipsoidal variables, and a few candidate cataclysmic variables in the same field.« less

Missing mass or missing light?

NASA Astrophysics Data System (ADS)

Davies, J. I.

1990-07-01

Disney et al. (1989) have argued that the observational data are consistent with disk galaxies being optically thick, particularly in their inner regions. Here, these results are used to reinterpret the radial surface-brightness distributions of spiral galaxies. It is found that the fitting of a profile with an absorbed disk plus bulge leads to both disk and bulge masses (mass in luminous material) that are larger than previously assumed. In addition, it is shown how the rotation velocity, as determined from optical data in the central regions, may systematically underestimate the true rotational velocity in an optically thick disk. If the bulges of late-type galaxies are as large as is hypothesized, then this has important implications in models of galaxy evolution and galaxy dynamics. The model greatly reduces or even eliminates the need for dark matter within the optical radius; it removes a major argument against S0 evolution from later-type galaxies; it accounts for the similarity of rotation curve forms among galaxies of different morphological types; and it leads to a further reappraisal of the observed constancy of the extrapolated central surface brightness of galactic disks.

X-Ray Processing of ChaMPlane Fields: Methods and Initial Results for Selected Anti-Galactic Center Fields

NASA Astrophysics Data System (ADS)

Hong, JaeSub; van den Berg, Maureen; Schlegel, Eric M.; Grindlay, Jonathan E.; Koenig, Xavier; Laycock, Silas; Zhao, Ping

2005-12-01

We describe the X-ray analysis procedure of the ongoing Chandra Multiwavelength Plane (ChaMPlane) Survey and report the initial results from the analysis of 15 selected anti-Galactic center observations (90deg

Parameters of Six Selected Galactic Potential Models

NASA Astrophysics Data System (ADS)

Bajkova, Anisa; Bobylev, Vadim

2017-11-01

This paper is devoted to the refinement of the parameters of the six three-component (bulge, disk, halo) axisymmetric Galactic gravitational potential models on the basis of modern data on circular velocities of Galactic objects located at distances up to 200 kpc from the Galactic center. In all models the bulge and disk are described by the Miyamoto-Nagai expressions. To describe the halo, the models of Allen-Santillán (I), Wilkinson-Evans (II), Navarro- Frenk-White (III), Binney (IV), Plummer (V), and Hernquist (VI) are used. The sought-for parameters of potential models are determined by fitting the model rotation curves to the measured velocities, taking into account restrictions on the local dynamical matter density p⊙ - 0.1M⊙ pc-3 and the vertical force |Kz=1.1|/2πG = 77M⊙ pc-2. A comparative analysis of the refined potential models is made and for each of the models the estimates of a number of the Galactic characteristics are presented.

The Milky Way, the Galactic halo, and the Halos of Galaxies

NASA Astrophysics Data System (ADS)

Gerhard, Ortwin

2015-08-01

The Milky Way, "our" Galaxy, is currently the subject of intense study with many ground-based surveys, in anticipation of upcoming results from the GAIA mission. From this work we have been learning about the full three-dimensional structure of the Galactic box/peanut bulge, the distribution of stars in the bar and disk, and the many streams in the Galactic halo. The data tell us that most of the Galactic bulge formed from the disk, and that a large fraction of the Galactic halo has been accreted from outside. Similarly, in many external galaxy halos there is now evidence for tidal streams and accretion of satellites. To see these features requires exquisite data - mostly very deep photometry, but some halo substructures have also been found with kinematic data. These observations illustrate how galaxy halos are still growing, and sometimes can be used to "time" the accretion events. In comparison with cosmological simulations, the structure of galaxy halos gives us a vivid illustration of the hierarchical nature of our Universe.

The planetary nebulae populations in five galaxies: abundance patterns and evolution

NASA Astrophysics Data System (ADS)

Stasińska, G.; Richer, M. G.; McCall, M. L.

1998-08-01

We have collected photometric and spectroscopic data on planetary nebulae (PNe) in 5 galaxies: the Milky Way (bulge), M 31 (bulge), M 32, the LMC and the SMC. We have computed the abundances of O, Ne and N and compared them from one galaxy to another. In each Galaxy, the distribution of oxygen abundances has a large dispersion. The average O/H ratio is larger in the M 31 and the Galactic bulge PNe than in those in the Magellanic Clouds. In a given galaxy, it is also larger for PNe with [O III] luminosities greater than 100 L_⊙, which are likely to probe more recent epochs in the galaxy history. We find that the M 31 and the Galactic bulge PNe extend the very tight Ne/H-O/H correlation observed in the Galactic disk and Magellanic Clouds PNe towards higher metallicities. We note that the anticorrelation between N/O and O/H that was known to occur in the Magellanic Clouds and in the disk PNe is also marginally found in the PNe of the Galactic bulge. Furthermore, we find that high N/O ratios are higher for less luminous PNe. In M 32, all PNe have a large N/O ratio, indicating that the stellar nitrogen abundance is enhanced in this galaxy. We have also compared the PN evolution in the different galactic systems by constructing diagrams that are independent of abundances, and have found strikingly different behaviours of the various samples. In order to help in the interpretation of these data, we have constructed a grid of expanding, PN photoionization models in which the central stars evolve according to the evolutionary tracks of Bl{öcker (1995). These models show that the apparent spectroscopic properties of PNe are extremely dependent, not only on the central stars, but also on the masses and expansion velocities of the nebular envelopes. The main conclusion of the confrontation of the observed samples with the model grids is that the PN populations are indeed not the same in the various parent galaxies. Both stars and nebulae are different. In particular, the central stars of the Magellanic Clouds PNe are shown to evolve differently from the hydrogen burning stellar evolutionary models of Bl{öcker (1995). In the Galactic bulge, on the other hand, the behaviour of the observed PNe is roughly compatible with the theoretical stellar evolutionary tracks. The case of M 31 is not quite clear, and additional observations are necessary. It seems that the central star mass distribution is narrower for the M 31 PNe than for the Galactic bulge PNe. We show that spectroscopy of complete samples of PNe down to a factor 100 below the maximum luminosity would help to better characterize the PN central star mass distribution. Tables 1 and 2 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http: //cdsweb.u-strasbg.fr/Abstract.html

The peculiar Na-O anticorrelation of the bulge globular cluster NGC 6440

NASA Astrophysics Data System (ADS)

Muñoz, C.; Villanova, S.; Geisler, D.; Saviane, I.; Dias, B.; Cohen, R. E.; Mauro, F.

2017-08-01

Context. Galactic globular clusters (GCs) are essential tools for understanding the earliest epoch of the Milky Way, since they are among the oldest objects in the Universe and can be used to trace its formation and evolution. Current studies using high-resolution spectroscopy for many stars in each of a large sample of GCs allow us to develop a detailed observational picture of their formation and their relation with the Galaxy. However, it is necessary to complete this picture by including GCs that belong to all major Galactic components, including the bulge. Aims: Our aim is to perform a detailed chemical analysis of the bulge GC NGC 6440 in order to determine if this object has multiple populations (MPs) and investigate its relation with the bulge of the Milky Way and with the other Galactic GCs, especially those associated with the bulge, which are largely poorly studied. Methods: We determined the stellar parameters and the chemical abundances of light elements (Na, Al), iron-peak elements (Fe, Sc, Mn, Co, Ni), α-elements (O, Mg, Si, Ca, Ti) and heavy elements (Ba, Eu) in seven red giant members of NGC 6440 using high-resolution spectroscopy from FLAMES-UVES. Results: We found a mean iron content of [Fe/H] =-0.50 ± 0.03 dex in agreement with other studies. We found no internal iron spread. On the other hand, Na and Al show a significant intrinsic spread, but the cluster has no significant O-Na anticorrelation nor does it exhibit a Mg-Al anticorrelation. The α-elements show good agreement with the bulge field star trend, although they are at the high alpha end and are also higher than those of other GCs of comparable metallicity. The heavy elements are dominated by the r-process, indicating a strong contribution by SNeII. The chemical analysis suggests an origin similar to that of the bulge field stars.

Featured Image: Globular Cluster Orbits

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-04-01

This figure (click for the full view) shows the meridional galactic orbits of 12 globular clusters that orbit the Milky Way. The recent release of stellar parallax data from Gaia allowed a team of scientists at Dartmouth College to improve measurements of a number of galactic globular clusters very old clusters of stars that can either orbit within the galactic disk and bulge or more distantly in the galactic halo. In a recent publication led by Erin OMalley, the team presents their findings and combines their new measurements for the clusters with proper motions from past studies to calculate the orbits that these globulars take. These calculations show us whether the clusters reside in the galactic disk and bulge (as only NGC 104 does in the sample shown here, since its orbit is confined to 8 kpc radially and 4 kpc vertically of the galactic center), or if they are halo clusters. To learn more about the authors work, you can check out the paper below!CitationErin M. OMalley et al 2017 ApJ 838 162. doi:10.3847/1538-4357/aa6574

The Optical Gravitational Lensing Experiment: catalogue of stellar proper motions in the OGLE-II Galactic bulge fields

NASA Astrophysics Data System (ADS)

Sumi, T.; Wu, X.; Udalski, A.; Szymański, M.; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Woźniak, P.; Żebruń, K.; Szewczyk, O.; Wyrzykowski, Ł.

2004-03-01

We present a proper-motion (μ) catalogue of 5 080 236 stars in 49 Optical Gravitational Lensing Experiment II (OGLE-II) Galactic bulge (GB) fields, covering a range of -11° < l < 11° and -6° < b < 3°, the total area close to 11 deg2. The proper-motion measurements are based on 138-555 I-band images taken during four observing seasons: 1997-2000. The catalogue stars are in the magnitude range 11 < I < 18 mag. In particular, the catalogue includes red clump giants and red giants in the GB, and main-sequence stars in the Galactic disc. The proper motions up to μ= 500 mas yr-1 were measured with a mean accuracy of 0.8-3.5 mas yr-1, depending on the brightness of a star. This catalogue may be useful for studying the kinematics of stars in the GB and the Galactic disc.

VizieR Online Data Catalog: Extinction map towards the Galactic bulge (Chen+, 2013)

NASA Astrophysics Data System (ADS)

Chen, B.; Schultheis, M.; Jiang, B.; Gonzalez, O. A.; Robin, A. C.; Rejkuba, M.; Minniti, D.

2012-11-01

We combine the observations with the Besancon model of the Galaxy to investigate the variations of extinction along different lines of sight towards the inner Galactic bulge as a function of distance. The full results are listed in Table 1 and Table 2. These results will be also added into the BEAM calculator webpage (http://mill.astro.puc.cl/BEAM/calculator.php). For each position we give the E(J-Ks), E(H-Ks) as well as the corresponding sigma for each distance bin starting from 1 to 10kpc. (2 data files).

X-ray bursters and the X-ray sources of the galactic bulge

NASA Technical Reports Server (NTRS)

Lewin, W. H. G.; Joss, P. C.

1980-01-01

Type 1 X-ray bursts, optical, infrared, and radio properties of the galactic bulge sources, are discussed. It was proven that these burst sources are neutron stars in low mass, close binary stellar systems. Several burst sources are found in globular clusters with high central densities. Optical type 1 X-ray bursts were observed from three sources. Type 2 X-ray bursts, observed from the Rapid Burster, are due to an accretion instability which converts gravitational potential energy into heat and radiation, which makes them of a fundamentally different nature from Type 1 bursts.

Stellar populations, stellar masses and the formation of galaxy bulges and discs at z < 3 in CANDELS

NASA Astrophysics Data System (ADS)

Margalef-Bentabol, Berta; Conselice, Christopher J.; Mortlock, Alice; Hartley, Will; Duncan, Kenneth; Kennedy, Rebecca; Kocevski, Dale D.; Hasinger, Guenther

2018-02-01

We present a multicomponent structural analysis of the internal structure of 1074 high-redshift massive galaxies at 1 < z < 3 from the CANDELS HST Survey. In particular, we examine galaxies best fitted by two structural components, and thus likely forming discs and bulges. We examine the stellar mass, star formation rates (SFRs) and colours of both the inner 'bulge' and outer 'disc' components for these systems using Spectral Energy Distribution (SED) information from the resolved ACS+WFC3 HST imaging. We find that the majority of both inner and outer components lie in the star-forming region of UVJ space (68 and 90 per cent, respectively). However, the inner portions, or the likely forming bulges, are dominated by dusty star formation. Furthermore, we show that the outer components of these systems have a higher SFR than their inner regions, and the ratio of SFR between 'disc' and 'bulge' increases at lower redshifts. Despite the higher SFR of the outer component, the stellar mass ratio of inner to outer component remains constant through this epoch. This suggests that there is mass transfer from the outer to inner components for typical two-component-forming systems, thus building bulges from discs. Finally, using Chandra data we find that the presence of an active galactic nucleus is more common in both one-component spheroid-like galaxies and two-component systems (13 ± 3 and 11 ± 2 per cent) than in one-component disc-like galaxies (3 ± 1 per cent), demonstrating that the formation of a central inner component likely triggers the formation of central massive black holes in these galaxies.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferraro, F. R.; Dalessandro, E.; Lanzoni, B.

The Galactic bulge is dominated by an old, metal-rich stellar population. The possible presence and the amount of a young (a few gigayears old) minor component is one of the major issues debated in the literature. Recently, the bulge stellar system Terzan 5 was found to harbor three sub-populations with iron content varying by more than one order of magnitude (from 0.2 up to two times the solar value), with chemical abundance patterns strikingly similar to those observed in bulge field stars. Here we report on the detection of two distinct main-sequence turnoff points in Terzan 5, providing the agemore » of the two main stellar populations: 12 Gyr for the (dominant) sub-solar component and 4.5 Gyr for the component at super-solar metallicity. This discovery classifies Terzan 5 as a site in the Galactic bulge where multiple bursts of star formation occurred, thus suggesting a quite massive progenitor possibly resembling the giant clumps observed in star-forming galaxies at high redshifts. This connection opens a new route of investigation into the formation process and evolution of spheroids and their stellar content.« less

Near-infrared counterparts to the Galactic Bulge Survey X-ray source population

NASA Astrophysics Data System (ADS)

Greiss, S.; Steeghs, D.; Jonker, P. G.; Torres, M. A. P.; Maccarone, T. J.; Hynes, R. I.; Britt, C. T.; Nelemans, G.; Gänsicke, B. T.

2014-03-01

We report on the near-infrared matches, drawn from three surveys, to the 1640 unique X-ray sources detected by Chandra in the Galactic Bulge Survey (GBS). This survey targets faint X-ray sources in the bulge, with a particular focus on accreting compact objects. We present all viable counterpart candidates and associate a false alarm probability (FAP) to each near-infrared match in order to identify the most likely counterparts. The FAP takes into account a statistical study involving a chance alignment test, as well as considering the positional accuracy of the individual X-ray sources. We find that although the star density in the bulge is very high, ˜90 per cent of our sources have an FAP <10 per cent, indicating that for most X-ray sources, viable near-infrared counterparts candidates can be identified. In addition to the FAP, we provide positional and photometric information for candidate counterparts to ˜95 per cent of the GBS X-ray sources. This information in combination with optical photometry, spectroscopy and variability constraints will be crucial to characterize and classify secure counterparts.

MOA-2012-BLG-505Lb: A Super-Earth-mass Planet That Probably Resides in the Galactic Bulge

NASA Astrophysics Data System (ADS)

Nagakane, M.; Sumi, T.; Koshimoto, N.; Bennett, D. P.; Bond, I. A.; Rattenbury, N.; Suzuki, D.; Abe, F.; Asakura, Y.; Barry, R.; Bhattacharya, A.; Donachie, M.; Fukui, A.; Hirao, Y.; Itow, Y.; Li, M. C. A.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Matsuo, T.; Muraki, Y.; Ohnishi, K.; Ranc, C.; Saito, To.; Sharan, A.; Shibai, H.; Sullivan, D. J.; Tristram, P. J.; Yamada, T.; Yonehara, A.; MOA Collaboration

2017-07-01

We report the discovery of a super-Earth-mass planet in the microlensing event MOA-2012-BLG-505. This event has the second shortest event timescale of t E = 10 ± 1 days where the observed data show evidence of a planetary companion. Our 15 minute high cadence survey observation schedule revealed the short subtle planetary signature. The system shows the well known close/wide degeneracy. The planet/host-star mass ratio is q = 2.1 × 10-4 and the projected separation normalized by the Einstein radius is s = 1.1 or 0.9 for the wide and close solutions, respectively. We estimate the physical parameters of the system by using a Bayesian analysis and find that the lens consists of a super-Earth with a mass of {6.7}-3.6+10.7 {M}\\oplus orbiting around a brown dwarf or late-M-dwarf host with a mass of {0.10}-0.05+0.16 {M}⊙ with a projected star-planet separation of {0.9}-0.2+0.3 {au}. The system is at a distance of 7.2 ± 1.1 kpc, I.e., it is likely to be in the Galactic bulge. The small angular Einstein radius (θ E = 0.12 ± 0.02 mas) and short event timescale are typical for a low-mass lens in the Galactic bulge. Such low-mass planetary systems in the Bulge are rare because the detection efficiency of planets in short microlensing events is relatively low. This discovery may suggest that such low-mass planetary systems are abundant in the Bulge and currently on-going high cadence survey programs will detect more such events and may reveal an abundance of such planetary systems.

Characterization of the VVV Survey RR Lyrae Population across the Southern Galactic Plane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Minniti, Dante; Palma, Tali; Pullen, Joyce

Deep near-IR images from the VISTA Variables in the Vía Láctea (VVV) Survey were used to search for RR Lyrae stars in the Southern Galactic plane. A sizable sample of 404 RR Lyrae of type ab stars was identified across a thin slice of the fourth Galactic quadrant (295° < ℓ < 350°, −2.°24 < b < −1.°05). The sample’s distance distribution exhibits a maximum density that occurs at the bulge tangent point, which implies that this primarily Oosterhoff type I population of RRab stars does not trace the bar delineated by their red clump counterparts. The bulge RR Lyraemore » population does not extend beyond ℓ  ∼ 340°, and the sample’s spatial distribution presents evidence of density enhancements and substructure that warrants further investigation. Indeed, the sample may be employed to evaluate Galactic evolution models, and is particularly lucrative since half of the discovered RR Lyrae are within reach of Gaia astrometric observations.« less

Positron annihilation in the nuclear outflows of the Milky Way

NASA Astrophysics Data System (ADS)

Panther, Fiona H.; Crocker, Roland M.; Birnboim, Yuval; Seitenzahl, Ivo R.; Ruiter, Ashley J.

2018-02-01

Observations of soft gamma rays emanating from the Milky Way from SPI/INTEGRAL reveal the annihilation of ˜2 × 1043 positrons every second in the Galactic bulge. The origin of these positrons, which annihilate to produce a prominent emission line centred at 511 keV, has remained mysterious since their discovery almost 50 yr ago. A plausible origin for the positrons is in association with the intense star formation ongoing in the Galactic centre. Moreover, there is strong evidence for a nuclear outflow in the Milky Way. We find that advective transport and subsequent annihilation of positrons in such an outflow cannot simultaneously replicate the observed morphology of positron annihilation in the Galactic bulge and satisfy the requirement that 90 per cent of positrons annihilate once the outflow has cooled to 104 K.

The OGLE Collection of Variable Stars. Over 450 000 Eclipsing and Ellipsoidal Binary Systems Toward the Galactic Bulge

NASA Astrophysics Data System (ADS)

Soszyński, I.; Pawlak, M.; Pietrukowicz, P.; Udalski, A.; Szymański, M. K.; Wyrzykowski, Ł.; Ulaczyk, K.; Poleski, R.; Kozłowski, S.; Skowron, D. M.; Skowron, J.; Mróz, P.; Hamanowicz, A.

2016-12-01

We present a collection of 450 598 eclipsing and ellipsoidal binary systems detected in the OGLE fields toward the Galactic bulge. The collection consists of binary systems of all types: detached, semi-detached, and contact eclipsing binaries, RS CVn stars, cataclysmic variables, HW Vir binaries, double periodic variables, and even planetary transits. For all stars we provide the I- and V-band time-series photometry obtained during the OGLE-II, OGLE-III, and OGLE-IV surveys. We discuss methods used to identify binary systems in the OGLE data and present several objects of particular interest.

Gravitational microlensing by double stars and planetary systems

NASA Technical Reports Server (NTRS)

Mao, Shunde; Paczynski, Bohdan

1991-01-01

Almost all stars are in binary systems. When the separation between the two components is comparable to the Einstein ring radius corresponding to the combined mass of the binary acting as a gravitational lens, then an extra pair of images can be created, and the light curve of a lensed source becomes complicated. It is estimated that about 10 percent of all lensing episodes of the Galactic bulge stars will strongly display the binary nature of the lens. The effect is strong even if the companion is a planet. A massive search for microlensing of the Galactic bulge stars may lead to a discovery of the first extrasolar planetary systems.

Chemodynamical modelling of the galactic bulge and bar

NASA Astrophysics Data System (ADS)

Portail, Matthieu; Wegg, Christopher; Gerhard, Ortwin; Ness, Melissa

2017-09-01

We present the first self-consistent chemodynamical model fitted to reproduce data for the galactic bulge, bar and inner disc. We extend the Made-to-Measure method to an augmented phase-space including the metallicity of stars, and show its first application to the bar region of the Milky Way. Using data from the ARGOS and APOGEE (DR12) surveys, we adapt the recent dynamical model from Portail et al. to reproduce the observed spatial and kinematic variations as a function of metallicity, thus allowing the detailed study of the 3D density distributions, kinematics and orbital structure of stars in different metallicity bins. We find that metal-rich stars with [Fe/H] ≥ -0.5 are strongly barred and have dynamical properties that are consistent with a common disc origin. Metal-poor stars with [Fe/H] ≤ -0.5 show strong kinematic variations with metallicity, indicating varying contributions from the underlying stellar populations. Outside the central kpc, metal-poor stars are found to have the density and kinematics of a thick disc while in the inner kpc, evidence for an extra concentration of metal-poor stars is found. Finally, the combined orbit distributions of all metallicities in the model naturally reproduce the observed vertex deviations in the bulge. This paper demonstrates the power of Made-to-Measure chemodynamical models, that when extended to other chemical dimensions will be very powerful tools to maximize the information obtained from large spectroscopic surveys such as APOGEE, GALAH and MOONS.

Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars. IV. Two bulge populations

NASA Astrophysics Data System (ADS)

Bensby, T.; Adén, D.; Meléndez, J.; Gould, A.; Feltzing, S.; Asplund, M.; Johnson, J. A.; Lucatello, S.; Yee, J. C.; Ramírez, I.; Cohen, J. G.; Thompson, I.; Bond, I. A.; Gal-Yam, A.; Han, C.; Sumi, T.; Suzuki, D.; Wada, K.; Miyake, N.; Furusawa, K.; Ohmori, K.; Saito, To.; Tristram, P.; Bennett, D.

2011-09-01

Based on high-resolution (R ≈ 42 000 to 48 000) and high signal-to-noise (S/N ≈ 50 to 150) spectra obtained with UVES/VLT, we present detailed elemental abundances (O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, Y, and Ba) and stellar ages for 12 new microlensed dwarf and subgiant stars in the Galactic bulge. Including previous microlensing events, the sample of homogeneously analysed bulge dwarfs has now grown to 26. The analysis is based on equivalent width measurements and standard 1-D LTE MARCS model stellar atmospheres. We also present NLTE Li abundances based on line synthesis of the 7Li line at 670.8 nm. The results from the 26 microlensed dwarf and subgiant stars show that the bulge metallicity distribution (MDF) is double-peaked; one peak at [Fe/H] ≈ -0.6 and one at [Fe/H] ≈ + 0.3, and with a dearth of stars around solar metallicity. This is in contrast to the MDF derived from red giants in Baade's window, which peaks at this exact value. A simple significance test shows that it is extremely unlikely to have such a gap in the microlensed dwarf star MDF if the dwarf stars are drawn from the giant star MDF. To resolve this issue we discuss several possibilities, but we can not settle on a conclusive solution for the observed differences. We further find that the metal-poor bulge dwarf stars arepredominantly old with ages greater than 10 Gyr, while the metal-rich bulge dwarf stars show a wide range of ages. The metal-poor bulge sample is very similar to the Galactic thick disk in terms of average metallicity, elemental abundance trends, and stellar ages. Speculatively, the metal-rich bulge population might be the manifestation of the inner thin disk. If so, the two bulge populations could support the recent findings, based on kinematics, that there are no signatures of a classical bulge and that the Milky Way is a pure-disk galaxy. Also, recent claims of a flat IMF in the bulge based on the MDF of giant stars may have to be revised based on the MDF and abundance trends probed by our microlensed dwarf stars. Based on observations made with the European Southern Observatory telescopes (84.B-0837, 85.B-0399, and 86.B-0757). This paper also includes data gathered with the 6.5 m Magellan Telescopes located at the Las Campanas Observatory, Chile, and data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration.Tables 4 and 5 are available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/533/A134

CONSTRAINTS ON THE FORMATION OF THE GALACTIC BULGE FROM Na, Al, AND HEAVY-ELEMENT ABUNDANCES IN PLAUT's FIELD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Christian I.; Rich, R. Michael; Kobayashi, Chiaki

2012-04-20

We report chemical abundances of Na, Al, Zr, La, Nd, and Eu for 39 red giant branch (RGB) stars and 23 potential inner disk red clump stars located in Plaut's low-extinction window. We also measure lithium for a super Li-rich RGB star. The abundances were determined by spectrum synthesis of high-resolution (R Almost-Equal-To 25,000), high signal-to-noise (S/N {approx} 50-100 pixel{sup -1}) spectra obtained with the Blanco 4 m telescope and Hydra multifiber spectrograph. For the bulge RGB stars, we find a general increase in the [Na/Fe] and [Na/Al] ratios with increasing metallicity, and a similar decrease in [La/Fe] and [Nd/Fe].more » Additionally, the [Al/Fe] and [Eu/Fe] abundance trends almost identically follow those of the {alpha}-elements, and the [Zr/Fe] ratios exhibit relatively little change with [Fe/H]. The consistently low [La/Eu] ratios of the RGB stars indicate that at least a majority of bulge stars formed rapidly ({approx}<1 Gyr) and before the main s-process could become a significant pollution source. In contrast, we find that the potential inner disk clump stars exhibit abundance patterns more similar to those of the thin and thick disks. Comparisons between the abundance trends at different bulge locations suggest that the inner and outer bulges formed on similar timescales. However, we find evidence of some abundance differences between the most metal-poor and metal-rich stars in various bulge fields. The data also indicate that the halo may have had a more significant impact on the outer bulge initial composition than the inner bulge composition. The [Na/Fe], and to a lesser extent [La/Fe], abundances further indicate that the metal-poor bulge, at least at {approx}1 kpc from the Galactic center, and thick disk may not share an identical chemistry.« less

ALMA observations of molecular absorption in four directions toward the Galactic bulge

NASA Astrophysics Data System (ADS)

Liszt, H.; Gerin, M.

2018-02-01

Context. Alma Cycle 3 observations serendipitously showed strong absorption from diffuse molecular gas in the Galactic bulge at -200 km s-1 < v < -140 km s-1 toward the compact extragalactic continuum source J1744-3116 at (l, b) = -2.13∘, - 1.00∘. Aims: We aimed to test whether molecular gas in the bulge could also be detected toward the three other, sufficiently strong mm-wave continuum sources seen toward the bulge at |b| < 3∘. Methods: We took absorption profiles of HCO+ (1-0), HCN(1-0), C2H(1-0), CS(2-1) and H13CO+(1-0) in ALMA Cycle 4 toward J1713-3418, J1717-3341, J1733-3722 and J1744-3116. Results: Strong molecular absorption from disk gas at |ν| ≲ 30 km s-1 was detected in all directions, and absorption from the 3 kpc arm was newly detected toward J1717 and J1744. However, only the sightline toward J1744 is dominated by molecular gas overall and no other sightlines showed molecular absorption from gas deep inside the bulge. No molecular absorption was detected toward J1717 where H I emission from the bulge was previously known. As observed in HCO+, HCN, C2H and CS, the bulge gas toward J1744 at v < -135 km s-1 has chemistry and kinematics like that seen near the Sun and in the Milky Way disk generally. We measured isotopologic ratios N(HCO+)/N(H13CO+) > 51(3σ) for the bulge gas toward J1744 and 58 ± 9 and 64 ± 4 for the disk gas toward J1717 and J1744, respectively, all well above the value of 20-25 typical of the central molecular zone. Conclusions: The kinematics and chemistry of the bulge gas observed toward J1744 more nearly resemble that of gas in the Milky Way disk than in the central molecular zone.

GSFC Contributions to the NATO X-ray Astronomy Institute, Erice, July 1979. [X-ray spectra of supernova remants, galactic X-ray sources, active galactic nuclei, and clusters of galaxies

NASA Technical Reports Server (NTRS)

Holt, S. S.; Mushotzky, R. F.

1979-01-01

An overview of X-ray astronomical spectroscopy in general is presented and results obtained by HEAO 1 and 2 as well as earlier spacecraft are examined. Particular emphasis is given to the spectra of supernova remnants; galactic binary X-ray sources, cataclysmic variables, bulges, pulsars, and stars; the active nuclei of Seyfert 1 galaxy, BL Lac, and quasars; the diffuse X-ray background; and galactic clusters.

Can Jupiters be found by monitoring Galactic bulge microlensing events from northern sites?

NASA Astrophysics Data System (ADS)

Tsapras, Yiannis; Street, Rachel A.; Horne, Keith; Penny, Alan; Clarke, Fraser; Deeg, Hans; Garzon, Francisco; Kemp, Simon; Zapatero Osorio, Maria Rosa; Oscoz, Alejandro Abad; Sanchez, Santiago Madruga; Eiroa, Carlos; Mora, Alcione; Alberdi, Antxon; Collier Cameron, Andrew; Davies, John K.; Ferlet, Roger; Grady, Carol; Harris, Allan W.; Palacios, Javier; Quirrenbach, Andreas; Rauer, Heike; Schneider, Jean; de Winter, Dolf; Merin, Bruno; Solano, Enrique

2001-08-01

In 1998 the EXPORT team monitored microlensing event light curves using a charge-coupled device (CCD) camera on the IACQ4 0.8-m telescope on Tenerife to evaluate the prospect of using northern telescopes to find microlens anomalies that reveal planets orbiting the lens stars. The high airmass and more limited time available for observations of Galactic bulge sources make a northern site less favourable for microlensing planet searches. However, there are potentially a large number of northern 1-m class telescopes that could devote a few hours per night to monitor ongoing microlensing events. Our IAC observations indicate that accuracies sufficient to detect planets can be achieved despite the higher airmass.

Polycyclic Aromatic Hydrocarbon Emission Toward the Galactic Bulge

NASA Astrophysics Data System (ADS)

Shannon, M. J.; Peeters, E.; Cami, J.; Blommaert, J. A. D. L.

2018-03-01

We examine polycyclic aromatic hydrocarbon (PAH), dust, and atomic/molecular emission toward the Galactic bulge using Spitzer Space Telescope observations of four fields: C32, C35, OGLE, and NGC 6522. These fields are approximately centered on (l, b) = (0.°0, 1.°0), (0.°0, ‑1.°0), (0.°4, ‑2.°4), and (1.°0, ‑3.°8), respectively. Far-infrared photometric observations complement the Spitzer/IRS spectroscopic data and are used to construct spectral energy distributions. We find that the dust and PAH emission are exceptionally similar between C32 and C35 overall, in part explained due to their locations—they reside on or near boundaries of a 7 Myr old Galactic outflow event and are partly shock-heated. Within the C32 and C35 fields, we identify a region of elevated Hα emission that is coincident with elevated fine-structure and [O IV] line emission and weak PAH feature strengths. We are likely tracing a transition zone of the outflow into the nascent environment. PAH abundances in these fields are slightly depressed relative to typical ISM values. In the OGLE and NGC 6522 fields, we observe weak features on a continuum dominated by zodiacal dust. SED fitting indicates that thermal dust grains in C32 and C35 have temperatures comparable to those of diffuse, high-latitude cirrus clouds. Little variability is detected in the PAH properties between C32 and C35, indicating that a stable population of PAHs dominates the overall spectral appearance. In fact, their PAH features are exceptionally similar to that of the M82 superwind, emphasizing that we are probing a local Galactic wind environment.

The OGLE Collection of Variable Stars. Classical, Type II, and Anomalous Cepheids toward the Galactic Center

NASA Astrophysics Data System (ADS)

Soszyński, I.; Udalski, A.; Szymański, M. K.; Wyrzykowski, Ł.; Ulaczyk, K.; Poleski, R.; Pietrukowicz, P.; Kozłowski, S.; Skowron, D. M.; Skowron, J.; Mróz, P.; Pawlak, M.; Rybicki, K.; Jacyszyn-Dobrzeniecka, A.

2017-12-01

We present a collection of classical, typeII, and anomalous Cepheids detected in the OGLE fields toward the Galactic center. The sample contains 87 classical Cepheids pulsating in one, two or three radial modes, 924 type II Cepheids divided into BL Her, W Vir, peculiar W Vir, and RV Tau stars, and 20 anomalous Cepheids - first such objects found in the Galactic bulge. Additionally, we upgrade the OGLE Collection of RR Lyr stars in the Galactic bulge by adding 828 newly identified variables. For all Cepheids and RRLyr stars, we publish time-series VI photometry obtained during the OGLE-IV project, from 2010 through 2017. We discuss basic properties of our classical pulsators: their spatial distribution, light curve morphology, period-luminosity relations, and position in the Petersen diagram. We present the most interesting individual objects in our collection: a typeII Cepheid with additional eclipsing modulation, WVir stars with the period doubling effect and the RVb phenomenon, a mode-switching RR Lyr star, and a triple-mode anomalous RRd star.

Determining Mass-Loss Rates of Evolved Stars in the Galactic Bulge from Infrared Surveys

NASA Astrophysics Data System (ADS)

Riley, Allyssa; Sargent, Benjamin A.; Srinivasan, Sundar; Meixner, Margaret; Kastner, Joel H.

2018-06-01

To investigate the relationship between mass loss from evolved stars and host galaxy metallicity, we are computing the dust mass loss budget due to red supergiant (RSG) and asymptotic giant branch (AGB) stars in the Galactic Bulge and comparing this result to that previously obtained for the Magellanic Clouds. We construct spectral energy distributions (SEDs) for our candidate RSG and AGB stars using observations from various infrared surveys, including the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE). Because Robitaille et al (2008, AJ, 136, 2413) have already identified Intrinsically Red Objects from the GLIMPSE I and II surveys, we use their method as a starting point and expand the study by using the GLIMPSE 3D survey. Because AGB stars can be variable, we also match the GLIMPSE I, II, and 3D sources to other surveys, such as DEEP GLIMPSE, WISE, VVV, and DENIS, in order to characterize the variability across the spectral energy distribution (SED) of each source. This allows us to determine the source’s average SED over multiple epochs. We use extinction curves derived from Spitzer studies of extinction in the Galaxy to determine the extinction corrections for our sample. To establish mass-loss rates of evolved stars in the Bulge, we use the Grid of Red supergiant and Asymptotic giant branch ModelS (GRAMS) of dust-enshrouded evolved stars (2011, A&A, 532, A54; 2011, ApJ, 728, 93). This allows us to determine the total mass return to the Bulge from these stars. This work has been supported by NASA ADAP grant 80NSSC17K0057.

The density of dark matter in the Galactic bulge and implications for indirect detection

DOE PAGES

Hooper, Dan

2016-11-29

A recent study, making use of the number of horizontal branch stars observed in infrared photometric surveys and kinematic measurements of M-giant stars from the BRAVA survey, combined with N-body simulations of stellar populations, has presented a new determination of the dark matter mass within the bulge-bar region of the Milky Way. That study constrains the total mass within themore » $$\\pm 2.2 \\times \\pm 1.4 \\times \\pm 1.2$$ kpc volume of the bulge-bar region to be ($$1.84 \\pm 0.07) \\times 10^{10} \\, M_{\\odot}$$, of which 9-30% is made up of dark matter. Here, we use this result to constrain the the Milky Way's dark matter density profile, and discuss the implications for indirect dark matter searches. Furthermore uncertainties remain significant, these results favor dark matter distributions with a cusped density profile. For example, for a scale radius of 20 kpc and a local dark matter density of 0.4 GeV/cm$^3$, density profiles with an inner slope of 0.69 to 1.40 are favored, approximately centered around the standard NFW value. In contrast, profiles with large flat-density cores are disfavored by this information.« less

The Cool Stellar Populations of Early-Type Galaxies and the Galactic Bulge

NASA Astrophysics Data System (ADS)

Houdashelt, Mark Lee

1995-01-01

Red (6800-9200 A) and near-infrared (K-band) spectra have been obtained for 34 early-type galaxies in the Virgo cluster, the Coma cluster and the field. The strengths of the Ca II triplet (lambdalambda 8498, 8542, 8662 A), the Na I doublet ( lambdalambda8183, 8195 A), the Mg I lambda8807 A line, and molecular bands of TiO and VO were measured from the red spectra. Absorption due to the CO band with bandhead at 2.29 mu m was measured from the near-infrared spectra. The behavior of the spectral indices was examined for the Virgo galaxy nuclei as functions of luminosity and color. Overall, the CO, TiO and Na I indices were found to be stronger in redder and brighter galaxies. The Mg I and the Ca II triplet lines did not vary significantly among galaxies of different color or brightness. These trends are consistent with a change in chemical composition producing the well-known color-magnitude relation for early -type galaxies. No significant differences were detected among galaxies of similar luminosity in the Virgo cluster, the Coma cluster and the field. To simulate the stellar population changes implied by the radial color gradients observed in early-type galaxies, models were constructed to represent the integrated light of the Galactic bulge as a function of latitude. A field in Baade's Window (BW) was studied first and the stellar population there was found to be quite inhomogeneous. The BW model indicated that the integrated light of BW is giant -dominated, and the BW spectral energy distribution is very similar to that of the nucleus of a low-luminosity early -type galaxy. From models of BW and a field at b = -8^circ, radial gradients were estimated for the Galactic bulge and compared to the changes which occur along a luminosity sequence of early -type galaxies in the Virgo cluster. This comparison showed that: (1) the Na I and I(8197) indices increase steeply with redder colors in the Virgo galaxies but appear to decrease with color in the Galactic bulge; this effect is not understood but may be caused by some deficiency in the modelling; and (2) differences in the slopes of the TiO-color trends in E/S0 galaxies and in the Galactic bulge may indicate that the (Ti/Fe) ratio is changing differently in these two instances.

Before the Bar: Kinematic Detection of a Spheroidal Metal-poor Bulge Component

NASA Astrophysics Data System (ADS)

Kunder, Andrea; Rich, R. M.; Koch, A.; Storm, J.; Nataf, D. M.; De Propris, R.; Walker, A. R.; Bono, G.; Johnson, C. I.; Shen, Juntai; Li, Z.-Y.

2016-04-01

We present 947 radial velocities of RR Lyrae variable stars in four fields located toward the Galactic bulge, observed within the data from the ongoing Bulge RR Lyrae Radial Velocity Assay (BRAVA-RR). We show that these RR Lyrae stars (RRLs) exhibit hot kinematics and null or negligible rotation and are therefore members of a separate population from the bar/pseudobulge that currently dominates the mass and luminosity of the inner Galaxy. Our RRLs predate these structures and have metallicities, kinematics, and spatial distribution that are consistent with a “classical” bulge, although we cannot yet completely rule out the possibility that they are the metal-poor tail of a more metal-rich ([{Fe}/{{H}}]˜ -1 dex) halo-bulge population. The complete catalog of radial velocities for the BRAVA-RR stars is also published electronically.

VizieR Online Data Catalog: Metal-poor stars towards the Galactic bulge (Koch+, 2016)

NASA Astrophysics Data System (ADS)

Koch, A.; McWilliam, A.; Preston, G. W.; Thompson, I. B.

2015-11-01

The stars studied here were identified in a search for EMP stars in the Galactic bulge (Preston et al. unpublished), near b=-10°, employing the 2.5-m du Pont and 1-m Swope telescopes at Las Campanas Observatory. Observations of seven EMP candidates presented here were taken spread over six nights in July 2007 with a median seeing of 0.95", while individual exposures reached as high as 2" and notably better conditions (~0.6") during several nights. Our chosen set-up included a 0.5" slit, 2x1 binning in spectral and spatial dimensions and resulted in a resolving power of R~45000. An observing log is given in Table 1. (3 data files).

Gamma Rays from the Galactic Bulge and Large Extra Dimensions

NASA Astrophysics Data System (ADS)

Cassé, Michel; Paul, Jacques; Bertone, Gianfranco; Sigl, Günter

2004-03-01

An intriguing feature of extra dimensions is the possible production of Kaluza Klein gravitons by nucleon-nucleon bremsstrahlung, in the course of core collapse of massive stars, with gravitons then being trapped around the newly born neutron stars and decaying into two gamma rays, making neu­tron stars gamma-ray sources. We strengthen the limits on the radius of compactification of extra dimensions for a small number n of them, or alternatively the fundamental scale of quantum gravity, considering the gamma-ray emission of the whole population of neutron stars sitting in the Galactic bulge, instead of the closest member of this category. For n=1 the constraint on the compactification radius is R<400 μm.

SDSS-IV MaNGA - the spatially resolved transition from star formation to quiescence

NASA Astrophysics Data System (ADS)

Belfiore, Francesco; Maiolino, Roberto; Maraston, Claudia; Emsellem, Eric; Bershady, Matthew A.; Masters, Karen L.; Bizyaev, Dmitry; Boquien, Médéric; Brownstein, Joel R.; Bundy, Kevin; Diamond-Stanic, Aleksandar M.; Drory, Niv; Heckman, Timothy M.; Law, David R.; Malanushenko, Olena; Oravetz, Audrey; Pan, Kaike; Roman-Lopes, Alexandre; Thomas, Daniel; Weijmans, Anne-Marie; Westfall, Kyle B.; Yan, Renbin

2017-04-01

Using spatially resolved spectroscopy from SDSS-IV MaNGA we have demonstrated that low ionization emission-line regions (LIERs) in local galaxies result from photoionization by hot evolved stars, not active galactic nuclei, hence tracing galactic region hosting old stellar population where, despite the presence of ionized gas, star formation is no longer occurring. LIERs are ubiquitous in both quiescent galaxies and in the central regions of galaxies where star formation takes place at larger radii. We refer to these two classes of galaxies as extended LIER (eLIER) and central LIER (cLIER) galaxies, respectively. cLIERs are late-type galaxies primarily spread across the green valley, in the transition region between the star formation main sequence and quiescent galaxies. These galaxies display regular disc rotation in both stars and gas, although featuring a higher central stellar velocity dispersion than star-forming galaxies of the same mass. cLIERs are consistent with being slowly quenched inside-out; the transformation is associated with massive bulges, pointing towards the importance of bulge growth via secular evolution. eLIERs are morphologically early types and are indistinguishable from passive galaxies devoid of line emission in terms of their stellar populations, morphology and central stellar velocity dispersion. Ionized gas in eLIERs shows both disturbed and disc-like kinematics. When a large-scale flow/rotation is observed in the gas, it is often misaligned relative to the stellar component. These features indicate that eLIERs are passive galaxies harbouring a residual cold gas component, acquired mostly via external accretion. Importantly, quiescent galaxies devoid of line emission reside in denser environments and have significantly higher satellite fraction than eLIERs. Environmental effects thus represent the likely cause for the existence of line-less galaxies on the red sequence.

Establishing the connection between peanut-shaped bulges and galactic bars

NASA Technical Reports Server (NTRS)

Kuijken, Konrad; Merrifield, Michael R.

1995-01-01

It has been suggested that the peanut-shaped bulges seen in some edge-on disk galaxies are due to the presence of a central bar. Although bars cannot be detected photometrically in edge-on galaxies, we show that barred potentials produce a strong kinematic signature in the form of double-peaked line-of-sight velocity distributions with a characteristic 'figure-of-eight' variation with radius. We have obtained spectroscopic observations of two edge-on galaxies with peanut-shaped bulges (NGC 5746 and NGC 5965), and they reveal exactly such line-of-sight velocity distributions in both their gaseous (emission line) and their stellar (absorption line) components. These observations provide strong observational evidence that peanut-shaped bulges are a by-product of bar formation.

The intrinsic three-dimensional shape of galactic bars

NASA Astrophysics Data System (ADS)

Méndez-Abreu, J.; Costantin, L.; Aguerri, J. A. L.; de Lorenzo-Cáceres, A.; Corsini, E. M.

2018-06-01

We present the first statistical study on the intrinsic three-dimensional (3D) shape of a sample of 83 galactic bars extracted from the CALIFA survey. We use the galaXYZ code to derive the bar intrinsic shape with a statistical approach. The method uses only the geometric information (ellipticities and position angles) of bars and discs obtained from a multi-component photometric decomposition of the galaxy surface-brightness distributions. We find that bars are predominantly prolate-triaxial ellipsoids (68%), with a small fraction of oblate-triaxial ellipsoids (32%). The typical flattening (intrinsic C/A semiaxis ratio) of the bars in our sample is 0.34, which matches well the typical intrinsic flattening of stellar discs at these galaxy masses. We demonstrate that, for prolate-triaxial bars, the intrinsic shape of bars depends on the galaxy Hubble type and stellar mass (bars in massive S0 galaxies are thicker and more circular than those in less massive spirals). The bar intrinsic shape correlates with bulge, disc, and bar parameters. In particular with the bulge-to-total (B/T) luminosity ratio, disc g - r color, and central surface brightness of the bar, confirming the tight link between bars and their host galaxies. Combining the probability distributions of the intrinsic shape of bulges and bars in our sample we show that 52% (16%) of bulges are thicker (flatter) than the surrounding bar at 1σ level. We suggest that these percentages might be representative of the fraction of classical and disc-like bulges in our sample, respectively.

Observations of galactic X-ray sources by OSO-7

NASA Technical Reports Server (NTRS)

Markert, T. H.; Canizares, C. R.; Clark, G. W.; Hearn, D. R.; Li, F. K.; Sprott, G. F.; Winkler, P. F.

1977-01-01

We present the MIT data from the OSO-7 satellite for observations of the galactic plane between 1971 and 1974. A number of sources discovered in the MIT all-sky survey are described in detail: MX 0049 + 59, MX 0836 - 42, MX 1353 - 64, MX 1406 - 61, MX 1418 - 61, MX 1709 - 40, and MX 1608 - 52 (the persistent source suggested to be associated with the X-ray burst source XB 1608 - 52). Upper limits to the X-ray emission from a number of interesting objects are also derived. General results describing all of our observations of galactic sources are presented. Specifically, we display the number-intensity diagrams, luminosity functions, and color-color diagrams for all of the sources we detected. The data are divided between disk and bulge populations, and the characteristics of the two groups are contrasted. Finally, the concept of X-ray source populations and the relationship of globular cluster sources and burst sources to the disk and bulge populations are discussed.

Microlensing results toward the galactic bulge, theory of fitting blended light curves, and discussion of weak lensing corrections

NASA Astrophysics Data System (ADS)

Thomas, Christian L.

2006-06-01

Analysis and results (Chapters 2-5) of the full 7 year Macho Project dataset toward the Galactic bulge are presented. A total of 450 high quality, relatively large signal-to-noise ratio, events are found, including several events exhibiting exotic effects, and lensing events on possible Sagittarius dwarf galaxy stars. We examine the problem of blending in our sample and conclude that the subset of red clump giants are minimally blended. Using 42 red clump giant events near the Galactic center we calculate the optical depth toward the Galactic bulge to be t = [Special characters omitted.] × 10 -6 at ( l, b ) = ([Special characters omitted.] ) with a gradient of (1.06 ± 0.71) × 10 -6 deg -1 in latitude, and (0.29±0.43) × 10 -6 deg -1 in longitude, bringing measurements into consistency with the models for the first time. In Chapter 6 we reexamine the usefulness of fitting blended light-curve models to microlensing photometric data. We find agreement with previous workers (e.g. Wozniak & Paczynski) that this is a difficult proposition because of the degeneracy of blend fraction with other fit parameters. We show that follow-up observations at specific points along the light curve (peak region and wings) of high magnification events are the most helpful in removing degeneracies. We also show that very small errors in the baseline magnitude can result in problems in measuring the blend fraction, and study the importance of non- Gaussian errors in the fit results. The biases and skewness in the distribution of the recovered blend fraction is discussed. We also find a new approximation formula relating the blend fraction and the unblended fit parameters to the underlying event duration needed to estimate microlensing optical depth. In Chapter 7 we present work-in-progress on the possibility of correcting standard candle luminosities for the magnification due to weak lensing. We consider the importance of lenses in different mass ranges and look at the contribution from lenses that could not be observed. We conclude that it may be possible to perform this correction with relatively high precision (1-2%) and discuss possible sources of error and methods of improving our model.

The MACHO Project Sample of Galactic Bulge High-Amplitude δ Scuti Stars: Pulsation Behavior and Stellar Properties

NASA Astrophysics Data System (ADS)

Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T. S.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Freeman, K. C.; Geha, M.; Griest, K.; Lehner, M. J.; Marshall, S. L.; McNamara, B. J.; Minniti, D.; Nelson, C.; Peterson, B. A.; Popowski, P.; Pratt, M. R.; Quinn, P. J.; Rodgers, A. W.; Sutherland, W.; Templeton, M. R.; Vandehei, T.; Welch, D. L.

2000-06-01

We have detected 90 objects with periods and light-curve structures similar to those of field δ Scuti stars using the Massive Compact Halo Object (MACHO) Project database of Galactic bulge photometry. If we assume similar extinction values for all candidates and absolute magnitudes similar to those of other field high-amplitude δ Scuti stars (HADS), the majority of these objects lie in or near the Galactic bulge. At least two of these objects are likely foreground δ Scuti stars, one of which may be an evolved nonradial pulsator, similar to other evolved, disk-population δ Scuti stars. We have analyzed the light curves of these objects and find that they are similar to the light curves of field δ Scuti stars and the δ Scuti stars found by the Optical Gravitational Lens Experiment (OGLE). However, the amplitude distribution of these sources lies between those of low- and high-amplitude δ Scuti stars, which suggests that they may be an intermediate population. We have found nine double-mode HADS with frequency ratios ranging from 0.75 to 0.79, four probable double- and multiple-mode objects, and another four objects with marginal detections of secondary modes. The low frequencies (5-14 cycles day-1) and the observed period ratios of ~0.77 suggest that the majority of these objects are evolved stars pulsating in fundamental or first overtone radial modes.

VizieR Online Data Catalog: Li enrichment histories of the thick/thin disc (Fu+, 2018)

NASA Astrophysics Data System (ADS)

Fu, X.; Romano, D.; Bragaglia, A.; Mucciarelli, A.; Lind, K.; Delgado Mena, E.; Sousa, S. G.; Randich, S.; Bressan, A.; Sbordone, L.; Martell, S.; Korn, A. J.; Abia, C.; Smiljanic, R.; Jofre, P.; Pancino, E.; Tautvaisiene, G.; Tang, B.; Lanzafame, A. C.; Magrini, L.; Carraro, G.; Bensby, T.; Damiani, F.; Alfaro, E. J.; Flaccomio, E.; Morbidelli, L.; Zaggia, S.; Lardo, C.; Monaco, L.; Frasca, A.; Donati, P.; Drazdauskas, A.; Chorniy, Y.; Bayo, A.; Kordopatis, G.

2017-11-01

To investigate the Galactic lithium enrichment history we se- lect well-measured main sequence field stars with UVES spectra from the GES iDR4 catalogue. In our selection, 1884 UVES stars are marked as field stars, including those of the Galactic disc and halo designated as MW (GEMW) fields, standard CoRoT (GES D_CR) field, standard radial velocity (GES DRV) field, and stars to the Galactic Bulge direction (GEMWBL). (1 data file).

Magnetic activity in the Galactic Centre region - fast downflows along rising magnetic loops

NASA Astrophysics Data System (ADS)

Kakiuchi, Kensuke; Suzuki, Takeru K.; Fukui, Yasuo; Torii, Kazufumi; Enokiya, Rei; Machida, Mami; Matsumoto, Ryoji

2018-06-01

We studied roles of the magnetic field on the gas dynamics in the Galactic bulge by a three-dimensional global magnetohydrodynamical simulation data, particularly focusing on vertical flows that are ubiquitously excited by magnetic activity. In local regions where the magnetic field is stronger, it is frequently seen that fast downflows slide along inclined magnetic field lines that are associated with buoyantly rising magnetic loops. The vertical velocity of these downflows reaches ˜100 km s-1 near the footpoint of the loops by the gravitational acceleration towards the Galactic plane. The two footpoints of rising magnetic loops are generally located at different radial locations and the field lines are deformed by the differential rotation. The angular momentum is transported along the field lines, and the radial force balance breaks down. As a result, a fast downflow is often observed only at the one footpoint located at the inner radial position. The fast downflow compresses the gas to form a dense region near the footpoint, which will be important in star formation afterwards. Furthermore, the horizontal components of the velocity are also fast near the footpoint because the downflow is accelerated along the magnetic sliding slope. As a result, the high-velocity flow creates various characteristic features in a simulated position-velocity diagram, depending on the viewing angle.

The stellar population and luminosity function in M31 bulge and Inner Disk Fields

NASA Technical Reports Server (NTRS)

Rich, R. Michael; Mould, J. R.; Graham, James R.

1993-01-01

We report infrared photometry and stellar identifications for stars in five fields in the M31 bulge located from 2 to 11 arcmin from the nucleus. These fields have been chosen such that the bulge/disk star ratio predicted from Kent's (1989) small bulge model varies from 7:1 to 1:5, allowing a study of near pure disk and near pure bulge stellar populations. We reject the hypothesis of Davies et al. (1991) that luminous stars found within 500 pc of the nucleus are due to a contaminating disk population. We find that the bulge contains stars in excess of M(sub bol) = -5 mag and that the bulge luminosity function has a distinct shape different from the disk fields. We find many stars redder than (J-K) = 2 mag, and suggest that these stars may be the counterparts of the IRAS-selected Galactic bulge Miras studied by Whitelock et at. (1991). The number of bright stars (M(sub bol) is less than -5 mag) falls off more rapidly than the r band surface brightness. By building model fields out of a bulge luminosity function and artificial stars, we are able to show that the change in the luminosity function toward the center cannot be explained simply by the mismeasurement of overcrowded star images. However, these tests also raise the possibility that the asymptotic giant branch (AGB) tip may be approximately equal to 1 mag fainter than actually measured in our most crowded field, reaching only M(sub bol) = -5. We compare observed counts of AGB stars with those predicted from theoretical lifetimes using a technique of general interest for this problem, the Fuel Consumption Theorem of Renzini & Buzzoni (1986) Spectral Evolution of Galaxies (Reidel, Dordrecht). Our methodology is generally applicable to the study of other resolved extragalactic stellar populations. The number of observed stars per magnitude up to a luminosity of M(bol) = -5.5 mag is consistent with AGB evolution of the whole population of the innermost bulge field with the standard lifetime on the AGB of 1.3 Myr/mag. We advance the possibility that the bulge of M31 may be younger than the oldest Galactic globular clusters. We note that M33 has recently been found to have an r(exp 1/4)-law spheroid consisting of intermediate-age stars; bulges can form later than the old halo population.

CHARACTERIZATION OF A SAMPLE OF INTERMEDIATE-TYPE ACTIVE GALACTIC NUCLEI. II. HOST BULGE PROPERTIES AND BLACK HOLE MASS ESTIMATES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benitez, Erika; Cruz-Gonzalez, Irene; Martinez, Benoni

2013-02-15

We present a study of the host bulge properties and their relations with the black hole mass for a sample of 10 intermediate-type active galactic nuclei (AGNs). Our sample consists mainly of early-type spirals, four of them hosting a bar. For 70{sup +10} {sub -17}% of the galaxies, we have been able to determine the type of the bulge, and find that these objects probably harbor a pseudobulge or a combination of classical bulge/pseudobulge, suggesting that pseudobulges might be frequent in intermediate-type AGNs. In our sample, 50% {+-} 14% of the objects show double-peaked emission lines. Therefore, narrow double-peaked emissionmore » lines seem to be frequent in galaxies harboring a pseudobulge or a combination of classical bulge/pseudobulge. Depending on the bulge type, we estimated the black hole mass using the corresponding M {sub BH}-{sigma}* relation and found them within a range of 5.69 {+-} 0.21 < log M {sup {sigma}}*{sub BH} < 8.09 {+-} 0.24. Comparing these M {sup {sigma}}*{sub BH} values with masses derived from the FWHM of H{beta} and the continuum luminosity at 5100 A from their SDSS-DR7 spectra (M {sub BH}), we find that 8 out of 10 (80{sup +7} {sub -17}%) galaxies have black hole masses that are compatible within a factor of 3. This result would support that M {sub BH} and M {sup {sigma}}*{sub BH} are the same for intermediate-type AGNs, as has been found for type 1 AGNs. However, when the type of the bulge is taken into account, only three out of the seven (43{sup +18} {sub -15}%) objects of the sample have their M {sup {sigma}}*{sub BH} and M {sub BH} compatible within 3{sigma} errors. We also find that estimations based on the M {sub BH}-{sigma}* relation for pseudobulges are not compatible in 50% {+-} 20% of the objects.« less

Infrared Extinction and Stellar Populations in the Milky Way Midplane

NASA Astrophysics Data System (ADS)

Zasowski, Gail; Majewski, S. R.; Benjamin, R. A.; Nidever, D. L.; Skrutskie, M. F.; Indebetouw, R.; Patterson, R. J.; Meade, M. R.; Whitney, B. A.; Babler, B.; Churchwell, E.; Watson, C.

2012-01-01

The primary laboratory for developing and testing models of galaxy formation, structure, and evolution is our own Milky Way, the closest large galaxy and the only one in which we can resolve large numbers of individual stars. The recent availability of extensive stellar surveys, particularly infrared ones, has enabled precise, contiguous measurement of large-scale Galactic properties, a major improvement over inferences based on selected, but scattered, sightlines. However, our ability to fully exploit the Milky Way as a galactic laboratory is severely hampered by the fact that its midplane and central bulge -- where most of the Galactic stellar mass lies -- is heavily obscured by interstellar dust. Therefore, proper consideration of the interstellar extinction is crucial. This thesis describes a new extinction-correction method (the RJCE method) that measures the foreground extinction towards each star and, in many cases, enables recovery of its intrinsic stellar type. We have demonstrated the RJCE Method's validity and used it to produce new, reliable extinction maps of the heavily-reddened Galactic midplane. Taking advantage of the recovered stellar type information, we have generated maps probing the extinction at different heliocentric distances, thus yielding information on the elusive three-dimensional distribution of the interstellar dust. We also performed a study of the interstellar extinction law itself which revealed variations previously undetected in the diffuse ISM and established constraints on models of ISM grain formation and evolution. Furthermore, we undertook a study of large-scale stellar structure in the inner Galaxy -- the bar(s), bulge(s), and inner spiral arms. We used observed and extinction-corrected infrared photometry to map the coherent stellar features in these heavily-obscured parts of the Galaxy, placing constraints on models of the central stellar mass distribution.

Extinction maps toward the Milky Way bulge: Two-dimensional and three-dimensional tests with apogee

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schultheis, M.; Zasowski, G.; Allende Prieto, C.

Galactic interstellar extinction maps are powerful and necessary tools for Milky Way structure and stellar population analyses, particularly toward the heavily reddened bulge and in the midplane. However, due to the difficulty of obtaining reliable extinction measures and distances for a large number of stars that are independent of these maps, tests of their accuracy and systematics have been limited. Our goal is to assess a variety of photometric stellar extinction estimates, including both two-dimensional and three-dimensional extinction maps, using independent extinction measures based on a large spectroscopic sample of stars toward the Milky Way bulge. We employ stellar atmosphericmore » parameters derived from high-resolution H-band Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectra, combined with theoretical stellar isochrones, to calculate line-of-sight extinction and distances for a sample of more than 2400 giants toward the Milky Way bulge. We compare these extinction values to those predicted by individual near-IR and near+mid-IR stellar colors, two-dimensional bulge extinction maps, and three-dimensional extinction maps. The long baseline, near+mid-IR stellar colors are, on average, the most accurate predictors of the APOGEE extinction estimates, and the two-dimensional and three-dimensional extinction maps derived from different stellar populations along different sightlines show varying degrees of reliability. We present the results of all of the comparisons and discuss reasons for the observed discrepancies. We also demonstrate how the particular stellar atmospheric models adopted can have a strong impact on this type of analysis, and discuss related caveats.« less

Infrared Space Astrometry missions: JASMINE

NASA Astrophysics Data System (ADS)

Gouda, Naoteru

2015-08-01

JASMINE is an abbreviation for Japan Astrometry Satellite Mission for INfrared Exploration. We are now focusing on the development of two projects, those are Nano-JASMINE and Small-JASMINE. The Nano-JASMINE micro-satellite project, with a primary mirror aperture of 5-cm class, is currently underway to test part of the technologies used for Small-JASMINE and to produce scientific results based on the astrometric information of bright objects in the neighboring space. Despite its small aperture, the satellite is capable of a level of observational precision comparable to the Hipparcos satellite, and the combination of the observational data from Nano-JASMINE and the Hipparcos Catalogue is expected to produce more precise data on proper motions and annual parallaxes. The satellite is scheduled for launch in the near future. An additional plan is underway to launch a small-scale JASMINE satellite (Small-JASMINE), with a primary mirror aperture of 30-cm class, in around FY 2021. This satellite will engage in observations of only a limited area around the bulge and certain specific astronomical objects.. The main scientific objective of Small-JASMINE is to clarify the dynamical structure of the Galactic nuclear bulge and search for observational relics of a sequential merger of multiple black holes to form the supermassive black hole at the Galactic center. In particular, our main goal is that Small-JASMINE will provide an understanding of the past evolution processes of the supermassive black hole and a prediction of the future activities of our Galactic center through knowledge of the gravitational potential in the Galactic nuclear bulge, and that this understanding can contribute to a better understanding of the co-evolution of the supermassive black holes and bulges in external galaxies. Next to this primary goal, Small-JASMINE will have many other scientific targets. Small-JASMINE can measure the same target every 100 minutes, so it is useful to resolve phenomena with short periods such as X-ray binaries, extrasolar planetary systems and gravitational lens effects. For example, the orbital elements of the star accompanying Cygnus X-1 can be resolved by Small-JASMINE.

The intrinsic shape of bulges in the CALIFA survey

NASA Astrophysics Data System (ADS)

Costantin, L.; Méndez-Abreu, J.; Corsini, E. M.; Eliche-Moral, M. C.; Tapia, T.; Morelli, L.; Dalla Bontà, E.; Pizzella, A.

2018-02-01

Context. The intrinsic shape of galactic bulges in nearby galaxies provides crucial information to separate bulge types. Aims: We aim to derive accurate constraints to the intrinsic shape of bulges to provide new clues on their formation mechanisms and set new limitations for future simulations. Methods: We retrieved the intrinsic shape of a sample of CALIFA bulges using a statistical approach. Taking advantage of GalMer numerical simulations of binary mergers we estimated the reliability of the procedure. Analyzing the i-band mock images of resulting lenticular remnants, we studied the intrinsic shape of their bulges at different galaxy inclinations. Finally, we introduced a new (B/A, C/A) diagram to analyze possible correlations between the intrinsic shape and the properties of bulges. Results: We tested the method on simulated lenticular remnants, finding that for galaxies with inclinations of 25° ≤ θ ≤ 65° we can safely derive the intrinsic shape of their bulges. We found that our CALIFA bulges tend to be nearly oblate systems (66%), with a smaller fraction of prolate spheroids (19%), and triaxial ellipsoids (15%). The majority of triaxial bulges are in barred galaxies (75%). Moreover, we found that bulges with low Sérsic indices or in galaxies with low bulge-to-total luminosity ratios form a heterogeneous class of objects; additionally, bulges in late-type galaxies or in less massive galaxies have no preference for being oblate, prolate, or triaxial. On the contrary, bulges with high Sérsic index, in early-type galaxies, or in more massive galaxies are mostly oblate systems. Conclusions: We concluded that various evolutionary pathways may coexist in galaxies, with merging events and dissipative collapse being the main mechanisms driving the formation of the most massive oblate bulges and bar evolution reshaping the less massive triaxial bulges.

The Optical Gravitational Lensing Experiment Ogle-Ii Results

NASA Astrophysics Data System (ADS)

Żebruń, K.; Udalski, A.; Szymański, M.; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Woźniak, P.

2002-12-01

We present results of a search for microlensing events in the OGLE-II database of observations of stars from the Galactic Bulge (GB). Our main result is the Catalog of Microlensing events in the GB containing data about 214 cases of microlensing in 1997-1999. We present also the distribution of the normalized number of microlensing events in 24 lines of sight. Our results show that the majority of lenses are located in the Galactic Bar rather than in the Galactic disk. Details and the Catalog are available from the OGLE internet archive.

VizieR Online Data Catalog: OGLE-III Galactic bulge microlensing events (Wyrzykowski+, 2015)

NASA Astrophysics Data System (ADS)

Wyrzykowski, L.; Rynkiewicz, A. E.; Skowron, J.; Kozlowski, S.; Udalski, A.; Szymanski, M. K.; Kubiak, M.; Soszynski, I.; Pietrzynski, G.; Poleski, R.; Pietrukowicz, P.; Pawlak, M.

2015-02-01

The data used in this work were photometry of 150 million objects toward more than 31deg2 of the Galactic bulge observed in almost 74000 frames, i.e., about 11000 billion data points. We selected 91 fields out of all 177 ever observed by the Optical Gravitational Lensing Experiment (OGLE) Udalski et al. (2008AcA....58...69U) in its third phase from 2001 July until 2009 May, which had at least 250 observations. We use the re-reduced data obtained after the end of OGLE-III. For the final sample of microlensing events, we additionally produced new photometry which took into account the exact position of each event on the difference imaging technique (DIA, Wozniak 2000, J/AcA/50/421) image (see section 2). (4 data files).

Erratum: The MACHO Project: 45 Candidate Microlensing Events from the First Year Galactic Bulge Data

NASA Astrophysics Data System (ADS)

Alcock, C.; Allsman, R. A.; Alves, D.; Axelrod, T. S.; Bennett, D. P.; Cook, K. H.; Freeman, K. C.; Griest, K.; Guern, J.; Lehner, M. J.; Marshall, S. L.; Park, H.-S.; Perlmutter, S.; Peterson, B. A.; Pratt, M. R.; Quinn, P. J.; Rodgers, A. W.; Stubbs, C. W.; Sutherland, W.

1998-06-01

In the paper ``The MACHO Project: 45 Candidate Microlensing Events from the First-Year Galactic Bulge Data'' by C. Alcock, R. A. Allsman, D. Alves, T. S. Axelrod, D. P. Bennett, K. H. Cook, K. C. Freeman, K. Griest, J. Guern, M. J. Lehner, S. L. Marshall, H.-S. Park, S. Perlmutter, B. A. Peterson, M. R. Pratt, P. J. Quinn, A. W. Rodgers, C. W. Stubbs, and W. Sutherland (ApJ, 479, 119 [1997]), an incorrect version of Table 1 was inadvertently sent to the Journal with the revised version of the paper. The incorrect table used a different event numbering scheme from the correct table, rendering much of the paper incomprehensible. The correct version of Table 1 is available in the preprint version of the paper (astro-ph/9512146) and is also printed below.

The ISOGAL survey

NASA Astrophysics Data System (ADS)

Omont, A.; ISOGAL Collaboration

1999-03-01

ISOGAL is a 7-15 μm ISOCAM survey, with 6'' pixels and sensitivity below 10 mJy, of ~20 deg2, in the galactic plane mostly interior to |l| = 30o. In combination with KJI DENIS data, the ISO images allow detailed studies of cold stellar populations and galactic structures in regions highly obscured throughout the inner Galaxy, with a sensitivity and pixel surface two orders of magnitude better than IRAS. Data reduction is particularly difficult because of the high density of strong sources, of memory effects and of short integration times. However, an improved data reduction is almost complete for all the fields observed, with the use of CIA ISOCAM software and of a special source extraction. The data quality is acceptable, as concerns reliability, completeness and photometric accuracy of the sources, to allow a systematic scientific analysis. A few fields, in the bulge and in the galactic disk, exemplify the results expected from the ~200 fields observed. These results include: A complete census of mass-losing AGB stars in fields of the inner bulge. Even very weak mass-loss are very well characterised, down to the RGB tip. Such stars are by far the most numerous there. They form a very well defined sequence in ISOGAL-DENIS infrared colour-magnitude diagrams. The knowledge of Long Period Variables in two Baade's Window fields confirm that their luminosity is just above the tip of this sequence, and that the spectral type of the stars of the sequence is M6-9III. The same AGB sequence is also quite visible in 7-15 μm colour-magnitude diagrams in the galactic disk, even with a very large extinction. Such AGB stars are thus particularly numerous among the ~105 sources detected by ISOGAL. However, foreground red giants and dusty young stars are also quite numerous. The latter with a few solar masses are detectable through the galactic centre distance. A number of bright young stars are identified on lines of sight close to the Galactic Centre, The combination of ISOGAL and DENIS data allows a detailed estimate of the interstellar extinction for individual stars and lines of sight. Many dark globules and filaments are visible on the 7 and 15 μm images, corresponding to visible extinction larger than ~20-30. The very rich structure of the mid-infrared diffuse emission is often clearly associated with stars.

Identificación de objetos extensos en el VVV

NASA Astrophysics Data System (ADS)

Baravalle, L.; Alonso, M. V.; Nilo Castellón, J. L.; Minniti, D.

2017-10-01

The Vista Variables en la Via Lactea (VVV) is an ESO public survey in the near infrared of the bulge and southern mid-plane of the Milky Way. The main goal of the VVV is the study of the stellar population and variable stars but it can also be useful for extragalactic investigations behind the Galaxy. Using the VVV images and the combination of SExtractor + PSFEx, we have obtained astrometric and photometric data of two peripheric regions of the Galactic disk. Our goal is to identify and characterise the extragalactic sources. In this work we show our detection algorithm and adopted methodology.

Possible evidence for MeV dark matter in dwarf spheroidals.

PubMed

Hooper, Dan; Ferrer, Francesc; Boehm, Céline; Silk, Joseph; Paul, Jacques; Evans, N Wyn; Casse, Michel

2004-10-15

The observed 511 keV emission from the galactic bulge could be due to very light (MeV) annihilating dark matter particles. To distinguish this hypothesis from conventional astrophysical sources, we study dwarf spheroidals in the region observed by the International Gamma-Ray Astrophysics Laboratory/SPI such as Sagittarius. As these galaxies have comparatively few stars, the prospects for 511 keV emission from standard astrophysical scenarios are minimal. The dwarf spheroidals do, however, contain copious amounts of dark matter. The observation of 511 keV emission from Sagittarius should be a "smoking gun" for MeV dark matter.

Development of a near-infrared high-resolution spectrograph (WINERED) for a survey of bulge stars

NASA Astrophysics Data System (ADS)

Tsujimoto, T.; Kobayashi, N.; Yasui, C.; Kondo, S.; Minami, A.; Motohara, K.; Ikeda, Y.; Gouda, N.

2008-07-01

We are developing a new near-infrared high-resolution (R[max] = 100,000) and high-sensitive spectrograph WINERED, which is specifically customized for short NIR bands at 0.9 1.35 μm. WINERED employs an innovative optical system; a portable design and a warm optics without any cold stops. The planned astrometric space mission JASMINE will provide precise positions, distances, and proper motions of the bulge stars. The missing components, the radial velocity and chemical composition will be measured by WINERED. These combined data brought by JASMINE and WINERED will certainly reveal the nature of the Galactic bulge. We plan to complete this instrument for observations of single objects by the end of 2008 and to attach it to various 4 10m telescopes as a PI-type instrument. We hope to upgrade WINERED with a multi-object feed in the future for efficient survey of the JASMINE bulge stars.

Imaging Galactic Dark Matter with High-Energy Cosmic Neutrinos

NASA Astrophysics Data System (ADS)

Argüelles, Carlos A.; Kheirandish, Ali; Vincent, Aaron C.

2017-11-01

We show that the high-energy cosmic neutrinos seen by the IceCube Neutrino Observatory can be used to probe interactions between neutrinos and the dark sector that cannot be reached by current cosmological methods. The origin of the observed neutrinos is still unknown, and their arrival directions are compatible with an isotropic distribution. This observation, together with dedicated studies of Galactic plane correlations, suggests a predominantly extragalactic origin. Interactions between this isotropic extragalactic flux and the dense dark matter (DM) bulge of the Milky Way would thus lead to an observable imprint on the distribution, which would be seen by IceCube as (i) slightly suppressed fluxes at energies below a PeV and (ii) a deficit of events in the direction of the Galactic center. We perform an extended unbinned likelihood analysis using the four-year high-energy starting event data set to constrain the strength of DM-neutrino interactions for two model classes. We find that, in spite of low statistics, IceCube can probe regions of the parameter space inaccessible to current cosmological methods.

Imaging Galactic Dark Matter with High-Energy Cosmic Neutrinos.

PubMed

Argüelles, Carlos A; Kheirandish, Ali; Vincent, Aaron C

2017-11-17

We show that the high-energy cosmic neutrinos seen by the IceCube Neutrino Observatory can be used to probe interactions between neutrinos and the dark sector that cannot be reached by current cosmological methods. The origin of the observed neutrinos is still unknown, and their arrival directions are compatible with an isotropic distribution. This observation, together with dedicated studies of Galactic plane correlations, suggests a predominantly extragalactic origin. Interactions between this isotropic extragalactic flux and the dense dark matter (DM) bulge of the Milky Way would thus lead to an observable imprint on the distribution, which would be seen by IceCube as (i) slightly suppressed fluxes at energies below a PeV and (ii) a deficit of events in the direction of the Galactic center. We perform an extended unbinned likelihood analysis using the four-year high-energy starting event data set to constrain the strength of DM-neutrino interactions for two model classes. We find that, in spite of low statistics, IceCube can probe regions of the parameter space inaccessible to current cosmological methods.

One Thousand New Dwarf Novae from the OGLE Survey

NASA Astrophysics Data System (ADS)

Mróz, P.; Udalski, A.; Poleski, R.; Pietrukowicz, P.; Szymański, M. K.; Soszyński, I.; Wyrzykowski, Ł.; Ulaczyk, K.; Kozłowski, S.; Skowron, J.

2015-12-01

We present one of the largest collections of dwarf novae (DNe) containing 1091 objects that have been discovered in the long-term photometric data from the Optical Gravitational Lensing Experiment (OGLE) survey. They were found in the OGLE fields toward the Galactic bulge and the Magellanic Clouds. We analyze basic photometric properties of all systems and tentatively find a population of DNe from the Galactic bulge. We identify several dozen of WZ Sge-type DN candidates, including two with superhump periods longer than 0.09 d. Other interesting objects include SU UMa-type stars with "early" precursor outbursts or a Z Cam-type star showing outbursts during standstills. We also provide a list of DNe which will be observed during the K2 Campaign 9 microlensing experiment in 2016. Finally, we present the new OGLE-IV real-time data analysis system: CVOM, which has been designed to provide continuous real time photometric monitoring of selected CVs.

VizieR Online Data Catalog: DIA OGLE2 candidate variable stars catalog (Wozniak+, 2002)

NASA Astrophysics Data System (ADS)

Wozniak, P. R.; Udalski, A.; Szymanski, M.; Kubiak, M.; Pietrzynski, G.; Soszinski, I.; Zebrun, K.

2005-07-01

We present the first edition of a catalog of variable stars from OGLE-II Galactic bulge data covering 3 years: 1997-1999. Typically 200-300 I band data points are available in 49 fields between -11 and +11 degrees in galactic longitude, totaling roughly 11 square degrees in sky coverage. Photometry was obtained using the Difference Image Analysis (DIA) software and tied to the OGLE data base with the DoPhot package. The present version of the catalog comprises 221801 light curves. In this preliminary work the level of contamination by spurious detections is still about 10%. Parts of the catalog have only crude calibration, insufficient for distance determinations. The next, fully calibrated, edition will include the data collected in year 2000. The data is accessible via ftp, at ftp://bulge.princeton.edu/ogle/ogle2/bulgediavariables (1 data file).

Erratum: The MACHO Project: Microlensing Optical Depth toward the Galactic Bulge from Difference Image Analysis

NASA Astrophysics Data System (ADS)

Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T. S.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Drake, A. J.; Freeman, K. C.; Geha, M.; Griest, K.; Lehner, M. J.; Marshall, S. L.; Minniti, D.; Nelson, C. A.; Peterson, B. A.; Popowski, P.; Pratt, M. R.; Quinn, P. J.; Stubbs, C. W.; Sutherland, W.; Tomaney, A. B.; Vandehei, T.; Welch, D. L.

2001-08-01

In the paper ``The MACHO Project: Microlensing Optical Depth toward the Galactic Bulge from Difference Image Analysis'' by C. Alcock, R. A. Allsman, D. R. Alves, T. S. Axelrod, A. C. Becker, D. P. Bennett, K. H. Cook, A. J. Drake, K. C. Freeman, M. Geha, K. Griest, M. J. Lehner, S. L. Marshall, D. Minniti, C. A. Nelson, B. A. Peterson, P. Popowski, M. R. Pratt, P. J. Quinn, C. W. Stubbs, W. Sutherland, A. B. Tomaney, T. Vandehei, and D. L. Welch (ApJ, 541, 734 [2000]) an incorrect version of Table 3 was published. A second copy of Table 2 was given as Table 3. The correct version of Table 3 is available in the preprint version of the paper (astro-ph/0002510) and is printed below. This correction does not affect any of the results in the paper.

Star formation history of the Galactic bulge from deep HST imaging of low reddening windows

NASA Astrophysics Data System (ADS)

Bernard, Edouard J.; Schultheis, Mathias; Di Matteo, Paola; Hill, Vanessa; Haywood, Misha; Calamida, Annalisa

2018-07-01

Despite the huge amount of photometric and spectroscopic efforts targeting the Galactic bulge over the past few years, its age distribution remains controversial owing to both the complexity of determining the age of individual stars and the difficult observing conditions. Taking advantage of the recent release of very deep, proper-motion-cleaned colour-magnitude diagrams (CMDs) of four low reddening windows obtained with the Hubble Space Telescope (HST), we used the CMD-fitting technique to calculate the star formation history (SFH) of the bulge at -2° > b > -4° along the minor axis. We find that over 80 per cent of the stars formed before 8 Gyr ago, but that a significant fraction of the super-solar metallicity stars are younger than this age. Considering only the stars that are within reach of the current generation of spectrographs (i.e. V≲ 21), we find that 10 per cent of the bulge stars are younger than 5 Gyr, while this fraction rises to 20-25 per cent in the metal-rich peak. The age-metallicity relation is well parametrized by a linear fit, implying an enrichment rate of dZ/dt ˜ 0.005 Gyr-1. Our metallicity distribution function accurately reproduces that observed by several spectroscopic surveys of Baade's window, with the bulk of stars having metal content in the range [Fe/H]˜-0.7 to ˜0.6, along with a sparse tail to much lower metallicities.

Star formation history of the Galactic bulge from deep HST imaging of low reddening windows

NASA Astrophysics Data System (ADS)

Bernard, Edouard J.; Schultheis, Mathias; Di Matteo, Paola; Hill, Vanessa; Haywood, Misha; Calamida, Annalisa

2018-04-01

Despite the huge amount of photometric and spectroscopic efforts targetting the Galactic bulge over the past few years, its age distribution remains controversial owing to both the complexity of determining the age of individual stars and the difficult observing conditions. Taking advantage of the recent release of very deep, proper-motion-cleaned colour-magnitude diagrams (CMDs) of four low reddening windows obtained with the Hubble Space Telescope (HST), we used the CMD-fitting technique to calculate the star formation history (SFH) of the bulge at -2° > b > -4° along the minor axis. We find that over 80 percent of the stars formed before 8 Gyr ago, but that a significant fraction of the super-solar metallicity stars are younger than this age. Considering only the stars that are within reach of the current generation of spectrographs (i.e. V≲ 21), we find that 10 percent of the bulge stars are younger than 5 Gyr, while this fraction rises to 20-25 percent in the metal-rich peak. The age-metallicity relation is well parametrized by a linear fit implying an enrichment rate of dZ/dt ˜ 0.005 Gyr-1. Our metallicity distribution function accurately reproduces that observed by several spectroscopic surveys of Baade's window, with the bulk of stars having metal-content in the range [Fe/H]˜-0.7 to ˜0.6, along with a sparse tail to much lower metallicities.

Asymmetric 511 keV Positron Annihilation Line Emission from the Inner Galactic Disk

NASA Technical Reports Server (NTRS)

Skinner, Gerry; Weidenspointner, Georg; Jean, Pierre; Knodlseder, Jurgen; Ballmoos, Perer von; Bignami, Giovanni; Diehl, Roland; Strong, Andrew; Cordier, Bertrand; Schanne, Stephane;

Light, alpha, and Fe-peak element abundances in the galactic bulge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Christian I.; Rich, R. Michael; Kobayashi, Chiaki

2014-10-01

We present radial velocities and chemical abundances of O, Na, Mg, Al, Si, Ca, Cr, Fe, Co, Ni, and Cu for a sample of 156 red giant branch stars in two Galactic bulge fields centered near (l, b) = (+5.25,–3.02) and (0,–12). The (+5.25,–3.02) field also includes observations of the bulge globular cluster NGC 6553. The results are based on high-resolution (R ∼ 20,000), high signal-to-noise ration (S/N ≳ 70) FLAMES-GIRAFFE spectra obtained through the European Southern Observatory archive. However, we only selected a subset of the original observations that included spectra with both high S/N and that did notmore » show strong TiO absorption bands. This work extends previous analyses of this data set beyond Fe and the α-elements Mg, Si, Ca, and Ti. While we find reasonable agreement with past work, the data presented here indicate that the bulge may exhibit a different chemical composition than the local thick disk, especially at [Fe/H] ≳ –0.5. In particular, the bulge [α/Fe] ratios may remain enhanced to a slightly higher [Fe/H] than the thick disk, and the Fe-peak elements Co, Ni, and Cu appear enhanced compared to the disk. There is also some evidence that the [Na/Fe] (but not [Al/Fe]) trends between the bulge and local disk may be different at low and high metallicity. We also find that the velocity dispersion decreases as a function of increasing [Fe/H] for both fields, and do not detect any significant cold, high-velocity populations. A comparison with chemical enrichment models indicates that a significant fraction of hypernovae may be required to explain the bulge abundance trends, and that initial mass functions that are steep, top-heavy (and do not include strong outflow), or truncated to avoid including contributions from stars >40 M {sub ☉} are ruled out, in particular because of disagreement with the Fe-peak abundance data. For most elements, the NGC 6553 stars exhibit abundance trends nearly identical to comparable metallicity bulge field stars. However, the star-to-star scatter and mean [Na/Fe] ratios appear higher in the cluster, perhaps indicating additional self-enrichment.« less

The spectroscopic evolution of novae in the bulge of M31 and a search for their possible origin in the M31 globular cluster system

NASA Astrophysics Data System (ADS)

Tomaney, Austin Bede

Results are presented from a three year (1987 to 1989) spectroscopic and photometric survey of novae in M3l's bulge, the first comprehensive study of novae outside the Galactic and Magellanic Cloud systems. Nine novae were detected and monitored and their spectra cover a range of outburst states from early decline to the early nebular phases. Broad agreement in spectral morphology and evolution is found with Galactic novae. Since Galactic novae are mainly disk objects, this indicates that novae outburst properties are not critically dependent on the metallicity of the progenitor population. However, in this sample, and in a sample of four M31 nova spectra taken in 1983, no fast, violent outbursts frequently associated with nova systems containing ONeMg white dwarfs were found, suggestive of a systematic difference between the observed proportion of such outbursts between Galactic and M31 bulge novae. Three novae in the sample were observed on succeeding nights during the transition phase of their evolution. Extraordinary variations in some nightly line strengths, particularly the N III lines, were discovered. It is argued that this variability reflects the deposition of drag energy by the secondary star during the common envelope phase of nova evolution and is indicative of a key phase in mass loss from nova systems. Observations include the spectroscopic coverage of an extremely slow nova from 1987 to l990, during the object's evolution in the nebula phase. This provided a unique opportunity to make the first detailed comparison of the evolution and properties of an extra galactic nova with those in our own Galaxy. The roughly solar abundances obtained are typical of similar slow Galactic novae. Further observations are also presented of a unique outburst in 1988 that was independently discovered and reported by Rich et al. These data confirm the inferences of other observers that the outburst differed markedly from that of a typical classical nova. Finally an extensive spectroscopic survey of the M31 globular cluster system was made in an effort to find evidence of a previously suggested enhanced nova rate in these objects. No outbursts were detected during an effective survey time of one year for the entire system.

Galaxies Grow Their Bulges and Black Holes in Diverse Ways

NASA Astrophysics Data System (ADS)

Bell, Eric F.; Monachesi, Antonela; Harmsen, Benjamin; de Jong, Roelof S.; Bailin, Jeremy; Radburn-Smith, David J.; D'Souza, Richard; Holwerda, Benne W.

2017-03-01

Galaxies with Milky Way-like stellar masses have a wide range of bulge and black hole masses; in turn, these correlate with other properties such as star formation history. While many processes may drive bulge formation, major and minor mergers are expected to play a crucial role. Stellar halos offer a novel and robust measurement of galactic merger history; cosmologically motivated models predict that mergers with larger satellites produce more massive, higher-metallicity stellar halos, reproducing the recently observed stellar halo metallicity-mass relation. We quantify the relationship between stellar halo mass and bulge or black hole prominence using a sample of 18 Milky Way-mass galaxies with newly available measurements of (or limits on) stellar halo properties. There is an order of magnitude range in bulge mass, and two orders of magnitude in black hole mass, at a given stellar halo mass (or, equivalently, merger history). Galaxies with low-mass bulges show a wide range of quiet merger histories, implying formation mechanisms that do not require intense merging activity. Galaxies with massive “classical” bulges and central black holes also show a wide range of merger histories. While three of these galaxies have massive stellar halos consistent with a merger origin, two do not—merging appears to have had little impact on making these two massive “classical” bulges. Such galaxies may be ideal laboratories to study massive bulge formation through pathways such as early gas-rich accretion, violent disk instabilities, or misaligned infall of gas throughout cosmic time.

The wind speeds, dust content, and mass-loss rates of evolved AGB and RSG stars at varying metallicity

NASA Astrophysics Data System (ADS)

Goldman, Steven R.; van Loon, Jacco Th.; Zijlstra, Albert A.; Green, James A.; Wood, Peter R.; Nanni, Ambra; Imai, Hiroshi; Whitelock, Patricia A.; Matsuura, Mikako; Groenewegen, Martin A. T.; Gómez, José F.

2017-02-01

We present the results of our survey of 1612-MHz circumstellar OH maser emission from asymptotic giant branch (AGB) stars and red supergiants (RSGs) in the Large Magellanic Cloud (LMC). We have discovered four new circumstellar maser sources in the LMC, and increased the number of reliable wind speeds from infrared (IR) stars in the LMC from 5 to 13. Using our new wind speeds, as well as those from Galactic sources, we have derived an updated relation for dust-driven winds: vexp ∝ ZL0.4. We compare the subsolar metallicity LMC OH/IR stars with carefully selected samples of more metal-rich OH/IR stars, also at known distances, in the Galactic Centre and Galactic bulge. We derive pulsation periods for eight of the bulge stars for the first time by using near-IR photometry from the Vista Variables in the Via Lactea survey. We have modelled our LMC OH/IR stars and developed an empirical method of deriving gas-to-dust ratios and mass-loss rates by scaling the models to the results from maser profiles. We have done this also for samples in the Galactic Centre and bulge and derived a new mass-loss prescription which includes luminosity, pulsation period, and gas-to-dust ratio dot{M} = 1.06^{+3.5}_{-0.8} × }10^{-5 (L/10^4 L_{⊙})^{0.9± 0.1}(P/500 {d})^{0.75± 0.3} (r_gd/200)^{-0.03± 0.07} M⊙ yr-1. The tightest correlation is found between mass-loss rate and luminosity. We find that the gas-to-dust ratio has little effect on the mass-loss of oxygen-rich AGB stars and RSGs within the Galaxy and the LMC. This suggests that the mass-loss of oxygen-rich AGB stars and RSGs is (nearly) independent of metallicity between a half and twice solar.

Establishing the Galactic Centre distance using VVV Bulge RR Lyrae variables

NASA Astrophysics Data System (ADS)

Majaess, D.; Dékány, I.; Hajdu, G.; Minniti, D.; Turner, D.; Gieren, W.

2018-06-01

This study's objective was to exploit infrared VVV (VISTA Variables in the Via Lactea) photometry for high latitude RRab stars to establish an accurate Galactic Centre distance. RRab candidates were discovered and reaffirmed (n=4194) by matching Ks photometry with templates via χ 2 minimization, and contaminants were reduced by ensuring targets adhered to a strict period-amplitude (Δ Ks) trend and passed the Elorietta et al. classifier. The distance to the Galactic Centre was determined from a high latitude Bulge subsample (|b|>4°, R_{GC}=8.30 ± 0.36 kpc, random uncertainty is relatively negligible), and importantly, the comparatively low color-excess and uncrowded location mitigated uncertainties tied to the extinction law, the magnitude-limited nature of the analysis, and photometric contamination. Circumventing those problems resulted in a key uncertainty being the M_{Ks} relation, which was derived using LMC RRab stars (M_{Ks}=-(2.66± 0.06) log {P}-(1.03± 0.06), (J-Ks)0=(0.31± 0.04) log {P} + (0.35± 0.02), assuming μ _{0,LMC}=18.43). The Galactic Centre distance was not corrected for the cone-effect. Lastly, a new distance indicator emerged as brighter overdensities in the period-magnitude-amplitude diagrams analyzed, which arise from blended RRab and red clump stars. Blending may thrust faint extragalactic variables into the range of detectability.

Alpha Elements' Effects on Planet Formation and the Hunt for Extragalactic Planets

NASA Astrophysics Data System (ADS)

Penny, Matthew; Rodriguez, Joseph E.; Beatty, Thomas; Zhou, George

2018-01-01

A star's likelihood of hosting a giant planet is well known to be strongly dependent on metallicity. However, little is known about what elements cause this correlation (e.g. bulk metals, iron, or alpha elements such as silicon and oxygen). This is likely because most planet searches target stars in the Galactic disk, and due to Galactic chemical evolution, alpha element abundances are themselves correlated with metallicity within a population. We investigate the feasibility of simultaneous transiting planet search towards the alpha-poor Sagittarius dwarf galaxy and alpha-rich Galactic bulge in a single field of view of DECam, that would enable a comparative study of planet frequency over an [alpha/Fe] baseline of ~0.4 dex. We show that a modestly sized survey could detect planet candidates in both populations, but that false positive rejection in Sgr Dwarf may be prohibitively expensive. Conversely, two-filter survey observations alone would be sufficient to rule out a large fraction of bulge false positives, enabling statistical validation of candidates with a modest follow-up investment. Although over a shorter [alpha/Fe] baseline, this survey would provide a test of whether it is alpha or iron that causes the planet metallicity correlation.

The great escape - III. Placing post-main-sequence evolution of planetary and binary systems in a Galactic context

NASA Astrophysics Data System (ADS)

Veras, Dimitri; Evans, N. Wyn; Wyatt, Mark C.; Tout, Christopher A.

2014-01-01

Our improving understanding of the life cycle of planetary systems prompts investigations of the role of the Galenvironment before, during and after asymptotic giant branch (AGB) stellar evolution. Here, we investigate the interplay between stellar mass-loss, Galactic tidal perturbations and stellar flybys for evolving stars which host one planet, smaller body or stellar binary companion and reside in the Milky Way's bulge or disc. We find that the potential evolutionary pathways from a main sequence (MS) to a white dwarf (WD) planetary system are a strong function of Galactocentric distance only with respect to the prevalence of stellar flybys. Planetary ejection and collision with the parent star should be more common towards the bulge. At a given location anywhere in the Galaxy, if the mass-loss is adiabatic, then the secondary is likely to avoid close flybys during AGB evolution, and cannot eventually escape the resulting WD because of Galactic tides alone. Partly because AGB mass-loss will shrink a planetary system's Hill ellipsoid axes by about 20 to 40 per cent, Oort clouds orbiting WDs are likely to be more depleted and dynamically excited than on the MS.

A Near-infrared RR Lyrae Census along the Southern Galactic Plane: The Milky Way’s Stellar Fossil Brought to Light

NASA Astrophysics Data System (ADS)

Dékány, István; Hajdu, Gergely; Grebel, Eva K.; Catelan, Márcio; Elorrieta, Felipe; Eyheramendy, Susana; Majaess, Daniel; Jordán, Andrés

2018-04-01

RR Lyrae stars (RRLs) are tracers of the Milky Way’s fossil record, holding valuable information on its formation and early evolution. Owing to the high interstellar extinction endemic to the Galactic plane, distant RRLs lying at low Galactic latitudes have been elusive. We attained a census of 1892 high-confidence RRLs by exploiting the near-infrared photometric database of the VVV survey’s disk footprint spanning ∼70° of Galactic longitude, using a machine-learned classifier. Novel data-driven methods were employed to accurately characterize their spatial distribution using sparsely sampled multi-band photometry. The RRL metallicity distribution function (MDF) was derived from their K s -band light-curve parameters using machine-learning methods. The MDF shows remarkable structural similarities to both the spectroscopic MDF of red clump giants and the MDF of bulge RRLs. We model the MDF with a multi-component density distribution and find that the number density of stars associated with the different model components systematically changes with both the Galactocentric radius and vertical distance from the Galactic plane, equivalent to weak metallicity gradients. Based on the consistency with results from the ARGOS survey, three MDF modes are attributed to the old disk populations, while the most metal-poor RRLs are probably halo interlopers. We propose that the dominant [Fe/H] component with a mean of ‑1 dex might correspond to the outskirts of an ancient Galactic spheroid or classical bulge component residing in the central Milky Way. The physical origins of the RRLs in this study need to be verified by kinematical information.

Stellar photometry in the inner bulge of M31 using the Hubble Space Telescope wide field camera

NASA Technical Reports Server (NTRS)

Rich, R. M.; Mighell, K. J.

1995-01-01

We present photometry of two fields in the M31 bulge imaged with the Hubble Space Telescope (HST) Wide-Field Camara (WFC). The nuclear field (r less than 40 arcsecs = 150 pc) giant branch extends to I = 19.5, M(sub I) = -5 (Cousins system), a full 0.9 mag brighter than the giant-branch tips of metal-poor Galactic globular clusters and M31 halo fields. This is also approximately = 1.5 mag brighter than the giant branches of metal-rich Galactic globular clusters, but is no brighter than Mould's (1986) M31 bulge field 1 kpc from the nucleus. The data also suggest that the brighter stars may be preferentially concentrated to the center. The 648 luminous stars detected in 2 x 10(exp 9) solar luminosity is approximately = 25% that expected from a hypothetical population of evolved asymptotic giant branch (AGB) stars with lifetimes approximately = 10(exp 5) yr, with the cautionary note that we are near the detection limit. The number of bright stars is also consistent with the progeny of blue stragglers, if one uses a lifetime for the thermal-pulsing AGB of 2 x 10(exp 6) yr. We strongly caution that incompleteness becomes severe below I = 19.9 mag and that future surveys are likely to find numbers of bright stars too large to accomodate the blue straggler progeny hypothesis. We have imaged an additional field 2 arcmin = 500 pc south of the nucleus. The brightest stars in this field are also I = 19.5, but bright stars appear less numerous than in the nuclear field. If the population resembles that of the Galactic bulge, then M(sub bol) = -4.5 is a lower limit to the giant-branch tip luminosity; infrared studies should reveal stars 0.5 mag or more brighter. Either high-metallicity or (more likely) age approximately = 10 Gyr may be responsible for the presence of these luminous AGB stars. These observations confirm that previous ground-based infrared studies (e.g., Rich & Mould 1991) very likely detect an extended giant branch and not spurious luminous stars caused by crowding or disk contamination. However, published integrated colors for the M31 bulge/nucleus are extremely red, making it difficult to accomodate a young or intermediate-age population.

Infrared Space Astrometry Missions ˜ JASMINE Missions ˜

NASA Astrophysics Data System (ADS)

Gouda, N.

2012-08-01

"JASMINE" is an abbreviation of Japan Astrometry Satellite Mission for Infrared Exploration. Three satellites are planned as a series of JASMINE missions, as a step-by-step approach, to overcome technical issues and promote scientific results. These are Nano-JASMINE, Small-JASMINE and (medium-sized) JASMINE. JASMINE missions provide the positions and proper motions of celestial objects. Nano-JASMINE uses a very small nano-satellite and is scheduled to be launched in 2013. Nano-JASMINE will operate in zw-band (˜ 0.8μm) to perform an all sky survey with an accuracy of 3 milli-arcseconds for position and parallaxes. Small-JASMINE will observe towards a region around the Galactic center and other small regions, which include interesting scientific targets, with accuracies of 10 to 50 μ-arcseconds in an infrared Hw-band (˜ 1.7 μm). The target launch date is around 2017. (Medium-sized) JASMINE is an extended mission of Small-JASMINE, which will observe towards almost the whole region of the Galactic bulge with accuracies of ˜ 10 μ arcseconds in Kw-band (˜ 2.0μ m). The target launch date is the first half of the 2020s.

Mira variables in the Galactic Bulge .

NASA Astrophysics Data System (ADS)

Groenewegen, M. A. T.; Blommaert, J. A. D. L.

The 222 000 I-band light curves of variable stars detected by the OGLE-II survey in the direction of the Galactic Bulge have been fitted and have been correlated with the DENIS and 2MASS databases. Results are presented for 2691 objects with I-band semi-amplitude larger than 0.45 magnitude, corresponding to classical Mira variables. The Mira period distribution of 5 fields at similar longitude but spanning latitudes from -1.2 to -5.8 are statistically indistinguisable indicating similar populations with initial masses of 1.5-2 M⊙ (corresponding to ages of 1-3 Gyr). A field at similar longitude at b = -0.05 from Glass et al. (2001) does show a significantly different period distribution, indicating the presence of a younger population of 2.5-3 M⊙ and ages below 1 Gyr. The K-band period-luminosity relation is presented for the whole sample, and for sub-fields. Simulations are carried out to show that the observations are naturally explained using the model of disk and bulge stars of Binney et al. (1997), for a viewing angle (major-axis Bar - axis perpendicular to the line-of-sight to the Galactic Centre) of 43 ± 17 degrees. A comparison is made with similar objects in the Magellanic Clouds, studied in a previous paper. The slope of the PL-relation in the Bulge and the MCs agree within the errorbars. Assuming the zero point does not depend on metallicity, a distance modulus difference of 3.72 between Bulge and LMC is derived. This implies a LMC DM of 18.21 for an assumed distance to the Galactic Centre (GC) of 7.9 kpc, or, assuming a LMC DM of 18.50, a distance to the GC of 9.0 kpc. From the results in Groenewegen (2004) it is found for carbon-rich Miras that the PL-relation implies a relative SMC-LMC DM of 0.38, assuming no metallicity dependence. This is somewhat smaller than the often quoted value near 0.50. Following theoretical work by Wood (1990) a metallicity term of the form M_K ˜ beta log Z is introduced. If a relative SMC-LMC DM of 0.50 is imposed, beta = 0.4 is required, and for that value the distance to the GC becomes 8.6 ± 0.7 kpc (for a LMC DM of 18.50), within the errorbar of the geometric determination of 7.9 ± 0.4 kpc (Eisenhauer et al. 2003). An independent estimate using the absolute calibration of Feast (2004) leads to a distance estimate to the GC of 8.8 ± 0.4 kpc.

Galaxies Grow Their Bulges and Black Holes in Diverse Ways

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bell, Eric F.; Harmsen, Benjamin; D’Souza, Richard

Galaxies with Milky Way–like stellar masses have a wide range of bulge and black hole masses; in turn, these correlate with other properties such as star formation history. While many processes may drive bulge formation, major and minor mergers are expected to play a crucial role. Stellar halos offer a novel and robust measurement of galactic merger history; cosmologically motivated models predict that mergers with larger satellites produce more massive, higher-metallicity stellar halos, reproducing the recently observed stellar halo metallicity–mass relation. We quantify the relationship between stellar halo mass and bulge or black hole prominence using a sample of 18more » Milky Way-mass galaxies with newly available measurements of (or limits on) stellar halo properties. There is an order of magnitude range in bulge mass, and two orders of magnitude in black hole mass, at a given stellar halo mass (or, equivalently, merger history). Galaxies with low-mass bulges show a wide range of quiet merger histories, implying formation mechanisms that do not require intense merging activity. Galaxies with massive “classical” bulges and central black holes also show a wide range of merger histories. While three of these galaxies have massive stellar halos consistent with a merger origin, two do not—merging appears to have had little impact on making these two massive “classical” bulges. Such galaxies may be ideal laboratories to study massive bulge formation through pathways such as early gas-rich accretion, violent disk instabilities, or misaligned infall of gas throughout cosmic time.« less

Discovery of a Gas Giant Planet in Microlensing Event Ogle-2014-BLG-1760

NASA Technical Reports Server (NTRS)

Bhattacharya, A.; Bennett, D. P.; Bond, I. A.; Sumi, T.; Udalski, A.; Street, R.; Tsapras, Y.; Abe, F.; Freeman, M.; Fukui, A.

2016-01-01

We present the analysis of the planetary microlensing event OGLE-2014-BLG-1760, which shows a strong light-curve signal due to the presence of a Jupiter mass ratio planet. One unusual feature of this event is that the source star is quite blue, with V-I = 1.48 +/- 0.08. This is marginally consistent with a source star in the Galactic bulge, but it could possibly indicate a young source star on the far side of the disk. Assuming a bulge source, we perform a Bayesian analysis assuming a standard Galactic model, and this indicates that the planetary system resides in or near the Galactic bulge at D(sub L) = 6.9 +/- 1.1 kpc. It also indicates a host-star mass of M(sub *) = 0.51(sup + 0.44/sub -0.28) M(sub theta), a planet mass of m(sub p ) = 0.56(sup +0.34/sub -0.26) M(sub J), and a projected star-planet separation of a(perpendicular) = 1.75(sup +0.33/sub -0.34) au. The lens-source relative proper motion is micro(sub rel) = 6.5 +/- 1.1mas per yr. The lens (and stellar host star) is estimated to be very faint compared to the source star, so it is most likely that it can be detected only when the lens and source stars start to separate. Due to the relatively high relative proper motion, the lens and source will be resolved to about approximately 46 mas in 6-8 yr after the peak magnification. So, by 2020-2022, we can hope to detect the lens star with deep, high-resolution images.

New Method for Astrometric Measurements in Space Mission, JASMINE.

NASA Astrophysics Data System (ADS)

Yano, T.; Gouda, N.; Yamada, Y.

2006-08-01

We present a new method for measuring positions of stars in the Milky Way Galaxy by astrometric satellite, JASMINE, which is in progress at the National Astronomical Observatory of Japan. JASMINE is the acronym of the Japan Astrometry Satellite Mission for Infrared (z-band : 0.9 micron) Exploration, and is planned to be launched around 2015 The main objective of JASMINE is to study the fundamental structure and evolution of the bulge components of the Milky Way Galaxy. In order to accomplish these objectives, JASMINE will measure trigonometric parallaxes, positions and proper motions of about a few million stars during the observational program, with the precision of 10 microarcsec at z =14mag. The telescope of JASMINE has just one field of view, which is different from other astrometric satellites like Hipparcos and GAIA, that have two fields of view with large angle. These satellites, Hipparcos and GAIA, scan along the great circle with the spin axis perpendicular to both two fields of view to estimate the relative positions of stars on the great circle. They scan many different great circles to observe all the sky. On the other hand, JASMINE will take overlapping fields of view without any gaps to survey an area of about 20deg*10deg. Accordingly survey area covers the region of about 20deg*10deg in the bulge component. JASMINE will continue the above procedure for observing the area during the mission life. As a consequence, JASMINE will observe the restricted regions around the Galactic bulge and sweep repeatedly. The mission life is planned to be 5 years.

The Optical Gravitational Lensing Experiment

NASA Technical Reports Server (NTRS)

Udalski, A.; Szymanski, M.; Kaluzny, J.; Kubiak, M.; Mateo, Mario

1992-01-01

The technical features are described of the Optical Gravitational Lensing Experiment, which aims to detect a statistically significant number of microlensing events toward the Galactic bulge. Clusters of galaxies observed during the 1992 season are listed and discussed and the reduction methods are described. Future plans are addressed.

a Theoretical Calculation of Microlensing Signatures Caused by Free-Floating Planets Towards the Galactic Bulge

NASA Astrophysics Data System (ADS)

Hamolli, L.; Hafizi, M.; Nucita, A. A.

2013-08-01

Free-floating planets (FFPs) are recently drawing a special interest of the scientific community. Gravitational microlensing is up to now the exclusive method for the investigation of FFPs, including their spatial distribution function and mass function. In this paper, we examine the possibility that the future Euclid space-based observatory may allow to discover a substantial number of microlensing events caused by FFPs. Based on latest results about the free-floating planet (FFP) mass function in the mass range [10-5, 10-2]M⊙, we calculate the optical depth towards the Galactic bulge as well as the expected microlensing rate and find that Euclid may be able to detect hundreds to thousands of these events per month. Making use of a synthetic population, we also investigate the possibility of detecting parallax effect in simulated microlensing events due to FFPs and find a significant efficiency for the parallax detection that turns out to be around 30%.

Submillimeter evidence for the coeval growth of massive black holes and galaxy bulges.

PubMed

Page, M J; Stevens, J A; Mittaz, J P; Carrera, F J

2001-12-21

The correlation, found in nearby galaxies, between black hole mass and stellar bulge mass implies that the formation of these two components must be related. Here we report submillimeter photometry of eight x-ray-absorbed active galactic nuclei that have luminosities and redshifts characteristic of the sources that produce the bulk of the accretion luminosity in the universe. The four sources with the highest redshifts are detected at 850 micrometers, with flux densities between 5.9 and 10.1 millijanskies, and hence are ultraluminous infrared galaxies. If the emission is from dust heated by starbursts, then the majority of stars in spheroids were formed at the same time as their central black holes built up most of their mass by accretion. This would account for the observed demography of massive black holes in the local universe. The skewed rate of submillimeter detection with redshift is consistent with a high redshift epoch of star formation in radio-quiet active galactic nuclei, similar to that seen in radio galaxies.

Cosmic "Dig" Reveals Vestiges of the Milky Way's Building Blocks

NASA Astrophysics Data System (ADS)

2009-11-01

Peering through the thick dust clouds of our galaxy's "bulge" (the myriads of stars surrounding its centre), and revealing an amazing amount of detail, a team of astronomers has unveiled an unusual mix of stars in the stellar grouping known as Terzan 5. Never observed anywhere in the bulge before, this peculiar "cocktail" of stars suggests that Terzan 5 is in fact one of the bulge's primordial building blocks, most likely the relic of a proto-galaxy that merged with the Milky Way during its very early days. "The history of the Milky Way is encoded in its oldest fragments, globular clusters and other systems of stars that have witnessed the entire evolution of our galaxy," says Francesco Ferraro from the University of Bologna, lead author of a paper appearing in this week's issue of the journal Nature. "Our study opens a new window on yet another piece of our galactic past." Like archaeologists, who dig through the dust piling up on top of the remains of past civilisations and unearth crucial pieces of the history of mankind, astronomers have been gazing through the thick layers of interstellar dust obscuring the bulge of the Milky Way and have unveiled an extraordinary cosmic relic. The target of the study is the star cluster Terzan 5. The new observations show that this object, unlike all but a few exceptional globular clusters, does not harbour stars which are all born at the same time - what astronomers call a "single population" of stars. Instead, the multitude of glowing stars in Terzan 5 formed in at least two different epochs, the earliest probably some 12 billion years ago and then again 6 billion years ago. "Only one globular cluster with such a complex history of star formation has been observed in the halo of the Milky Way: Omega Centauri," says team member Emanuele Dalessandro. "This is the first time we see this in the bulge." The galactic bulge is the most inaccessible region of our galaxy for astronomical observations: only infrared light can penetrate the dust clouds and reveal its myriads of stars. "It is only thanks to the outstanding instruments mounted on ESO's Very Large Telescope," says co-author Barbara Lanzoni, "that we have finally been able to 'disperse the fog' and gain a new perspective on the origin of the galactic bulge itself." A technical jewel lies behind the scenes of this discovery, namely the Multi-conjugate Adaptive Optics Demonstrator (MAD), a cutting-edge instrument that allows the VLT to achieve superbly detailed images in the infrared. Adaptive optics is a technique through which astronomers can overcome the blurring that the Earth's turbulent atmosphere inflicts on astronomical images obtained from ground-based telescopes; MAD is a prototype of even more powerful, next-generation adaptive optics instruments [1]. Through the sharp eye of the VLT, the astronomers also found that Terzan 5 is more massive than previously thought: along with the complex composition and troubled star formation history of the system, this suggests that it might be the surviving remnant of a disrupted proto-galaxy, which merged with the Milky Way during its very early stages and thus contributed to form the galactic bulge. "This could be the first of a series of further discoveries shedding light on the origin of bulges in galaxies, which is still hotly debated," concludes Ferraro. "Several similar systems could be hidden behind the bulge's dust: it is in these objects that the formation history of our Milky Way is written." Notes [1] Telescopes on the ground suffer from a blurring effect introduced by atmospheric turbulence. This turbulence causes the stars to twinkle in a way that delights poets but frustrates astronomers, since it smears out the fine details of the images. However, with adaptive optics (AO) techniques, this major drawback can be overcome so that the telescope produces images that are as sharp as theoretically possible, i.e. approaching conditions in space. Adaptive optics systems work by means of a computer-controlled deformable mirror that counteracts the image distortion introduced by atmospheric turbulence. It is based on real-time optical corrections computed at very high speed (many hundreds of times each second) from image data obtained by a wavefront sensor (a special camera) that monitors light from a reference star, Present AO systems can only correct the effect of atmospheric turbulence in a very small region of the sky - typically 15 arcseconds or less - the correction degrading very quickly when moving away from the reference star. Engineers have therefore developed new techniques to overcome this limitation, one of which is multi-conjugate adaptive optics. MAD uses up to three guide stars instead of one as references to remove the blur caused by atmospheric turbulence over a field of view thirty times larger than existing techniques (eso0719). More information This research was presented in a paper that appears in the 26 November 2009 issue of Nature , "The cluster Terzan 5 as a remnant of a primordial building block of the Galactic bulge", by F. R. Ferraro et al.. The team is composed of Francesco Ferraro, Emanuele Dalessandro, Alessio Mucciarelli and Barbara Lanzoni (Department of Astronomy, University of Bologna, Italy), Giacomo Beccari (ESA, Space Science Department, Noordwijk, Netherlands), Mike Rich (Department of Physics and Astronomy, UCLA, Los Angeles, USA), Livia Origlia, Michele Bellazzini and Gabriele Cocozza (INAF - Osservatorio Astronomico di Bologna, Italy), Robert T. Rood (Astronomy Department, University of Virginia, Charlottesville, USA), Elena Valenti (ESO and Pontificia Universidad Catolica de Chile, Departamento de Astronomia, Santiago, Chile) and Scott Ransom (National Radio Astronomy Observatory, Charlottesville, USA). ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

Galactic Angular Momentum in Cosmological Zoom-in Simulations. I. Disk and Bulge Components and the Galaxy-Halo Connection

NASA Astrophysics Data System (ADS)

Sokołowska, Aleksandra; Capelo, Pedro R.; Fall, S. Michael; Mayer, Lucio; Shen, Sijing; Bonoli, Silvia

2017-02-01

We investigate the angular momentum evolution of four disk galaxies residing in Milky-Way-sized halos formed in cosmological zoom-in simulations with various sub-grid physics and merging histories. We decompose these galaxies, kinematically and photometrically, into their disk and bulge components. The simulated galaxies and their components lie on the observed sequences in the j *-M * diagram, relating the specific angular momentum and mass of the stellar component. We find that galaxies in low-density environments follow the relation {j}* \\propto {M}* α past major mergers, with α ˜ 0.6 in the case of strong feedback, when bulge-to-disk ratios are relatively constant, and α ˜ 1.4 in the other cases, when secular processes operate on shorter timescales. We compute the retention factors (I.e., the ratio of the specific angular momenta of stars and dark matter) for both disks and bulges and show that they vary relatively slowly after averaging over numerous but brief fluctuations. For disks, the retention factors are usually close to unity, while for bulges, they are a few times smaller. Our simulations therefore indicate that galaxies and their halos grow in a quasi-homologous way.

Investigating ChaMPlane X-Ray Sources in the Galactic Bulge with Magellan LDSS2 Spectra

NASA Astrophysics Data System (ADS)

Koenig, Xavier; Grindlay, Jonathan E.; van den Berg, Maureen; Laycock, Silas; Zhao, Ping; Hong, JaeSub; Schlegel, Eric M.

2008-09-01

We have carried out optical and X-ray spectral analyses on a sample of 136 candidate optical counterparts of X-ray sources found in five Galactic bulge fields included in our Chandra Multiwavelength Plane Survey. We use a combination of optical spectral fitting and quantile X-ray analysis to obtain the hydrogen column density toward each object, and a three-dimensional dust model of the Galaxy to estimate the most probable distance in each case. We present the discovery of a population of stellar coronal emission sources, likely consisting of pre-main-sequence, young main-sequence, and main-sequence stars, as well as a component of active binaries of RS CVn or BY Dra type. We identify one candidate quiescent low-mass X-ray binary with a subgiant companion; we note that this object may also be an RS CVn system. We report the discovery of three new X-ray-detected cataclysmic variables (CVs) in the direction of the Galactic center (at distances lesssim2 kpc). This number is in excess of predictions made with a simple CV model based on a local CV space density of lesssim10-5 pc-3, and a scale height ~200 pc. We discuss several possible reasons for this observed excess.

Peculiar Behaviors of Faint Galactic Bulge Transients

NASA Technical Reports Server (NTRS)

Swank, J. H.

2004-01-01

The Rossi X-ray Timing Explorer PCA scans of the Galactic bulge (galactic longitude plus or minus 11 degrees) have detected 8 recent transients which have peak intensities of 10 to 400 mCrab. Some of the transient events have a fast rise and slow decay typical of accretion disk instabilities. It is common for these decays to be oscillatory, rather than steady, as if there are waves within the disk. There are also outbursts with symmetric light curves. In particular, the source in Terzan 2 which had a very long (decade) doubling of intensity peaking near the beginning of 1997, in 2004 has had two 30 day brightenings by a factor of 5 only 100 days apart. During each of these a burst was observed in snapshot observations near the peak. The source SLX 1735-269, also a burster, though not in our observations, has had irregularly repeated occurrences of fast swings between close to zero and 2-4 times normal. Some examples, such as the increase, drop, and slow recovery of GS 1826-238 suggest a change in the accretion disk such as emptying and refilling or a peculiar alignment. Follow up observations have provided deeper information about these transient sources and possible explanations for their behavior will be addressed.

Central stars of planetary nebulae in the Galactic bulge

NASA Astrophysics Data System (ADS)

Hultzsch, P. J. N.; Puls, J.; Méndez, R. H.; Pauldrach, A. W. A.; Kudritzki, R.-P.; Hoffmann, T. L.; McCarthy, J. K.

2007-06-01

Context: Optical high-resolution spectra of five central stars of planetary nebulae (CSPN) in the Galactic bulge have been obtained with Keck/HIRES in order to derive their parameters. Since the distance of the objects is quite well known, such a method has the advantage that stellar luminosities and masses can in principle be determined without relying on theoretical relations between both quantities. Aims: By alternatively combining the results of our spectroscopic investigation with evolutionary tracks, we obtain so-called spectroscopic distances, which can be compared with the known (average) distance of the bulge-CSPN. This offers the possibility to test the validity of model atmospheres and present date post-AGB evolution. Methods: We analyze optical H/He profiles of five Galactic bulge CSPN (plus one comparison object) by means of profile fitting based on state of the art non-LTE modeling tools, to constrain their basic atmospheric parameters (Teff, log g, helium abundance and wind strength). Masses and other stellar radius dependent quantities are obtained from both the known distances and from evolutionary tracks, and the results from both approaches are compared. Results: The major result of the present investigation is that the derived spectroscopic distances depend crucially on the applied reddening law. Assuming either standard reddening or values based on radio-Hβ extinctions, we find a mean distance of 9.0±1.6 kpc and 12.2±2.1 kpc, respectively. An “average extinction law” leads to a distance of 10.7±1.2 kpc, which is still considerably larger than the Galactic center distance of 8 kpc. In all cases, however, we find a remarkable internal agreement of the individual spectroscopic distances of our sample objects, within ±10% to ±15% for the different reddening laws. Conclusions: Due to the uncertain reddening correction, the analysis presented here cannot yet be regarded as a consistency check for our method, and a rigorous test of the CSPN evolution theory becomes only possible if this problem has been solved. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Appendix A is only available in electronic form at http://www.aanda.org

Rates of collapse and evaporation of globular clusters

NASA Technical Reports Server (NTRS)

Hut, Piet; Djorgovski, S.

1992-01-01

Observational estimates of the dynamical relaxation times of Galactic globular clusters are used here to estimate the present rate at which core collapse and evaporation are occurring in them. A core collapse rate of 2 +/- 1 per Gyr is found, which for a Galactic age of about 12 Gyr agrees well with the fact that 27 clusters have surface brightness profiles with the morphology expected for the postcollapse phase. A destruction and evaporation rate of 5 +/- 3 per Gyr is found, suggesting that a significant fraction of the Galaxy's original complement of globular clusters have perished through the combined effects of mechanisms such as relaxation-driven evaporation and shocking due to interaction with the Galactic disk and bulge.

SDSS IV MaNGA: Dependence of Global and Spatially Resolved SFR–M ∗ Relations on Galaxy Properties

NASA Astrophysics Data System (ADS)

Pan, Hsi-An; Lin, Lihwai; Hsieh, Bau-Ching; Sánchez, Sebastián F.; Ibarra-Medel, Héctor; Boquien, Médéric; Lacerna, Ivan; Argudo-Fernández, Maria; Bizyaev, Dmitry; Cano-Díaz, Mariana; Drory, Niv; Gao, Yang; Masters, Karen; Pan, Kaike; Tabor, Martha; Tissera, Patricia; Xiao, Ting

2018-02-01

The galaxy integrated Hα star formation rate–stellar mass relation, or SFR(global)–M *(global) relation, is crucial for understanding star formation history and evolution of galaxies. However, many studies have dealt with SFR using unresolved measurements, which makes it difficult to separate out the contamination from other ionizing sources, such as active galactic nuclei and evolved stars. Using the integral field spectroscopic observations from SDSS-IV MaNGA, we spatially disentangle the contribution from different Hα powering sources for ∼1000 galaxies. We find that, when including regions dominated by all ionizing sources in galaxies, the spatially resolved relation between Hα surface density (ΣHα (all)) and stellar mass surface density (Σ*(all)) progressively turns over at the high Σ*(all) end for increasing M *(global) and/or bulge dominance (bulge-to-total light ratio, B/T). This in turn leads to the flattening of the integrated Hα(global)–M *(global) relation in the literature. By contrast, there is no noticeable flattening in both integrated Hα(H II)–M *(H II) and spatially resolved ΣHα (H II)–Σ*(H II) relations when only regions where star formation dominates the ionization are considered. In other words, the flattening can be attributed to the increasing regions powered by non-star-formation sources, which generally have lower ionizing ability than star formation. An analysis of the fractional contribution of non-star-formation sources to total Hα luminosity of a galaxy suggests a decreasing role of star formation as an ionizing source toward high-mass, high-B/T galaxies and bulge regions. This result indicates that the appearance of the galaxy integrated SFR–M * relation critically depends on their global properties (M *(global) and B/T) and relative abundances of various ionizing sources within the galaxies.

JASMINE-Astrometric Map of the Galactic Bulge-

NASA Astrophysics Data System (ADS)

Gouda, N.; Kobayashi, Y.; Yamada, Y.; Yano, T.; Tsujimoto, T.; Suganuma, M.; Niwa, Y.; Yamauchi, M.; Kawakatsu, Y.; Matsuhara, H.; Moda, A.; Tsuiki, A.; Utashima, M.; Ogawa, A.; Sako, N.

2006-08-01

We introduce a Japanese plan of infrared(z-band:0.9μm) space astrometry (JASMINE-project). JASMINE is the satellite (Japan Astrometry Satellite Mission for INfrared Exploration) which will measure the distances and apparent motions of stars around the center of the Milky Way with yet unprecedented precision. It will measure parallaxes, positions with the accuracy of 10 micro-arcsec and proper motions with the accuracy of 4 micro-arcsec/year for stars brighter than z=14mag. JASMINE can observe about ten million stars belonging to the bulge components of our Galaxy, which are hidden by the interstellar dust extinction in optical bands. Number of stars with sigma/pi <0.1 in the direction of the Galactic central bulge is about 1000 times larger than those observed in optical bands, where pi is a parallax and sigma is an error of the parallax. With the completely new "map of the bulge in the Milky Way", it is expected that many new exciting scientific results will be obtained in various fields of astronomy. We will introduce some scientific topics which will be obtained by JASMINE. Presently, JASMINE is in a development phase, with a target launch date around 2015. We adopt the following instrument design of JASMINE in order to get the accurate positions of many stars. We adopt a 3-mirrors optical system (modified Korsch system) with a primary mirror of 0.75m. On the astro-focal plane, we put dozens of new type of CCDs for z-band to get a wide field of view. The consideration of overall system(bus) design is now going on in cooperation with Japan Aerospace Exploration Agency (JAXA). The introduction of JASMINE and the present status of the project will be shown in the presentation.

RR Lyrae stars in and around NGC 6441: signatures of dissolving cluster stars

NASA Astrophysics Data System (ADS)

Kunder, Andrea

2018-06-01

Detailed elemental abundance patterns of metal-poor ([Fe/H]~ -1 dex) stars in the Galactic bulge indicate that a number of them are consistent with globular cluster (GC) stars and may be former members of dissolved GCs. This would indicate that a few per cent of the Galactic bulge was built up from destruction and/or evaporation of globular clusters. Here an attempt is made to identify such presumptive destroyed stars originating from the massive, inner Galaxy globular cluster NGC~6441 using its rich RR Lyrae variable star (RRL) population. We present radial velocities of forty RRLs centered on the globular cluster NGC~6441. All of the 13 RRLs observed within the cluster tidal radius have velocities consistent with cluster membership, with an average radial velocity of 24 +- 5~km/s and a star-to-star scatter of 11~km/s. This includes two new RRLs that were previously not associated with the cluster. Eight RRLs with radial velocities consistent with cluster membership but up to three time the distance from the tidal radius are also reported. These potential extra-tidal RRLs also have exceptionally long periods, which is a curious characteristic of the NGC~6441 RRL population that hosts RRLs with periods longer than seen anywhere else in the Milky Way. As expected of stripped cluster stars, most are inline with the cluster's orbit. Therefore, either the tidal radius of NGC~6441 is underestimated and/or we are seeing dissolving cluster stars stemming from NGC~6441 that are building up the old spheroidal bulge. Both the mean velocity of the cluster as well as the underlying field population is consistent with belonging to an old spheroidal bulge with low rotation and high velocity dispersion that formed before the bar.

Bulge Growth and Quenching since z = 2.5 in CANDELS/3D-HST

NASA Astrophysics Data System (ADS)

Lang, Philipp; Wuyts, Stijn; Somerville, Rachel S.; Förster Schreiber, Natascha M.; Genzel, Reinhard; Bell, Eric F.; Brammer, Gabe; Dekel, Avishai; Faber, Sandra M.; Ferguson, Henry C.; Grogin, Norman A.; Kocevski, Dale D.; Koekemoer, Anton M.; Lutz, Dieter; McGrath, Elizabeth J.; Momcheva, Ivelina; Nelson, Erica J.; Primack, Joel R.; Rosario, David J.; Skelton, Rosalind E.; Tacconi, Linda J.; van Dokkum, Pieter G.; Whitaker, Katherine E.

2014-06-01

Exploiting the deep high-resolution imaging of all five CANDELS fields, and accurate redshift information provided by 3D-HST, we investigate the relation between structure and stellar populations for a mass-selected sample of 6764 galaxies above 1010 M ⊙, spanning the redshift range 0.5 < z < 2.5. For the first time, we fit two-dimensional models comprising a single Sérsic fit and two-component (i.e., bulge + disk) decompositions not only to the H-band light distributions, but also to the stellar mass maps reconstructed from resolved stellar population modeling. We confirm that the increased bulge prominence among quiescent galaxies, as reported previously based on rest-optical observations, remains in place when considering the distributions of stellar mass. Moreover, we observe an increase of the typical Sérsic index and bulge-to-total ratio (with median B/T reaching 40%-50%) among star-forming galaxies above 1011 M ⊙. Given that quenching for these most massive systems is likely to be imminent, our findings suggest that significant bulge growth precedes a departure from the star-forming main sequence. We demonstrate that the bulge mass (and ideally knowledge of the bulge and total mass) is a more reliable predictor of the star-forming versus quiescent state of a galaxy than the total stellar mass. The same trends are predicted by the state-of-the-art, semi-analytic model by Somerville et al. In this model, bulges and black holes grow hand in hand through merging and/or disk instabilities, and feedback from active galactic nuclei shuts off star formation. Further observations will be required to pin down star formation quenching mechanisms, but our results imply that they must be internal to the galaxies and closely associated with bulge growth.

The Chemical Composition of the Galactic Bulge and Implications for its Evolution

NASA Astrophysics Data System (ADS)

McWilliam, Andrew

2016-08-01

At a bulge latitude of b = -4°, the average [Fe/H] and [Mg/H] values are +0.06 and +0.17 dex, roughly 0.2 and 0.7 dex higher than the local thin and thick disk values, respectively, suggesting a large bulge effective yield, perhaps due to efficient retention of supernova ejecta. The bulge vertical [Fe/H] gradient, at ∼0.5 dex/kpc, appears to be due to a changing mixture of sub-populations (near +0.3 dex and -0.3 dex and one possibly near -0.7 dex) with latitude. At solar [Fe/H], the bulge [Al/Fe] and [α/Fe] ratios are ∼ +0.15 dex. Below [Fe/H] ∼ -0.5 dex, the bulge and local thick disk compositions are very similar; but the measured [Mg/Fe], [/Fe], [La/Eu] and dramatic [Cu/Fe] ratios suggest higher SFR in the bulge. However, these composition differences with the thick disk could be due to measurement errors and non-LTE effects. Unusual zig-zag trends of [Cu/Fe] and [Na/Fe] suggest metallicity-dependent nucleosynthesis by core-collapse supernovae in the Type Ia supernova time-delay scenario. The bulge sub-population compositions resemble the local thin and thick disks, but at higher [Fe/H], suggesting a radial [Fe/H] gradient of -0.04 to -0.05 dex/kpc for both the thin and thick disks. If the bulge formed through accretion of inner thin and thick disk stars, it appears that these stars retained vertical scale heights characteristic of their kinematic origin, resulting in the vertical [Fe/H] gradient and [α/Fe] trends seen today.

Bulge Region as a Putative Hair Follicle Stem Cells Niche: A Brief Review

PubMed Central

JOULAI VEIJOUYE, Sanaz; YARI, Abazar; HEIDARI, Fatemeh; SAJEDI, Nayereh; GHOROGHI MOGHANI, Fatemeh; NOBAKHT, Maliheh

2017-01-01

Background: Hair follicle stem cells exist in different sites. Most of the hair follicle stem cells are reside in niche called bulge. Bulge region is located between the opening of sebaceous gland and the attachment site of the arrector pili muscle. Methods: Data were collected using databases and resources of PubMed, Web of Science, Science Direct, Scopus, MEDLINE and their references from the earliest available published to identify English observational studies on hair follicle bulge region. Results: Bulge stem cells are pluripotent with high proliferative capacity. Specific markers allow the bulge cells to be isolated from mouse or human hair follicle. Stem cells isolated from bulge region are label retaining and slow cycling hence these cells are defined as label-retaining cells. Bulge cell populations, due to their plasticity nature are able to differentiate into distinct linage and could contribute in tissue regeneration. Conclusion: The current review discuss about bulge stem cells characteristics and biology including their cycle, location, plasticity, specific markers and regenerative nature. Also the differences between mouse and human hair follicles are investigated. PMID:29026781

Galactic Bulge Giants: Probing Stellar and Galactic Evolution. 1. Catalogue of Spitzer IRAC and MIPS Sources (PREPRINT)

DTIC Science & Technology

2010-12-29

1997), the 2 Micron All Sky Survey ( 2MASS ; Skrutskie et al. 2006), the Midcourse Space Experiment (MSX) catalogue, and the Infra- Red Astronomical...made for these sources with a search radius of 3.′′0 with DENIS and 2MASS , and 30.′′0 for identification with an MSX or IRAS counterpart. The... 2MASS and DENIS counterpart (depending on the field, between 3.1% and 6.7% of the sources), or (ii) a DENIS and 2MASS counterpart at a distance

Post-Newtonian Dynamical Modeling of Supermassive Black Holes in Galactic-scale Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rantala, Antti; Pihajoki, Pauli; Johansson, Peter H.

We present KETJU, a new extension of the widely used smoothed particle hydrodynamics simulation code GADGET-3. The key feature of the code is the inclusion of algorithmically regularized regions around every supermassive black hole (SMBH). This allows for simultaneously following global galactic-scale dynamical and astrophysical processes, while solving the dynamics of SMBHs, SMBH binaries, and surrounding stellar systems at subparsec scales. The KETJU code includes post-Newtonian terms in the equations of motions of the SMBHs, which enables a new SMBH merger criterion based on the gravitational wave coalescence timescale, pushing the merger separation of SMBHs down to ∼0.005 pc. Wemore » test the performance of our code by comparison to NBODY7 and rVINE. We set up dynamically stable multicomponent merger progenitor galaxies to study the SMBH binary evolution during galaxy mergers. In our simulation sample the SMBH binaries do not suffer from the final-parsec problem, which we attribute to the nonspherical shape of the merger remnants. For bulge-only models, the hardening rate decreases with increasing resolution, whereas for models that in addition include massive dark matter halos, the SMBH binary hardening rate becomes practically independent of the mass resolution of the stellar bulge. The SMBHs coalesce on average 200 Myr after the formation of the SMBH binary. However, small differences in the initial SMBH binary eccentricities can result in large differences in the SMBH coalescence times. Finally, we discuss the future prospects of KETJU, which allows for a straightforward inclusion of gas physics in the simulations.« less

New variable stars discovered in the fields of three Galactic open clusters using the VVV survey

NASA Astrophysics Data System (ADS)

Palma, T.; Minniti, D.; Dékány, I.; Clariá, J. J.; Alonso-García, J.; Gramajo, L. V.; Ramírez Alegría, S.; Bonatto, C.

2016-11-01

This project is a massive near-infrared (NIR) search for variable stars in highly reddened and obscured open cluster (OC) fields projected on regions of the Galactic bulge and disk. The search is performed using photometric NIR data in the J-, H- and Ks- bands obtained from the Vista Variables in the Vía Láctea (VVV) Survey. We performed in each cluster field a variability search using Stetson's variability statistics to select the variable candidates. Later, those candidates were subjected to a frequency analysis using the Generalized Lomb-Scargle and the Phase Dispersion Minimization algorithms. The number of independent observations range between 63 and 73. The newly discovered variables in this study, 157 in total in three different known OCs, are classified based on their light curve shapes, periods, amplitudes and their location in the corresponding color-magnitude (J -Ks ,Ks) and color-color (H -Ks , J - H) diagrams. We found 5 possible Cepheid stars which, based on the period-luminosity relation, are very likely type II Cepheids located behind the bulge. Among the newly discovered variables, there are eclipsing binaries, δ Scuti, as well as background RR Lyrae stars. Using the new version of the Wilson & Devinney code as well as the "Physics Of Eclipsing Binaries" (PHOEBE) code, we analyzed some of the best eclipsing binaries we discovered. Our results show that these studied systems turn out to be ranging from detached to double-contact binaries, with low eccentricities and high inclinations of approximately 80°. Their surface temperatures range between 3500 K and 8000 K.

Sgr A* as Source of the Positrons Observed in the Galactic Center Region

NASA Astrophysics Data System (ADS)

Jean, Pierre; Guessoum, Nidhal; Ferrière, Katia

2017-01-01

We explore the possibility that a substantial fraction of the positrons observed to annihilate in the central region of our Galaxy come from the supermassive black hole Sgr A* that lies at the center. This idea was proposed by several authors, but the propagation of the emitted positrons into the bulge and beyond remained a serious problem for models of the origin of GC positrons. We assume models of positron production with different energies. The propagation of positrons from their production site is followed in detail with Monte-Carlo simulations, taking into account the physical conditions of the propagation regions as well as various physical interactions. Using the known physics of positron annihilation in astrophysical environments, we calculate the properties of the annihilation emission (time evolution and spatial distribution) for the different models under consideration. We present the results of these simulations and the conclusions/constraints that can be inferred from them.

Electrodynamic parameters in the nighttime sector during auroral substorms

NASA Technical Reports Server (NTRS)

Fujii, R.; Hoffman, R. A.; Anderson, P. C.; Craven, J. D.; Sugiura, M.; Frank, L. A.; Maynard, N. C.

1994-01-01

The characteristics of the large-scale electrodynamic parameters, field-aligned currents (FACs), electric fields, and electron precipitation, which are associated with auroral substorm events in the nighttime sector, have been obtained through a unique analysis which places the ionospheric measurements of these parameters into the context of a generic substorm determined from global auroral images. A generic bulge-type auroral emission region has been deduced from auroral images taken by the Dynamics Explorer 1 (DE 1) satellite during a number of isolated substorms, and the form has been divided into six sectors, based on the peculiar emission characteristics in each sector: west of bulge, surge horn, surge, middle surge, eastern bulge, and east of bulge. By comparing the location of passes of the Dynamics Explorer 2 (DE 2) satellite to the simultaneously obtained auroral images, each pass is placed onto the generic aurora. The organization of DE 2 data in this way has systematically clarified peculiar characteristics in the electrodynamic parameters. An upward net current mainly appears in the surge, with little net current in the surge horn and the west of bulge. The downward net current is distributed over wide longitudinal regions from the eastern bulge to the east of bulge. Near the poleward boundary of the expanding auroral bulge, a pair of oppositely directed FAC sheets is observed, with the downward FAC on the poleward side. This downward FAC and most of the upward FAC in the surge and the middle surge are assoc iated with narrow, intense antisunwqard convection, corresponding to an equatorward directed spikelike electric field. This pair of currents decreases in amplitude and latitudinal width toward dusk in the surge and the west of bulge, and the region 1 and 2 FACs become embedded in the sunward convection region. The upward FAC region associated with the spikelike field on the poleward edge of the bulge coincides well with intense electron precipitation and aurora appearing in this western and poleward protion of the bulge. The convection reversal is sharp in the west of bulge and surge horn sectors, and near the high-latitude boundary of the upward region 1, with a near stagnation region often extending over a large interval of latitude. In the eastern bulge and east of bulge sectors, the region 1 and 2 FACs are located in the sunward convection region, while a spikelike electric field occasionally appears poleward of the aurora but usually not associated with a pair of FAC sheets. In the eastern bulge, magnetic field data show complicated FAC distributions which correspond to current segments and filamentary currents.

Infrared space astrometry project JASMINE

NASA Astrophysics Data System (ADS)

Gouda, N.; Kobayashi, Y.; Yamada, Y.; Yano, T.; Yano

2008-07-01

A Japanese plan of an infrared (z-band:0.9 μas or k-band:2.2 μas) space astrometry (JASMINE-project) is introduced. JASMINE (Japan Astrometry Satellite Mission for INfrared Exploration) will measure distances and tangential motions of stars in the bulge of the Milky Way. It will measure parallaxes, positions with an accuracy of 10 μas and proper motions with an accuracy of 10 μas/year for stars brighter than z=14 mag or k=11 mag. JASMINE will observe about ten million stars belonging to the bulge component of our Galaxy. With a completely new “map” of the Galactic bulge, it is expected that many new exciting scientific results will be obtained in various fields of astronomy. Presently, JASMINE is in a development phase, with a targeted launch date around 2016. Science targets, preliminary design of instruments, observing strategy, critical technical issues in JASMINE and also Nano-JASMINE project are described in this paper.

Habitability in Different Milky Way Stellar Environments: A Stellar Interaction Dynamical Approach

PubMed Central

Pichardo, Bárbara; Lake, George; Segura, Antígona

2013-01-01

Abstract Every Galactic environment is characterized by a stellar density and a velocity dispersion. With this information from literature, we simulated flyby encounters for several Galactic regions, numerically calculating stellar trajectories as well as orbits for particles in disks; our aim was to understand the effect of typical stellar flybys on planetary (debris) disks in the Milky Way Galaxy. For the solar neighborhood, we examined nearby stars with known distance, proper motions, and radial velocities. We found occurrence of a disturbing impact to the solar planetary disk within the next 8 Myr to be highly unlikely; perturbations to the Oort cloud seem unlikely as well. Current knowledge of the full phase space of stars in the solar neighborhood, however, is rather poor; thus we cannot rule out the existence of a star that is more likely to approach than those for which we have complete kinematic information. We studied the effect of stellar encounters on planetary orbits within the habitable zones of stars in more crowded stellar environments, such as stellar clusters. We found that in open clusters habitable zones are not readily disrupted; this is true if they evaporate in less than 108 yr. For older clusters the results may not be the same. We specifically studied the case of Messier 67, one of the oldest open clusters known, and show the effect of this environment on debris disks. We also considered the conditions in globular clusters, the Galactic nucleus, and the Galactic bulge-bar. We calculated the probability of whether Oort clouds exist in these Galactic environments. Key Words: Stellar interactions—Galactic habitable zone—Oort cloud. Astrobiology 13, 491–509. PMID:23659647

LIFTING THE DUSTY VEIL WITH NEAR- AND MID-INFRARED PHOTOMETRY. III. TWO-DIMENSIONAL EXTINCTION MAPS OF THE GALACTIC MIDPLANE USING THE RAYLEIGH-JEANS COLOR EXCESS METHOD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nidever, David L.; Zasowski, Gail; Majewski, Steven R., E-mail: dln5q@virginia.edu, E-mail: gz2n@virginia.edu, E-mail: srm4n@virginia.edu

We provide new, high-resolution A(K{sub s} ) extinction maps of the heavily reddened Galactic midplane based on the Rayleigh-Jeans Color Excess ({sup R}JCE{sup )} method. RJCE determines star-by-star reddening based on a combination of near- and mid-infrared photometry. The new RJCE-generated maps have 2' Multiplication-Sign 2' pixels and span some of the most severely extinguished regions of the Galaxy-those covered with Spitzer/IRAC imaging by the GLIMPSE-I, -II, -3D, and Vela-Carina surveys, from 256 Degree-Sign < l < 65 Degree-Sign and, in general, for |b| {<=} 1 Degree-Sign -1.{sup 0}5 (extending up to |b| {<=} 4 Degree-Sign in the bulge). Usingmore » RJCE extinction measurements, we generate dereddened color-magnitude diagrams and, in turn, create maps based on main sequence, red clump, and red giant star tracers, each probing different distances and thereby providing coarse three-dimensional information on the relative placement of dust cloud structures. The maps generated from red giant stars, which reach to {approx}18-20 kpc, probe beyond most of the Milky Way extinction in most directions and provide close to a 'total Galactic extinction' map-at minimum they provide high angular resolution maps of lower limits on A(K{sub s} ). Because these maps are generated directly from measurements of reddening by the very dust being mapped, rather than inferred on the basis of some less direct means, they are likely the most accurate to date for charting in detail the highly patchy differential extinction in the Galactic midplane. We provide downloadable FITS files and an IDL tool for retrieving extinction values for any line of sight within our mapped regions.« less

Galaxy Zoo: secular evolution of barred galaxies from structural decomposition of multiband images

NASA Astrophysics Data System (ADS)

Kruk, Sandor J.; Lintott, Chris J.; Bamford, Steven P.; Masters, Karen L.; Simmons, Brooke D.; Häußler, Boris; Cardamone, Carolin N.; Hart, Ross E.; Kelvin, Lee; Schawinski, Kevin; Smethurst, Rebecca J.; Vika, Marina

2018-02-01

We present the results of two-component (disc+bar) and three-component (disc+bar+bulge) multiwavelength 2D photometric decompositions of barred galaxies in five Sloan Digital Sky Survey (SDSS) bands (ugriz). This sample of ∼3500 nearby (z < 0.06) galaxies with strong bars selected from the Galaxy Zoo citizen science project is the largest sample of barred galaxies to be studied using photometric decompositions that include a bar component. With detailed structural analysis, we obtain physical quantities such as the bar- and bulge-to-total luminosity ratios, effective radii, Sérsic indices and colours of the individual components. We observe a clear difference in the colours of the components, the discs being bluer than the bars and bulges. An overwhelming fraction of bulge components have Sérsic indices consistent with being pseudo-bulges. By comparing the barred galaxies with a mass-matched and volume-limited sample of unbarred galaxies, we examine the connection between the presence of a large-scale galactic bar and the properties of discs and bulges. We find that the discs of unbarred galaxies are significantly bluer compared to the discs of barred galaxies, while there is no significant difference in the colours of the bulges. We find possible evidence of secular evolution via bars that leads to the build-up of pseudo-bulges and to the quenching of star formation in the discs. We identify a subsample of unbarred galaxies with an inner lens/oval and find that their properties are similar to barred galaxies, consistent with an evolutionary scenario in which bars dissolve into lenses. This scenario deserves further investigation through both theoretical and observational work.

METALLICITY DISTRIBUTION FUNCTIONS, RADIAL VELOCITIES, AND ALPHA ELEMENT ABUNDANCES IN THREE OFF-AXIS BULGE FIELDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Christian I.; Rich, R. Michael; Kobayashi, Chiaki

2013-03-10

We present radial velocities and chemical abundance ratios of [Fe/H], [O/Fe], [Si/Fe], and [Ca/Fe] for 264 red giant branch stars in three Galactic bulge off-axis fields located near (l, b) = (-5.5, -7), (-4, -9), and (+8.5, +9). The results are based on equivalent width and spectrum synthesis analyses of moderate resolution (R Almost-Equal-To 18,000), high signal-to-noise ratio (S/N {approx} 75-300 pixel{sup -1}) spectra obtained with the Hydra spectrographs on the Blanco 4 m and WIYN 3.5 m telescopes. The targets were selected from the blue side of the giant branch to avoid cool stars that would be strongly affectedmore » by CN and TiO; however, a comparison of the color-metallicity distribution in literature samples suggests that our selection of bluer targets should not present a significant bias against metal-rich stars. We find a full range in metallicity that spans [Fe/H] Almost-Equal-To -1.5 to +0.5, and that, in accordance with the previously observed minor-axis vertical metallicity gradient, the median [Fe/H] also declines with increasing Galactic latitude in off-axis fields. The off-axis vertical [Fe/H] gradient in the southern bulge is estimated to be {approx}0.4 dex kpc{sup -1}; however, comparison with the minor-axis data suggests that a strong radial gradient does not exist. The (+8.5, +9) field exhibits a higher than expected metallicity, with a median [Fe/H] = -0.23, that might be related to a stronger presence of the X-shaped bulge structure along that line-of-sight. This could also be the cause of an anomalous increase in the median radial velocity for intermediate metallicity stars in the (+8.5, +9) field. However, the overall radial velocity and dispersion for each field are in good agreement with recent surveys and bulge models. All fields exhibit an identical, strong decrease in velocity dispersion with increasing metallicity that is consistent with observations in similar minor-axis outer bulge fields. Additionally, the [O/Fe], [Si/Fe], and [Ca/Fe] versus [Fe/H] trends are identical among our three fields, and are in good agreement with past bulge studies. We find that stars with [Fe/H] {approx}< -0.5 are {alpha}-enhanced, and that the [{alpha}/Fe] ratios decline at higher metallicity. At [Fe/H] {approx}< 0, the {alpha}-element trends are indistinguishable from the halo and thick disk, and the variations in the behavior of individual {alpha}-elements are consistent with production in massive stars and a rapid bulge formation timescale.« less

Habitability in different Milky Way stellar environments: a stellar interaction dynamical approach.

PubMed

Jiménez-Torres, Juan J; Pichardo, Bárbara; Lake, George; Segura, Antígona

2013-05-01

Every Galactic environment is characterized by a stellar density and a velocity dispersion. With this information from literature, we simulated flyby encounters for several Galactic regions, numerically calculating stellar trajectories as well as orbits for particles in disks; our aim was to understand the effect of typical stellar flybys on planetary (debris) disks in the Milky Way Galaxy. For the solar neighborhood, we examined nearby stars with known distance, proper motions, and radial velocities. We found occurrence of a disturbing impact to the solar planetary disk within the next 8 Myr to be highly unlikely; perturbations to the Oort cloud seem unlikely as well. Current knowledge of the full phase space of stars in the solar neighborhood, however, is rather poor; thus we cannot rule out the existence of a star that is more likely to approach than those for which we have complete kinematic information. We studied the effect of stellar encounters on planetary orbits within the habitable zones of stars in more crowded stellar environments, such as stellar clusters. We found that in open clusters habitable zones are not readily disrupted; this is true if they evaporate in less than 10(8) yr. For older clusters the results may not be the same. We specifically studied the case of Messier 67, one of the oldest open clusters known, and show the effect of this environment on debris disks. We also considered the conditions in globular clusters, the Galactic nucleus, and the Galactic bulge-bar. We calculated the probability of whether Oort clouds exist in these Galactic environments.

X-ray Selected Symbiotic Candidates in the Galactic Bulge Survey

NASA Astrophysics Data System (ADS)

Hynes, Robert I.; Wetuski, Joshua` D.; Jonker, Peter; Torres, Manuel; Heinke, Craig O.; Maccarone, Tom; Steeghs, Danny; Britt, Christopher; Johnson, Christopher; Nelemans, Gijs

2017-06-01

The Galactic Bulge Survey (GBS) is a broad, shallow survey of Bulge X-ray sources with extensive multiwavelength support. The limiting sensitivity, about 2×1032 erg/s at the Bulge distance, is well suited to finding symbiotic X-ray binaries (SyXBs) containing neutron stars accreting from a cool giant wind, as well as X-ray bright white dwarf systems. Giant counterparts can be securely detected in IR photometry, allowing us to estimate the total number of symbiotics detected by the GBS, and identify a good number of promising candidates. Such an X-ray selected symbiotic sample may be quite different to the traditional symbiotic star population which is usually selected by optical spectroscopy, and consequently biased towards systems with rich line emission. Of the 1640 unique X-ray sources identified by the GBS we find 91 significant matches with candidate Bulge giants. We expect 68 coincidences, so estimate a total sample of about 23 X-ray emitting cool giants detected by the GBS. Most of these are likely to be SyXBs or symbiotics of some type. Narrowing our search to sources coincident to 1", we find 23 matches, with only 8 coincidences expected, so this subsample has a relatively high purity, and likely includes most of the GBS symbiotics. The properties of this subsample are mostly consistent with cool giants, with typical SEDs, long-term lightcurves, and spectra. The sources are inconsistent in color with nearby M dwarfs and show small proper motions, so the foreground contamination is likely small. We present a selection of the best studied objects, focusing on one extremely variable X-ray source coincident with a carbon giant. This is quite an unusual object as carbon stars are rare in the Bulge. The scientific results reported in this article are based on observations made by the Chandra X-ray Observatory and data obtained from the Chandra Data Archive. Support for this work was provided by the National Aeronautics and Space Administration through Chandra Award Numbers GO4-15047X and AR5-16004X issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the National Aeronautics Space Administration under contract NAS8-03060.

The Non-Axisymmetric Milky Way

NASA Technical Reports Server (NTRS)

Spergel, David N.

1996-01-01

The Dwek et al. model represents the current state-of-the-art model for the stellar structure of our Galaxy. The improvements we have made to this model take a number of forms: (1) the construction of a more detailed dust model so that we can extend our modeling to the galactic plane; (2) simultaneous fits to the bulge and the disk; (3) the construction of the first self-consistent model for a galactic bar; and (4) the development and application of algorithms for constructing nonparametric bar models. The improved Galaxy model has enabled a number of exciting science projects. In Zhao et al., we show that the number and duration of microlensing events seen by the OGLE and MACHO collaborations towards the bulge were consistent with the predictions of our bar model. In Malhotra et al., we constructed an infrared Tully-Fisher (TF) relation for the local group. We found the tightest TF relation ever seen in any band and in any group of galaxies. The tightness of the correlation places strong constraints on galaxy formation models and provides a independent check of the Cepheid distance scale.

VVV Survey Search for Habitable Planets around M Dwarfs

NASA Astrophysics Data System (ADS)

Minniti, Dante

2015-08-01

VISTA Variables in the Vía Láctea (VVV) is a public ESO near- infrared (near-IR) variability survey aimed at scanning the Milky Way Bulge and an adjacent section of the mid-plane. The survey covers an area of 562 sqdeg in the Galactic bulge and the southern disk, containing a billion point sources. In this work we discuss the selection of nearby M-type dwarf stars using multicolor cuts. The ZYJHKs photometry allows an accurate estimation of the spectral types of the M-dwarf candidates. Our procedure is applied for fields located far from the Galactic center where the photometric quality is best. The results of this search covering 15 sqdeg allow us to estimate the total number of M-dwarfs that can be photometrically monitored in the VVV database. In addition, we analyze the light curves of the ~10000 best candidate M-dwarf stars searching for extrasolar planetary transits. In this poster we present the light curves of a hundred good transit candidates, and select those that lie in the HZ around their parent stars.

ISOGAL: A deep survey of the obscured inner Milky Way with ISO at 7 mu m and 15 mu m and with DENIS in the near-infrared

NASA Astrophysics Data System (ADS)

Omont, A.; Gilmore, G. F.; Alard, C.; Aracil, B.; August, T.; Baliyan, K.; Beaulieu, S.; Bégon, S.; Bertou, X.; Blommaert, J. A. D. L.; Borsenberger, J.; Burgdorf, M.; Caillaud, B.; Cesarsky, C.; Chitre, A.; Copet, E.; de Batz, B.; Egan, M. P.; Egret, D.; Epchtein, N.; Felli, M.; Fouqué, P.; Ganesh, S.; Genzel, R.; Glass, I. S.; Gredel, R.; Groenewegen, M. A. T.; Guglielmo, F.; Habing, H. J.; Hennebelle, P.; Jiang, B.; Joshi, U. C.; Kimeswenger, S.; Messineo, M.; Miville-Deschênes, M. A.; Moneti, A.; Morris, M.; Ojha, D. K.; Ortiz, R.; Ott, S.; Parthasarathy, M.; Pérault, M.; Price, S. D.; Robin, A. C.; Schultheis, M.; Schuller, F.; Simon, G.; Soive, A.; Testi, L.; Teyssier, D.; Tiphène, D.; Unavane, M.; van Loon, J. T.; Wyse, R.

2003-06-01

The ISOGAL project is an infrared survey of specific regions sampling the Galactic Plane selected to provide information on Galactic structure, stellar populations, stellar mass-loss and the recent star formation history of the inner disk and Bulge of the Galaxy. ISOGAL combines 7 and 15 μm ISOCAM observations -- with a resolution of 6 arcsec at worst -- with DENIS IJKs data to determine the nature of the sources and the interstellar extinction. We have observed about 16 square degrees with a sensitivity approaching 10-20 mJy, detecting ˜105 sources, mostly AGB stars, red giants and young stars. The main features of the ISOGAL survey and the observations are summarized in this paper, together with a brief discussion of data processing and quality. The primary ISOGAL products are described briefly (a full desciption is given in Schuller et al. 2003): viz. the images and the ISOGAL-DENIS five-wavelength point source catalogue. The main scientific results already derived or in progress are summarized. These include astrometrically calibrated 7 and 15 μm images, determining structures of resolved sources; identification and properties of interstellar dark clouds; quantification of the infrared extinction law and source dereddening; analysis of red giant and (especially) AGB stellar populations in the central Bulge, determining luminosity, presence of circumstellar dust and mass-loss rate, and source classification, supplemented in some cases by ISO/CVF spectroscopy; detection of young stellar objects of diverse types, especially in the inner Bulge with information about the present and recent star formation rate; identification of foreground sources with mid-IR excess. These results are the subject of about 25 refereed papers published or in preparation. This is paper No. 20 in a refereed journal based on data from the ISOGAL project. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, The Netherlands and the UK) and with the participation of ISAS and NASA. Based on observations collected at the European Southern Observatory, La Silla, Chile.

Consistency between the luminosity function of resolved millisecond pulsars and the galactic center excess

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ploeg, Harrison; Gordon, Chris; Crocker, Roland

Fermi Large Area Telescope data reveal an excess of GeV gamma rays from the direction of the Galactic Center and bulge. Several explanations have been proposed for this excess including an unresolved population of millisecond pulsars (MSPs) and self-annihilating dark matter. It has been claimed that a key discriminant for or against the MSP explanation can be extracted from the properties of the luminosity function describing this source population. Specifically, is the luminosity function of the putative MSPs in the Galactic Center consistent with that characterizing the resolved MSPs in the Galactic disk? To investigate this we have used amore » Bayesian Markov Chain Monte Carlo to evaluate the posterior distribution of the parameters of the MSP luminosity function describing both resolved MSPs and the Galactic Center excess. At variance with some other claims, our analysis reveals that, within current uncertainties, both data sets can be well fit with the same luminosity function.« less

QSO Emission Lines and the Black Hole-Galaxy Bulge Relation

NASA Astrophysics Data System (ADS)

Shields, G. A.; Gebhardt, K.; Salviander, S.; Wills, B. J.; Yuan, M.; Xie, B.; Dietrich, M.

2002-05-01

Supermassive black holes in galactic nuclei have masses closely related to the properties of the host galaxy bulge. In particular, MBH varies as the fourth power of σ , the stellar velocity dispersion (Tremaine et al. 2002, ApJ in press, and references therein). The origin of the black hole-bulge relation is unknown, although theoretical suggestions abound. An important clue would be provided by knowledge of how the relation has evolved over cosmic time. This requires measurement of black hole masses and galactic potentials at large look-back times, which is difficult to do directly. However, black hole masses may be derived from the continuum luminosity and the widths of the broad Balmer lines of QSOs (e.g., Kaspi et al. 2000, ApJ 533, 631), and σ may be derived from the widths of the narrow [O III] lines (Nelson 2000, ApJ, 544, L91). We have carried out this program for a set of published and unpublished observations of Seyfert galaxies and QSOs. Results for low redshift objects support the use of this method to derive MBH and σ . The few available measurements of high redshift QSOs are consistent little or no change in the MBH-σ relation between the present and redshifts up to z = 3.3, when the universe was only two billion years old. This material is based in part upon work supported by the Texas Advanced Research Program under Grant No. 003658-0177-2001.

Toward a Galactic Distribution of Planets. I. Methodology and Planet Sensitivities of the 2015 High-cadence Spitzer Microlens Sample

NASA Astrophysics Data System (ADS)

Zhu, Wei; Udalski, A.; Calchi Novati, S.; Chung, S.-J.; Jung, Y. K.; Ryu, Y.-H.; Shin, I.-G.; Gould, A.; Lee, C.-U.; Albrow, M. D.; Yee, J. C.; Han, C.; Hwang, K.-H.; Cha, S.-M.; Kim, D.-J.; Kim, H.-W.; Kim, S.-L.; Kim, Y.-H.; Lee, Y.; Park, B.-G.; Pogge, R. W.; KMTNet Collaboration; Poleski, R.; Mróz, P.; Pietrukowicz, P.; Skowron, J.; Szymański, M. K.; KozLowski, S.; Ulaczyk, K.; Pawlak, M.; OGLE Collaboration; Beichman, C.; Bryden, G.; Carey, S.; Fausnaugh, M.; Gaudi, B. S.; Henderson, C. B.; Shvartzvald, Y.; Wibking, B.; Spitzer Team

2017-11-01

We analyze an ensemble of microlensing events from the 2015 Spitzer microlensing campaign, all of which were densely monitored by ground-based high-cadence survey teams. The simultaneous observations from Spitzer and the ground yield measurements of the microlensing parallax vector {{\\boldsymbol{π }}}{{E}}, from which compact constraints on the microlens properties are derived, including ≲25% uncertainties on the lens mass and distance. With the current sample, we demonstrate that the majority of microlenses are indeed in the mass range of M dwarfs. The planet sensitivities of all 41 events in the sample are calculated, from which we provide constraints on the planet distribution function. In particular, assuming a planet distribution function that is uniform in {log}q, where q is the planet-to-star mass ratio, we find a 95% upper limit on the fraction of stars that host typical microlensing planets of 49%, which is consistent with previous studies. Based on this planet-free sample, we develop the methodology to statistically study the Galactic distribution of planets using microlensing parallax measurements. Under the assumption that the planet distributions are the same in the bulge as in the disk, we predict that ∼1/3 of all planet detections from the microlensing campaigns with Spitzer should be in the bulge. This prediction will be tested with a much larger sample, and deviations from it can be used to constrain the abundance of planets in the bulge relative to the disk.

Binary Microlensing Events from the MACHO Project

NASA Astrophysics Data System (ADS)

Alcock, C.; Allsman, R. A.; Alves, D.; Axelrod, T. S.; Baines, D.; Becker, A. C.; Bennett, D. P.; Bourke, A.; Brakel, A.; Cook, K. H.; Crook, B.; Crouch, A.; Dan, J.; Drake, A. J.; Fragile, P. C.; Freeman, K. C.; Gal-Yam, A.; Geha, M.; Gray, J.; Griest, K.; Gurtierrez, A.; Heller, A.; Howard, J.; Johnson, B. R.; Kaspi, S.; Keane, M.; Kovo, O.; Leach, C.; Leach, T.; Leibowitz, E. M.; Lehner, M. J.; Lipkin, Y.; Maoz, D.; Marshall, S. L.; McDowell, D.; McKeown, S.; Mendelson, H.; Messenger, B.; Minniti, D.; Nelson, C.; Peterson, B. A.; Popowski, P.; Pozza, E.; Purcell, P.; Pratt, M. R.; Quinn, J.; Quinn, P. J.; Rhie, S. H.; Rodgers, A. W.; Salmon, A.; Shemmer, O.; Stetson, P.; Stubbs, C. W.; Sutherland, W.; Thomson, S.; Tomaney, A.; Vandehei, T.; Walker, A.; Ward, K.; Wyper, G.

2000-09-01

We present the light curves of 21 gravitational microlensing events from the first six years of the MACHO Project gravitational microlensing survey that are likely examples of lensing by binary systems. These events were manually selected from a total sample of ~350 candidate microlensing events that were either detected by the MACHO Alert System or discovered through retrospective analyses of the MACHO database. At least 14 of these 21 events exhibit strong (caustic) features, and four of the events are well fit with lensing by large mass ratio (brown dwarf or planetary) systems, although these fits are not necessarily unique. The total binary event rate is roughly consistent with predictions based upon our knowledge of the properties of binary stars, but a precise comparison cannot be made without a determination of our binary lens event detection efficiency. Toward the Galactic bulge, we find a ratio of caustic crossing to noncaustic crossing binary lensing events of 12:4, excluding one event for which we present two fits. This suggests significant incompleteness in our ability to detect and characterize noncaustic crossing binary lensing. The distribution of mass ratios, N(q), for these binary lenses appears relatively flat. We are also able to reliably measure source-face crossing times in four of the bulge caustic crossing events, and recover from them a distribution of lens proper motions, masses, and distances consistent with a population of Galactic bulge lenses at a distance of 7+/-1 kpc. This analysis yields two systems with companions of ~0.05 Msolar.

The Milky Way, the Galactic Halo, and the Halos of Galaxies

NASA Astrophysics Data System (ADS)

Gerhard, Ortwin

2016-08-01

The Milky Way, ``our'' Galaxy, is currently the subject of intense study with many ground-based surveys, in anticipation of upcoming results from the Gaia mission. From this work we have been learning about the full three-dimensional structure of the Galactic box/peanut bulge, the distribution of stars in the bar and disk, and the many streams and substructures in the Galactic halo. The data indicate that a large fraction of the Galactic halo has been accreted from outside. Similarly, in many external galaxy halos there is now evidence for tidal streams and accretion of satellites. To study these features requires exquisite, deep photometry and spectroscopy. These observations illustrate how galaxy halos are still growing, and sometimes can be used to ``time'' the accretion events. In comparison with cosmological simulations, the structure of galaxy halos gives us a vivid illustration of the hierarchical nature of our Universe.

The best and brightest metal-poor stars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schlaufman, Kevin C.; Casey, Andrew R., E-mail: kschlauf@mit.edu, E-mail: arc@ast.cam.ac.uk

2014-12-10

The chemical abundances of large samples of extremely metal-poor (EMP) stars can be used to investigate metal-free stellar populations, supernovae, and nucleosynthesis as well as the formation and galactic chemical evolution of the Milky Way and its progenitor halos. However, current progress on the study of EMP stars is being limited by their faint apparent magnitudes. The acquisition of high signal-to-noise spectra for faint EMP stars requires a major telescope time commitment, making the construction of large samples of EMP star abundances prohibitively expensive. We have developed a new, efficient selection that uses only public, all-sky APASS optical, 2MASS near-infrared,more » and WISE mid-infrared photometry to identify bright metal-poor star candidates through their lack of molecular absorption near 4.6 microns. We have used our selection to identify 11,916 metal-poor star candidates with V < 14, increasing the number of publicly available candidates by more than a factor of five in this magnitude range. Their bright apparent magnitudes have greatly eased high-resolution follow-up observations that have identified seven previously unknown stars with [Fe/H] ≲ –3.0. Our follow-up campaign has revealed that 3.8{sub −1.1}{sup +1.3}% of our candidates have [Fe/H] ≲ –3.0 and 32.5{sub −2.9}{sup +3.0}% have –3.0 ≲ [Fe/H] ≲ –2.0. The bulge is the most likely location of any existing Galactic Population III stars, and an infrared-only variant of our selection is well suited to the identification of metal-poor stars in the bulge. Indeed, two of our confirmed metal-poor stars with [Fe/H] ≲ –2.7 are within about 2 kpc of the Galactic center. They are among the most metal-poor stars known in the bulge.« less

Bulge growth and quenching since z = 2.5 in CANDELS/3D-HST

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lang, Philipp; Wuyts, Stijn; Schreiber, Natascha M. Förster

2014-06-10

Exploiting the deep high-resolution imaging of all five CANDELS fields, and accurate redshift information provided by 3D-HST, we investigate the relation between structure and stellar populations for a mass-selected sample of 6764 galaxies above 10{sup 10} M {sub ☉}, spanning the redshift range 0.5 < z < 2.5. For the first time, we fit two-dimensional models comprising a single Sérsic fit and two-component (i.e., bulge + disk) decompositions not only to the H-band light distributions, but also to the stellar mass maps reconstructed from resolved stellar population modeling. We confirm that the increased bulge prominence among quiescent galaxies, as reportedmore » previously based on rest-optical observations, remains in place when considering the distributions of stellar mass. Moreover, we observe an increase of the typical Sérsic index and bulge-to-total ratio (with median B/T reaching 40%-50%) among star-forming galaxies above 10{sup 11} M {sub ☉}. Given that quenching for these most massive systems is likely to be imminent, our findings suggest that significant bulge growth precedes a departure from the star-forming main sequence. We demonstrate that the bulge mass (and ideally knowledge of the bulge and total mass) is a more reliable predictor of the star-forming versus quiescent state of a galaxy than the total stellar mass. The same trends are predicted by the state-of-the-art, semi-analytic model by Somerville et al. In this model, bulges and black holes grow hand in hand through merging and/or disk instabilities, and feedback from active galactic nuclei shuts off star formation. Further observations will be required to pin down star formation quenching mechanisms, but our results imply that they must be internal to the galaxies and closely associated with bulge growth.« less

Masses of Black Holes in Active Galactic Nuclei

NASA Technical Reports Server (NTRS)

Peterson, Bradley M.

2003-01-01

We present a progress report on a project whose goal is to improve both the precision and accuracy of reverberation-based black-hole masses. Reverberation masses appear to be accurate to a factor of about three, and the black-hole mass/bulge velocity dispersion (M-sigma) relationship appears to be the same in active and quiescent galaxies.

Dusty Mass Loss from Galactic Asymptotic Giant Branch Stars

NASA Astrophysics Data System (ADS)

Sargent, Benjamin A.; Srinivasan, Sundar; Meixner, Margaret; Kastner, Joel H.

2016-06-01

We are probing how mass loss from Asymptotic Giant Branch (AGB) stars depends upon their metallicity. Asymptotic giant branch (AGB) stars are evolved stars that eject large parts of their mass in outflows of dust and gas in the final stages of their lives. Our previous studies focused on mass loss from AGB stars in lower metallicity galaxies: the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC). In our present study, we analyze AGB star mass loss in the Galaxy, with special attention to the Bulge, to investigate how mass loss differs in an overall higher metallicity environment. We construct radiative transfer models of the spectral energy distributions (SEDs) of stars in the Galaxy identified as AGB stars from infrared and optical surveys. Our Magellanic Cloud studies found that the AGB stars with the highest mass loss rates tended to have outflows with carbon-rich dust, and that overall more carbon-rich (C-rich) dust than oxygen-rich (O-rich) was produced by AGB stars in both LMC and SMC. Our radiative transfer models have enabled us to determine reliably the dust chemistry of the AGB star from the best-fit model. For our Galactic sample, we are investigating both the dust chemistries of the AGB stars and their mass-loss rates, to compare the balance of C-rich dust to O-rich dust between the Galactic bulge and the Magellanic Clouds. We are also constructing detailed dust opacity models of AGB stars in the Galaxy for which we have infrared spectra; e.g., from the Spitzer Space Telescope Infrared Spectrograph (IRS). This detailed dust modeling of spectra informs our choice of dust properties to use in radiative transfer modeling of SEDs of Galactic AGB stars. BAS acknowledges funding from NASA ADAP grant NNX15AF15G.

Extinction Map of Baade's Window

NASA Astrophysics Data System (ADS)

Stanek, K. Z.

1996-03-01

Recently Wozniak & Stanek proposed a new method to investigate interstellar extinction, based on two-band photometry, which uses red clump stars as a means to construct the reddening curve. I apply this method to the color-magnitude diagrams obtained by the Optical Gravitational Lensing Experiment to construct an extinction map of a 40' x 40' region of Baade's window, with resolution of ~30". Such a map should be useful for studies of this frequently observed region of the Galactic bulge. The map and software useful for its applications are available via anonymous ftp. The total extinction AV varies from 1.26 to 2.79 mag within the 40' x 40' field of view centered on ( alpha 2000, delta 2000) = (18:03:20.9, -30:02:06), i.e., (l, b) = (1.001, -3.885). The ratio AV/E(V - I) = 2.49 +/- 0.02 is determined with this new method.

Chemical and kinematical properties of galactic bulge stars surrounding the stellar system Terzan 5

DOE Office of Scientific and Technical Information (OSTI.GOV)

Massari, D.; Mucciarelli, A.; Ferraro, F. R.

2014-08-20

As part of a study aimed at determining the kinematical and chemical properties of Terzan 5, we present the first characterization of the bulge stars surrounding this puzzling stellar system. We observed 615 targets located well beyond the tidal radius of Terzan 5 and found that their radial velocity distribution is well described by a Gaussian function peaked at (v {sub rad}) = +21.0 ± 4.6 km s{sup –1} with dispersion σ {sub v} = 113.0 ± 2.7 km s{sup –1}. This is one of the few high-precision spectroscopic surveys of radial velocities for a large sample of bulge starsmore » in such a low and positive latitude environment (b = +1.°7). We found no evidence of the peak at (v {sub rad}) ∼ +200 km s{sup –1} found in Nidever et al. Strong contamination of many observed spectra by TiO bands prevented us from deriving the iron abundance for the entire spectroscopic sample, introducing a selection bias. The metallicity distribution was finally derived for a subsample of 112 stars in a magnitude range where the effect of the selection bias is negligible. The distribution is quite broad and roughly peaked at solar metallicity ([Fe/H] ≅ +0.05 dex) with a similar number of stars in the super-solar and in the sub-solar ranges. The population number ratios in different metallicity ranges agree well with those observed in other low-latitude bulge fields, suggesting (1) the possible presence of a plateau for |b| < 4° in the ratio between stars in the super-solar (0 < [Fe/H] <0.5 dex) and sub-solar (–0.5 < [Fe/H] <0 dex) metallicity ranges; (2) a severe drop in the metal-poor component ([Fe/H] <–0.5) as a function of Galactic latitude.« less

Space astrometry project JASMINE

NASA Astrophysics Data System (ADS)

Gouda, N.; Kobayashi, Y.; Yamada, Y.; Yano, Y.; Jasmine Working Group

A Japanese plan for an infrared ( z-band: 0.9 m) space astrometry project, JASMINE, is introduced. JASMINE is a satellite (Japan Astrometry Satellite Mission for INfrared Exploration) to measure distances and apparent motions of stars in the bulge of the Milky Way with yet unprecedented precision. It will measure parallaxes and positions with an accuracy of 10 μarcsec and proper motions with an accuracy of 4 μarcsec/year for stars brighter than z = 14 mag. JASMINE will observe about 10 million stars belonging to the bulge component of our Galaxy. With a completely new "map of the Galactic bulge", it is expected that many new exciting scientific results will be obtained in various fields of astronomy. Presently, JASMINE is in the development phase, with a target launch date around 2015. Overall system (bus) design is presently ongoing, in cooperation with the Japanese Aerospace Exploration Agency (JAXA). Preliminary design of instruments, observing strategy, data reduction, and critical technical issues for JASMINE will be described.

A near-infrared high-resolution spectroscopic survey of bulge stars - JASMINE prestudy

NASA Astrophysics Data System (ADS)

Tsujimoto, T.; Gouda, N.; Kobayashi, N.; Yasui, C.; Kondo, S.; Minami, A.; Motohara, K.; Ikeda, Y.

2006-08-01

We are developing a new near-infrared high-resolution (R[max]= 100,000) and high-sensitive spectrograph WINERED, which is specifically customized for short NIR bands at 0.9-1.35 μm. WINERED employs the novelty in the optical system; a potable design and a warm optics without any cold stops. The planned astrometric space mission JASMINE will provide the exact positions, distances, and proper motions of the bulge stars. The missing components, the radial velocity and chemical compositions will be measured by WINERED with high accuracies (δV< 1km/s). These combined data brought by JASMINE and WINERED will certainly reveal the nature of the Galactic bulge. We plan to complete this instrument for the observation of a single object by the end of 2008 and hope to attach it to various 4-10m telescopes as a PI-type instrument. In succession, we will develop it to the design for a simultaneous multi-object spectroscopy.

Diffuse X-ray sky in the Galactic center

NASA Astrophysics Data System (ADS)

Koyama, Katsuji

2018-01-01

The Galactic diffuse X-ray emission (GDXE) in the Milky Way Galaxy is spatially and spectrally decomposed into the Galactic center X-ray emission (GCXE), the Galactic ridge X-ray emission (GRXE), and the Galactic bulge X-ray emission (GBXE). The X-ray spectra of the GDXE are characterized by the strong K-shell lines of the highly ionized atoms, and the brightest lines are the K-shell transition (principal quantum number transition of n = 2 → 1) of neutral iron (Fe I-Kα), He-like iron (Fe XXV-Heα), and He-like sulfur (S XV-Heα). Accordingly, the GDXE is composed of a high-temperature plasma of ˜7 keV (HTP) and a low-temperature plasma of ˜1 keV, which emit the Fe XXV-Heα and S XV-Heα lines, respectively. The Fe I-Kα line is emitted from nearly neutral irons, and hence the third component of the GDXE is a cool gas (CG). The Fe I-Kα distribution in the GCXE region is clumpy (Fe I-Kα clump), associated with giant molecular cloud (MC) complexes (Sagittarius A, B, C, D, and E) in the central molecular zone. The origin of the Fe I-Kα clumps is the fluorescence and Thomson scattering from the MCs irradiated by past big flares of the supermassive black hole Sagittarius A*. The scale heights and equivalent widths of the Fe I-Kα, Fe XXV-Heα, and Fe XXVI-Lyα (n = 2 → 1 transition of H-like iron) lines are different among the GCXE, GBXE, and GRXE. Therefore, their structures and origins are separately examined. This paper gives an overview of the research history and the present understandings of the GDXE, while in particular focusing on the origin of the HTP and CG in the GCXE.

Extended Red Emission in the Evil Eye Galaxy

NASA Astrophysics Data System (ADS)

Pierini, D.; Majeed, A.; Boroson, T. A.; Witt, A. N.

2001-05-01

The Evil Eye Galaxy (NGC 4826) is a nearby galaxy with an asymmetrically placed, strongly absorbing dust lane across its prominent bulge, associated to an active star formation (SF) region. We obtained accurate low--resolution (4.2 Å/pixel) spectroscopy (KPNO 4-m) of NGC 4826 in the wavelength range 5300--9100Å with a slit of 4.4' length, positioned across the nucleus of the galaxy and encompassing its bulge size. We were able to study the wavelength dependent effects of absorption and scattering by the dust by comparing the stellar SEDs at corresponding positions on the bulge, symmetrically placed with respect to the nucleus, under the assumption that the intrinsic (i.e. unobscured by the dust lane) ISRF is radially symmetric, except for the ongoing SF region. We report on the detection of strong extended red emission (ERE) from the dust lane of NGC 4826 within a radial distance of about 15{' '} from its nucleus, adjacent to the active SF region. At the nucleus, the ERE band extends from about 5800 Å to 9100 Å, with peak near 8300 Å, and the ERE-to-scattered light integrated intensity ratio is about 0.7. At farther distances, approaching the ongoing SF region, the ERE band and peak shift to longer wavelengths, while the integrated ERE intensity diminishes and, finally, vanishes there. The H α line intensity and the index [NII]λ 6583/H α constrain the Lyman continuum photon rate and the effective temperatures of the OB association stars. The ERE-to-scattered light ratio decreases as well but shows a secondary maximum where the opacity of the dust lane peaks. We interpret the ERE nature as photoluminescence by nanometer--sized clusters, illuminated by UV/visible photons of the local radiation field. When examined within the context of ERE observations in the diffuse ISM of our Galaxy and in a variety of other dusty environments, we conclude that the ERE photon conversion efficiency in NGC 4826 is as high as found elsewhere, but that the characteristic size of the nanoparticles there is about twice as large as that inferred in the Galactic diffuse ISM.

Zinc abundances in Galactic bulge field red giants: Implications for damped Lyman-α systems

NASA Astrophysics Data System (ADS)

Barbuy, B.; Friaça, A. C. S.; da Silveira, C. R.; Hill, V.; Zoccali, M.; Minniti, D.; Renzini, A.; Ortolani, S.; Gómez, A.

2015-08-01

Context. Zinc in stars is an important reference element because it is a proxy to Fe in studies of damped Lyman-α systems (DLAs), permitting a comparison of chemical evolution histories of bulge stellar populations and DLAs. In terms of nucleosynthesis, it behaves as an alpha element because it is enhanced in metal-poor stars. Abundance studies in different stellar populations can give hints to the Zn production in different sites. Aims: The aim of this work is to derive the iron-peak element Zn abundances in 56 bulge giants from high resolution spectra. These results are compared with data from other bulge samples, as well as from disk and halo stars, and damped Lyman-α systems, in order to better understand the chemical evolution in these environments. Methods: High-resolution spectra were obtained using FLAMES+UVES on the Very Large Telescope. We computed the Zn abundances using the Zn i lines at 4810.53 and 6362.34 Å. We considered the strong depression in the continuum of the Zn i 6362.34 Å line, which is caused by the wings of the Ca i 6361.79 Å line suffering from autoionization. CN lines blending the Zn i 6362.34 Å line are also included in the calculations. Results: We find [Zn/Fe] = +0.24 ± 0.02 in the range -1.3 < [Fe/H] < -0.5 and [Zn/Fe] = + 0.06 ± 0.02 in the range -0.5 < [Fe/H] < -0.1, whereas for [Fe/H] ≥ -0.1, it shows a spread of -0.60 < [Zn/Fe] < + 0.15, with most of these stars having low [Zn/Fe] < 0.0. These low zinc abundances at the high metallicity end of the bulge define a decreasing trend in [Zn/Fe] with increasing metallicities. A comparison with Zn abundances in DLA systems is presented, where a dust-depletion correction was applied for both Zn and Fe. When we take these corrections into account, the [Zn/Fe] vs. [Fe/H] of the DLAs fall in the same region as the thick disk and bulge stars. Finally, we present a chemical evolution model of Zn enrichment in massive spheroids, representing a typical classical bulge evolution. Observations collected both at the European Southern Observatory, Paranal, Chile (ESO programmes 71.B-0617A, 73.B0074A, and GTO 71.B-0196).Table 6 is available in electronic form at http://www.aanda.org

MASSIVE GALAXIES IN COSMOS: EVOLUTION OF BLACK HOLE VERSUS BULGE MASS BUT NOT VERSUS TOTAL STELLAR MASS OVER THE LAST 9 Gyr?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jahnke, Knud; Cisternas, Mauricio; Inskip, Katherine

2009-12-01

We constrain the ratio of black hole (BH) mass to total stellar mass of type-1 active galactic nuclei (AGNs) in the COSMOS survey at 1 < z < 2. For 10 AGNs at mean redshift z approx 1.4 with both Hubble Space Telescope (HST)/ACS and HST/NICMOS imaging data, we are able to compute the total stellar mass M {sub *,total}, based on rest-frame UV-to-optical host galaxy colors which constrain mass-to-light ratios. All objects have virial M {sub BH} estimates available from the COSMOS Magellan/IMACS and zCOSMOS surveys. We find within errors zero difference between the M {sub BH}-M {sub *,total}more » relation at z approx 1.4 and the M {sub BH}-M {sub *,bulge} relation in the local universe. Our interpretation is (1) if our objects were purely bulge-dominated, the M {sub BH}-M {sub *,bulge} relation has not evolved since z approx 1.4. However, (2) since we have evidence for substantial disk components, the bulges of massive galaxies (M {sub *,total} = 11.1 +- 0.3 or log M {sub BH} approx 8.3 +- 0.2) must have grown over the last 9 Gyr predominantly by redistribution of the disk into the bulge mass. Since all necessary stellar mass exists in galaxies at z = 1.4, no star formation or addition of external stellar material is required, but only a redistribution, e.g., induced by minor and major merging or through disk instabilities. Merging, in addition to redistributing mass in the galaxy, will add both BH and stellar/bulge mass, but does not change the overall final M {sub BH}/M {sub *,bulge} ratio. Since the overall cosmic stellar and BH mass buildup trace each other tightly over time, our scenario of bulge formation in massive galaxies is independent of any strong BH feedback and means that the mechanism coupling BH and bulge mass until the present is very indirect.« less

Spectroscopic classification of X-ray sources in the Galactic Bulge Survey

NASA Astrophysics Data System (ADS)

Wevers, T.; Torres, M. A. P.; Jonker, P. G.; Nelemans, G.; Heinke, C.; Mata Sánchez, D.; Johnson, C. B.; Gazer, R.; Steeghs, D. T. H.; Maccarone, T. J.; Hynes, R. I.; Casares, J.; Udalski, A.; Wetuski, J.; Britt, C. T.; Kostrzewa-Rutkowska, Z.; Wyrzykowski, Ł.

2017-10-01

We present the classification of 26 optical counterparts to X-ray sources discovered in the Galactic Bulge Survey. We use (time-resolved) photometric and spectroscopic observations to classify the X-ray sources based on their multiwavelength properties. We find a variety of source classes, spanning different phases of stellar/binary evolution. We classify CX21 as a quiescent cataclysmic variable (CV) below the period gap, and CX118 as a high accretion rate (nova-like) CV. CXB12 displays excess UV emission, and could contain a compact object with a giant star companion, making it a candidate symbiotic binary or quiescent low-mass X-ray binary (although other scenarios cannot be ruled out). CXB34 is a magnetic CV (polar) that shows photometric evidence for a change in accretion state. The magnetic classification is based on the detection of X-ray pulsations with a period of 81 ± 2 min. CXB42 is identified as a young stellar object, namely a weak-lined T Tauri star exhibiting (to date unexplained) UX Ori-like photometric variability. The optical spectrum of CXB43 contains two (resolved) unidentified double-peaked emission lines. No known scenario, such as an active galactic nucleus or symbiotic binary, can easily explain its characteristics. We additionally classify 20 objects as likely active stars based on optical spectroscopy, their X-ray to optical flux ratios and photometric variability. In four cases we identify the sources as binary stars.

Advances in stellar evolution; Proceedings of the Workshop on Stellar Ecology, Marciana Marina, Italy, June 23-29, 1996

NASA Astrophysics Data System (ADS)

Rood, R. T.; Renzini, A.

1997-01-01

The present volume on stellar evolution discusses fundamentals of stellar evolution and star clusters, variable stars, AGB stars and planetary nebulae, white dwarfs, binary star evolution, and stars in galaxies. Attention is given to the stellar population in the Galactic bulge, a photometric study of NGC 458, and HST observations of high-density globular clusters. Other topics addressed include the Cepheid instability strip in external galaxies, Hyades cluster white dwarfs and the initial-final mass relation, element diffusion in novae, mass function of the stars in the solar neighborhood, synthetic spectral indices for elliptical galaxies, and stars at the Galactic center.

Radial Velocities of RR Lyrae Stars in and around NGC 6441

NASA Astrophysics Data System (ADS)

Kunder, Andrea; Mills, Arthur; Edgecomb, Joseph; Thomas, Mathew; Schilter, Levi; Boyle, Craig; Parker, Stephen; Bellevue, Gordon; Rich, R. Michael; Koch, Andreas; Johnson, Christian I.; Nataf, David M.

2018-04-01

Detailed elemental abundance patterns of metal-poor ([Fe/H] ∼ ‑1 dex) stars in the Galactic bulge indicate that a number of them are consistent with globular cluster (GC) stars and may be former members of dissolved GCs. This would indicate that a few per cent of the Galactic bulge was built up from destruction and/or evaporation of GCs. Here, an attempt is made to identify such presumptive stripped stars originating from the massive, inner Galaxy GC NGC 6441 using its rich RR Lyrae variable star (RRL) population. We present radial velocities of 40 RRLs centered on the GC NGC 6441. All 13 of the RRLs observed within the cluster tidal radius have velocities consistent with cluster membership, with an average radial velocity of 24 ± 5 km s‑1 and a star-to-star scatter of 11 km s‑1. This includes two new RRLs that were previously not associated with the cluster. Eight RRLs with radial velocities consistent with cluster membership but up to three time the distance from the tidal radius are also reported. These potential extra-tidal RRLs also have exceptionally long periods, which is a curious characteristic of the NGC 6441 RRL population that hosts RRLs with periods longer than seen anywhere else in the Milky Way. As expected of stripped cluster stars, most are inline with the cluster’s orbit. Therefore, either the tidal radius of NGC 6441 is underestimated and/or we are seeing dissolving cluster stars stemming from NGC 6441 that are building up the old spheroidal bulge.

Self-consistent Bulge/Disk/Halo Galaxy Dynamical Modeling Using Integral Field Kinematics

NASA Astrophysics Data System (ADS)

Taranu, D. S.; Obreschkow, D.; Dubinski, J. J.; Fogarty, L. M. R.; van de Sande, J.; Catinella, B.; Cortese, L.; Moffett, A.; Robotham, A. S. G.; Allen, J. T.; Bland-Hawthorn, J.; Bryant, J. J.; Colless, M.; Croom, S. M.; D'Eugenio, F.; Davies, R. L.; Drinkwater, M. J.; Driver, S. P.; Goodwin, M.; Konstantopoulos, I. S.; Lawrence, J. S.; López-Sánchez, Á. R.; Lorente, N. P. F.; Medling, A. M.; Mould, J. R.; Owers, M. S.; Power, C.; Richards, S. N.; Tonini, C.

2017-11-01

We introduce a method for modeling disk galaxies designed to take full advantage of data from integral field spectroscopy (IFS). The method fits equilibrium models to simultaneously reproduce the surface brightness, rotation, and velocity dispersion profiles of a galaxy. The models are fully self-consistent 6D distribution functions for a galaxy with a Sérsic profile stellar bulge, exponential disk, and parametric dark-matter halo, generated by an updated version of GalactICS. By creating realistic flux-weighted maps of the kinematic moments (flux, mean velocity, and dispersion), we simultaneously fit photometric and spectroscopic data using both maximum-likelihood and Bayesian (MCMC) techniques. We apply the method to a GAMA spiral galaxy (G79635) with kinematics from the SAMI Galaxy Survey and deep g- and r-band photometry from the VST-KiDS survey, comparing parameter constraints with those from traditional 2D bulge-disk decomposition. Our method returns broadly consistent results for shared parameters while constraining the mass-to-light ratios of stellar components and reproducing the H I-inferred circular velocity well beyond the limits of the SAMI data. Although the method is tailored for fitting integral field kinematic data, it can use other dynamical constraints like central fiber dispersions and H I circular velocities, and is well-suited for modeling galaxies with a combination of deep imaging and H I and/or optical spectra (resolved or otherwise). Our implementation (MagRite) is computationally efficient and can generate well-resolved models and kinematic maps in under a minute on modern processors.

Pathway to the Galactic Distribution of Planets: Combined Spitzer and Ground-Based Microlens Parallax Measurements of 21 Single-Lens Events

NASA Technical Reports Server (NTRS)

Novati, S. Calchi; Gould, A.; Udalski, A.; Menzies, J. W.; Bond, I. A.; Shvartzvald, Y.; Street, R. A.; Hundertmark, M.; Beichman, C. A.; Barry, R. K.

2015-01-01

We present microlens parallax measurements for 21 (apparently) isolated lenses observed toward the Galactic bulge that were imaged simultaneously from Earth and Spitzer, which was approximately 1 Astronomical Unit west of Earth in projection. We combine these measurements with a kinematic model of the Galaxy to derive distance estimates for each lens, with error bars that are small compared to the Sun's galactocentric distance. The ensemble therefore yields a well-defined cumulative distribution of lens distances. In principle, it is possible to compare this distribution against a set of planets detected in the same experiment in order to measure the Galactic distribution of planets. Since these Spitzer observations yielded only one planet, this is not yet possible in practice. However, it will become possible as larger samples are accumulated.

Pathway to the Galactic Distribution of Planets: Combined Spitzer and Ground-Based Microlens Parallax Measurements of 21 Single-Lens Events

NASA Astrophysics Data System (ADS)

Calchi Novati, S.; Gould, A.; Udalski, A.; Menzies, J. W.; Bond, I. A.; Shvartzvald, Y.; Street, R. A.; Hundertmark, M.; Beichman, C. A.; Yee, J. C.; Carey, S.; Poleski, R.; Skowron, J.; Kozłowski, S.; Mróz, P.; Pietrukowicz, P.; Pietrzyński, G.; Szymański, M. K.; Soszyński, I.; Ulaczyk, K.; Wyrzykowski, Ł.; OGLE Collaboration; Albrow, M.; Beaulieu, J. P.; Caldwell, J. A. R.; Cassan, A.; Coutures, C.; Danielski, C.; Dominis Prester, D.; Donatowicz, J.; Lončarić, K.; McDougall, A.; Morales, J. C.; Ranc, C.; Zhu, W.; PLANET Collaboration; Abe, F.; Barry, R. K.; Bennett, D. P.; Bhattacharya, A.; Fukunaga, D.; Inayama, K.; Koshimoto, N.; Namba, S.; Sumi, T.; Suzuki, D.; Tristram, P. J.; Wakiyama, Y.; Yonehara, A.; MOA Collaboration; Maoz, D.; Kaspi, S.; Friedmann, M.; Wise Group; Bachelet, E.; Figuera Jaimes, R.; Bramich, D. M.; Tsapras, Y.; Horne, K.; Snodgrass, C.; Wambsganss, J.; Steele, I. A.; Kains, N.; RoboNet Collaboration; Bozza, V.; Dominik, M.; Jørgensen, U. G.; Alsubai, K. A.; Ciceri, S.; D'Ago, G.; Haugbølle, T.; Hessman, F. V.; Hinse, T. C.; Juncher, D.; Korhonen, H.; Mancini, L.; Popovas, A.; Rabus, M.; Rahvar, S.; Scarpetta, G.; Schmidt, R. W.; Skottfelt, J.; Southworth, J.; Starkey, D.; Surdej, J.; Wertz, O.; Zarucki, M.; MiNDSTEp Consortium; Gaudi, B. S.; Pogge, R. W.; DePoy, D. L.; μFUN Collaboration

2015-05-01

We present microlens parallax measurements for 21 (apparently) isolated lenses observed toward the Galactic bulge that were imaged simultaneously from Earth and Spitzer, which was ˜1 AU west of Earth in projection. We combine these measurements with a kinematic model of the Galaxy to derive distance estimates for each lens, with error bars that are small compared to the Sun’s galactocentric distance. The ensemble therefore yields a well-defined cumulative distribution of lens distances. In principle, it is possible to compare this distribution against a set of planets detected in the same experiment in order to measure the Galactic distribution of planets. Since these Spitzer observations yielded only one planet, this is not yet possible in practice. However, it will become possible as larger samples are accumulated.

Dark Kinetic Heating of Neutron Stars and an Infrared Window on WIMPs, SIMPs, and Pure Higgsinos

NASA Astrophysics Data System (ADS)

Baryakhtar, Masha; Bramante, Joseph; Li, Shirley Weishi; Linden, Tim; Raj, Nirmal

2017-09-01

We identify a largely model-independent signature of dark matter (DM) interactions with nucleons and electrons. DM in the local galactic halo, gravitationally accelerated to over half the speed of light, scatters against and deposits kinetic energy into neutron stars, heating them to infrared blackbody temperatures. The resulting radiation could potentially be detected by the James Webb Space Telescope, the Thirty Meter Telescope, or the European Extremely Large Telescope. This mechanism also produces optical emission from neutron stars in the galactic bulge, and x-ray emission near the galactic center because dark matter is denser in these regions. For GeV-PeV mass dark matter, dark kinetic heating would initially unmask any spin-independent or spin-dependent dark matter-nucleon cross sections exceeding 2 ×10-45 cm2, with improved sensitivity after more telescope exposure. For lighter-than-GeV dark matter, cross-section sensitivity scales inversely with dark matter mass because of Pauli blocking; for heavier-than-PeV dark matter, it scales linearly with mass as a result of needing multiple scatters for capture. Future observations of dark sector-warmed neutron stars could determine whether dark matter annihilates in or only kinetically heats neutron stars. Because inelastic interstate transitions of up to a few GeV would occur in relativistic scattering against nucleons, elusive inelastic dark matter like pure Higgsinos can also be discovered.

Dark Kinetic Heating of Neutron Stars and an Infrared Window on WIMPs, SIMPs, and Pure Higgsinos.

PubMed

Baryakhtar, Masha; Bramante, Joseph; Li, Shirley Weishi; Linden, Tim; Raj, Nirmal

2017-09-29

We identify a largely model-independent signature of dark matter (DM) interactions with nucleons and electrons. DM in the local galactic halo, gravitationally accelerated to over half the speed of light, scatters against and deposits kinetic energy into neutron stars, heating them to infrared blackbody temperatures. The resulting radiation could potentially be detected by the James Webb Space Telescope, the Thirty Meter Telescope, or the European Extremely Large Telescope. This mechanism also produces optical emission from neutron stars in the galactic bulge, and x-ray emission near the galactic center because dark matter is denser in these regions. For GeV-PeV mass dark matter, dark kinetic heating would initially unmask any spin-independent or spin-dependent dark matter-nucleon cross sections exceeding 2×10^{-45}  cm^{2}, with improved sensitivity after more telescope exposure. For lighter-than-GeV dark matter, cross-section sensitivity scales inversely with dark matter mass because of Pauli blocking; for heavier-than-PeV dark matter, it scales linearly with mass as a result of needing multiple scatters for capture. Future observations of dark sector-warmed neutron stars could determine whether dark matter annihilates in or only kinetically heats neutron stars. Because inelastic interstate transitions of up to a few GeV would occur in relativistic scattering against nucleons, elusive inelastic dark matter like pure Higgsinos can also be discovered.

Ordinary Dark Matter versus Mysterious Dark Matter in Galactic Rotation

NASA Astrophysics Data System (ADS)

Gallo, C. F.; Feng, James

2008-04-01

To theoretically describe the measured rotational velocity curves of spiral galaxies, there are two different approaches and conclusions. (1) ORDINARY DARK MATTER. We assume Newtonian gravity/dynamics and successfully find (via computer) mass distributions in bulge/disk configurations that duplicate the measured rotational velocities. There is ordinary dark matter within the galactic disk towards the cooler periphery which has lower emissivity/opacity. There are no mysteries in this scenario based on verified physics. (2) MYSTERIOUS DARK MATTER. Others INaccurately assume the galactic mass distributions follow the measured light distributions, and then the measured rotational velocity curves are NOT duplicated. To alleviate this discrepancy, speculations are invoked re ``Massive Peripheral Spherical Halos of Mysterious Dark Matter.'' But NO matter has been detected in this UNtenable Halo configuration. Many UNverified ``Mysteries'' are invoked as necessary and convenient. CONCLUSION. The first approach utilizing Newtonian gravity/dynamics and searching for the ordinary mass distributions within the galactic disk simulates reality and agrees with data.

The Profile of the Galactic Halo from Pan-STARRS1 3π RR Lyrae

NASA Astrophysics Data System (ADS)

Hernitschek, Nina; Cohen, Judith G.; Rix, Hans-Walter; Sesar, Branimir; Martin, Nicolas F.; Magnier, Eugene; Wainscoat, Richard; Kaiser, Nick; Tonry, John L.; Kudritzki, Rolf-Peter; Hodapp, Klaus; Chambers, Ken; Flewelling, Heather; Burgett, William

2018-05-01

We characterize the spatial density of the Pan-STARRS1 (PS1) sample of Rrab stars to study the properties of the old Galactic stellar halo. This sample, containing 44,403 sources, spans galactocentric radii of 0.55 kpc ≤ R gc ≤ 141 kpc with a distance precision of 3% and thus is able to trace the halo out to larger distances than most previous studies. After excising stars that are attributed to dense regions such as stellar streams, the Galactic disk and bulge, and halo globular clusters, the sample contains ∼11,000 sources within 20 kpc ≤ R gc ≤ 131 kpc. We then apply forward modeling using Galactic halo profile models with a sample selection function. Specifically, we use ellipsoidal stellar density models ρ(l, b, R gc) with a constant and a radius-dependent halo flattening q(R gc). Assuming constant flattening q, the distribution of the sources is reasonably well fit by a single power law with n={4.40}-0.04+0.05 and q={0.918}-0.014+0.016 and comparably well fit by an Einasto profile with n={9.53}-0.28+0.27, an effective radius r eff = 1.07 ± 0.10 kpc, and a halo flattening of q = 0.923 ± 0.007. If we allow for a radius-dependent flattening q(R gc), we find evidence for a distinct flattening of q ∼ 0.8 of the inner halo at ∼25 kpc. Additionally, we find that the south Galactic hemisphere is more flattened than the north Galactic hemisphere. The results of our work are largely consistent with many earlier results (e.g., Watkins et al.; Iorio et al.). We find that the stellar halo, as traced in RR Lyrae stars, exhibits a substantial number of further significant over- and underdensities, even after masking all known overdensities.

The star formation history of the Hubble sequence: spatially resolved colour distributions of intermediate-redshift galaxies in the Hubble Deep Field

NASA Astrophysics Data System (ADS)

Abraham, R. G.; Ellis, R. S.; Fabian, A. C.; Tanvir, N. R.; Glazebrook, K.

1999-03-01

We analyse the spatially resolved colours of distant galaxies of known redshift in the Hubble Deep Field, using a new technique based on matching resolved four-band colour data to the predictions of evolutionary synthesis models. Given some simplifying assumptions, we demonstrate how our technique is capable of probing the evolutionary history of high-redshift systems, noting the specific advantage of observing galaxies at an epoch closer to the time of their formation. We quantify the relative age, dispersion in age, on-going star formation rate and star formation history of distinct components. We explicitly test for the presence of dust and quantify its effect on our conclusions. To demonstrate the potential of the method, we study the spirals and ellipticals in the near-complete sample of 32 I_814<21.9 mag galaxies with z~0.5 studied by Bouwens, Broadhurst & Silk. The dispersion of the internal colours of a sample of 0.4

Active Galactic Nuclei in Dwarf Galaxies

NASA Astrophysics Data System (ADS)

Hein, Megan; Secrest, N.; Satyapal, S.

2014-01-01

Supermassive black holes (SMBHs) one million to a few billion times the mass of our sun are thought to reside in the center of most, if not all, bulge-dominated galaxies. It has been observed that the mass of these SMBHs is strongly correlated with the mass of these bulges, leading to the popular view that these central black holes are formed by galaxy mergers, which induce the growth of the galaxy's bulge and provide matter with which to feed the black hole. Although these properties and their possible consequences have been studied extensively in high mass galaxies and galaxies with large bulges, there is very little research on the possible existence and subsequent properties of SMBHs in low mass galaxies or galaxies with small or no central bulges. This is a significant weakness in the research of these objects as the study of this population of galaxies would allow us to gain valuable insight into SMBH seeds, black holes thought to have formed in the early universe. Strong X-rays are a good indicator of an accreting black hole, because they require more energy to produce and SMBHs are highly energetic, as well as being easier to see due to their ability to penetrate matter more easily than other forms of radiation. In this poster, I will present the results from an X-ray investigation using data matched from the Chandra X-ray observatory to a sample of low mass galaxies (with a mass of log(M) < 9).

The Secret Lives of Galaxies

NASA Technical Reports Server (NTRS)

2001-01-01

The ground-based image in visible light locates the hub imaged with the Hubble Space Telescope. This barred galaxy feeds material into its hub, igniting star birth. The Hubble NICMOS instrument penetrates beneath the dust to reveal clusters of young stars. Footage shows ground-based, WFPC2, and NICMOS images of NGS 1365. An animation of a large spiral galaxy zooms from the edge to the galactic bulge.

Microlensing Signature of Binary Black Holes

NASA Technical Reports Server (NTRS)

Schnittman, Jeremy; Sahu, Kailash; Littenberg, Tyson

2012-01-01

We calculate the light curves of galactic bulge stars magnified via microlensing by stellar-mass binary black holes along the line-of-sight. We show the sensitivity to measuring various lens parameters for a range of survey cadences and photometric precision. Using public data from the OGLE collaboration, we identify two candidates for massive binary systems, and discuss implications for theories of star formation and binary evolution.

Forming supermassive black holes by accreting dark and baryon matter

NASA Astrophysics Data System (ADS)

Hu, Jian; Shen, Yue; Lou, Yu-Qing; Zhang, Shuangnan

2006-01-01

Given a large-scale mixture of self-interacting dark matter (SIDM) particles and baryon matter distributed in the early Universe, we advance here a two-phase accretion scenario for forming supermassive black holes (SMBHs) with masses around ~109Msolar at high redshifts z(>~6). The first phase is conceived to involve a rapid quasi-spherical and quasi-steady Bondi accretion of mainly SIDM particles embedded with baryon matter on to seed black holes (BHs) created at redshifts z<~ 30 by the first generation of massive Population III stars; this earlier phase rapidly gives birth to significantly enlarged seed BH masses of during z~ 20-15, where σ0 is the cross-section per unit mass of SIDM particles and Cs is the velocity dispersion in the SIDM halo referred to as an effective `sound speed'. The second phase of BH mass growth is envisaged to proceed primarily via baryon accretion, eventually leading to SMBH masses of MBH~ 109Msolar such SMBHs may form either by z~ 6 for a sustained accretion at the Eddington limit or later at lower z for sub-Eddington mean accretion rates. In between these two phases, there is a transitional yet sustained diffusively limited accretion of SIDM particles which in an eventual steady state would be much lower than the accretion rates of the two main phases. We intend to account for the reported detections of a few SMBHs at early epochs, e.g. Sloan Digital Sky Survey (SDSS) 1148+5251 and so forth, without necessarily resorting to either super-Eddington baryon accretion or very frequent BH merging processes. Only extremely massive dark SIDM haloes associated with rare peaks of density fluctuations in the early Universe may harbour such early SMBHs or quasars. Observational consequences are discussed. During the final stage of accumulating a SMBH mass, violent feedback in circumnuclear environs of a galactic nucleus leads to the central bulge formation and gives rise to the familiar empirical MBH-σb correlation inferred for nearby normal galaxies with σb being the stellar velocity dispersion in the galactic bulge; in our scenario, the central SMBH formation precedes that of the galactic bulge.

Proper motions in the VVV Survey: Results for more than 15 million stars across NGC 6544

NASA Astrophysics Data System (ADS)

Contreras Ramos, R.; Zoccali, M.; Rojas, F.; Rojas-Arriagada, A.; Gárate, M.; Huijse, P.; Gran, F.; Soto, M.; Valcarce, A. A. R.; Estévez, P. A.; Minniti, D.

2017-12-01

Context. In the last six years, the VISTA Variable in the Vía Láctea (VVV) survey mapped 562 sq. deg. across the bulge and southern disk of the Galaxy. However, a detailed study of these regions, which includes 36 globular clusters (GCs) and thousands of open clusters is by no means an easy challenge. High differential reddening and severe crowding along the line of sight makes highly hamper to reliably distinguish stars belonging to different populations and/or systems. Aims: The aim of this study is to separate stars that likely belong to the Galactic GC NGC 6544 from its surrounding field by means of proper motion (PM) techniques. Methods: This work was based upon a new astrometric reduction method optimized for images of the VVV survey. Results: PSF-fitting photometry over the six years baseline of the survey allowed us to obtain a mean precision of 0.51 mas yr-1, in each PM coordinate, for stars with Ks< 15 mag. In the area studied here, cluster stars separate very well from field stars, down to the main sequence turnoff and below, allowing us to derive for the first time the absolute PM of NGC 6544. Isochrone fitting on the clean and differential reddening corrected cluster color magnitude diagram yields an age of 11-13 Gyr, and metallicity [Fe/H] =-1.5 dex, in agreement with previous studies restricted to the cluster core. We were able to derive the cluster orbit assuming an axisymmetric model of the Galaxy and conclude that NGC 6544 is likely a halo GC. We have not detected tidal tail signatures associated to the cluster, but a remarkable elongation in the galactic center direction has been found. The precision achieved in the PM determination also allows us to separate bulge stars from foreground disk stars, enabling the kinematical selection of bona fide bulge stars across the whole survey area. Conclusions: Kinematical techniques are a fundamental step toward disentangling different stellar populations that overlap in a studied field. Our results show that VVV data is perfectly suitable for this kind of analysis. Based on observations taken with ESO telescopes at Paranal Observatory under programme IDs 179.B-2002.

Failed Radiatively Accelerated Dusty Outflow Model of the Broad Line Region in Active Galactic Nuclei. I. Analytical Solution

NASA Astrophysics Data System (ADS)

Czerny, B.; Li, Yan-Rong; Hryniewicz, K.; Panda, S.; Wildy, C.; Sniegowska, M.; Wang, J.-M.; Sredzinska, J.; Karas, V.

2017-09-01

The physical origin of the broad line region in active galactic nuclei is still unclear despite many years of observational studies. The reason is that the region is unresolved, and the reverberation mapping results imply a complex velocity field. We adopt a theory-motivated approach to identify the principal mechanism responsible for this complex phenomenon. We consider the possibility that the role of dust is essential. We assume that the local radiation pressure acting on the dust in the accretion disk atmosphere launches the outflow of material, but higher above the disk the irradiation from the central parts causes dust evaporation and a subsequent fallback. This failed radiatively accelerated dusty outflow is expected to represent the material forming low ionization lines. In this paper we formulate simple analytical equations to describe the cloud motion, including the evaporation phase. The model is fully described just by the basic parameters of black hole mass, accretion rate, black hole spin, and viewing angle. We study how the spectral line generic profiles correspond to this dynamic. We show that the virial factor calculated from our model strongly depends on the black hole mass in the case of enhanced dust opacity, and thus it then correlates with the line width. This could explain why the virial factor measured in galaxies with pseudobulges differs from that obtained from objects with classical bulges, although the trend predicted by the current version of the model is opposite to the observed trend.

STUDYING THE INTERSTELLAR MEDIUM AND THE INNER REGION OF NPS/LOOP 1 WITH SHADOW OBSERVATIONS TOWARD MBM36

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ursino, E.; Galeazzi, M.; Liu, W., E-mail: galeazzi@physics.miami.edu

2016-01-01

We analyzed data from a shadow observation of the high density molecular cloud MBM36 (l ∼ 4°, b ∼ 35°) with Suzaku. MBM36 is located in a region that emits relatively weakly in the 3/4 keV band compared to the surrounding North Polar Spur (NPS)/Loop 1 structure and the Galactic Bulge (GB). The contrast between high and low density targets in the MBM36 area allows one to separate the local and distant contributors to the soft diffuse X-ray background, providing a much better characterization of the individual components compared to single pointing observations. We identify two non-local thermal components, one at kT ≈ 0.12 keV andmore » one at kT ≈ 0.29 keV. The colder component matches well with models of emission from the higher latitude region of the GB. The emission of the warmer component is in agreement with models predicting that the NPS is due to a hypershell from the center of the Milky Way. Geometrical and pressure calculations rule out a nearby bubble as responsible for the emission associated with the NPS. Any Galactic Halo/circumgalactic halo emission, if present, is outshined by the other components. We also report an excess emission around 0.9 keV, likely due to an overabundance of Ne ix.« less

Metallicity-dependent kinematics and morphology of the Milky Way bulge

NASA Astrophysics Data System (ADS)

Athanassoula, E.; Rodionov, S. A.; Prantzos, N.

2017-05-01

We use N-body chemo-dynamic simulations to study the coupling between morphology, kinematics and metallicity of the bar/bulge region of our Galaxy. We make qualitative comparisons of our results with available observations and find very good agreement. We conclude that this region is complex, since it comprises several stellar components with different properties - I.e. a boxy/peanut bulge, thin and thick disc components, and, to lesser extents, a disky pseudo-bulge, a stellar halo and a small classical bulge - all cohabiting in dynamical equilibrium. Our models show strong links between kinematics and metallicity, or morphology and metallicity, as already suggested by a number of recent observations. We discuss and explain these links.

JASMINE: galactic structure surveyor

NASA Astrophysics Data System (ADS)

Gouda, Naoteru; Kobayashi, Yukiyasu; Yamada, Yoshiyuki; Yano, Taihei; Tsujimoto, Takuji; Suganuma, Masahiro; Niwa, Yoshito; Yamauchi, Masahiro; Kawakatsu, Yasuhiro; Matsuhara, Hideo; Noda, Atsushi; Tsuiki, Atsuo; Utashima, Masayoshi; Ogawa, Akira

2006-06-01

We introduce a Japanese plan of infrared(z-band:0.9μm) space astrometry(JASMINE-project). JASMINE is the satellite (Japan Astrometry Satellite Mission for INfrared Exploration) which will measure distances and apparent motions of stars around the center of the Milky Way with yet unprecedented precision. It will measure parallaxes, positions with the accuracy of 10 micro-arcsec and proper motions with the accuracy of ~ 4microarcsec/ year for stars brighter than z=14mag. JASMINE can observe about ten million stars belonging to the bulge components of our Galaxy, which are hidden by the interstellar dust extinction in optical bands. Number of stars with σ/π < 0.1 in the direction of the Galactic central bulge is about 1000 times larger than those observed in optical bands, where π is a parallax and σ is an error of the parallax. With the completely new "map of the bulge in the Milky Way", it is expected that many new exciting scientific results will be obtained in various fields of astronomy. Presently, JASMINE is in a development phase, with a target launch date around 2015. We adopt the following instrument design of JASMINE in order to get the accurate positions of many stars. A 3-mirrors optical system(modified Korsch system)with a primary mirror of~ 0.85m is one of the candidate for the optical system. On the astro-focal plane, we put dozens of new type of CCDs for z-band to get a wide field of view. The accurate measurements of the astrometric parameters requires the instrument line-of-sight highly stability and the opto-mechanical highly stability of the payload in the JASMINE spacecraft. The consideration of overall system(bus) design is now going on in cooperation with Japan Aerospace Exploration Agency(JAXA).

GalMod: A Galactic Synthesis Population Model

NASA Astrophysics Data System (ADS)

Pasetto, Stefano; Grebel, Eva K.; Chiosi, Cesare; Crnojević, Denija; Zeidler, Peter; Busso, Giorgia; Cassarà, Letizia P.; Piovan, Lorenzo; Tantalo, Rosaria; Brogliato, Claudio

2018-06-01

We present a new Galaxy population synthesis Model, GalMod. GalMod is a star-count model featuring an asymmetric bar/bulge as well as spiral arms and related extinction. The model, initially introduced in Pasetto et al., has been here completed with a central bar, a new bulge description, new disk vertical profiles, and several new bolometric corrections. The model can generate synthetic mock catalogs of visible portions of the Milky Way, external galaxies like M31, or N-body simulation initial conditions. At any given time, e.g., at a chosen age of the Galaxy, the model contains a sum of discrete stellar populations, namely the bulge/bar, disk, and halo. These populations are in turn the sum of different components: the disk is the sum of the spiral arms, thin disks, a thick disk, and various gas components, while the halo is the sum of a stellar component, a hot coronal gas, and a dark-matter component. The Galactic potential is computed from these population density profiles and used to generate detailed kinematics by considering up to the first four moments of the collisionless Boltzmann equation. The same density profiles are then used to define the observed color–magnitude diagrams in a user-defined field of view (FoV) from an arbitrary solar location. Several photometric systems have been included and made available online, and no limits on the size of the FoV are imposed thus allowing full-sky simulations, too. Finally, we model the extinction by adopting a dust model with advanced ray-tracing solutions. The model's Web page (and tutorial) can be accessed at www.GalMod.org and support is provided at Galaxy.Model@yahoo.com.

Spectroscopic study of the elusive globular cluster ESO452-SC11 and its surroundings

NASA Astrophysics Data System (ADS)

Koch, Andreas; Hansen, Camilla Juul; Kunder, Andrea

2017-08-01

Globular clusters (GCs) have long been recognized as being amongst the oldest objects in the Galaxy. As such, they have the potential of playing a pivotal role in deciphering the Milky Way's early history. Here we present the first spectroscopic study of the low-mass system ESO452-SC11 using the AAOmega multifibre spectrograph at medium resolution. Given the stellar sparsity of this object and the high degree of foreground contamination due to its location toward the Galactic bulge, very few details are known for this cluster - there is no consensus, for instance, about its age, metallicity, or its association with the disk or bulge. We identify five member candidates based on common radial velocity, calcium-triplet metallicity, and position within the GC. Using spectral synthesis, the measurement of accurate Fe-abundances from Fe-lines, and abundances of several α-, Fe-peak, and neutron-capture elements (Si, Ca, Ti,Cr, Co, Ni, Sr, and Eu) is carried out, albeit with large uncertainties. We find that two of the five cluster candidates are likely non-members, as they have deviating iron abundances and [α/Fe] ratios. The cluster mean heliocentric velocity is 19 ± 2 km s-1 with a velocity dispersion of 2.8 ± 3.4 km s-1, a low value in line with its sparse nature and low mass. The mean Fe-abundance from spectral fitting is -0.88 ± 0.03 dex, where the spread is driven by observational errors. Furthermore, the α-elements of the GC candidates are marginally lower than expected for the bulge at similar metallicities. As spectra of hundreds of stars were collected in a 2-degree field centered on ESO452-SC11, a detailed abundance study of the surrounding field was also enabled. The majority of the non-members have slightly higher [α/Fe] ratios, in line with the typical nearby bulge population. A subset of the spectra with measured Fe-peak abundance ratios shows a large scatter around solar values, albeit with large uncertainties. Furthermore, our study provides the first systematic measurements of strontium abundances in a Galactic bulge GC. Here, the Eu and Sr abundances of the GC candidates are broadly consistent with a disk or bulge association. Recent proper motions and our orbital calculations place ESO452 on an elliptical orbit in the central 3 kpc of the Milky Way, establishing a firm connection with the bulge. Finally, while the radial velocities and preferential position of a dozen of stars outside the GC radius appear to imply the presence of extra-tidal stars, their significantly different chemical composition refutes this hypothesis. Full Tables 2-5 are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/604/A41

Tidal Disruption Event Host Galaxies in the Context of the Local Galaxy Population

NASA Astrophysics Data System (ADS)

Law-Smith, Jamie; Ramirez-Ruiz, Enrico; Ellison, Sara L.; Foley, Ryan J.

2017-11-01

We study the properties of tidal disruption event (TDE) host galaxies in the context of a catalog of ˜500,000 galaxies from the Sloan Digital Sky Survey. We explore whether selection effects can account for the overrepresentation of TDEs in E+A/post-starburst galaxies by creating matched galaxy samples. Accounting for possible selection effects due to black hole (BH) mass, redshift completeness, strong active galactic nucleus presence, bulge colors, and surface brightness can reduce the apparent overrepresentation of TDEs in E+A host galaxies by a factor of ˜4 (from ˜×100-190 to ˜×25-48), but cannot fully explain the preference. We find that TDE host galaxies have atypical photometric properties compared to similar, “typical” galaxies. In particular, TDE host galaxies tend to live in or near the “green valley” between star-forming and passive galaxies, and have bluer bulge colors ({{Δ }}(g-r)≈ 0.3 mag), lower half-light surface brightnesses (by ˜1 mag/arcsec2), higher Sérsic indices ({{Δ }}{n}{{g}}≈ 3), and higher bulge-to-total-light ratios ({{Δ }}B/T≈ 0.5) than galaxies with matched BH masses. We find that TDE host galaxies appear more centrally concentrated and that all have high galaxy Sérsic indices and B/T fractions—on average in the top 10% of galaxies of the same BH mass—suggesting a higher nuclear stellar density. We identify a region in the Sérsic index and BH mass parameter space that contains ˜2% of our reference catalog galaxies but ≥slant 60 % of TDE host galaxies. The unique photometric properties of TDE host galaxies may be useful for selecting candidate TDEs for spectroscopic follow-up observations in large transient surveys.

The suppression of star formation by powerful active galactic nuclei.

PubMed

Page, M J; Symeonidis, M; Vieira, J D; Altieri, B; Amblard, A; Arumugam, V; Aussel, H; Babbedge, T; Blain, A; Bock, J; Boselli, A; Buat, V; Castro-Rodríguez, N; Cava, A; Chanial, P; Clements, D L; Conley, A; Conversi, L; Cooray, A; Dowell, C D; Dubois, E N; Dunlop, J S; Dwek, E; Dye, S; Eales, S; Elbaz, D; Farrah, D; Fox, M; Franceschini, A; Gear, W; Glenn, J; Griffin, M; Halpern, M; Hatziminaoglou, E; Ibar, E; Isaak, K; Ivison, R J; Lagache, G; Levenson, L; Lu, N; Madden, S; Maffei, B; Mainetti, G; Marchetti, L; Nguyen, H T; O'Halloran, B; Oliver, S J; Omont, A; Panuzzo, P; Papageorgiou, A; Pearson, C P; Pérez-Fournon, I; Pohlen, M; Rawlings, J I; Rigopoulou, D; Riguccini, L; Rizzo, D; Rodighiero, G; Roseboom, I G; Rowan-Robinson, M; Sánchez Portal, M; Schulz, B; Scott, D; Seymour, N; Shupe, D L; Smith, A J; Stevens, J A; Trichas, M; Tugwell, K E; Vaccari, M; Valtchanov, I; Viero, M; Vigroux, L; Wang, L; Ward, R; Wright, G; Xu, C K; Zemcov, M

2012-05-09

The old, red stars that constitute the bulges of galaxies, and the massive black holes at their centres, are the relics of a period in cosmic history when galaxies formed stars at remarkable rates and active galactic nuclei (AGN) shone brightly as a result of accretion onto black holes. It is widely suspected, but unproved, that the tight correlation between the mass of the black hole and the mass of the stellar bulge results from the AGN quenching the surrounding star formation as it approaches its peak luminosity. X-rays trace emission from AGN unambiguously, whereas powerful star-forming galaxies are usually dust-obscured and are brightest at infrared and submillimetre wavelengths. Here we report submillimetre and X-ray observations that show that rapid star formation was common in the host galaxies of AGN when the Universe was 2-6 billion years old, but that the most vigorous star formation is not observed around black holes above an X-ray luminosity of 10(44) ergs per second. This suppression of star formation in the host galaxy of a powerful AGN is a key prediction of models in which the AGN drives an outflow, expelling the interstellar medium of its host and transforming the galaxy's properties in a brief period of cosmic time.

The Suppression of Star Formation by Powerful Active Galactic Nuclei

NASA Technical Reports Server (NTRS)

Dwek, E.

2012-01-01

The old, red stars that constitute the bulges of galaxies, and the massive black holes at their centres, are the relics of a period in cosmic history when galaxies formed stars at remarkable rates and active galactic nuclei (AGN) shone brightly as a result of accretion onto black holes. It is widely suspected, but unproved, that the tight corre1ation between the mass of the black hole and the mas. of the stellar bulge results from the AGN quenching the surrounding star formation as it approaches its peak luminosity. X-rays trace emission from AGN unambiguously, whereas powerful star-forming ga1axies are usually dust-obscured and are brightest at infrared and submillimeter wavelengths. Here we report submillimetre and X-ray observations that show that rapid star formation was common in the host galaxies of AGN when the Universe was 2-6 billion years old, but that the most vigorous star formation is not observed around black holes above an X-ray luminosity of 10(exp 44) ergs per second. This suppression of star formation in the host galaxy of a powerful AGN is a key prediction of models in which the AGN drives an outflow, expe11ing the interstellar medium of its host and transforming the galaxy's properties in a brief period of cosmic time.

What Turns Galaxies Off? the Different Morphologies of Star-Forming and Quiescent Galaxies Since z Approximates 2 from CANDELS

NASA Technical Reports Server (NTRS)

Bell, Eric F.; VanDerWel, Arjen; Papovich, Casey; Kocevski, Dale; Lotz, Jennifer; McIntosh, Daniel H.; Kartaltepe, Jeyhan; Faber, S. M.; Ferguson, Harry; Koekemoer, Anton;

Finding A Planet Through the Dust

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-05-01

Finding planets in the crowded galactic center is a difficult task, but infrared microlensing surveys give us a fighting chance! Preliminary results from such a study have already revealed a new exoplanet lurking in the dust of the galactic bulge.Detection BiasesUKIRT-2017 microlensing survey fields (blue), plotted over a map showing the galactic-plane dust extinction. The location of the newly discovered giant planet is marked with blue crosshairs. [Shvartzvald et al. 2018]Most exoplanets weve uncovered thus far were found either via transits dips in a stars light as the planet passes in front of its host star or via radial velocity wobbles of the star as the orbiting planet tugs on it. These techniques, while highly effective, introduce a selection bias in the types of exoplanets we detect: both methods tend to favor discovery of close-in, large planets orbiting small stars; these systems produce the most easily measurable signals on short timescales.For this reason, microlensing surveys for exoplanets have something new to add to the field.Search for a LensIn gravitational microlensing, we observe a background star as it is briefly magnified by a passing foreground star acting as a lens. If that foreground star hosts a planet, we observe a characteristic shape in the observed brightening of the background star, and the properties of that shape can reveal information about the foreground planet.A diagram of how planets are detected via gravitational microlensing. The detectable planet is in orbit around the foreground lens star. [NASA]This technique for planet detection is unique in its ability to explore untapped regions of exoplanet parameter space with microlensing, we can survey for planets around all different types of stars (rather than primarily small, dim ones), planets of all masses near the further-out snowlines where gas and ice giants are likely to form, and even free-floating planets.In a new study led by a Yossi Shvartzvald, a NASA postdoctoral fellow at the Jet Propulsion Laboratory (JPL), a team of scientists now presents preliminary results from a near-infrared microlensing survey conducted with the United Kingdom Infrared Telescope (UKIRT) in Hawaii. Though the full study has not yet been published, the team reports on their first outcome: the detection of a giant planet in the galactic bulge.Giant Planet FoundThe light curve of UKIRT-2017-BLG-001. The inset shows a close-up of the anomaly in the curve, produced by the presence of the planet. [Shvartzvald et al. 2018]UKIRT-2017-BLG-001 is a giant planet detected at an angle of just 0.35 from the dusty, crowded Galactic center. It suffers from a high degree of extinction, implying that this planet could only have been detected via a near-infrared survey. The mass ratio of UKIRT-2017-BLG-001 to its host star is about 1.5 times that of Jupiter to the Sun, and its host star appears to be about 80% the mass of the Sun.The starplanet pair is roughly 20,500 light-years from us, which likely places it in the galactic bulge. Intriguingly, evidence suggests that the source star the star that the foreground starplanet lensed lies in the far galactic disk. If this is true, this would be the first source star of a microlensing event to be identified as belonging to the far disk.Artists impression of the WFIRST mission. [NASA]Looking AheadWhats next for microlensing exoplanet studies? The goal of the UKIRT near-infrared microlensing survey isnt just to discover planets its to characterize the exoplanet occurrence rates in different parts of the galaxy to inform future surveys.In particular, the UKIRT survey explored potential fields for the upcoming Wide Field Infrared Survey Telescope (WFIRST) mission, slated to launch in the mid-2020s. This powerful space telescope stands to vastly expand the reach of infrared microlensing detection, broadly surveying our galaxy for planets hiding in the dust.CitationY. Shvartzvald et al 2018 ApJL 857 L8. doi:10.3847/2041-8213/aab71b

Millisecond pulsars and the Galactic Center gamma-ray excess: the importance of luminosity function and secondary emission

NASA Astrophysics Data System (ADS)

Petrović, Jovana; Serpico, Pasquale D.; Zaharijas, Gabrijela

2015-02-01

Several groups of authors have analyzed Fermi LAT data in a region around the Galactic Center finding an unaccounted gamma-ray excess over diffuse backgrounds in the GeV energy range. It has been argued that it is difficult or even impossible to explain this diffuse emission by the leading astrophysical candidates—millisecond pulsars (MSPs). Here we provide a new estimate of the contribution to the excess by a population of yet unresolved MSP located in the bulge of the Milky Way. We simulate this population with the GALPLOT package by adopting a parametric approach, with the range of free parameters gauged on the MSP characteristics reported by the second pulsar catalogue (2PC). We find that the conclusions strongly depend on the details of the MSP luminosity function (in particular, its high luminosity end) and other explicit or tacit assumptions on the MSP statistical properties, which we discuss. Notably, for the first time we study the importance of the possible secondary emission of the MSPs in the Galactic Center, i.e. the emission via inverse Compton losses of electrons injected in the interstellar medium. Differently from a majority of other authors, we find that within current uncertainties a large if not dominant contribution of MSPs to the excess cannot be excluded. We also show that the sensitivities of future instruments or possibly already of the latest LAT data analysis (Pass 8) provide good perspectives to test this scenario by resolving a significant number of MSPs.

A model of the 8-25 micron point source infrared sky

NASA Technical Reports Server (NTRS)

Wainscoat, Richard J.; Cohen, Martin; Volk, Kevin; Walker, Helen J.; Schwartz, Deborah E.

1992-01-01

We present a detailed model for the IR point-source sky that comprises geometrically and physically realistic representations of the Galactic disk, bulge, stellar halo, spiral arms (including the 'local arm'), molecular ring, and the extragalactic sky. We represent each of the distinct Galactic components by up to 87 types of Galactic source, each fully characterized by scale heights, space densities, and absolute magnitudes at BVJHK, 12, and 25 microns. The model is guided by a parallel Monte Carlo simulation of the Galaxy at 12 microns. The content of our Galactic source table constitutes a good match to the 12 micron luminosity function in the simulation, as well as to the luminosity functions at V and K. We are able to produce differential and cumulative IR source counts for any bandpass lying fully within the IRAS Low-Resolution Spectrometer's range (7.7-22.7 microns as well as for the IRAS 12 and 25 micron bands. These source counts match the IRAS observations well. The model can be used to predict the character of the point source sky expected for observations from IR space experiments.

One more neighbor: The first brown dwarf in the VVV survey

NASA Astrophysics Data System (ADS)

Beamín, J. C.; Minniti, D.; Gromadzki, M.; Kurtev, R.; Ivanov, V. D.; Beletsky, Y.; Lucas, P.; Saito, R. K.; Borissova, J.

2013-09-01

Context. The discovery of brown dwarfs (BDs) in the solar neighborhood and young star clusters has helped to constraint the low-mass end of the stellar mass function and the initial mass function. We use data of the Vista Variables in the Vía Láctea (VVV), a near-infrared (NIR) multi-wavelength (ZYJHKs) multi-epoch (Ks) ESO Public Survey mapping the Milky Way bulge and southern Galactic plane to search for nearby BDs. Aims: The ultimate aim of the project is to improve the completeness of the census of nearby stellar and substellar objects towards the Galactic bulge and inner disk regions. Methods: Taking advantage of the homogeneous sample of VVV multi-epoch data, we identified stars with high proper motion ( ≥ 0.1'' yr-1), and then selected low-mass objects using NIR colors. We searched for a possible parallax signature using the all available Ks band epochs. We set some constraints on the month-to-year scale Ks band variability of our candidates, and even searched for possible transiting companions. We obtained NIR spectra to properly classify spectral type and then the physical properties of the final list of candidates. Results: We report the discovery of VVV BD001, a new member of the local volume-limited sample (within 20 pc from the Sun) with well defined proper motion, distance, and luminosity. The spectral type of this new object is an L5 ± 1, unusually blue dwarf. The proper motion for this BD is PM(α) = -0.5455 ± 0.004'' yr-1, PM(δ) = -0.3255 ± 0.004'' yr-1, and it has a parallax of 57 ± 4 mas which translates into a distance of 17.5 ± 1.1 pc. VVV BD001 shows no evidence of variability (ΔKs < 0.05 mag) over two years, especially constrained on a six month scale during the year 2012. Based on observations taken within the ESO VISTA Public Survey VVV, Programme ID 179.B-2002.

Tube Bulge Process : Theoretical Analysis and Finite Element Simulations

NASA Astrophysics Data System (ADS)

Velasco, Raphael; Boudeau, Nathalie

2007-05-01

This paper is focused on the determination of mechanics characteristics for tubular materials, using tube bulge process. A comparative study is made between two different models: theoretical model and finite element analysis. The theoretical model is completely developed, based first on a geometrical analysis of the tube profile during bulging, which is assumed to strain in arc of circles. Strain and stress analysis complete the theoretical model, which allows to evaluate tube thickness and state of stress, at any point of the free bulge region. Free bulging of a 304L stainless steel is simulated using Ls-Dyna 970. To validate FE simulations approach, a comparison between theoretical and finite elements models is led on several parameters such as: thickness variation at the free bulge region pole with bulge height, tube thickness variation with z axial coordinate, and von Mises stress variation with plastic strain. Finally, the influence of geometrical parameters deviations on flow stress curve is observed using analytical model: deviations of the tube outer diameter, its initial thickness and the bulge height measurement are taken into account to obtain a resulting error on plastic strain and von Mises stress.

On the nature of the barlens component in barred galaxies: what do boxy/peanut bulges look like when viewed face-on?

NASA Astrophysics Data System (ADS)

Athanassoula, E.; Laurikainen, E.; Salo, H.; Bosma, A.

2015-12-01

Barred galaxies have interesting morphological features whose presence and properties set constraints on galactic evolution. Here we examine barlenses, i.e. lens-like components whose extent along the bar major axis is shorter than that of the bar and whose outline is oval or circular. We identify and analyse barlenses in N-body plus SPH simulations, compare them extensively with those from the NIRS0S (Near-IR S0 galaxy Survey) and the S4G samples (Spitzer Survey of Stellar Structure in Galaxies) and find very good agreement. We observe barlenses in our simulations from different viewing angles. This reveals that barlenses are the vertically thick part of the bar seen face-on, i.e. a barlens seen edge-on is a boxy/peanut/X bulge. In morphological studies, and in the absence of kinematics or photometry, a barlens, or part of it, may be mistaken for a classical bulge. Thus the true importance of classical bulges, both in numbers and mass, is smaller than currently assumed, which has implications for galaxy formation studies. Finally, using the shape of the isodensity curves, we propose a rule of thumb for measuring the barlens extent along the bar major axis of moderately inclined galaxies, thus providing an estimate of which part of the bar is thicker.

Tick, Tock, Tick, Tock...

NASA Astrophysics Data System (ADS)

Evans, N. W.; Molloy, M.

2014-07-01

The Gaia dataset will require a huge leap forward in terms of modelling of the Milky Way. Two problems are highlighted here. First, models of the Galactic Bar remain primitive as compared to the Galactic Disk and Stellar Halo. Although Schwarzschild and N-body methods are useful, the future belongs to Made-to-Measure (M2M) models which have significant advantages in terms of storage and flexibility. Second, the Milky Way potential will need much better representation than hitherto. Most models still use very simple building blocks (Miyamoto-Nagai disks or Hernquist bulges) and these will not be fit for purpose in the Gaia Era. Expansions in terms of basis functions offer the possibility of incorporating cosmological information as priors, as well as mych greater adaptability.

An infrared sky model based on the IRAS point source data

NASA Technical Reports Server (NTRS)

Cohen, Martin; Walker, Russell; Wainscoat, Richard; Volk, Kevin; Walker, Helen; Schwartz, Deborah

1990-01-01

A detailed model for the infrared point source sky is presented that comprises geometrically and physically realistic representations of the galactic disk, bulge, spheroid, spiral arms, molecular ring, and absolute magnitudes. The model was guided by a parallel Monte Carlo simulation of the Galaxy. The content of the galactic source table constitutes an excellent match to the 12 micrometer luminosity function in the simulation, as well as the luminosity functions at V and K. Models are given for predicting the density of asteroids to be observed, and the diffuse background radiance of the Zodiacal cloud. The model can be used to predict the character of the point source sky expected for observations from future infrared space experiments.

Quantifying the (X/peanut)-shaped structure of the Milky Way - new constraints on the bar geometry

NASA Astrophysics Data System (ADS)

Ciambur, Bogdan C.; Graham, Alister W.; Bland-Hawthorn, Joss

2017-11-01

The nature, size and orientation of the Milky Way's bar and `bulge' have been the subject of conflicting interpretations in the literature. Here, we present a novel approach to inferring the properties of the long bar, which extends beyond the inner `bulge', by using information encoded in the Galaxy's X/peanut (X/P)-shaped structure. We perform a quantitative analysis of the X/P feature seen in WISE wide-field images, at 3.4 and 4.6 μm, by measuring the deviations of the isophotes from pure ellipses and using the radial profile of their sixth-order Fourier harmonic (cosine term, B6). In addition to the vertical height and integrated `strength' of the observed X/P instability, we report an intrinsic radius RΠ,int = 1.67 ± 0.27 kpc, and an orientation angle of α = 37°+7°-10° with respect to our line of sight to the Galactic Centre. Based on X/P structures observed in other galaxies, we assume that the Milky Way's X/P structure is intrinsically symmetric, aligned with the long Galactic bar, and that its size is correlated with this bar. The implications for the Galactic bar are that it is oriented at a 37° angle and has a radius of ≈4.2 kpc, but possibly as low as ≈3.2 kpc. We have investigated how the Milky Way's X/P structure compares with analogues in other galaxies, and find that it is consistent with recently established scaling relations, though with a marginally stronger X/P instability than expected. We additionally perform a photometric decomposition of the Milky Way's major axis surface brightness profile, accounting for spiral structure, and determine an average disc scalelength of h = 2.54 ± 0.16 kpc.

BINARY ASTROMETRIC MICROLENSING WITH GAIA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sajadian, Sedighe, E-mail: sajadian@ipm.ir; Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran

2015-04-15

We investigate whether or not Gaia can specify the binary fractions of massive stellar populations in the Galactic disk through astrometric microlensing. Furthermore, we study whether or not some information about their mass distributions can be inferred via this method. In this regard, we simulate the binary astrometric microlensing events due to massive stellar populations according to the Gaia observing strategy by considering (i) stellar-mass black holes, (ii) neutron stars, (iii) white dwarfs, and (iv) main-sequence stars as microlenses. The Gaia efficiency for detecting the binary signatures in binary astrometric microlensing events is ∼10%–20%. By calculating the optical depth duemore » to the mentioned stellar populations, the numbers of the binary astrometric microlensing events being observed with Gaia with detectable binary signatures, for the binary fraction of about 0.1, are estimated to be 6, 11, 77, and 1316, respectively. Consequently, Gaia can potentially specify the binary fractions of these massive stellar populations. However, the binary fraction of black holes measured with this method has a large uncertainty owing to a low number of the estimated events. Knowing the binary fractions in massive stellar populations helps with studying the gravitational waves. Moreover, we investigate the number of massive microlenses for which Gaia specifies masses through astrometric microlensing of single lenses toward the Galactic bulge. The resulting efficiencies of measuring the mass of mentioned populations are 9.8%, 2.9%, 1.2%, and 0.8%, respectively. The numbers of their astrometric microlensing events being observed in the Gaia era in which the lens mass can be inferred with the relative error less than 0.5 toward the Galactic bulge are estimated as 45, 34, 76, and 786, respectively. Hence, Gaia potentially gives us some information about the mass distribution of these massive stellar populations.« less

Failed Radiatively Accelerated Dusty Outflow Model of the Broad Line Region in Active Galactic Nuclei. I. Analytical Solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Czerny, B.; Panda, S.; Wildy, C.

2017-09-10

The physical origin of the broad line region in active galactic nuclei is still unclear despite many years of observational studies. The reason is that the region is unresolved, and the reverberation mapping results imply a complex velocity field. We adopt a theory-motivated approach to identify the principal mechanism responsible for this complex phenomenon. We consider the possibility that the role of dust is essential. We assume that the local radiation pressure acting on the dust in the accretion disk atmosphere launches the outflow of material, but higher above the disk the irradiation from the central parts causes dust evaporationmore » and a subsequent fallback. This failed radiatively accelerated dusty outflow is expected to represent the material forming low ionization lines. In this paper we formulate simple analytical equations to describe the cloud motion, including the evaporation phase. The model is fully described just by the basic parameters of black hole mass, accretion rate, black hole spin, and viewing angle. We study how the spectral line generic profiles correspond to this dynamic. We show that the virial factor calculated from our model strongly depends on the black hole mass in the case of enhanced dust opacity, and thus it then correlates with the line width. This could explain why the virial factor measured in galaxies with pseudobulges differs from that obtained from objects with classical bulges, although the trend predicted by the current version of the model is opposite to the observed trend.« less

Human platelet lysate versus minoxidil stimulates hair growth by activating anagen promoting signaling pathways.

PubMed

Dastan, Maryam; Najafzadeh, Nowruz; Abedelahi, Ali; Sarvi, Mohammadreza; Niapour, Ali

2016-12-01

Minoxidil and human platelet lysate (HPL) are commonly used to treat patients with hair loss. However, the roles of HPL versus minoxidil in hair follicle biology largely remain unknown. Here, we hypothesized that bulge and dermal papilla (DP) cells may express specific genes, including Kras, Erk, Akt, Shh and β-catenin after exposure to minoxidil or HPL. The mouse hair follicles were isolated on day 10 after depilation and bulge or DP regions were dissected. The bulge and DP cells were cultured for 14days in DMEM/F12 medium. Then, the cells were treated with 100μM minoxidil and 10% HPL for 10 days. Nuclear morphology was identified using DAPi staining. Reverse transcriptase and real-time polymerase chain reaction (PCR) analysis were also performed to examine the expression of Kras, Erk, Akt, Shh and β-catenin mRNA levels in the treated bulge and DP regions after organ culture. Here, we found that minoxidil influences bulge and DP cell survival (P<0.05). Apoptosis in DP cells was also meaningfully decreased by HPL treatment (P=0.014). In addition, Kras, Akt, Erk, Shh and β-catenin mRNA levels were changed in response to minoxidil treatment in both bulge and DP cells. HPL mediated Erk upregulation in both bulge and DP cells (P<0.05), but Kras and Akt mRNA levels were not considerably different in the HPL-treated cells. β-catenin mRNA level was also significantly increased in the bulge region by HPL. We also found that Shh mRNA level was considerably higher in HPL-treated bulge cells than in minoxidil-treated bulge cells. In contrast, the expression of β-cateinin and Shh in the DP cells was not meaningfully increased after treatment with HPL. Our results suggest that minoxidil and HPL can promote hair growth by activating the main anagen inducing signaling pathways. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Velocity Dispersions Across Bulge Types

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fabricius, Maximilian; Bender, Ralf; Hopp, Ulrich

2010-06-08

We present first results from a long-slit spectroscopic survey of bulge kinematics in local spiral galaxies. Our optical spectra were obtained at the Hobby-Eberly Telescope with the LRS spectrograph and have a velocity resolution of 45 km/s (sigma*), which allows us to resolve the velocity dispersions in the bulge regions of most objects in our sample. We find that the velocity dispersion profiles in morphological classical bulge galaxies are always centrally peaked while the velocity dispersion of morphologically disk-like bulges stays relatively flat towards the center--once strongly barred galaxies are discarded.

Results from the MACHO Galactic Pixel Lensing Search

NASA Astrophysics Data System (ADS)

Drake, Andrew J.; Minniti, Dante; Alcock, Charles; Allsman, Robyn A.; Alves, David; Axelrod, Tim S.; Becker, Andrew C.; Bennett, David; Cook, Kem H.; Freeman, Ken C.; Griest, Kim; Lehner, Matt; Marshall, Stuart; Peterson, Bruce; Pratt, Mark; Quinn, Peter; Rodgers, Alex; Stubbs, Chris; Sutherland, Will; Tomaney, Austin; Vandehei, Thor; Welch, Doug L.

The MACHO, EROS, OGLE and AGAPE collaborations have been studying nature of the galactic halo for a number of years using microlensing events. The MACHO group undertakes observations of the LMC, SMC and Galactic Bulge monitoring the light curves of millions of stars to detect microlensing. Most of these fields are crowded to the extent that all the monitored stars are blended. Such crowding makes the performance of accurate photometry difficult. We apply the new technique of Difference Image Analysis (DIA) on archival data to improve the photometry and increase both the detection sensitivity and effective search area. The application of this technique also allows us to detect so called `pixel lensing' events. These are microlensing events where the source star is only detectable during lensing. The detection of these events will allow us to make a large increase in the number of detected microlensing events. We present a light curve demonstrating the detection of a pixel lensing event with this technique.

VizieR Online Data Catalog: Stellar populations in the Magellanic bridge (Skowron+, 2014)

NASA Astrophysics Data System (ADS)

Skowron, D. M.; Jacyszyn, A. M.; Udalski, A.; Szymanski, M. K.; Skowron, J.; Poleski, R.; Kozlowski, S.; Kubiak, M.; Pietrzynski, G.; Soszynski, I.; Mroz, P.; Pietrukowicz, P.; Ulaczyk, K.; Wyrzykowski, L.

2017-05-01

The current, fourth phase of the OGLE survey (OGLE-IV) started in 2010 March with the commissioning of a large new-generation 256 Megapixel 32 chip mosaic camera. The Galactic bulge and disk, the Magellanic Clouds, and the Magellanic Bridge, including vast areas around them, are the primary observing targets for the OGLE-IV survey. Regular monitoring of the selected sky regions by the OGLE survey is carried out with the 1.3 m Warsaw telescope located at the Las Campanas Observatory in Chile (operated by the Carnegie Institution for Science). The field of view of the camera is 1.4 deg2 with a pixel size of ~0.26''. The magnitude range of the standard OGLE survey is approximately 12-21 mag in the I band and 12.5-21.5 mag in the V band. (1 data file).

Mapping a stellar disk into a boxy bulge: The outside-in part of the Milky Way bulge formation

NASA Astrophysics Data System (ADS)

Di Matteo, P.; Haywood, M.; Gómez, A.; van Damme, L.; Combes, F.; Hallé, A.; Semelin, B.; Lehnert, M. D.; Katz, D.

2014-07-01

By means of idealized, dissipationless N-body simulations that follow the formation and subsequent buckling of a stellar bar, we study the characteristics of boxy/peanut-shaped bulges and compare them with the properties of the stellar populations in the Milky Way (MW) bulge. The main results of our modeling, valid for the general family of boxy/peanut shaped bulges, are the following: (i) Because of the spatial redistribution in the disk initiated at the epoch of bar formation, stars from the innermost regions to the outer Lindblad resonance (OLR) of the stellar bar are mapped into a boxy bulge. (ii) The contribution of stars to the local bulge density depends on their birth radius: stars born in the innermost disk tend to dominate the innermost regions of the boxy bulge, while stars originating closer to the OLR are preferably found in the outer regions of the boxy/peanut structure. (iii) Stellar birth radii are imprinted in the bulge kinematics: the larger the birth radii of stars ending up in the bulge, the greater their rotational support and the higher their line-of-sight velocity dispersions (but note that this last trend depends on the bar viewing angle). (iv) The higher the classical bulge-over-disk ratio, the larger its fractional contribution of stars at large vertical distance from the galaxy midplane. Comparing these results with the properties of the stellar populations of the MW bulge recently revealed by the ARGOS survey, we conclude that (I) the two most metal-rich populations of the MW bulge, labeled A and B in the ARGOS survey, originate in the disk, with the population of A having formed on average closer to the Galaxy center than the population of component B; (II) a massive (B/D ~ 0.25) classical spheroid can be excluded for the MW, thus confirming previous findings that the MW bulge is composed of populations that mostly have a disk origin. On the basis of their chemical and kinematic characteristics, the results of our modeling suggest that the populations A, B, and C, as defined by the ARGOS survey, can be associated, respectively, with the inner thin disk, to the young thick and to the old thick disk, following the nomenclature that we recently suggested for stars in the solar neighborhood. Appendix A is available in electronic form at http://www.aanda.org

New insights into the origin and evolution of the old, metal-rich open cluster NGC 6791

NASA Astrophysics Data System (ADS)

Martinez-Medina, Luis A.; Gieles, Mark; Pichardo, Barbara; Peimbert, Antonio

2018-02-01

NGC 6791 is one of the most studied open clusters, it is massive (˜5000 M⊙), located at the solar circle, old (˜8 Gyr) and yet the most metal-rich cluster ([Fe/H] ≃ 0.4) known in the Milky Way. By performing an orbital analysis within a Galactic model including spiral arms and a bar, we found that it is plausible that NGC 6791 formed in the inner thin disc or in the bulge, and later displaced by radial migration to its current orbit. We apply different tools to simulate NGC 6791, including direct N-body summation in time-varying potentials, to test its survivability when going through different Galactic environments. In order to survive the 8-Gyr journey moving on a migrating orbit, NGC 6791 must have been more massive, M0 ≥ 5 × 104 M⊙, when formed. We find independent confirmation of this initial mass in the stellar mass function, which is observed to be flat; this can only be explained if the average tidal field strength experienced by the cluster is stronger than what it is at its current orbit. Therefore, the birth place and journeys of NGC 6791 are imprinted in its chemical composition, in its mass-loss and in its flat stellar mass function, supporting its origin in the inner thin disc or in the bulge.

Observational Evidence for the Effect of Amplification Bias in Gravitational Microlensing Experiments

NASA Astrophysics Data System (ADS)

Han, Cheongho; Jeong, Youngjin; Kim, Ho-Il

1998-11-01

Recently Alard, Mao, & Guibert and Alard proposed to detect the shift of a star's image centroid, δx, as a method to identify the lensed source among blended stars. Goldberg & Woźniak actually applied this method to the OGLE-1 database and found that seven of 15 events showed significant centroid shifts of δx >~ 0.2". The amount of centroid shift has been estimated theoretically by Goldberg; however, he treated the problem in general and did not apply it to a particular survey or field and therefore based his estimate on simple toy model luminosity functions (i.e., power laws). In this paper, we construct the expected distribution of δx for Galactic bulge events based on the precise stellar luminosity function observed by Holtzman et al. using the Hubble Space Telescope. Their luminosity function is complete up to MI ~ 9.0 (MV ~ 12), which corresponds to faint M-type stars. In our analysis we find that regular blending cannot produce a large fraction of events with measurable centroid shifts. By contrast, a significant fraction of events would have measurable centroid shifts if they are affected by amplification-bias blending. Therefore, the measurements of large centroid shifts for an important fraction of microlensing events of Goldberg & Woźniak confirm the prediction of Han & Alard that a large fraction of Galactic bulge events are affected by amplification-bias blending.

Pristine Survey : High-Resolution Spectral Analyses of New Metal-poor Stars

NASA Astrophysics Data System (ADS)

Venn, Kim; Starkenburg, Else; Martin, Nicolas; Kielty, Collin; Youakim, Kris; Arnetsen, Anke

2018-06-01

The Pristine survey (Starkenburg et al. 2017) is a new and very successful metal-poor star survey. Combining high-quality narrow-band CaHK CFHT/MegaCam photometry with existing broadband photometry from SDSS, then very metal-poor stars have been found as confirmed from low-resolution spectroscopy (Youakim et al. 2017). Furthermore, we have extended this survey towards the Galactic bulge in a pilot program to test the capabilities in the highly crowded and (inhomogeneously) extincted bulge (Arentsen et al. 2018). High resolution spectral follow-up analyses have been initiated at the CFHT with Espadons (V<15) and the Gemini/GRACES long optical fibre that also feeds the Espadons spectrograph (15

OGLE-2017-BLG-1522: A Giant Planet around a Brown Dwarf Located in the Galactic Bulge

NASA Astrophysics Data System (ADS)

Jung, Y. K.; Udalski, A.; Gould, A.; Ryu, Y.-H.; Yee, J. C.; and; Han, C.; Albrow, M. D.; Lee, C.-U.; Kim, S.-L.; Hwang, K.-H.; Chung, S.-J.; Shin, I.-G.; Zhu, W.; Cha, S.-M.; Kim, D.-J.; Lee, Y.; Park, B.-G.; Lee, D.-J.; Kim, H.-W.; Pogge, R. W.; The KMTNet Collaboration; Szymański, M. K.; Mróz, P.; Poleski, R.; Skowron, J.; Pietrukowicz, P.; Soszyński, I.; Kozłowski, S.; Ulaczyk, K.; Pawlak, M.; Rybicki, K.; The OGLE Collaboration

2018-05-01

We report the discovery of a giant planet in the OGLE-2017-BLG-1522 microlensing event. The planetary perturbations were clearly identified by high-cadence survey experiments despite the relatively short event timescale of t E ∼ 7.5 days. The Einstein radius is unusually small, θ E = 0.065 mas, implying that the lens system either has very low mass or lies much closer to the microlensed source than the Sun, or both. A Bayesian analysis yields component masses ({M}host},{M}planet})=({46}-25+79,{0.75}-0.40+1.26) {M}{{J}} and source-lens distance {D}LS}={0.99}-0.54+0.91 {kpc}, implying that this is a brown-dwarf/Jupiter system that probably lies in the Galactic bulge, a location that is also consistent with the relatively low lens-source relative proper motion μ = 3.2 ± 0.5 mas yr‑1. The projected companion-host separation is {0.59}-0.11+0.12 {au}, indicating that the planet is placed beyond the snow line of the host, i.e., a sl ∼ 0.12 au. Planet formation scenarios combined with the small companion-host mass ratio q ∼ 0.016 and separation suggest that the companion could be the first discovery of a giant planet that formed in a protoplanetary disk around a brown-dwarf host.

AN OFF-CENTERED ACTIVE GALACTIC NUCLEUS IN NGC 3115

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menezes, R. B.; Steiner, J. E.; Ricci, T. V., E-mail: robertobm@astro.iag.usp.br

2014-11-20

NGC 3115 is an S0 galaxy that has always been considered to have a pure absorption-line spectrum. Some recent studies have detected a compact radio-emitting nucleus in this object, coinciding with the photometric center and with a candidate for the X-ray nucleus. This is evidence of the existence of a low-luminosity active galactic nucleus (AGN) in the galaxy, although no emission line has ever been observed. We report the detection of an emission-line spectrum of a type 1 AGN in NGC 3115, with an Hα luminosity of L {sub Hα} = (4.2 ± 0.4) × 10{sup 37} erg s{sup –1}. Our analysismore » revealed that this AGN is located at a projected distance of ∼0.''29 ± 0.''05 (corresponding to ∼14.3 ± 2.5 pc) from the stellar bulge center, which is coincident with the kinematic center of this object's stellar velocity map. The black hole corresponding to the observed off-centered AGN may form a binary system with a black hole located at the stellar bulge center. However, it is also possible that the displaced black hole is the merged remnant of the binary system coalescence, after the ''kick'' caused by the asymmetric emission of gravitational waves. We propose that certain features in the stellar velocity dispersion map are the result of perturbations caused by the off-centered AGN.« less

Hiding in the night sky

NASA Image and Video Library

2016-04-04

This striking NASA/ESA Hubble Space Telescope image captures the galaxy UGC 477, located just over 110 million light-years away in the constellation of Pisces (The Fish). UGC 477 is a low surface brightness (LSB) galaxy. First proposed in 1976 by Mike Disney, the existence of LSB galaxies was confirmed only in 1986 with the discovery of Malin 1. LSB galaxies like UGC 477 are more diffusely distributed than galaxies such as Andromeda and the Milky Way. With surface brightnesses up to 250 times fainter than the night sky, these galaxies can be incredibly difficult to detect. Most of the matter present in LSB galaxies is in the form of hydrogen gas, rather than stars. Unlike the bulges of normal spiral galaxies, the centres of LSB galaxies do not contain large numbers of stars. Astronomers suspect that this is because LSB galaxies are mainly found in regions devoid of other galaxies, and have therefore experienced fewer galactic interactions and mergers capable of triggering high rates of star formation. LSB galaxies such as UGC 477 instead appear to be dominated by dark matter, making them excellent objects to study to further our understanding of this elusive substance. However, due to an underrepresentation in galactic surveys — caused by their characteristic low brightness — their importance has only been realised relatively recently.

Gravitational Microlensing Observations of Two New Exoplanets Using the Deep Impact High Resolution Instrument

NASA Astrophysics Data System (ADS)

Barry, Richard K.; Bennett, D. P.; Klaasen, K.; Becker, A. C.; Christiansen, J.; Albrow, M.

2014-01-01

We have worked to characterize two exoplanets newly detected from the ground: OGLE-2012-BLG-0406 and OGLE-2012-BLG-0838, using microlensing observations of the Galactic Bulge recently obtained by NASA’s Deep Impact (DI) spacecraft, in combination with ground data. These observations of the crowded Bulge fields from Earth and from an observatory at a distance of ~1 AU have permitted the extraction of a microlensing parallax signature - critical for breaking exoplanet model degeneracies. For this effort, we used DI’s High Resolution Instrument, launched with a permanent defocus aberration due to an error in cryogenic testing. We show how the effects of a very large, chromatic PSF can be reduced in differencing photometry. We also compare two approaches to differencing photometry - one of which employs the Bramich algorithm and another using the Fruchter & Hook drizzle algorithm.

Spectroscopic Results of Gravitational Microlenses: Are These Dark Objects or Faint Stars?

NASA Astrophysics Data System (ADS)

Joseph, C. L.; Gallagher, J.; Phillips, M.

1994-12-01

We report on the spectroscopic results obtained in October 1994 with the 4-meter telescope on Cerro Tololo Interamerican Observatory (CTIO). Spectra of 2 recent microlens candidates toward the Galactic bulge reported by the Optical Gravitational Lens Experiment (OGLE) as well as one caught in the early phases of brightening toward the LMC reported by the MAssive Compact Halo Object (MACHO) Project have been obtained. The spectral coverage is from 6500 to 9800 Angstroms at a resolution of 6 Angstroms. The long-term goal of this spectroscopic study is to obtain censored statistical evidence on the luminosity of the microlenses, constraining the nature of these lenses. Several models of composite spectra of a bulge or LMC star plus a cool lensing star of different spectral types are presented to demonstrate the ranges in the product of luminosity times distance that the faint star could be detected in a composite spectrum.

Black hole demographics from the M•-σ relation

NASA Astrophysics Data System (ADS)

Merritt, David; Ferrarese, Laura

2001-01-01

We analyse a sample of 32 galaxies for which a dynamical estimate of the mass of the hot stellar component, Mbulge, is available. For each of these galaxies, we calculate the mass of the central black hole, M•, using the tight empirical correlation between M• and bulge stellar velocity dispersion. The frequency function N[log(M•Mbulge)] is reasonably well described as a Gaussian with ~-2.90 and standard deviation ~0.45 the implied mean ratio of black hole mass to bulge mass is a factor of ~5 smaller than generally quoted in the literature. We present marginal evidence for a lower, average black hole mass fraction in more massive galaxies. The total mass density in black holes in the local Universe is estimated to be ~ 5×105MsolarMpc-3, consistent with that inferred from high-redshift (z~2) active galactic nuclei.

CONNECTING STAR FORMATION QUENCHING WITH GALAXY STRUCTURE AND SUPERMASSIVE BLACK HOLES THROUGH GRAVITATIONAL HEATING OF COOLING FLOWS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Fulai, E-mail: fulai.guo@phys.ethz.ch

2014-12-20

Recent observations suggested that star formation quenching in galaxies is related to galaxy structure. Here we propose a new mechanism to explain the physical origin of this correlation. We assume that while quenching is maintained in quiescent galaxies by a feedback mechanism, cooling flows in the hot halo gas can still develop intermittently. We study cooling flows in a large suite of around 90 hydrodynamic simulations of an isolated galaxy group, and find that the flow development depends significantly on the gravitational potential well in the central galaxy. If the galaxy's gravity is not strong enough, cooling flows result inmore » a central cooling catastrophe, supplying cold gas and feeding star formation to galactic bulges. When the bulge grows prominent enough, compressional heating starts to offset radiative cooling and maintains cooling flows in a long-term hot mode without producing a cooling catastrophe. Our model thus describes a self-limited growth channel for galaxy bulges and naturally explains the connection between quenching and bulge prominence. In particular, we explicitly demonstrate that M{sub ∗}/R{sub eff}{sup 1.5} is a good structural predictor of quenching. We further find that the gravity from the central supermassive black hole also affects the bimodal fate of cooling flows, and we predict a more general quenching predictor to be M{sub bh}{sup 1.6}M{sub ∗}/R{sub eff}{sup 1.5}, which may be tested in future observational studies.« less

a Study of the AGB in Local Group Bulge Populations

NASA Astrophysics Data System (ADS)

Rich, R.

1994-01-01

We propose to survey the bolometric luminosities, colors, and space distribution of the most luminous asymptotic giant branch (AGB) stars in the bulges of M31, M32, and M33. We seek to discover whether the bulges of these galaxies are relatively young, of order 10 Gyr rather than 15 Gyr. We will use WFPC2 and the R, I, and F1042M (1 micron) filters. Knowing that F1042M falls on the first continuum point of M giants, we have shown that we can use 1.04 micron fluxes to reliably calculate bolometric magnitudes for these very red stars. Color information from R and I will permit (1) comparison with Galactic bulge M giants, (2) an estimate of the spread of abundance and (3) increase the accuracy of the bolometric magnitudes. Frames with the damaged HST show signs of resolution to within 3" of the M31 nucleus; Red images with the aberrated HST show a red star cluster associated with the nucleus. Ground-based studies of M32 find an intermediate-age population from spectroscopy and infrared photometry. The repaired HST should resolve stars close to the nuclei of these galaxies. We will measure bolometric luminosity functions to determine if the populations are intermediate age, and attempt to measure the abundance range for stars near the nuclei of these galaxies. If metals have been lost due to winds, theory predicts that we should see a substantial spread of abundances even near the nucleus.

Introducing galactic structure finder: the multiple stellar kinematic structures of a simulated Milky Way mass galaxy

NASA Astrophysics Data System (ADS)

Obreja, Aura; Macciò, Andrea V.; Moster, Benjamin; Dutton, Aaron A.; Buck, Tobias; Wang, Gregory S. Stinson Liang

2018-04-01

We present the first results of applying Gaussian Mixture Models in the stellar kinematic space of normalized angular momentum and binding energy on NIHAO high resolution galaxies to separate the stars into multiple components. We exemplify this method using a simulated Milky Way analogue, whose stellar component hosts: thin and thick discs, classical and pseudo bulges, and a stellar halo. The properties of these stellar structures are in good agreement with observational expectations in terms of sizes, shapes and rotational support. Interestingly, the two kinematic discs show surface mass density profiles more centrally concentrated than exponentials, while the bulges and the stellar halo are purely exponential. We trace back in time the Lagrangian mass of each component separately to study their formation history. Between z ˜ 3 and the end of halo virialization, z ˜ 1.3, all components lose a fraction of their angular momentum. The classical bulge loses the most (˜95%) and the thin disc the least (˜60%). Both bulges formed their stars in-situ at high redshift, while the thin disc formed ˜98% in-situ, but with a constant SFR ˜ 1.5M⊙yr-1 over the last ˜ 11 Gyr. Accreted stars (6% of total stellar mass) are mainly incorporated to the thick disc or the stellar halo, which formed ex-situ 8% and 45% of their respective masses. Our analysis pipeline is freely available at https://github.com/aobr/gsf.

Stellar Photometric Structures of the Host Galaxies of Nearby Type 1 Active Galactic Nuclei

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Minjin; Ho, Luis C.; Peng, Chien Y.

2017-10-01

We present detailed image analysis of rest-frame optical images of 235 low-redshift ( z ≲ 0.35) Type 1 active galactic nuclei (AGNs) observed with the Hubble Space Telescope . The high-resolution images enable us to perform rigorous two-dimensional image modeling to decouple the luminous central point source from the host galaxy, which, when warranted, is further decomposed into its principal structural components (bulge, bar, and disk). In many cases, care must be taken to account for structural complexities such as spiral arms, tidal features, and overlapping or interacting companion galaxies. We employ Fourier modes to characterize the degree of asymmetrymore » of the light distribution of the stars as a quantitative measure of morphological distortion due to interactions or mergers. We examine the dependence of the physical parameters of the host galaxies on the properties of the AGNs, namely, radio-loudness and the width of the broad emission lines. In accordance with previous studies, narrow-line (H β FWHM ≤ 2000 km s{sup −1}) Type 1 AGNs, in contrast to their broad-line (H β FWHM > 2000 km s{sup −1}) counterparts, are preferentially hosted in later-type, lower-luminosity galaxies, which have a higher incidence of pseudo-bulges, are more frequently barred, and are less morphologically disturbed. This suggests that narrow-line Type 1 AGNs experienced a more quiescent evolutionary history driven primarily by internal secular evolution instead of external dynamical perturbations. The fraction of AGN hosts showing merger signatures is larger for more luminous sources. Radio-loud AGNs generally preferentially live in earlier-type (bulge-dominated), more massive hosts, although a minority of them appear to contain a significant disk component. We do not find convincing evidence for enhanced merger signatures in the radio-loud population.« less

Recognition of DNA/RNA bulges by antimicrobial and antitumor metallohelices.

PubMed

Malina, Jaroslav; Scott, Peter; Brabec, Viktor

2015-09-07

Bulged structures have been identified in nucleic acids and have been shown to be linked to biomolecular processes involved in numerous diseases. Thus, chemical agents with affinity for bulged nucleic acids are of general biological significance. Herein, the mechanism of specific recognition and stabilization of bulged DNA and RNA by helical bimetallic species was established through detailed molecular biophysics and biochemistry assays. These agents, known as 'flexicates', are potential mimetics of α-helical peptides in cancer treatment, exhibiting antimicrobial and antitumor effects. The flexicates have positive impacts on the thermal stability of DNA duplexes containing bulges, which means that the flexicates interact with the duplexes containing bulges, and that these interactions stabilize the secondary structures of these duplexes. Notably, the stabilising effect of the flexicates increases with the size of the bulge, the maximal stabilization is observed for the duplexes containing a bulge composed of at least three bases. The flexicates bind most preferentially to the bulges composed of pyrimidines flanked on both sides also by pyrimidines. It is suggested that it is so because these bulges exhibit greatest conformational variability in comparison with other combinations of bases in the bulge loop and bases flanking the bulge. Finally, the results indicate that there is only one dominant binding site for the flexicates on the DNA and RNA bulges and that the flexicates bind directly to the bulge or in its close proximity. It is also shown that the flexicates effectively bind to RNA duplexes containing the bulged region of HIV-1 TAR RNA.

Stellar Variability in the VVV Survey: An Update

NASA Astrophysics Data System (ADS)

Catelan, M.; Dekany, I.; Hempel, M.; Minniti, D.

The Vista Variables in the Via Lactea (VVV) ESO Public Survey consists in a near-infrared time-series survey of the Galactic bulge and inner disk; covering 562 square degrees of the sky; over a total timespan of more than 5 years. In this paper; we provide an updated account of the current status of the survey; especially in the context of stellar variability studies. In this sense; we give a first description of our efforts towards the construction of the VVV Variable Star Catalog (VVV-VSC).

A new model for gravitational potential perturbations in disks of spiral galaxies. An application to our Galaxy

NASA Astrophysics Data System (ADS)

Junqueira, T. C.; Lépine, J. R. D.; Braga, C. A. S.; Barros, D. A.

2013-02-01

Aims: We propose a new, more realistic description of the perturbed gravitational potential of spiral galaxies, with spiral arms having Gaussian-shaped groove profiles. The aim is to reach a self-consistent description of the spiral structure, that is, one in which an initial potential perturbation generates, by means of the stellar orbits, spiral arms with a profile similar to that of the imposed perturbation. Self-consistency is a condition for having long-lived structures. Methods: Using the new perturbed potential, we investigate the stable stellar orbits in galactic disks for galaxies with no bar or with only a weak bar. The model is applied to our Galaxy by making use of the axisymmetric component of the potential computed from the Galactic rotation curve, in addition to other input parameters similar to those of our Galaxy. The influence of the bulge mass on the stellar orbits in the inner regions of a disk is also investigated. Results: The new description offers the advantage of easy control of the parameters of the Gaussian profile of its potential. We compute the density contrast between arm and inter-arm regions. We find a range of values for the perturbation amplitude from 400 to 800 km2 s-2 kpc-1, which implies an approximate maximum ratio of the tangential force to the axisymmetric force between 3% and 6%. Good self-consistency of arm shapes is obtained between the Inner Lindblad resonance (ILR) and the 4:1 resonance. Near the 4:1 resonance the response density starts to deviate from the imposed logarithmic spiral form. This creates bifurcations that appear as short arms. Therefore the deviation from a perfect logarithmic spiral in galaxies can be understood as a natural effect of the 4:1 resonance. Beyond the 4:1 resonance we find closed orbits that have similarities with the arms observed in our Galaxy. In regions near the center, elongated stellar orbits appear naturally, in the presence of a massive bulge, without imposing any bar-shaped potential, but only extending the spiral perturbation a little inward of the ILR. This suggests that a bar is formed with a half-size ~3 kpc by a mechanism similar to that of the spiral arms. Conclusions: The potential energy perturbation that we adopted represents an important step in the direction of self-consistency, compared to previous sine function descriptions of the potential. In addition, our model produces a realistic description of the spiral structure, which is able to explain several details that were not yet understood.

Age bimodality in the central region of pseudo-bulges in S0 galaxies

NASA Astrophysics Data System (ADS)

Mishra, Preetish K.; Barway, Sudhanshu; Wadadekar, Yogesh

2017-11-01

We present evidence for bimodal stellar age distribution of pseudo-bulges of S0 galaxies as probed by the Dn(4000) index. We do not observe any bimodality in age distribution for pseudo-bulges in spiral galaxies. Our sample is flux limited and contains 2067 S0 and 2630 spiral galaxies drawn from the Sloan Digital Sky Survey. We identify pseudo-bulges in S0 and spiral galaxies, based on the position of the bulge on the Kormendy diagram and their central velocity dispersion. Dividing the pseudo-bulges of S0 galaxies into those containing old and young stellar populations, we study the connection between global star formation and pseudo-bulge age on the u - r colour-mass diagram. We find that most old pseudo-bulges are hosted by passive galaxies while majority of young bulges are hosted by galaxies that are star forming. Dividing our sample of S0 galaxies into early-type S0s and S0/a galaxies, we find that old pseudo-bulges are mainly hosted by early-type S0 galaxies while most of the pseudo-bulges in S0/a galaxies are young. We speculate that morphology plays a strong role in quenching of star formation in the disc of these S0 galaxies, which stops the growth of pseudo-bulges, giving rise to old pseudo-bulges and the observed age bimodality.

NuSTAR Hard X-Ray Survey of the Galactic Center Region. II. X-Ray Point Sources

NASA Technical Reports Server (NTRS)

Hong, Jaesub; Mori, Kaya; Hailey, Charles J.; Nynka, Melania; Zhang, Shou; Gotthelf, Eric; Fornasini, Francesca M.; Krivonos, Roman; Bauer, Franz; Perez, Kerstin;

Grains in galactic haloes

NASA Technical Reports Server (NTRS)

Ferrara, Andrea; Barsella, Bruno; Ferrini, F.; Greenberg, J. Mayo; Aiello, Santi

1989-01-01

Researchers considered the effect of extensive forces on dust grains subjected to the light and matter distribution of a spiral galaxy (Greenberg et al. (1987), Ferrini et al. (1987), Barsella et al (1988). Researchers showed that the combined force on a small particle located above the plane of a galactic disk may be either attractive or repulsive depending on a variety of parameters. They found, for example, that graphite grains from 20 nm to 250 nm radius are expelled from a typical galaxy, while silicates and other forms of dielectrics, after initial expulsion, may settle in potential minimum within the halo. They discuss only the statistical behavior of the forces for 17 galaxies whose luminosity and matter distribution in the disk, bulge and halo components are reasonably well known. The preliminary results of the study of the motion of a dust grain for NGC 3198 are given.

Chemically-dissected Rotation Curves of the Galactic Bulge from Hubble Space Telescope Proper Motions on the Main Sequence

NASA Astrophysics Data System (ADS)

Clarkson, William I.; Calamida, Annalisa; Sahu, Kailash C.; Gennaro, Mario; Brown, Thomas M.; Avila, Roberto J.; Rich, R. Michael; Debattista, Victor P.

2018-01-01

We report results from a pilot study using archival Hubble Space Telescope imaging observations in seven filters over a multi-year time-baseline to probe the co-dependence of chemical abundance and kinematics, using proper motion-based rotation curves selected on relative metallicity. With spectroscopic studies suggesting the metallicity distribution of the Bulge may be bimodal, we follow a data-driven approach to classify stars as belonging to metal-rich or metal-poor ends of the observed relative photometric metallicity distribution, with classification implemented using standard unsupervised learning techniques. We detect clear differences in both slope and amplitude of the proper motion-based rotation curve as traced by the more “metal-rich” and “metal-poor” samples. The sense of the discrepancy is qualitatively in agreement both with recent observational and theoretical indications; the “metal-poor” sample does indeed show a weaker rotation signature.This is the first study to dissect the proper motion rotation curve of the Bulge by chemical abundance using main-sequence targets, which are orders of magnitude more common on the sky than bright giants. These techniques thus offer a pencil-beam complement to wide-field studies that use more traditional tracer populations.

SiO maser emission as a density tracer of circumstellar envelopes

NASA Astrophysics Data System (ADS)

Stroh, Michael; Pihlstrom, Ylva; Sjouwerman, Lorant

2018-06-01

The circumstellar envelopes (CSEs) of evolved stars offer a method to construct a sample of point-masses along the full Galactic plane, which can be used to test models of the gravitational potential. In the CSEs of red giants, SiO maser emission is frequently observed at 43 and 86 GHz, providing line-of-sight velocities. The Bulge Asymmetries and Dynamical Evolution (BAaDE) project aims to explore the complex structure of the inner Galaxy and Galactic Bulge, by observing 43 GHz SiO at the Very Large Array and 86 GHz SiO at the Atacama Large Millimeter/submillimeter Array, with an expected final sample of about 20,000 line-of-sight velocities and positions. We observed the 43 GHz and 86 GHz transitions near-simultaneously in a subsample of the sources using the Australia Telescope Compact Array and found that on average the 43 GHz v=1 line is 1.3 times stronger than the 86 GHz v=1 line. The presence of a detectable 43 GHz v=3 line alters the statistics, consistent with the SiO masers displaying 43 GHz v=3 emission arising in a denser regime in the circumstellar shell compared to those without. Comparing our results with radiative models implies that the 43 GHz v=3 line is a tracer of density variations caused by stellar pulsations. We will discuss these results in the context of the BAaDE project.

RED RUNAWAYS II: LOW-MASS HILLS STARS IN SDSS STRIPE 82

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yanqiong; Smith, Martin C.; Carlin, Jeffrey L., E-mail: zhangyq@shao.ac.cn, E-mail: msmith@shao.ac.cn

Stars ejected from the Galactic Center can be used to place important constraints on the Milky Way potential. Since existing hypervelocity stars are too distant to accurately determine orbits, we have conducted a search for nearby candidates using full three-dimensional velocities. Since the efficacy of such studies is often hampered by deficiencies in proper motion catalogs, we have chosen to utilize the reliable, high-precision Sloan Digital Sky Survey (SDSS) Stripe 82 proper motion catalog. Although we do not find any candidates which have velocities in excess of the escape speed, we identify 226 stars on orbits that are consistent withmore » Galactic Center ejection. This number is significantly larger than what we would expect for halo stars on radial orbits and cannot be explained by disk or bulge contamination. If we restrict ourselves to metal-rich stars, we find 29 candidates with [Fe/H] > −0.8 dex and 10 with [Fe/H] > −0.6 dex. Their metallicities are more consistent with what we expect for bulge ejecta, and so we believe these candidates are especially deserving of further study. We have supplemented this sample using our own radial velocities, developing an algorithm to use proper motions for optimizing candidate selection. This technique provides considerable improvement on the blind spectroscopic sample of SDSS, being able to identify candidates with an efficiency around 20 times better than a blind search.« less

Introducing galactic structure finder: the multiple stellar kinematic structures of a simulated Milky Way mass galaxy

NASA Astrophysics Data System (ADS)

Obreja, Aura; Macciò, Andrea V.; Moster, Benjamin; Dutton, Aaron A.; Buck, Tobias; Stinson, Gregory S.; Wang, Liang

2018-07-01

We present the first results of applying Gaussian Mixture Models in the stellar kinematic space of normalized angular momentum and binding energy on NIHAO high-resolution galaxies to separate the stars into multiple components. We exemplify this method, using a simulated Milky Way analogue, whose stellar component hosts thin and thick discs, classical and pseudo bulges, and a stellar halo. The properties of these stellar structures are in good agreement with observational expectations in terms of sizes, shapes, and rotational support. Interestingly, the two kinematic discs show surface mass density profiles more centrally concentrated than exponentials, while the bulges and the stellar halo are purely exponential. We trace back in time the Lagrangian mass of each component separately to study their formation history. Between z ˜ 3 and the end of halo virialization, z ˜ 1.3, all components lose a fraction of their angular momentum. The classical bulge loses the most (˜ 95 per cent) and the thin disc the least (˜ 60 per cent). Both bulges formed their stars in situ at high redshift, while the thin disc formed ˜ 98 per cent in situ, but with a constant SFR ˜ 1.5 M⊙ yr-1 over the last ˜11 Gyr. Accreted stars (6 per cent of total stellar mass) are mainly incorporated to the thick disc or the stellar halo, which formed ex situ 8 per cent and 45 per cent of their respective masses. Our analysis pipeline is freely available at https://github.com/aobr/gsf.

Exploring the Chemical Composition and Double Horizontal Branch of the Bulge Globular Cluster NGC 6569

NASA Astrophysics Data System (ADS)

Johnson, Christian I.; Rich, R. Michael; Caldwell, Nelson; Mateo, Mario; Bailey, John I., III; Olszewski, Edward W.; Walker, Matthew G.

2018-02-01

Photometric and spectroscopic analyses have shown that the Galactic bulge cluster Terzan 5 hosts several populations with different metallicities and ages that manifest as a double red horizontal branch (HB). A recent investigation of the massive bulge cluster NGC 6569 revealed a similar, though less extended, HB luminosity split, but little is known about the cluster’s detailed chemical composition. Therefore, we have used high-resolution spectra from the Magellan–M2FS and VLT–FLAMES spectrographs to investigate the chemical compositions and radial velocity distributions of red giant branch and HB stars in NGC 6569. We found the cluster to have a mean heliocentric radial velocity of ‑48.8 km s‑1 (σ = 5.3 km s‑1 148 stars) and < [{Fe}/{{H}}]> =-0.87 dex (19 stars), but the cluster’s 0.05 dex [Fe/H] dispersion precludes a significant metallicity spread. NGC 6569 exhibits light- and heavy-element distributions that are common among old bulge/inner Galaxy globular clusters, including clear (anti)correlations between [O/Fe], [Na/Fe], and [Al/Fe]. The light-element data suggest that NGC 6569 may be composed of at least two distinct populations, and the cluster’s low < [{La}/{Eu}]> =-0.11 dex indicates significant pollution with r-process material. We confirm that both HBs contain cluster members, but metallicity and light-element variations are largely ruled out as sources for the luminosity difference. However, He mass fraction differences as small as ΔY ∼ 0.02 cannot be ruled out and may be sufficient to reproduce the double HB.

Special Features of Galactic Dynamics

NASA Astrophysics Data System (ADS)

Efthymiopoulos, Christos; Voglis, Nikos; Kalapotharakos, Constantinos

This is an introductory article to some basic notions and currently open problems of galactic dynamics. The focus is on topics mostly relevant to the so-called `new methods' of celestial mechanics or Hamiltonian dynamics, as applied to the ellipsoidal components of galaxies, i.e., to the elliptical galaxies and to the dark halos and bulges of disk galaxies. Traditional topics such as Jeans theorem, the role of a `third integral' of motion, Nekhoroshev theory, violent relaxation, and the statistical mechanics of collisionless stellar systems are first discussed. The emphasis is on modern extrapolations of these old topics. Recent results from orbital and global dynamical studies of galaxies are then shortly reviewed. The role of various families of orbits in supporting self-consistency, as well as the role of chaos in galaxies, are stressed. A description is then given of the main numerical techniques of integration of the N-body problem in the framework of stellar dynamics and of the results obtained via N-Body experiments. A final topic is the secular evolution and self-organization of galactic systems.

The continuous rise of bulges out of galactic disks

NASA Astrophysics Data System (ADS)

Breda, Iris; Papaderos, Polychronis

2018-06-01

Context. A key subject in extragalactic astronomy concerns the chronology and driving mechanisms of bulge formation in late-type galaxies (LTGs). The standard scenario distinguishes between classical bulges and pseudo-bulges (CBs and PBs, respectively), the first thought to form monolithically prior to disks and the second gradually out of disks. These two bulge formation routes obviously yield antipodal predictions on the bulge age and bulge-to-disk age contrast, both expected to be high (low) in CBs (PBs). Aims: Our main goal is to explore whether bulges in present-day LTGs segregate into two evolutionary distinct classes, as expected from the standard scenario. Other questions motivating this study center on evolutionary relations between LTG bulges and their hosting disks, and the occurrence of accretion-powered nuclear activity as a function of bulge stellar mass ℳ⋆ and stellar surface density Σ⋆. Methods: In this study, we have combined three techniques - surface photometry, spectral modeling of integral field spectroscopy data and suppression of stellar populations younger than an adjustable age cutoff with the code REMOVEYOUNG (ℛ𝒴) - toward a systematic analysis of the physical and evolutionary properties (e.g., ℳ⋆, Σ⋆ and mass-weighted stellar age ℳ and metallicity ℳ, respectively) of a representative sample of 135 nearby (≤ 130 Mpc) LTGs from the CALIFA survey that cover a range between 108.9 M⊙ and 1011.5 M⊙ in total stellar mass ℳ⋆,T. In particular, the analysis here revolves around ⟨δμ9G⟩, a new distance- and formally extinction-independent measure of the contribution by stellar populations of age ≥ 9 Gyr to the mean r-band surface brightness of the bulge. We argue that ⟨δμ9G⟩ offers a handy semi-empirical tracer of the physical and evolutionary properties of LTG bulges and a promising means for their characterization. Results: The essential insight from this study is that LTG bulges form over 3 dex in ℳ⋆ and more than 1 dex in Σ⋆ a tight continuous sequence of increasing ⟨δμ9G⟩ with increasing ℳ⋆, Σ⋆, ℳ and ℳ. Along this continuum of physical and evolutionary properties, our sample spans a range of 4 mag in ⟨δμ9G⟩: high-⟨δμ9G⟩ bulges are the oldest, densest and most massive ones (ℳ 11.7 Gyr, Σ⋆ > 109 M⊙ kpc-2, ℳ⋆ ≥ 1010 M⊙), whereas the opposite is the case for low-⟨δμ9G⟩ bulges (ℳ 7 Gyr) that generally reside in low-mass LTGs. Furthermore, we find that the bulge-to-disk age and metallicity contrast, as well as the bulge-to-disk mass ratio, show a positive trend with ℳ⋆,T, raising from, respectively, 0 Gyr, 0 dex and 0.25 to 3 Gyr, 0.3 dex and 0.67 across the mass range covered by our sample. Whereas gas excitation in lower-mass (≲ 109.7 M⊙) bulges is invariably dominated by star formation (SF), LINER- and Seyfert-specific emission-line ratios were exclusively documented in high-mass (≳ 1010 M⊙), high-Σ⋆ (≳ 109 M⊙ kpc-2) bulges. This is in agreement with previous work and consistent with the notion that the Eddington ratio or the black hole-to-bulge mass ratio scale with ℳ⋆. The coexistence of Seyfert and SF activity in 20% of higher-ℳ⋆, high-Σ⋆ bulges being spectroscopically classified as Composites suggests that the onset of AGN-driven feedback does not necessarily lead to an abrupt termination of SF in LTG nuclei. Conclusions: The continuity both in the properties of LTG bulges themselves and in their age and metallicity contrast to their parent diskssuggests that these components evolve alongside in a concurrent process that leads to a continuum of physical and evolutionary characteristics. Our results are consistent with a picture where bulge growth in LTGs is driven by a superposition of quick-early and slow-secular processes, the relative importance of which increases with ℳ⋆,T. These processes, which presumably combine in situ SF in the bulge and inward migration of material from the disk, are expected to lead to a non-homologous radial growth of Σ⋆ and a trend for an increasing Sérsic index with increasing galaxy mass. Table C.1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/614/A48

DEFLECTION PRESSURE TESTER

DOEpatents

Cooper, C.M.

1961-01-01

A method and apparatus for determining whether the jacket of a nuclear- fuel slug has a leak are described. The region of the jacket to be leak-tested is sealed off, and gas under pressure is applied thereto. If there is an imperfection, the gas will enter the jacket and bulge another region of the jacket. The bulge occurring is measured by a gage.

The effect of the solar motion on the flux of long-period comets

NASA Astrophysics Data System (ADS)

Gardner, E.; Nurmi, P.; Flynn, C.; Mikkola, S.

2011-02-01

The long-term dynamics of Oort cloud comets are studied under the influence of both the radial and the vertical components of the Galactic tidal field. Sporadic dynamical perturbation processes, such as passing stars, are ignored since we aim to study the influence of just the axisymmetric Galactic tidal field on the cometary motion and how it changes in time. We use a model of the Galaxy with a disc, bulge and dark halo, and a local disc density and disc scalelength constrained to fit the best available observational constraints. By integrating a few million of cometary orbits over 1 Gyr, we calculate the time variable flux of Oort cloud comets that enter the inner Solar system for the cases of a constant Galactic tidal field and a realistically varying tidal field, which is a function of the Sun's orbit. The applied method calculates the evolution of the comets by using first-order averaged mean elements. We find that the periodicity in the cometary flux is complicated and quasi-periodic. The amplitude of the variations in the flux is of the order of 30 per cent. The radial motion of the Sun is the chief cause of this behaviour, and should be taken into account when the Galactic influence on the Oort cloud comets is studied.

On the calibration of the COBE/IRAS dust emission reddening maps

NASA Astrophysics Data System (ADS)

Dutra, C. M.; Ahumada, A. V.; Clariá, J. J.; Bica, E.; Barbuy, B.

2003-09-01

In this work we study the spectral properties (3600-6800 Å) of the nuclear region of early-type galaxies at low (|b|<25deg), intermediate (including surroundings of the Magellanic Clouds) and high (South Polar Cap) Galactic latitudes. We determine the E(B-V) reddening values of the galaxies by matching their continuum distribution with respect to those of reddening-free spectral galaxy templates with similar stellar populations. We also compare the spectroscopic reddening value of each galaxy with that derived from 100 mu m dust emission (E(B-V)FIR) in its line of sight, and we find that there is agreement up to E(B-V)=0.25. Beyond this limit E(B-V)FIR values are higher. Taking into account the data up to E(B-V) ~ 0.7, we derive a calibration factor of 0.016 between the spectroscopic E(B-V) values and Schlegel et al.'s (\\cite{Schlegel1998}) opacities. By combining this result with an AK extinction map built within ten degrees of the Galactic centre using Bulge giants as probes (Dutra et al. \\cite{Dutra2003}), we extended the calibration of dust emission reddening maps to low Galactic latitudes down to |b|=4deg and E(B-V)= 1.6 (AV ~ 5). According to this new calibration, a multiplicative factor of ~0.75 must be applied to the COBE/IRAS dust emission reddening maps. Based on observations made at Complejo Astronómico El Leoncito, which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Pata, Córdoba and San Juan, Argentina.

Si K EDGE STRUCTURE AND VARIABILITY IN GALACTIC X-RAY BINARIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schulz, Norbert S.; Corrales, Lia; Canizares, Claude R.

2016-08-10

We survey the Si K edge structure in various absorbed Galactic low-mass X-ray binaries (LMXBs) to study states of silicon in the inter- and circum-stellar medium. The bulk of these LMXBs lie toward the Galactic bulge region and all have column densities above 10{sup 22} cm{sup −2}. The observations were performed using the Chandra High Energy Transmission Grating Spectrometer. The Si K edge in all sources appears at an energy value of 1844 ± 0.001 eV. The edge exhibits significant substructure that can be described by a near edge absorption feature at 1849 ± 0.002 eV and a far edgemore » absorption feature at 1865 ± 0.002 eV. Both of these absorption features appear variable with equivalent widths up to several mÅ. We can describe the edge structure using several components: multiple edge functions, near edge absorption excesses from silicates in dust form, signatures from X-ray scattering optical depths, and a variable warm absorber from ionized atomic silicon. The measured optical depths of the edges indicate much higher values than expected from atomic silicon cross sections and interstellar medium abundances, and they appear consistent with predictions from silicate X-ray absorption and scattering. A comparison with models also indicates a preference for larger dust grain sizes. In many cases, we identify Si xiii resonance absorption and determine ionization parameters between log ξ = 1.8 and 2.8 and turbulent velocities between 300 and 1000 km s{sup −1}. This places the warm absorber in close vicinity of the X-ray binaries. In some data, we observe a weak edge at 1.840 keV, potentially from a lesser contribution of neutral atomic silicon.« less

Interstellar matter in early-type galaxies. II - The relationship between gaseous components and galaxy types

NASA Technical Reports Server (NTRS)

Bregman, Joel N.; Hogg, David E.; Roberts, Morton S.

1992-01-01

Interstellar components of early-type galaxies are established by galactic type and luminosity in order to search for relationships between the different interstellar components and to test the predictions of theoretical models. Some of the data include observations of neutral hydrogen, carbon monoxide, and radio continuum emission. An alternative distance model which yields LX varies as LB sup 2.45, a relation which is in conflict with simple cooling flow models, is discussed. The dispersion of the X-ray luminosity about this regression line is unlikely to result from stripping. The striking lack of clear correlations between hot and cold interstellar components, taken together with their morphologies, suggests that the cold gas is a disk phenomenon while the hot gas is a bulge phenomenon, with little interaction between the two. The progression of galaxy type from E to Sa is not only a sequence of decreasing stellar bulge-to-disk ratio, but also of hot-to-cold-gas ratio.

High resolution infrared spectra of Bulge Globular Clusters: Liller 1, NGC 6553, and Ter 5

NASA Astrophysics Data System (ADS)

Origlia, L.; Rich, R. M.; Castro, S. M.

2001-12-01

Using the NIRSPEC spectrograph at Keck II, we have obtained echelle spectra covering the range 1.5-1.8μ m for 2 of the brightest giants in Liller 1 and NGC 6553, old metal rich globular clusters in the Galactic bulge. We also report a preliminary analysis for two giants in the obscured bulge globular cluster Ter 5. We use spectrum synthesis for the abundance analysis, and find [Fe/H]=-0.3+/-0.2 and [O/H]=+0.3+/- 0.1 (from the OH lines) for the giants in Liller 1 and NGC 6553. We measure strong lines for the alpha elements Mg, Ca, and Si, but the lower sensitivity of these lines to abundance permits us to only state a general [α /Fe]=+0.3+/-0.2 dex. The composition of the clusters is similar to that of field stars in the bulge and is consistent with a scenario in which the clusters formed early, with rapid enrichment. Our iron abundance for NGC 6553 is poorly consistent with either the low or the high values recently reported in the literature, unless unusally large, or no α -element enhancements are adopted, respectively. We will also present an abundance analsyis for 2 giants in the highly reddened bulge cluster Ter 5, which appears to be near the Solar metallicity. R. Michael Rich acknowledges finacial support from grant AST-0098739, from the National Science Foundation. Data presented herein were obtained at the W.M.Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors gratefully acknowledge those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests. Without their generous hospitality, none of the observations presented would have been possible.

DISK ASSEMBLY AND THE M {sub BH}-{sigma} {sub e} RELATION OF SUPERMASSIVE BLACK HOLES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Debattista, Victor P.; Kazantzidis, Stelios; Van den Bosch, Frank C., E-mail: vpdebattista@gmail.com, E-mail: stelios@mps.ohio-state.edu, E-mail: frank.vandenbosch@yale.edu

2013-03-01

Recent Hubble Space Telescope observations have revealed that a majority of active galactic nuclei (AGNs) at z {approx} 1-3 are resident in isolated disk galaxies, contrary to the usual expectation that AGNs are triggered by mergers. Here we develop a new test of the cosmic evolution of supermassive black holes (SMBHs) in disk galaxies by considering the local population of SMBHs. We show that substantial SMBH growth in spiral galaxies is required as disks assemble. SMBHs exhibit a tight relation between their mass and the velocity dispersion of the spheroid within which they reside, the M {sub .}-{sigma} {sub e}more » relation. In disk galaxies the bulge is the spheroid of interest. We explore the evolution of the M {sub .}-{sigma} {sub e} relation when bulges form together with SMBHs on the M {sub .}-{sigma} {sub e} relation and then slowly re-form a disk around them. The formation of the disk compresses the bulge, raising its {sigma} {sub e}. We present evidence for such compression in the form of larger velocity dispersion of classical bulges compared with elliptical galaxies at the same mass. This compression leads to an offset in the M {sub .}-{sigma} {sub e} relation if it is not accompanied by an increased M {sub .}. We quantify the expected offset based on photometric data and show that, on average, SMBHs must grow by {approx}50%-65% just to remain on the M {sub .}-{sigma} {sub e} relation. We find no significant offset in the M {sub .}-{sigma} {sub e} relations of classical bulges and of ellipticals, implying that SMBHs have been growing along with disks. Our simulations demonstrate that SMBH growth is necessary for the local population of disk galaxies to have remained on the M {sub .}-{sigma} {sub e} relation.« less

The first eclipsing binary catalogue from the MOA-II data base

NASA Astrophysics Data System (ADS)

Li, M. C. A.; Rattenbury, N. J.; Bond, I. A.; Sumi, T.; Bennett, D. P.; Koshimoto, N.; Abe, F.; Asakura, Y.; Barry, R.; Bhattacharya, A.; Donachie, M.; Evans, P.; Freeman, M.; Fukui, A.; Hirao, Y.; Itow, Y.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Muraki, Y.; Nagakane, M.; Ohnishi, K.; Saito, To.; Sharan, A.; Sullivan, D. J.; Suzuki, D.; Tristram, P. J.; Yonehara, A.

2017-09-01

We present the first catalogue of eclipsing binaries in two MOA (Microlensing Observations in Astrophysics) fields towards the Galactic bulge, in which over 8000 candidates, mostly contact and semidetached binaries of periods <1 d, were identified. In this paper, the light curves of a small number of interesting candidates, including eccentric binaries, binaries with noteworthy phase modulations and eclipsing RS Canum Venaticorum type stars, are shown as examples. In addition, we identified three triple object candidates by detecting the light-travel-time effect in their eclipse time variation curves.

The SPM Kinematic Catalogue of Planetary Nebulae

NASA Astrophysics Data System (ADS)

López, J. A.; Richer, M.; Riesgo, H.; Steffen, W.; Meaburn, J.; García-Segura, G.; Escalante, K.

2006-06-01

We present a progress report on the San Pedro Mártir Kinematic Catalogue of Planetary Nebulae. Both, galactic PNe from the disk, bulge and halo populations, and PNe from galaxies in the local group from a diverse range of metallicities have been observed. Most of the observations have been made with the 2.1-m SPM telescope and the Manchester Echelle Spectrometer (Meaburn et al. 2003, RevMexAA, 39, 185). The data consists of spatially resoved long slit spectra at resolutions of ˜ 10 km s^{-1}. For most galactic targets more than one slit positions has been observed. The interpretation of the 3D structures and outflows derived from the kinematic data is being performed with the aid of SHAPE (see the contributions by Steffen, López, & Escalante, Steffen & López in this symposium). This unique database of high dispersion spectra will allow a firm characterisation of nebular shell properties in relation to progenitors from diverse stellar populations.

Jupiter's hydrogen bulge: A Cassini perspective

NASA Astrophysics Data System (ADS)

Melin, Henrik; Stallard, T. S.

2016-11-01

We present observations of H Ly-α and H2 emissions on the body of Jupiter obtained during the Cassini flyby in late 2000 and early 2001. The H Ly-α emission is highly organised by System III longitude and latitude, peaking at a brightness of 22 kR between 90 and 120° longitude. This is known as the H Ly-α 'bulge'. These observations add to a number of previous studies, showing that the feature is very long-lived, present over several decades. We show that there is a strong correlation between the prevailing solar H Ly-α flux (measured at Earth) and the peak brightness of the H Ly-α bulge at Jupiter, which supports the notion that it is primarily driven by solar resonance scatter. The H Ly-α brightness distribution is not aligned with the jovigraphic equator, but is approximately aligned with the particle drift equator of some, but not all, major Jupiter magnetic field models. On the time scale of days, the bulge region appears twice as variable as the non-bulge region. We propose that the electron recombination of H3+ is an important reaction for the generation of the H Ly-α bulge, which requires an enhancement of soft electrons at the location of the bulge. We derive an equatorial H3+ lifetime of 1.6 ± 0.4 h and a corresponding column averaged electron density of 1.7 × 109 m-3.

River bulge evolution and dynamics in a non-tidal sea - Daugava River plume in the Gulf of Riga, Baltic Sea

NASA Astrophysics Data System (ADS)

Soosaar, E.; Maljutenko, I.; Uiboupin, R.; Skudra, M.; Raudsepp, U.

2015-10-01

Satellite remote sensing imagery and numerical modelling were used for the study of river bulge evolution and dynamics in a non-tidal sea, the Gulf of Riga (GoR) in the Baltic Sea. Total suspended matter (TSM) images showed a clearly formed anti-cyclonically rotating river bulge from Daugava River discharge during the studied low wind period. In about 7-8 days the bulge grew up to 20 km in diameter, before being diluted. Bulge growth rate was estimated as rb ~ t 0.31± 0.23 (R2 = 0.87). A high resolution (horizontal grid step of 125 m) General Estuarine Transport Model (GETM) was used for detailed description of the development of the river plume in the southern GoR over the period when satellite images were acquired. In the model simulation, the rb ~ t 0.5± 0.04 (R2 = 0.90). Both the model simulation and the satellite images showed that river water was mainly contained in the bulge and there were numerous intrusions at the outer perimeter of the bulge. We made numerical sensitivity tests with actual bathymetry and measured river runoff without wind forcing: (1) having initial 3-dimensional density distribution, (2) using initially a homogeneous ambient density field. In the first case, the anti-cyclonic bulge did not develop within the course of the model simulation and coastal current was kept offshore due to ambient density-driven circulation. In the second case, the river plume developed steadily into an anti-cyclonically recirculating bulge and a coastal current. This showed a significant effect of the wind in the evolution of the river bulge, even if the wind speed was moderate (3-4 m s-1). In the second case, rb ~ t 0.28± 0.01 (R2 = 0.98). While previous studies conclude that mid-field bulge region is governed by balance between centrifugal, Coriolis and pressure gradient terms, our study showed that geostrophic balance is valid for the entire mid-field of the bulge. In addition, while there is discharge into the homogenous GoR in case of high inflow Rossby number, the river inflow might split into two jets, with strong mixing zone in-between, in the plume near field region.

A Comparison of Galaxy Bulge+Disk Decomposition Between Pan-STARRS and SDSS

NASA Astrophysics Data System (ADS)

Lokken, Martine Elena; McPartland, Conor; Sanders, David B.

2018-01-01

Measurements of the size and shape of bulges in galaxies provide key constraints for models of galaxy evolution. A comprehensive catalog of bulge measurements for Sloan Digital Sky Survey (SDSS) DR7 galaxies is currently available to the public. However, the Pan-STARRS1 (PS1) 3π survey now covers the same region with ~1-2 mag deeper photometry, a ~10-30% smaller PSF, and additional coverage in y-band. To test how much improvement in galaxy parameter measurements (e.g. bulge + disk) can be achieved using the new PS1 data, we make use of ultra-deep imaging data from the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP). We fit bulge+disk models to images of 372 bright (mi < 18.5) galaxies detected in all three surveys. Comparison of galaxy parameters derived from SDSS and PS1 images with those measured from HSC-SSP images shows a tighter correlation between PS1 and SSP measurements for both bulge and disk parameters. Bulge parameters, such as bulge-to-total fraction and bulge radius, show the strongest improvement. However, measurements of all parameters degrade for galaxies with total r-band magnitude below the SDSS spectroscopic limit, mr = 17.7. We plan to use the PS1 3π survey data to produce an updated catalog of bulge+disk decomposition measurements for the entire SDSS DR7 spectroscopic galaxy sample.

Ongoing Massive Star Formation in the Bulge of M51

NASA Astrophysics Data System (ADS)

Lamers, H. J. G. L. M.; Panagia, N.; Scuderi, S.; Romaniello, M.; Spaans, M.; de Wit, W. J.; Kirshner, R.

2002-02-01

We present a study of Hubble Space Telescope Wide Field Planetary Camera 2 observations of the inner kiloparsec of the interacting galaxy M51 in six bands from 2550 to 8140 Å. The images show an oval-shaped area (which we call the ``bulge'') of about 11''×16'', or 450×650 pc, around the nucleus that is dominated by a smooth ``yellow/reddish'' background population with overimposed dust lanes. These dust lanes are the inner extensions of the spiral arms. The extinction properties, derived in four fields in and outside dust lanes, are similar to the Galactic extinction law. The reddish stellar population has an intrinsic color of (B-V)0~=1.0, suggesting an age in excess of 5 Gyr. We found 30 bright pointlike sources in the bulge of M51, i.e., within 110-350 pc from the nucleus. The point sources have 21.4

Detailed histological structure of human hair follicle bulge region at different ages: a visible niche for nesting adult stem cells.

PubMed

Wang, Xiong; Shi, Ying; Zhou, Qiong; Liu, Xiaoming; Xu, Shizheng; Lei, Tiechi

2012-10-01

In the bulge region of the hair follicle, a densely and concentrically packed cell mass is encircled by the arrector pili muscle (APM), which offers a specilized microenvironment (niche) for housing heterogeneous adult stem cells. However, the detailed histological architecture and the cellular composition of the bulge region warrants intensive study and may have implications for the regulation of hair follicle growth regulation. This study was designed to define the gene-expression profiles of putative stem cells and lineage-specific precursors in the mid-portions of plucked hair follicles prepared according to the presence of detectable autofluorescence. The structure was also characterized by using a consecutive sectioning technique. The bulge region of the hair follicle with autofluorescence was precisely excised by employing a micro-dissection procedure. Semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) was performed to identify the gene expression profiles specific for epithelial, melanocyte and stromal stem cells in the bulge region of the hair follicle visualized by autofluorescence. The morphology and its age-dependent changes of bulge region of the hair follicles with autofluorescence segment were also examined in 9 scalp skin specimens collected from patients aged 30 weeks to 75 years, by serial sectioning and immuno-staining. Gene expression profile analysis revealed that there were cells with mRNA transcripts of Dct(Hi)Tyrase(Lo)-Tyrp1(Lo)MC1R(Lo)MITF(Lo)/K15(Hi)/NPNT(Hi) in the bulge region of the hair follicle with autofluorescence segments, which differed from the patterns in hair bulbs. Small cell-protrusions that sprouted from the outer root sheath (ORS) were clearly observed at the APM inserting level in serial sections of hair follicles by immunohistological staining, which were characteristically replete with K15+/K19+expressing cells. Likewise, the muscle bundles of APM positive for smooth muscle actin intimately encircled these cell-protrusions, and the occurrence frequency of the cell-protrusions was increased in fetal scalp skin compared with adult scalp skin. This study provided the evidence that the cell-protrusions occurring at the ORS relative to the APM insertion are more likely to be characteristic of the visible niches that are filled with abundant stem cells. The occurrence frequency of these cell-protrusions was significantly increased in fetal scalp skin samples (128%) as compared with the scalp skins of younger (49.4%) and older (25.4%) adults (P<0.01), but difference in the frequency between the two adult groups were not significant. These results indicated that these cell-protrusions function as a niche house for the myriad stem cells and/or precursors to meet the needs of the development of hair follicles in an embryo. The micro-dissection used in this study was simple and reliable in excising the bulge region of the hair follicle with autofluorescence segments dependent on their autofluorescence is of value for the study of stem cell culture.

Stellar Photometric Structures of the Host Galaxies of Nearby Type 1 Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Kim, Minjin; Ho, Luis C.; Peng, Chien Y.; Barth, Aaron J.; Im, Myungshin

2017-10-01

We present detailed image analysis of rest-frame optical images of 235 low-redshift (z ≲ 0.35) Type 1 active galactic nuclei (AGNs) observed with the Hubble Space Telescope. The high-resolution images enable us to perform rigorous two-dimensional image modeling to decouple the luminous central point source from the host galaxy, which, when warranted, is further decomposed into its principal structural components (bulge, bar, and disk). In many cases, care must be taken to account for structural complexities such as spiral arms, tidal features, and overlapping or interacting companion galaxies. We employ Fourier modes to characterize the degree of asymmetry of the light distribution of the stars as a quantitative measure of morphological distortion due to interactions or mergers. We examine the dependence of the physical parameters of the host galaxies on the properties of the AGNs, namely, radio-loudness and the width of the broad emission lines. In accordance with previous studies, narrow-line (Hβ FWHM ≤ 2000 km s-1) Type 1 AGNs, in contrast to their broad-line (Hβ FWHM > 2000 km s-1) counterparts, are preferentially hosted in later-type, lower-luminosity galaxies, which have a higher incidence of pseudo-bulges, are more frequently barred, and are less morphologically disturbed. This suggests that narrow-line Type 1 AGNs experienced a more quiescent evolutionary history driven primarily by internal secular evolution instead of external dynamical perturbations. The fraction of AGN hosts showing merger signatures is larger for more luminous sources. Radio-loud AGNs generally preferentially live in earlier-type (bulge-dominated), more massive hosts, although a minority of them appear to contain a significant disk component. We do not find convincing evidence for enhanced merger signatures in the radio-loud population. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS5-26555. These data are associated with program AR-12133 and AR-12818.

Photometric evolution of seven recent novae and the double-component characterizing the light curve of those emitting in gamma rays

NASA Astrophysics Data System (ADS)

Munari, U.; Hambsch, F.-J.; Frigo, A.

2017-08-01

The BVI light curves of seven recent novae (I.e. V1534 Sco, V1535 Sco, V2949 Oph, V3661 Oph, MASTER OT J010603.18-744715.8, TCP J1734475-240942 and ASASSN-16ma) have been extensively mapped with daily robotic observations from Atacama (Chile): five belong to the Galactic bulge, one to the Small Magellanic Cloud and another is a Galactic disc object. The two programme novae detected in γ-rays by Fermi-LAT (I.e. TCP J1734475-240942 and ASASSN-16ma) are bulge objects with unevolved companions. They distinguish themselves by showing a double-component optical light curve. The first component to develop is the fireball from freely expanding, ballistic-launched ejecta, with a time of passage through maximum that is strongly dependent on wavelength (˜1 d delay between the B and I bands). The second component, emerging simultaneously with the nova detection in γ-rays, evolves at a slower pace, its optical brightness being proportional to the γ-ray flux, and its passage through maximum not dependent on wavelength. The fact that γ-rays are detected at a flux level that differs by four times from novae at the distance of the bulge seems to suggest that γ-ray emission is not a widespread property of normal novae. We discuss the advantages offered by high-quality photometric observations collected with only one telescope (as opposed to data provided by a number of different instruments). We also observe the effects of the wavelength dependence of fireball expansion, the recombination in the flashed wind of a giant companion, the subtle presence of hiccups and plateaus, and the super-soft X-ray emission and its switch-off. Four programme novae (V2949 Oph, V3661 Oph, TCP J18102829-2729590 and ASASSN-16ma) have normal dwarf companions: V1534 Sco contains an M3 III giant, V1535 Sco a K-type giant and MASTER OT J010603.18-744715.8 a subgiant. We also comment briefly on the maximum absolute magnitude relation with decline time (MMRD).

Dynamics of Gas Near the Galactic Centre

NASA Astrophysics Data System (ADS)

Jenkins, A.; Binney, J.

1994-10-01

We simulate the flow of gas in the Binney et al. model of the bar at the centre of the Milky Way. We argue that the flow of a clumpy interstellar medium is most realistically simulated by a sticky-particle scheme, and investigate two such schemes. In both schemes orbits close to the cusped orbit rapidly become depopulated. This depopulation places a lower limit on the pattern speed since it implies that in the (1, v) plane the cusped orbit lies significantly inside the peak of the Hi terminal-velocity envelope at 1 20. We find that the size of the central molecular disc and the magnitudes of the observed forbidden velocities constrain the eccentricity of the Galactic bar to values similar to that arbitrarily assumed by Binney et al. We study the accretion by the nuclear disc of matter shed by dying bulge stars. We estimate that mass loss by the bulge can replenish the Hi in the nuclear disc within two bar rotation periods, in good agreement with the predictions of the simulations. When accretion of gas from the bulge is included, fine-scale irregular structure persists in the nuclear disc. This structure gives rise to features in longitude-velocity plots which depend significantly on viewing angle, and consequently give rise to asymmetries in longitude. These asymmetries are, however, much less pronounced than those in the observational plots. We conclude that the addition of hydrodynamics to the Binney et al. model does not resolve some important discrepancies between theory and observation. The model's basic idea does, however, have high a priori probability and has enjoyed some significant successes, while a number of potentially important physical processes - most notably the self-gravity of interstellar gas - are neglected in the present simulations. In view of the deficiencies of our simulations and interesting parallels we do observe between simulated and observational longitude-velocity plots, we believe it would be premature to reject the Binney et al. model prior to exploring high-quality three-dimensional simulations that include self-gravitating stars and gas. Key words: accretion, accretion discs - ISM: kinematics and dynamics - ISM: structure -Galaxy: centre - Galaxy: kinematics and dynamics - radio lines: ISM.

Image decomposition of barred galaxies and AGN hosts

NASA Astrophysics Data System (ADS)

Gadotti, Dimitri Alexei

2008-02-01

I present the results of multicomponent decomposition of V and R broad-band images of a sample of 17 nearby galaxies, most of them hosting bars and active galactic nuclei (AGN). I use BUDDA v2.1 to produce the fits, allowing the inclusion of bars and AGN in the models. A comparison with previous results from the literature shows a fairly good agreement. It is found that the axial ratio of bars, as measured from ellipse fits, can be severely underestimated if the galaxy axisymmetric component is relatively luminous. Thus, reliable bar axial ratios can only be determined by taking into account the contributions of bulge and disc to the light distribution in the galaxy image. Through a number of tests, I show that neglecting bars when modelling barred galaxies can result in an overestimation of the bulge-to-total luminosity ratio of a factor of 2. Similar effects result when bright, type 1 AGN are not considered in the models. By artificially redshifting the images, I show that the structural parameters of more distant galaxies can in general be reliably retrieved through image fitting, at least up to the point where the physical spatial resolution is ~1.5kpc. This corresponds, for instance, to images of galaxies at z = 0.05 with a seeing full width at half-maximum (FWHM) of 1.5arcsec, typical of the Sloan Digital Sky Survey (SDSS). In addition, such a resolution is also similar to what can be achieved with the Hubble Space Telescope (HST), and ground-based telescopes with adaptive optics, at z ~ 1-2. Thus, these results also concern deeper studies such as COSMOS and SINS. This exercise shows that disc parameters are particularly robust, but bulge parameters are prone to errors if its effective radius is small compared to the seeing radius, and might suffer from systematic effects. For instance, the bulge-to-total luminosity ratio is systematically overestimated, on average, by 0.05 (i.e. 5 per cent of the galaxy total luminosity). In this low-resolution regime, the effects of ignoring bars are still present, but AGN light is smeared out. I briefly discuss the consequences of these results to studies of the structural properties of galaxies, in particular on the stellar mass budget in the local Universe. With reasonable assumptions, it is possible to show that the stellar content in bars can be similar to that in classical bulges and elliptical galaxies. Finally, I revisit the cases of NGC4608 and 5701 and show that the lack of stars in the disc region inside the bar radius is significant. Accordingly, the best-fitting model for the former uses a Freeman type II disc.

River bulge evolution and dynamics in a non-tidal sea - Daugava River plume in the Gulf of Riga, Baltic Sea

NASA Astrophysics Data System (ADS)

Soosaar, Edith; Maljutenko, Ilja; Uiboupin, Rivo; Skudra, Maris; Raudsepp, Urmas

2016-03-01

Satellite remote sensing imagery and numerical modelling were used for the study of river bulge evolution and dynamics in a non-tidal sea, the Gulf of Riga (GoR) in the Baltic Sea. Total suspended matter (TSM) images showed a clearly formed anti-cyclonically rotating river bulge from Daugava River discharge during the studied low wind period. In about 7-8 days the bulge grew up to 20 km in diameter, before being diluted. A high-resolution (horizontal grid step of 125 m) General Estuarine Transport Model (GETM) was used for detailed description of the development of the river plume in the southern GoR over the period when satellite images were acquired. In the model simulation, the bulge growth rate was estimated as rb ˜ t0.5 ± 0.04 (R2 = 0.90). Both the model simulation and the satellite images showed that river water was mainly contained in the bulge and there were numerous intrusions at the outer perimeter of the bulge. We performed numerical sensitivity tests with actual bathymetry and measured river runoff without wind forcing (1) having an initial three-dimensional density distribution, and (2) using initially a homogeneous ambient density field. In the first case, the anti-cyclonic bulge did not develop within the course of the model simulation and the coastal current was kept offshore due to ambient density-driven circulation. In the second case, the river plume developed steadily into an anti-cyclonically recirculating bulge, with rb ˜ t0.28 ± 0.01 (R2 = 0.98), and a coastal current. Additional simulations with constant cross-shore and alongshore winds showed a significant effect of the wind in the evolution of the river bulge, even if the wind speed was moderate (3-4 m s-1). While previous studies conclude that the mid-field bulge region is governed by a balance between centrifugal, Coriolis and pressure gradient terms, our study showed that geostrophic balance is valid for the entire mid-field of the bulge, except during the 1-1.5 rotation period at the beginning of the bulge formation. In addition, while there is discharge into the homogenous GoR in the case of a high inflow Rossby number, the river inflow might split into two jets, with strong mixing zone in-between, in the plume near-field region.

The Host Galaxies of X-Ray Selected Active Galactic Nuclei to z - 2.5: Structure, Star-Formation and Their Relationships from CANDELS and Herschel/Pacs

NASA Technical Reports Server (NTRS)

Rosario, D.J.; McIntosh, D. H.; van der Wel, A.; Kartaltepe, J.; Lang, P.; Santini, P.; Wuyts, S.; Lutz, D.; Rafelski, M.; Villforth, C.;

MACHO RR Lyrae in the Inner Halo and Bulge

NASA Astrophysics Data System (ADS)

Minniti, Dante; Alcock, Charles; Allsman, Robyn A.; Alves, David; Axelrod, Tim S.; Becker, Andrew C.; Bennett, David; Cook, Kem H.; Drake, Andrew J.; Freeman, Ken C.; Griest, Kim; Lehner, Matt; Marshall, Stuart; Peterson, Bruce; Pratt, Mark; Quinn, Peter; Rodgers, Alex; Stubbs, Chris; Sutherland, Will; Tomaney, Austin; Vandehei, Thor; Welch, Doug L.

The RR Lyrae in the bulge have been proposed to be the oldest populations in the Milky Way, tracers of how the galaxy formed. We study here the distribution of ~1600 bulge RR Lyrae stars found by the MACHO Project. The RR Lyrae with Galactocentric radius 0.4

Gemini NIFS survey of feeding and feedback processes in nearby active galaxies - I. Stellar kinematics

NASA Astrophysics Data System (ADS)

Riffel, Rogemar A.; Storchi-Bergmann, Thaisa; Riffel, Rogerio; Dahmer-Hahn, Luis G.; Diniz, Marlon R.; Schönell, Astor J.; Dametto, Natacha Z.

2017-09-01

We use the Gemini Near-Infrared Integral Field Spectrograph (NIFS) to map the stellar kinematics of the inner few hundred parsecs of a sample of 16 nearby Seyfert galaxies, at a spatial resolution of tens of parsecs and spectral resolution of 40 km s- 1. We find that the line-of-sight (LOS) velocity fields for most galaxies are well reproduced by rotating disc models. The kinematic position angle (PA) derived for the LOS velocity field is consistent with the large-scale photometric PA. The residual velocities are correlated with the hard X-ray luminosity, suggesting that more luminous active galactic nuclei have a larger impact in the surrounding stellar dynamics. The central velocity dispersion values are usually higher than the rotation velocity amplitude, what we attribute to the strong contribution of bulge kinematics in these inner regions. For 50 per cent of the galaxies, we find an inverse correlation between the velocities and the h3 Gauss-Hermitte moment, implying red wings in the blueshifted side and blue wings in the redshifted side of the velocity field, attributed to the movement of the bulge stars lagging the rotation. Two of the 16 galaxies (NGC 5899 and Mrk 1066) show an S-shape zero velocity line, attributed to the gravitational potential of a nuclear bar. Velocity dispersion (σ) maps show rings of low-σ values (˜50-80 km s- 1) for four objects and 'patches' of low σ for six galaxies at 150-250 pc from the nucleus, attributed to young/ intermediate age stellar populations.

Hidden Broad-line Regions in Seyfert 2 Galaxies: From the Spectropolarimetric Perspective

NASA Astrophysics Data System (ADS)

Du, Pu; Wang, Jian-Min; Zhang, Zhi-Xiang

2017-05-01

The hidden broad-line regions (BLRs) in Seyfert 2 galaxies, which display broad emission lines (BELs) in their polarized spectra, are a key piece of evidence in support of the unified model for active galactic nuclei (AGNs). However, the detailed kinematics and geometry of hidden BLRs are still not fully understood. The virial factor obtained from reverberation mapping of type 1 AGNs may be a useful diagnostic of the nature of hidden BLRs in type 2 objects. In order to understand the hidden BLRs, we compile six type 2 objects from the literature with polarized BELs and dynamical measurements of black hole masses. All of them contain pseudobulges. We estimate their virial factors, and find the average value is 0.60 and the standard deviation is 0.69, which agree well with the value of type 1 AGNs with pseudobulges. This study demonstrates that (1) the geometry and kinematics of BLR are similar in type 1 and type 2 AGNs of the same bulge type (pseudobulges), and (2) the small values of virial factors in Seyfert 2 galaxies suggest that, similar to type 1 AGNs, BLRs tend to be very thick disks in type 2 objects.

Hidden Broad-line Regions in Seyfert 2 Galaxies: From the Spectropolarimetric Perspective

DOE Office of Scientific and Technical Information (OSTI.GOV)

Du, Pu; Wang, Jian-Min; Zhang, Zhi-Xiang, E-mail: dupu@ihep.ac.cn

2017-05-01

The hidden broad-line regions (BLRs) in Seyfert 2 galaxies, which display broad emission lines (BELs) in their polarized spectra, are a key piece of evidence in support of the unified model for active galactic nuclei (AGNs). However, the detailed kinematics and geometry of hidden BLRs are still not fully understood. The virial factor obtained from reverberation mapping of type 1 AGNs may be a useful diagnostic of the nature of hidden BLRs in type 2 objects. In order to understand the hidden BLRs, we compile six type 2 objects from the literature with polarized BELs and dynamical measurements of blackmore » hole masses. All of them contain pseudobulges. We estimate their virial factors, and find the average value is 0.60 and the standard deviation is 0.69, which agree well with the value of type 1 AGNs with pseudobulges. This study demonstrates that (1) the geometry and kinematics of BLR are similar in type 1 and type 2 AGNs of the same bulge type (pseudobulges), and (2) the small values of virial factors in Seyfert 2 galaxies suggest that, similar to type 1 AGNs, BLRs tend to be very thick disks in type 2 objects.« less

Hydrogeologic processes of large-scale tectonomagmatic complexes in Mongolia-southern Siberia and on Mars

USGS Publications Warehouse

Komatsu, G.; Dohm, J.M.; Hare, T.M.

2004-01-01

Large-scale tectonomagmatic complexes are common on Earth and Mars. Many of these complexes are created or at least influenced by mantle processes, including a wide array of plume types ranging from superplumes to mantle plumes. Among the most prominent complexes, the Mongolian plateau on Earth and the Tharsis bulge on Mars share remarkable similarities in terms of large domal uplifted areas, great rift canyon systems, and widespread volcanism on their surfaces. Water has also played an important role in the development of the two complexes. In general, atmospheric and surface water play a bigger role in the development of the present-day Mongolian plateau than for the Tharsis bulge, as evidenced by highly developed drainages and thick accumulation of sediments in the basins of the Baikal rift system. On the Tharsis bulge, however, water appears to have remained as ground ice except during periods of elevated magmatic activity. Glacial and periglacial processes are well documented for the Mongolian plateau and are also reported for parts of the Tharsis bulge. Ice-magma interactions, which are represented by the formation of subice volcanoes in parts of the Mongolian plateau region, have been reported for the Valles Marineris region of Mars. The complexes are also characterized by cataclysmic floods, but their triggering mechanism may differ: mainly ice-dam failures for the Mongolian plateau and outburst of groundwater for the Tharsis bulge, probably by magma-ice interactions, although ice-dam failures within the Valles Marineris region cannot be ruled out as a possible contributor. Comparative studies of the Mongolian plateau and Tharsis bulge provide excellent opportunities for understanding surface manifestations of plume-driven processes on terrestrial planets and how they interact with hydro-cryospheres. ?? 2004 Geological Society of America.

Small helium-cooled infrared telescope experiment for Spacelab-2 (IRT)

NASA Technical Reports Server (NTRS)

Fazio, Giovanni G.

1990-01-01

The Infrared Telescope (IRT) experiment, flown on Spacelab-2, was used to make infrared measurements between 2 and 120 microns. The objectives were multidisciplinary in nature with astrophysical goals of mapping the diffuse cosmic emission and extended infrared sources and technical goals of measuring the induced Shuttle environment, studying properties of superfluid helium in space, and testing various infrared telescope system designs. Astrophysically, new data were obtained on the structure of the Galaxy at near-infrared wavelengths. A summary of the large scale diffuse near-infrared observations of the Galaxy by the IRT is presented, as well as a summary of the preliminary results obtained from this data on the structure of the galactic disk and bulge. The importance of combining CO and near-infrared maps of similar resolution to determine a 3-D model of galactic extinction is demonstrated. The IRT data are used, in conjunction with a proposed galactic model, to make preliminary measurements of the global scale parameters of the Galaxy. During the mission substantial amounts of data were obtained concerning the induced Shuttle environment. An experiment was also performed to measure spacecraft glow in the IR.

Cepheid variables in the flared outer disk of our galaxy.

PubMed

Feast, Michael W; Menzies, John W; Matsunaga, Noriyuki; Whitelock, Patricia A

2014-05-15

Flaring and warping of the disk of the Milky Way have been inferred from observations of atomic hydrogen but stars associated with flaring have not hitherto been reported. In the area beyond the Galactic centre the stars are largely hidden from view by dust, and the kinematic distances of the gas cannot be estimated. Thirty-two possible Cepheid stars (young pulsating variable stars) in the direction of the Galactic bulge were recently identified. With their well-calibrated period-luminosity relationships, Cepheid stars are useful distance indicators. When observations of these stars are made in two colours, so that their distance and reddening can be determined simultaneously, the problems of dust obscuration are minimized. Here we report that five of the candidates are classical Cepheid stars. These five stars are distributed from approximately one to two kiloparsecs above and below the plane of the Galaxy, at radial distances of about 13 to 22 kiloparsecs from the centre. The presence of these relatively young (less than 130 million years old) stars so far from the Galactic plane is puzzling, unless they are in the flared outer disk. If so, they may be associated with the outer molecular arm.

The Heavy Ion Afternoon Bulge: Structure and Formation Mechanisms

NASA Astrophysics Data System (ADS)

Fernandes, P. A.; Larsen, B.; Skoug, R. M.; Reeves, G. D.; Denton, M.; Engel, M.; Ferradas, C.; Funsten, H. O.; Henderson, M. G.; Jahn, J. M.; Morley, S.; Thomsen, M. F.

2017-12-01

Recent observations of near-equatorial inner magnetosphere plasma composition indicate the presence of an "afternoon bulge" plasma population at low L-shell. A detailed statistical survey using HOPE data characterized this afternoon bulge as an enhancement in 10 keV O+ and He+ ions extending from 1100-2200 MLT and 2 ≤ L ≤ 4 during quiet/moderate geomagnetic activity (Kp < 5). This statistical HOPE study postulated that formation of the bulge is caused by variations in Kp: 10 keV particles have access to low L-shells during geomagnetically active times and become trapped during the transition to quiet times. In this study, we expand on previous observations of the afternoon bulge by examining individual transits of this feature by the Van Allen Probes. We analyze periods with optimal spacecraft transits of the afternoon bulge region, including: May - Oct. 2013, Feb. - June 2014, and Apr. - Aug. 2015. We determine the presence and duration of the bulge during case studies representing three categories of geomagnetic activity: 1) extended quiet geomagnetic conditions; 2) sharp transitions of Kp from active to quiet conditions; and 3) rises and falls in Kp on the time scales of spacecraft orbits to days. We thoroughly characterize the energy structure of the bulge as a function of Kp. We also analyze these transits of the bulge in the context of plasma access using both drift path modeling and UBK-derived energy access maps.

Construction of Database for Pulsating Variable Stars

NASA Astrophysics Data System (ADS)

Chen, B. Q.; Yang, M.; Jiang, B. W.

2011-07-01

A database for the pulsating variable stars is constructed for Chinese astronomers to study the variable stars conveniently. The database includes about 230000 variable stars in the Galactic bulge, LMC and SMC observed by the MACHO (MAssive Compact Halo Objects) and OGLE (Optical Gravitational Lensing Experiment) projects at present. The software used for the construction is LAMP, i.e., Linux+Apache+MySQL+PHP. A web page is provided to search the photometric data and the light curve in the database through the right ascension and declination of the object. More data will be incorporated into the database.

Ring Around the Black Hole

NASA Technical Reports Server (NTRS)

Wanjek, Christopher

2003-01-01

Regardless of size, black holes easily acquire accretion disks. Supermassive black holes can feast on the bountiful interstellar gas in galactic nuclei. Small black holes formed from collapsing stars often belong to binary systems in which a bulging companion star can spill some of its gas into the black hole s reach. In the chaotic mess of the accretion disk, atoms collide with one another. Swirling plasma reaches speeds upward of 10% that of light and glows brightly in many wavebands, particularly in X-rays. Gas gets blown back by a wind of radiation from the inner disk. New material enters the disks from different directions.

A scaling law of radial gas distribution in disk galaxies

NASA Technical Reports Server (NTRS)

Wang, Zhong

1990-01-01

Based on the idea that local conditions within a galactic disk largely determine the region's evolution time scale, researchers built a theoretical model to take into account molecular cloud and star formations in the disk evolution process. Despite some variations that may be caused by spiral arms and central bulge masses, they found that many late-type galaxies show consistency with the model in their radial atomic and molecular gas profiles. In particular, researchers propose that a scaling law be used to generalize the gas distribution characteristics. This scaling law may be useful in helping to understand the observed gas contents in many galaxies. Their model assumes an exponential mass distribution with disk radius. Most of the mass are in atomic gas state at the beginning of the evolution. Molecular clouds form through a modified Schmidt Law which takes into account gravitational instabilities in a possible three-phase structure of diffuse interstellar medium (McKee and Ostriker, 1977; Balbus and Cowie, 1985); whereas star formation proceeds presumably unaffected by the environmental conditions outside of molecular clouds (Young, 1987). In such a model both atomic and molecular gas profiles in a typical galactic disk (as a result of the evolution) can be fitted simultaneously by adjusting the efficiency constants. Galaxies of different sizes and masses, on the other hand, can be compared with the model by simply scaling their characteristic length scales and shifting their radial ranges to match the assumed disk total mass profile sigma tot(r).

Black Holes Lead Galaxy Growth, New Research Shows

NASA Astrophysics Data System (ADS)

2009-01-01

Astronomers may have solved a cosmic chicken-and-egg problem -- the question of which formed first in the early Universe -- galaxies or the supermassive black holes seen at their cores. "It looks like the black holes came first. The evidence is piling up," said Chris Carilli, of the National Radio Astronomy Observatory (NRAO). Carilli outlined the conclusions from recent research done by an international team studying conditions in the first billion years of the Universe's history in a lecture presented to the American Astronomical Society's meeting in Long Beach, California. Gas in Distant Galaxy VLA image (right) of gas in young galaxy seen as it was when the Universe was only 870 million years old. CREDIT: NRAO/AUI/NSF, SDSS Full-size JPEG, 323 KB PDF file, 180 KB Galaxy image, no annotation, JPEG 21 KB Earlier studies of galaxies and their central black holes in the nearby Universe revealed an intriguing linkage between the masses of the black holes and of the central "bulges" of stars and gas in the galaxies. The ratio of the black hole and the bulge mass is nearly the same for a wide range of galactic sizes and ages. For central black holes from a few million to many billions of times the mass of our Sun, the black hole's mass is about one one-thousandth of the mass of the surrounding galactic bulge. "This constant ratio indicates that the black hole and the bulge affect each others' growth in some sort of interactive relationship," said Dominik Riechers, of Caltech. "The big question has been whether one grows before the other or if they grow together, maintaining their mass ratio throughout the entire process." In the past few years, scientists have used the National Science Foundation's Very Large Array radio telescope and the Plateau de Bure Interferometer in France to peer far back in the 13.7 billion-year history of the Universe, to the dawn of the first galaxies. "We finally have been able to measure black-hole and bulge masses in several galaxies seen as they were in the first billion years after the Big Bang, and the evidence suggests that the constant ratio seen nearby may not hold in the early Universe. The black holes in these young galaxies are much more massive compared to the bulges than those seen in the nearby Universe," said Fabian Walter of the Max-Planck Institute for Astronomy (MPIfA) in Germany. "The implication is that the black holes started growing first." The next challenge is to figure out how the black hole and the bulge affect each others' growth. "We don't know what mechanism is at work here, and why, at some point in the process, the 'standard' ratio between the masses is established," Riechers said. New telescopes now under construction will be key tools for unraveling this mystery, Carilli explained. "The Expanded Very Large Array (EVLA) and the Atacama Large Millimeter/submillimeter Array (ALMA) will give us dramatic improvements in sensitivity and the resolving power to image the gas in these galaxies on the small scales required to make detailed studies of their dynamics," he said. "To understand how the Universe got to be the way it is today, we must understand how the first stars and galaxies were formed when the Universe was young. With the new observatories we'll have in the next few years, we'll have the opportunity to learn important details from the era when the Universe was only a toddler compared to today's adult," Carilli said. Carilli, Riechers and Walter worked with Frank Bertoldi of Bonn University; Karl Menten of MPIfR; and Pierre Cox and Roberto Neri of the Insitute for Millimeter Radio Astronomy (IRAM) in France.

Radial Distribution of X-Ray Point Sources Near the Galactic Center

NASA Astrophysics Data System (ADS)

Hong, Jae Sub; van den Berg, Maureen; Grindlay, Jonathan E.; Laycock, Silas

2009-11-01

We present the log N-log S and spatial distributions of X-ray point sources in seven Galactic bulge (GB) fields within 4° from the Galactic center (GC). We compare the properties of 1159 X-ray point sources discovered in our deep (100 ks) Chandra observations of three low extinction Window fields near the GC with the X-ray sources in the other GB fields centered around Sgr B2, Sgr C, the Arches Cluster, and Sgr A* using Chandra archival data. To reduce the systematic errors induced by the uncertain X-ray spectra of the sources coupled with field-and-distance-dependent extinction, we classify the X-ray sources using quantile analysis and estimate their fluxes accordingly. The result indicates that the GB X-ray population is highly concentrated at the center, more heavily than the stellar distribution models. It extends out to more than 1fdg4 from the GC, and the projected density follows an empirical radial relation inversely proportional to the offset from the GC. We also compare the total X-ray and infrared surface brightness using the Chandra and Spitzer observations of the regions. The radial distribution of the total infrared surface brightness from the 3.6 band μm images appears to resemble the radial distribution of the X-ray point sources better than that predicted by the stellar distribution models. Assuming a simple power-law model for the X-ray spectra, the closer to the GC the intrinsically harder the X-ray spectra appear, but adding an iron emission line at 6.7 keV in the model allows the spectra of the GB X-ray sources to be largely consistent across the region. This implies that the majority of these GB X-ray sources can be of the same or similar type. Their X-ray luminosity and spectral properties support the idea that the most likely candidate is magnetic cataclysmic variables (CVs), primarily intermediate polars (IPs). Their observed number density is also consistent with the majority being IPs, provided the relative CV to star density in the GB is not smaller than the value in the local solar neighborhood.

On the effect of galactic outflows in cosmological simulations of disc galaxies

NASA Astrophysics Data System (ADS)

Valentini, Milena; Murante, Giuseppe; Borgani, Stefano; Monaco, Pierluigi; Bressan, Alessandro; Beck, Alexander M.

2017-09-01

We investigate the impact of galactic outflow modelling on the formation and evolution of a disc galaxy, by performing a suite of cosmological simulations with zoomed-in initial conditions (ICs) of a Milky Way-sized halo. We verify how sensitive the general properties of the simulated galaxy are to the way in which stellar feedback triggered outflows are implemented, keeping ICs, simulation code and star formation (SF) model all fixed. We present simulations that are based on a version of the gadget3 code where our sub-resolution model is coupled with an advanced implementation of smoothed particle hydrodynamics that ensures a more accurate fluid sampling and an improved description of gas mixing and hydrodynamical instabilities. We quantify the strong interplay between the adopted hydrodynamic scheme and the sub-resolution model describing SF and feedback. We consider four different galactic outflow models, including the one introduced by Dalla Vecchia & Schaye (2012) and a scheme that is inspired by the Springel & Hernquist (2003) model. We find that the sub-resolution prescriptions adopted to generate galactic outflows are the main shaping factor of the stellar disc component at low redshift. The key requirement that a feedback model must have to be successful in producing a disc-dominated galaxy is the ability to regulate the high-redshift SF (responsible for the formation of the bulge component), the cosmological infall of gas from the large-scale environment, and gas fall-back within the galactic radius at low redshift, in order to avoid a too high SF rate at z = 0.

A case against an X-shaped structure in the Milky Way young bulge

NASA Astrophysics Data System (ADS)

López-Corredoira, Martín

2016-09-01

Context. A number of recent papers have claimed the discovery of an X-shape structure in the bulge of our Galaxy in the population of the red clumps. Aims: We endeavor to analyze the stellar density of bulge stars in the same regions using a different stellar population that is characteristic of the young bulge (≲ 5 Gyr). Particularly, we use F0-F5 main-sequence stars with distances derived through photometric parallax. Methods: We extract these stars from extinction-corrected color-magnitude diagrams in the near-infrared of VISTA-VVV data in some bulge regions and calculate the densities along the line of sight. We take the uncertaintity in the photometric parallax and the contamination of other sources into account, and we see that these errors do not avoid the detection of a possible double peak along some lines of sight as expected for a X-shape bulge if it existed. Results: Only a single peak in the density distribution along the line of sight is observed, so apparently there is no X-shape structure for this population of stars. Nonetheless, the effects of the dispersion of absolute magnitudes in the selected population might be an alternative explanation, although in principle these effects are insufficient to explain this lack of double peak according to our calculations. Conclusions: The results of the present paper do not demonstrate that previous claims of X-shaped bulge using only red clump stars are incorrect, but there are apparently some puzzling questions if we want to maintain the validity of both the red-clump results and the results of this paper.

What the Milky Way bulge reveals about the initial metallicity gradients in the disc

NASA Astrophysics Data System (ADS)

Fragkoudi, F.; Di Matteo, P.; Haywood, M.; Khoperskov, S.; Gomez, A.; Schultheis, M.; Combes, F.; Semelin, B.

2017-11-01

We use APOGEE DR13 data to examine the metallicity trends in the Milky Way (MW) bulge and we explore their origin by comparing two N-body models of isolated galaxies that develop a bar and a boxy/peanut (b/p) bulge. Both models have been proposed as scenarios for reconciling a disc origin of the MW bulge with a negative vertical metallicity gradient. The first model is a superposition of co-spatial, I.e. overlapping, disc populations with different scale heights, kinematics, and metallicities. In this model the thick, metal-poor, and centrally concentrated disc populations contribute significantly to the stellar mass budget in the inner galaxy. The second model is a single disc with an initial steep radial metallicity gradient; this disc is mapped by the bar into the b/p bulge in such a way that the vertical metallicity gradient of the MW bulge is reproduced, as has been shown already in previous works in the literature. However, as we show here, the latter model does not reproduce the positive longitudinal metallicity gradient of the inner disc, nor the metal-poor innermost regions seen in the data. On the other hand, the model with co-spatial thin and thick disc populations reproduces all the aforementioned trends. We therefore see that it is possible to reconcile a (primarily) disc origin for the MW bulge with the observed trends in metallicity by mapping the inner thin and thick discs of the MW into a b/p. For this scenario to reproduce the observations, the α-enhanced, metal-poor, thick disc populations must have a significant mass contribution in the inner regions, as has been suggested for the Milky Way.

The phase space of boxy-peanut and X-shaped bulges in galaxies - I. Properties of non-periodic orbits

NASA Astrophysics Data System (ADS)

Patsis, P. A.; Katsanikas, M.

2014-12-01

The investigation of the phase-space properties of structures encountered in a dynamical system is essential for understanding their formation and enhancement. In this paper, we explore the phase space in energy intervals where we have orbits that act as building blocks for boxy-peanut (b/p) and `X-shaped' structures in rotating potentials of galactic type. We underline the significance of the rotational tori around the 3D families x1v1 and x1v1' that have been bifurcated from the planar x1 family. These tori play a multiple role: (i) they belong to quasi-periodic orbits that reinforce the local density. (ii) They act as obstacles for the diffusion of chaotic orbits and (iii) they attract a large number of chaotic orbits that become sticky to them. There are also bifurcations of unstable families (x1v2, x1v2'). Their unstable asymptotic curves wind around the x1v1 and x1v1' tori generating orbits with hybrid morphologies between that of x1v1 and x1v2. In addition, a new family of multiplicity 2, called x1mul2, is found to be important for the peanut construction. This family produces stickiness phenomena in the critical area of the radial and vertical inner Lindblad resonances (ILRs) and reinforces b/p bulges. Our work shows also that there are peanut-supporting orbits before the vertical ILR. Non-periodic orbits associated with the x1 family secure this contribution as well as the support of b/p structures at several other energy intervals. Non-linear phenomena associated with complex instability of single and double multiplicity families of periodic orbits show that these structures are not interrupted in regions where such orbits prevail. Depending on the main mechanism behind their formation, boxy bulges exhibit different morphological features. Finally, our analysis indicates that `X' features shaped by orbits in the neighbourhood of x1v1 and x1v1' periodic orbits are pronounced only in side-on or nearly end-on views of the bar.

Shape and evolution of wind-blown bubbles of massive stars: on the effect of the interstellar magnetic field

NASA Astrophysics Data System (ADS)

van Marle, A. J.; Meliani, Z.; Marcowith, A.

2015-12-01

Context. The winds of massive stars create large (>10 pc) bubbles around their progenitors. As these bubbles expand they encounter the interstellar coherent magnetic field which, depending on its strength, can influence the shape of the bubble. Aims: We wish to investigate if, and how much, the interstellar magnetic field can contribute to the shape of an expanding circumstellar bubble around a massive star. Methods: We use the MPI-AMRVAC code to make magneto-hydrodynamical simulations of bubbles, using a single star model, combined with several different field strengths: B = 5, 10, and 20 μG for the interstellar magnetic field. This covers the typical field strengths of the interstellar magnetic fields found in the galactic disk and bulge. Furthermore, we present two simulations that include both a 5 μG interstellar magnetic field and a warm (10 000 K) interstellar medium (ISM) and two different ISM densities to demonstrate how the magnetic field can combine with other external factors to influence the morphology of the circumstellar bubbles. Results: Our results show that low magnetic fields, as found in the galactic disk, inhibit the growth of the circumstellar bubbles in the direction perpendicular to the field. As a result, the bubbles become ovoid, rather than spherical. Strong interstellar fields, such as observed for the galactic bulge, can completely stop the expansion of the bubble in the direction perpendicular to the field, leading to the formation of a tube-like bubble. When combined with an ISM that is both warm and high density the bubble is greatly reduced in size, causing a dramatic change in the evolution of temporary features inside the bubble such as Wolf-Rayet ring nebulae. Conclusions: The magnetic field of the interstellar medium can affect the shape of circumstellar bubbles. This effect may have consequences for the shape and evolution of circumstellar nebulae and supernova remnants, which are formed within the main wind-blown bubble. Appendices and movies associated to Figs. A.1-A.12 are available in electronic form at http://www.aanda.org

On the orbits that generate the X-shape in the Milky Way bulge

NASA Astrophysics Data System (ADS)

Abbott, Caleb G.; Valluri, Monica; Shen, Juntai; Debattista, Victor P.

2017-09-01

The Milky Way (MW) bulge shows a boxy/peanut or X-shaped bulge (hereafter BP/X) when viewed in infrared or microwave bands. We examine orbits in an N-body model of a barred disc galaxy that is scaled to match the kinematics of the MW bulge. We generate maps of projected stellar surface density, unsharp masked images, 3D excess-mass distributions (showing mass outside ellipsoids), line-of-sight number count distributions, and 2D line-of-sight kinematics for the simulation as well as co-added orbit families, in order to identify the orbits primarily responsible for the BP/X shape. We estimate that between 19 and 23 per cent of the mass of the bar in this model is associated with the BP/X shape and that the majority of bar orbits contribute to this shape that is clearly seen in projected surface density maps and 3D excess mass for non-resonant box orbits, 'banana' orbits, 'fish/pretzel' orbits and 'brezel' orbits. Although only the latter two families (comprising 7.5 per cent of the total mass) show a distinct X-shape in unsharp masked images, we find that nearly all bar orbit families contribute some mass to the 3D BP/X-shape. All co-added orbit families show a bifurcation in stellar number count distribution with distance that resembles the bifurcation observed in red clump stars in the MW. However, only the box orbit family shows an increasing separation of peaks with increasing galactic latitude |b|, similar to that observed. Our analysis suggests that no single orbit family fully explains all the observed features associated with the MW's BP/X-shaped bulge, but collectively the non-resonant boxes and various resonant boxlet orbits contribute at different distances from the centre to produce this feature. We propose that since box orbits (which are the dominant population in bars) have three incommensurable orbital fundamental frequencies, their 3D shapes are highly flexible and, like Lissajous figures, this family of orbits is most easily able to adapt to evolution in the shape of the underlying potential.

Variations in ion and neutral composition at Venus - Evidence of solar control of the formation of the predawn bulges in H/+/ and He1

NASA Technical Reports Server (NTRS)

Taylor, H. A., Jr.; Mayr, H.; Brinton, H.; Niemann, H.; Hartle, R.; Daniell, R. E., Jr.

1982-01-01

A comparison of ion and neutral composition measurements at Venus for periods of greatly different solar activity provides qualitative evidence of solar control of the day-to-night transport of light ion and neutral species. Concentrations of H(+) and He in the predawn bulge near solar maximum in November, 1979, exhibit a depletion signature correlated with a pronounced modulation in the solar F10.7 and EUV fluxes. This perturbation, not observed in the predawn region during an earlier period of relative quiet solar conditions, is interpreted as resulting from pronounced changes in solar heating and photoionization on the dayside, which in turn modulate the transport of ions and neutrals into the bulge region.

Evaporation of planetary atmospheres due to XUV illumination by quasars

NASA Astrophysics Data System (ADS)

Forbes, John C.; Loeb, Abraham

2018-06-01

Planetary atmospheres are subject to mass loss through a variety of mechanisms including irradiation by XUV photons from their host star. Here we explore the consequences of XUV irradiation by supermassive black holes as they grow by the accretion of gas in galactic nuclei. Based on the mass distribution of stars in galactic bulges and disks and the luminosity history of individual black holes, we estimate the probability distribution function of XUV fluences as a function of galaxy halo mass, redshift, and stellar component. We find that about 50% of all planets in the universe may lose a mass of hydrogen of ˜2.5 × 1019 g (the total mass of the Martian atmosphere), 10% may lose ˜5.1 × 1021 g (the total mass of Earth's atmosphere), and 0.2% may lose ˜1.4 × 1024 g (the total mass of Earth's oceans). The fractions are appreciably higher in the spheroidal components of galaxies, and depend strongly on galaxy mass, but only weakly on redshift.

On the relevance of chaos for halo stars in the solar neighbourhood II

NASA Astrophysics Data System (ADS)

Maffione, Nicolas P.; Gómez, Facundo A.; Cincotta, Pablo M.; Giordano, Claudia M.; Grand, Robert J. J.; Marinacci, Federico; Pakmor, Rüdiger; Simpson, Christine M.; Springel, Volker; Frenk, Carlos S.

2018-05-01

In a previous paper based on dark matter only simulations we show that, in the approximation of an analytic and static potential describing the strongly triaxial and cuspy shape of Milky Way-sized haloes, diffusion due to chaotic mixing in the neighbourhood of the Sun does not efficiently erase phase space signatures of past accretion events. In this second paper we further explore the effect of chaotic mixing using multicomponent Galactic potential models and solar neighbourhood-like volumes extracted from fully cosmological hydrodynamic simulations, thus naturally accounting for the gravitational potential associated with baryonic components, such as the bulge and disc. Despite the strong change in the global Galactic potentials with respect to those obtained in dark matter only simulations, our results confirm that a large fraction of halo particles evolving on chaotic orbits exhibit their chaotic behaviour after periods of time significantly larger than a Hubble time. In addition, significant diffusion in phase space is not observed on those particles that do exhibit chaotic behaviour within a Hubble time.

WFIRST: Searching for Microlens Planets in Very Wide Orbits and the MOA Microlensing Data Release

NASA Astrophysics Data System (ADS)

Hirao, Yuki; Bennett, David; Sumi, Takahiro; MOA Collaboration

2018-01-01

Gravitational microlensing is an unique technique to detect exoplanets down to low mass planets beyond the snow line because it is sensitive to planets orbiting near the Einstein ring radius of a few AU away from its host star, which is complementary to the other methods. Detecting such planets are important for understanding the formation of our solar system because gas giants and ice giants planets are believed to be formed beyond the snow line, where the protoplanetary disk is cold enough for ice to condense, in the core accretion theory. Microlensing Observations in Astrophysics (MOA) group has conducted high cadence survey observations towards the Galactic bulge to detect exoplanets since 2006 at Mt.John University Observatory in NZ using MOA-II 1.8 meter telescope equipped with a very wide field-of-view MOA-cam3 CCD camera. MOA has alerted about 600 microlensing events every year and detected dozens of exoplanets in wide orbits. Future space telescope, WFIRST will conduct survey observations towards the Galactic bulge and is expected to detect thousands of planets in wide orbit via microlensing to complete the census of exoplanets begun by Kepler Space telescope which found planets in close orbits via transit method. To contribute to the WFIRST and make the microlensing community larger, MOA will open its data from 2006 to 2014 to the public. Through the off-line analysis, we have found some short binary events which were not detected in the real time analysis. Short-timescale microlensing events are important because they are candidates of free-floating or wide-separation planets. The poster will present the data release and some results of the analysis of short-timescale binary events.

Effect of Binary Source Companions on the Microlensing Optical Depth Determination toward the Galactic Bulge Field

NASA Astrophysics Data System (ADS)

Han, Cheongho

2005-11-01

Currently, gravitational microlensing survey experiments toward the Galactic bulge field use two different methods of minimizing the blending effect for the accurate determination of the optical depth τ. One is measuring τ based on clump giant (CG) source stars, and the other is using ``difference image analysis'' (DIA) photometry to measure the unblended source flux variation. Despite the expectation that the two estimates should be the same assuming that blending is properly considered, the estimates based on CG stars systematically fall below the DIA results based on all events with source stars down to the detection limit. Prompted by the gap, we investigate the previously unconsidered effect of companion-associated events on τ determination. Although the image of a companion is blended with that of its primary star and thus not resolved, the event associated with the companion can be detected if the companion flux is highly magnified. Therefore, companions work effectively as source stars to microlensing, and thus the neglect of them in the source star count could result in a wrong τ estimation. By carrying out simulations based on the assumption that companions follow the same luminosity function as primary stars, we estimate that the contribution of the companion-associated events to the total event rate is ~5fbi% for current surveys and can reach up to ~6fbi% for future surveys monitoring fainter stars, where fbi is the binary frequency. Therefore, we conclude that the companion-associated events comprise a nonnegligible fraction of all events. However, their contribution to the optical depth is not large enough to explain the systematic difference between the optical depth estimates based on the two different methods.

Peculiar double-periodic pulsation in RR Lyrae stars of the OGLE collection - II. Short-period stars with a dominant radial fundamental mode

NASA Astrophysics Data System (ADS)

Prudil, Z.; Smolec, R.; Skarka, M.; Netzel, H.

2017-03-01

We report the discovery of a new group of double-periodic stars in the OGLE Galactic bulge photometry. In 38 stars identified as fundamental-mode RR Lyrae and four classified as first-overtone RR Lyrae, we detected an additional shorter periodicity. The periods of the dominant variability in the newly discovered group are 0.28 < PD < 0.41 d. Period ratios (0.68-0.72) are smaller than the period ratios of the Galactic bulge RRd stars. The typical amplitude ratio (of the additional to the dominant periodicity) is 20 per cent for the stars identified as fundamental-mode RR Lyrae and 50 per cent for stars classified as first-overtone RR Lyrae. 10 stars from our sample exhibit equidistant peaks in the frequency spectrum, which suggests the Blazhko-type modulation of the main pulsation frequency and/or additional periodicity. The Fourier coefficients R21 and R31 are some of the lowest among fundamental-mode RR Lyrae stars, but among the highest for the first-overtone pulsators. For the phase Fourier coefficients φ21 and φ31, our stars lie between RRab and RRc stars. The stars discussed were compared with radial linear pulsation models. Their position in the Petersen diagram cannot be reproduced by assuming that two radial modes are excited and their physical parameters are like those characteristic of RR Lyrae stars. The non-radial-mode scenario also faces difficulties. We conclude that the dominant variability is most likely due to pulsation in the radial fundamental mode, which applies to stars classified as first-overtone mode pulsators. At this point, we cannot explain the nature of the additional periodicity. Even more, the classification of the stars as RR Lyrae should be treated as tentative.

A Search for Novae in the M31 Globular Cluster System

NASA Astrophysics Data System (ADS)

Tomaney, Austin; Crotts, Arlin; Shafter, Allen

1992-12-01

Roughly 10% of all low mass X-ray binaries (LMXB's, neutron star - low mass sequence close binaries) are found in Galactic globular clusters (GC's) implying an enhancement per unit mass of roughly three orders of magnitude of these objects inside GC's compared with the field. Fabian, Pringle and Rees (1975) suggested that these lcose binary systems may be formed via tidal capture in the dense cluster cores. Similar arguments are likely to apply to nova systems which are cataclysmic variables (CV's) consisting of a close binary white dwarf - low mass main sequence star. Supporting arguments include the discovery over the past century of two novae in Galactic GC's, and the existence of low luminosity X-ray sources in GC's (Hertz and Grindlay 1983). In addition, surveys for novae in M31 indicate that the specfic density of novae in its bulge is an order of magnitude higher than its disk and it has been argued by Ciardullo et al. (1987) that novae in the bulge of M31 have been spawned inside GC's and subsequently ejected into the field. We present the results of a search (during 1988 and 1989) of over 200 M31 GC's using a fibre multi-object spectrograph to detect Hα emission, a signature of a potential nova eruptions. No eruptions were detected over an effective survey time of one year for the entire known M31 GC system. Although the lower mass of white dwarfs compared with neutron stars implies their effective capture cross section is smaller, we argue that since novae occur much more frequently on high mass white dwarfs this survey provides a sensitive test to the number of high mass CV's in GC's and their enhancement is unlikely to be as high as LMXB's.

Merger-driven fueling of active galactic nuclei: Six dual and of AGNs discovered with Chandra and Hubble Space Telescope observations

DOE PAGES

Comerford, Julia M.; Pooley, David; Barrows, R. Scott; ...

2015-06-19

Dual active galactic nuclei (AGNs) and offset AGNs are kpc-scale separation supermassive black holes pairs created during galaxy mergers, where both or one of the black holes are AGNs, respectively. These dual and offset AGNs are valuable probes of the link between mergers and AGNs but are challenging to identify. Here we present Chandra/ACIS observations of 12 optically selected dual AGN candidates atmore » $$z\\lt 0.34$$, where we use the X-rays to identify AGNs. We also present Hubble Space Telescope/Wide Field Camera 3 observations of 10 of these candidates, which reveal any stellar bulges accompanying the AGNs. We discover a dual AGN system with separation $${\\rm \\Delta }x=2.2$$ kpc, where the two stellar bulges have coincident [O iii] λ5007 and X-ray sources. This system is an extremely minor merger (460:1) that may include a dwarf galaxy hosting an intermediate mass black hole. We also find six single AGNs, and five systems that are either dual or offset AGNs with separations $${\\rm \\Delta }x\\lt 10$$ kpc. Four of the six dual AGNs and dual/offset AGNs are in ongoing major mergers, and these AGNs are 10 times more luminous, on average, than the single AGNs in our sample. This hints that major mergers may preferentially trigger higher luminosity AGNs. Further, we find that confirmed dual AGNs have hard X-ray luminosities that are half of those of single AGNs at fixed [O III] λ5007 luminosity, on average. Lastly, this could be explained by high densities of gas funneled to galaxy centers during mergers, and emphasizes the need for deeper X-ray observations of dual AGN candidates.« less

Unveiling the inner morphology and gas kinematics of NGC 5135 with ALMA

NASA Astrophysics Data System (ADS)

Sabatini, G.; Gruppioni, C.; Massardi, M.; Giannetti, A.; Burkutean, S.; Cimatti, A.; Pozzi, F.; Talia, M.

2018-06-01

The local Seyfert 2 galaxy NGC 5135, thanks to its almost face-on appearance, a bulge overdensity of stars, the presence of a large-scale bar, an active galactic nucleus (AGN) and a supernova remnant, is an excellent target to investigate the dynamics of inflows, outflows, star formation, and AGN feedback. Here, we present a reconstruction of the gas morphology and kinematics in the inner regions of this galaxy, based on the analysis of Atacama Large Millimeter Array (ALMA) archival data. For this purpose, we combine the available ˜100 pc resolution ALMA 1.3 and 0.45 mm observations of dust continuum emission, the spectroscopic maps of two transitions of the CO molecule (tracer of molecular gas mass in star-forming and nuclear regions), and of the CS molecule (tracer of the dense star-forming regions) with the outcome of the spectral energy distribution decomposition. By applying the 3DBAROLO software (3D-Based Analysis of Rotating Objects from Line Observations), we have been able to fit the galaxy rotation curve using a 3D tilted-ring model of the disc. Most of the observed emitting features are described by our kinematic model. We also attempt an interpretation for the emission in a few regions that the axisymmetric model fails to reproduce. The most relevant of these is a region at the northern edge of the inner bar, where multiple velocity components overlap, as a possible consequence of the expansion of a superbubble.

Stellar populations of bulges in galaxies with a low surface-brightness disc

NASA Astrophysics Data System (ADS)

Morelli, L.; Corsini, E. M.; Pizzella, A.; Dalla Bontà, E.; Coccato, L.; Méndez-Abreu, J.

2015-03-01

The radial profiles of the Hβ, Mg, and Fe line-strength indices are presented for a sample of eight spiral galaxies with a low surface-brightness stellar disc and a bulge. The correlations between the central values of the line-strength indices and velocity dispersion are consistent to those known for early-type galaxies and bulges of high surface-brightness galaxies. The age, metallicity, and α/Fe enhancement of the stellar populations in the bulge-dominated region are obtained using stellar population models with variable element abundance ratios. Almost all the sample bulges are characterized by a young stellar population, on-going star formation, and a solar α/Fe enhancement. Their metallicity spans from high to sub-solar values. No significant gradient in age and α/Fe enhancement is measured, whereas only in a few cases a negative metallicity gradient is found. These properties suggest that a pure dissipative collapse is not able to explain formation of all the sample bulges and that other phenomena, like mergers or acquisition events, need to be invoked. Such a picture is also supported by the lack of a correlation between the central value and gradient of the metallicity in bulges with very low metallicity. The stellar populations of the bulges hosted by low surface-brightness discs share many properties with those of high surface-brightness galaxies. Therefore, they are likely to have common formation scenarios and evolution histories. A strong interplay between bulges and discs is ruled out by the fact that in spite of being hosted by discs with extremely different properties, the bulges of low and high surface-brightness discs are remarkably similar.

The plasmapause revisited

NASA Technical Reports Server (NTRS)

Maynard, N. C.; Gebowsky, J. M.

1976-01-01

Saturation of the dc double probe instrument on Explorer 45 was used to identify the plasmapause. A data base was developed to statistically study the average position of the plasmapause over 14.5 hours of magnetic local time under differing magnetic conditions. The afternoon-evening bulge in the L coordinate of the plasmapause versus local time was found centered between 20 and 21 hours MLT during magnetically quiet periods and shifted toward dusk as activity increased, but always post dusk. During quiet periods a bulge in the L coordinate near noon was also seen, which disappeared as activity increased. The average local time distribution plasmapause position during high magnetic activity was irregular in the afternoon region where large scale convection models predict the creation of plasmatails or detached plasma regions from increases in the solar wind induced convection. The results suggest that solar wind induced convection is partially shielded from the dayside. As the intensity of the convection is increased, it more effectively penetrates the dayside, which shifts the post dusk bulge nearer to dusk and eliminates the quiet-time bulge near noon.

Gas inflow patterns and nuclear rings in barred galaxies

NASA Astrophysics Data System (ADS)

Shen, Juntai; Li, Zhi

2017-06-01

Nuclear rings, dust lanes, and nuclear spirals are common structures in the inner region of barred galaxies, with their shapes and properties linked to the physical parameters of the galaxies. We use high-resolution hydrodynamical simulations to study gas inflow patterns in barred galaxies, with special attention on the nuclear rings. The location and thickness of nuclear ringsare tightly correlated with galactic properties, such as the bar pattern speed and bulge central density, within certain ranges. We identify the backbone of nuclear rings with a major orbital family of bars. The rings form exactly at the radius where the residual angular momentum of inflowing gas balances the centrifugal force. We propose a new simple method to predict the bar pattern speed for barred galaxies possessing a nuclear ring, without actually doing simulations. We apply this method to some real galaxies and find that our predicted bar pattern speed compare reasonably well with other estimates. Our study may have important implications for using nuclear ringsto measure the parameters of real barred galaxies with detailed gas kinematics. We have also extended current hydrodynamical simulations to model gas features in the Milky Way.

Hu 1-2: a metal-poor bipolar planetary nebula with fast collimated outflows

NASA Astrophysics Data System (ADS)

Fang, X.; Guerrero, M. A.; Miranda, L. F.; Riera, A.; Velázquez, P. F.; Raga, A. C.

2015-09-01

We present narrow-band optical and near-IR imaging and optical long-slit spectroscopic observations of Hu 1-2, a Galactic planetary nebula (PN) with a pair of [N II]-bright, fast-moving (>340 km s-1) bipolar knots. Intermediate-dispersion spectra are used to derive physical conditions and abundances across the nebula, and high-dispersion spectra to study the spatio-kinematical structure. Generally, Hu 1-2 has high He/H (≈0.14) and N/O ratios (≈0.9), typical of Type I PNe. On the other hand, its abundances of O, Ne, S, and Ar are low as compared with the average abundances of Galactic bulge and disc PNe. The position-velocity maps can be generally described as an hour-glass shaped nebula with bipolar expansion, although the morphology and kinematics of the innermost regions cannot be satisfactorily explained with a simple, tilted equatorial torus. The spatio-kinematical study confines the inclination angle of its major axis to be within 10° of the plane of sky. As in the irradiated bow-shocks of IC 4634 and NGC 7009, there is a clear stratification in the emission peaks of [O III], Hα, and [N II] in the north-west (NW) knot of Hu 1-2. Fast collimated outflows in PNe exhibit higher excitation than other low-ionization structures. This is particularly the case for the bipolar knots of Hu 1-2, with He II emission levels above those of collimated outflows in other Galactic PNe. The excitation of the knots in Hu 1-2 is consistent with the combined effects of shocks and UV radiation from the central star. The mechanical energy and luminosity of the knots are similar to those observed in the PNe known to harbour a post-common envelope (post-CE) close binary central star.

Review of the fermionic dark matter model applied to galactic structures

NASA Astrophysics Data System (ADS)

Krut, A.; Argüelles, C. R.; Rueda, J.; Ruffini, R.

2015-12-01

Baryonic components (e.g. bulge and disk) of galactic structures are assumed to be embedded in an isothermal dark matter halo of fermionic nature. Besides the Pauli principle only gravitational interaction is considered. Using the underlying Fermi-Dirac phase space distribution, typical of collisionless relaxation processes, it yields an one-parameter family of scaled solutions which reproduces the observed flat rotation curves in galaxies, and additionally predicts a degenerate core through their centers. In order to provide the right DM halo properties of galaxies a set of four parameters (particle mass, degeneracy parameter at the galactic center, central density and the velocity dispersion) is necessary. The more general density profile shows three regimes depending on radius: an almost uniform very dense quantum core followed by a steep fall, a plateau in the diluted regime and a Boltzmannian tail representing the halo. In contrast to purely Boltzmannian configurations the fermionic DM model containing a quantum core allows to determine the particle mass. We show that the quantum core can be well approximated by a polytrope of index n = 3/2, while the halo can be perfectly described by an isothermal sphere with a halo scale length radius equal to approximately 3/4 of the King-radius.

Review of the fermionic dark matter model applied to galactic structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krut, A.; Argüelles, C. R.; Rueda, J.

2015-12-17

Baryonic components (e.g. bulge and disk) of galactic structures are assumed to be embedded in an isothermal dark matter halo of fermionic nature. Besides the Pauli principle only gravitational interaction is considered. Using the underlying Fermi-Dirac phase space distribution, typical of collisionless relaxation processes, it yields an one-parameter family of scaled solutions which reproduces the observed flat rotation curves in galaxies, and additionally predicts a degenerate core through their centers. In order to provide the right DM halo properties of galaxies a set of four parameters (particle mass, degeneracy parameter at the galactic center, central density and the velocity dispersion)more » is necessary. The more general density profile shows three regimes depending on radius: an almost uniform very dense quantum core followed by a steep fall, a plateau in the diluted regime and a Boltzmannian tail representing the halo. In contrast to purely Boltzmannian configurations the fermionic DM model containing a quantum core allows to determine the particle mass. We show that the quantum core can be well approximated by a polytrope of index n = 3/2, while the halo can be perfectly described by an isothermal sphere with a halo scale length radius equal to approximately 3/4 of the King-radius.« less

Paired and interacting galaxies: Conference summary

NASA Technical Reports Server (NTRS)

Norman, Colin A.

1990-01-01

The author gives a summary of the conference proceedings. The conference began with the presentation of the basic data sets on pairs, groups, and interacting galaxies with the latter being further discussed with respect to both global properties and properties of the galactic nuclei. Then followed the theory, modelling and interpretation using analytic techniques, simulations and general modelling for spirals and ellipticals, starbursts and active galactic nuclei. Before the conference the author wrote down the three questions concerning pairs, groups and interacting galaxies that he hoped would be answered at the meeting: (1) How do they form, including the role of initial conditions, the importance of subclustering, the evolution of groups to compact groups, and the fate of compact groups; (2) How do they evolve, including issues such as relevant timescales, the role of halos and the problem of overmerging, the triggering and enhancement of star formation and activity in the galactic nuclei, and the relative importance of dwarf versus giant encounters; and (3) Are they important, including the frequency of pairs and interactions, whether merging and interactions are very important aspects of the life of a normal galaxy at formation, during its evolution, in forming bars, shells, rings, bulges, etc., and in the formation and evolution of active galaxies? Where possible he focuses on these three central issues in the summary.

The nature of giant clumps in distant galaxies probed by the anatomy of the cosmic snake

NASA Astrophysics Data System (ADS)

Cava, Antonio; Schaerer, Daniel; Richard, Johan; Pérez-González, Pablo G.; Dessauges-Zavadsky, Miroslava; Mayer, Lucio; Tamburello, Valentina

2018-01-01

Giant stellar clumps are ubiquitous in high-redshift galaxies1,2. They are thought to play an important role in the build-up of galactic bulges3 and as diagnostics of star formation feedback in galactic discs4. Hubble Space Telescope (HST) blank field imaging surveys have estimated that these clumps have masses of up to 109.5 M⊙ and linear sizes of ≳1 kpc5,6. Recently, gravitational lensing has also been used to get higher spatial resolution7-9. However, both recent lensed observations10,11 and models12,13 suggest that the clumps' properties may be overestimated by the limited resolution of standard imaging techniques. A definitive proof of this observational bias is nevertheless still missing. Here we investigate directly the effect of resolution on clump properties by analysing multiple gravitationally lensed images of the same galaxy at different spatial resolutions, down to 30 pc. We show that the typical mass and size of giant clumps, generally observed at 1 kpc resolution in high-redshift galaxies, are systematically overestimated. The high spatial resolution data, only enabled by strong gravitational lensing using currently available facilities, support smaller scales of clump formation by fragmentation of the galactic gas disk via gravitational instabilities.

Loops formed by tidal tails as fossil records of a major merger

NASA Astrophysics Data System (ADS)

Wang, J.; Hammer, F.; Athanassoula, E.; Puech, M.; Yang, Y.; Flores, H.

2012-02-01

Context. Many haloes of nearby disc galaxies contain faint and extended features, including loops, which are often interpreted as relics of satellite infall in the main galaxy's potential well. In most cases, however, the residual nucleus of the satellite is not seen, although it is predicted by numerical simulations. Aims: We test whether such faint and extended features can be associated to gas-rich, major mergers, which may also lead to disc rebuilding and thus be a corner stone for the formation of spiral galaxies. Our goal is to test whether the major merger scenario can provide a good model for a particularly difficult case, that of NGC 5907, and to compare to the scenario of a satellite infall. Methods: Using the TreeSPH code GADGET-2, we model the formation of an almost bulge-less galaxy similar to NGC 5907 (B/T ≲ 0.2) after a gas-rich major merger. First, we trace tidal tail particles captured by the galaxy gravitational potential to verify whether they can form loops similar to those discovered in the galactic haloes. Results: We indeed find that 3:1 major mergers can form features similar to the loops found in many galactic haloes, including in NGC 5907, and can reproduce an extended thin disc, a bulge, as well as the pronounced warp of the gaseous disc. Relatively small bulge fractions can be reproduced by a large gas fraction in the progenitors, as well as appropriate orbital parameters. Conclusions: Even though it remains difficult to fully cover the large volume of free parameters, the present modelling of the loops in NGC 5907 proves that they could well be the result of a major merger. It has many advantages over the satellite infall scenario; e.g., it solves the problem of the visibility of the satellite remnant, and it may explain some additional features in the NGC 5907 halo, as well as some gas properties of this system. For orbital parameters derived from cosmological simulations, the loops in NGC 5907 can be reproduced by major mergers (3:1 to 5:1) and possibly by intermediate mergers (5:1 to 12:1). The major merger scenario thus challenges the minor merger one and could explain many properties that haloes of spiral galaxies have in common, including their red colours and the presence of faint extended features.

Photometric detection of high proper motions in dense stellar fields using difference image analysis

NASA Astrophysics Data System (ADS)

Eyer, L.; Woźniak, P. R.

2001-10-01

The difference image analysis (DIA) of the images obtained by the Optical Gravitational Lensing Experiment (OGLE-II) revealed a peculiar artefact in the sample of stars proposed as variable by Woźniak in one of the Galactic bulge fields: the occurrence of pairs of candidate variables showing anti-correlated light curves monotonic over a period of 3yr. This effect can be understood, quantified and related to the stellar proper motions. DIA photometry supplemented with a simple model offers an effective and easy way to detect high proper motion stars in very dense stellar fields, where conventional astrometric searches are extremely inefficient.

Clues to the Formation of Lenticular Galaxies Using Spectroscopic Bulge-Disk Decomposition

NASA Astrophysics Data System (ADS)

Johnston, E. J.; Aragón-Salamanca, A.; Merrifield, M. R.; Bedregal, A. G.

2014-03-01

Lenticular galaxies have long been thought of as evolved spirals, but the processes involved to quench the star formation are still unclear. By studying the individual star formation histories of the bulges and disks of lenticulars, it is possible to look for clues to the processes that triggered their transformation from spirals. To accomplish this feat, we present a new method for spectroscopic bulge-disk decomposition, in which a long-slit spectrum is decomposed into two one-dimensional spectra representing purely the bulge and disk light. We present preliminary results from applying this method to lenticular galaxies in the Virgo and Fornax Clusters, in which we show that the most recent star formation activity in these galaxies occurred within the bulges. We also find that the star formation timescales of the bulges are longer than the disks, and that more massive galaxies take longer to lose their gas during the transformation. These results point towards slow processes, such as ram-pressure stripping or harassment, being the mechanism responsible for the quenching of star formation in spirals, followed by a burst of star formation in the central regions from the gas that has been funnelled inwards through the disk.

The First Simultaneous Microlensing Observations by Two Space Telescopes: Spitzer and Swift Reveal a Brown Dwarf in Event OGLE-2015-BLG-1319

NASA Technical Reports Server (NTRS)

Shvartzvald, Y.; Li, Z.; Udalski, A.; Gould, A.; Sumi, T.; Street, R. A.; Calchi Novati, S.; Hundertmark, M.; Bozza, V.; Beichman, C.;

Maximum density echogram analysis : a novel approach to study the characteristics of oblique echoes observed by MARSIS/Mars Express

NASA Astrophysics Data System (ADS)

P, M.; Narukull, V. R.; Rao, S. V. B.

2017-12-01

The ionograms of the Mars Advance Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument aboard Mars Express spacecraft show vertical and oblique echoes from the Martian ionosphere. The vertical echoes are from the normal ionosphere while the oblique echoes are believed to be from ionization bulges that occur in regions of strong vertical magnetic fields. These oblique echoes appear as downward facing hyperbolas when plotted as radargram (at 1.9 MHz), which is a color coded plot of apparent altitude as a function of time at a single frequency. In order to extract further information from these ionization bulges, we considered the peak density of the oblique echoes and plotted them in a format similar to a radargram and called it as a 'maximum density radargram' (MDR). Thus, an MDR shows the peak densities in entire ionization bulge. This analysis revealed several new aspects of the ionization bulges. We found that there is an asymmetry in the ionization bulge so that the density on one side of the hyperbola is different than the other side. In some cases, the density on the same side of the hyperbola, between the edge and apex, changes. Occasionally, the radargrams show only one side of the hyperbola, while the MDRs show a full hyperbola. When the density structures are repeatedly observed over the same location with a few days interval, the MDR analysis shows that the density inside the bulge varies from one pass to another. Finally, the ionization bulges in the MDR displays are clearly observed on several nights. Several of these nighttime bulges were not apparent in radargram analysis. These observations are discussed in the light of current understanding on the ionization bulges.

Bulgeless Galaxies Hosting 107 M⊙ AGN in Galaxy Zoo: The Growth of Black Holes via Secular Processes

NASA Astrophysics Data System (ADS)

Simmons, Brooke; Lintott, C. J.; Schawinski, K.; Moran, E. C.; Han, A.; Kaviraj, S.; Masters, K. L.; Urry, C. M.; Willett, K.; Bamford, S. P.; Nichol, R.

2013-01-01

The growth of supermassive black holes (SMBHs) appears to proceed via multiple pathways including mergers and secular processes, but these are difficult to disentangle for most galaxies given their complex evolutionary histories. In order to understand the effects of secular galaxy evolution on black hole growth, we require a sample of active galactic nuclei (AGN) in galaxies with a calm formation history free of significant mergers, a population that heretofore has been difficult to locate. Here we present a sample of 13 AGN in massive galaxies lacking the classical bulges believed inevitably to result from mergers; they also either lack or have extremely small pseudobulges, meaning they have had very calm accretion histories. This is the largest sample to date of massive, bulgeless AGN host galaxies selected without any direct restriction on the SMBH mass. The broad-line objects in the sample have black hole masses of 106-7 M⊙ Eddington arguments imply similar masses for the rest of the sample, meaning these black holes have grown substantially in the absence of mergers or other bulge-building processes such as violent disk instabilities. The black hole masses are systematically higher than expected from established bulge-black hole relations. However, these systems may be consistent with the correlation between black hole mass and total stellar mass. We discuss these results in the context of other studies and consider the implication that the details of stellar galaxy evolution and dynamics may not be fundamental to the co-evolution of galaxies and black holes.

Discovery of a population of bulgeless galaxies with extremely red MID-IR colors: Obscured AGN activity in the low-mass regime?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Satyapal, S.; Secrest, N. J.; McAlpine, W.

2014-04-01

In contrast to massive, bulge hosting galaxies, very few supermassive black holes (SMBHs) are known in either low-mass or bulgeless galaxies. Such a population could provide clues to the origins of SMBHs and to secular pathways for their growth. Using the all-sky Wide-field Infrared Survey Explorer (WISE ) survey, and bulge-to-disk decompositions from the Sloan Digital Sky Survey (SDSS) Data Release 7, we report the discovery of a population of local (z < 0.3) bulgeless disk galaxies with extremely red mid-infrared colors which are highly suggestive of a dominant active galactic nucleus (AGN), despite having no optical AGN signatures inmore » their SDSS spectra. Using various mid-infrared selection criteria from the literature, there are between 30 and over 300 bulgeless galaxies with possible AGNs. Other known scenarios that can heat the dust to high temperatures do not appear to explain the observed colors of this sample. If these galaxies are confirmed to host AGNs, this study will provide a breakthrough in characterizing the properties of SMBHs in the low bulge mass regime and in understanding their relation with their host galaxies. Mid-infrared selection identifies AGNs that dominate their host galaxy's emission and therefore reveal a different AGN population than that uncovered by optical studies. We find that the fraction of all galaxies identified as candidate AGNs by WISE is highest at lower stellar masses and drops dramatically in higher mass galaxies, in striking contrast to the findings from optical studies.« less

LLAMA: nuclear stellar properties of Swift-BAT AGN and matched inactive galaxies

NASA Astrophysics Data System (ADS)

Lin, Ming-Yi; Davies, R. I.; Hicks, E. K. S.; Burtscher, L.; Contursi, A.; Genzel, R.; Koss, M.; Lutz, D.; Maciejewski, W.; Müller-Sánchez, F.; Orban de Xivry, G.; Ricci, C.; Riffel, R.; Riffel, R. A.; Rosario, D.; Schartmann, M.; Schnorr-Müller, A.; Shimizu, T.; Sternberg, A.; Sturm, E.; Storchi-Bergmann, T.; Tacconi, L.; Veilleux, S.

2018-02-01

In a complete sample of local 14-195 keV selected active galactic nuclei (AGNs) and inactive galaxies, matched by their host galaxy properties, we study the spatially resolved stellar kinematics and luminosity distributions at near-infrared wavelengths on scales of 10-150 pc, using SINFONI on the VLT. In this paper, we present the first half of the sample, which comprises 13 galaxies, eight AGNs and five inactive galaxies. The stellar velocity fields show a disc-like rotating pattern, for which the kinematic position angle is in agreement with the photometric position angle obtained from large scale images. For this set of galaxies, the stellar surface brightness of the inactive galaxy sample is generally comparable to the matched sample of AGN, but extends to lower surface brightness. After removal of the bulge contribution, we find a nuclear stellar light excess with an extended nuclear disc structure, which exhibits a size-luminosity relation. While we expect the excess luminosity to be associated with a dynamically cooler young stellar population, we do not typically see a matching drop in dispersion. This may be because these galaxies have pseudo-bulges in which the intrinsic dispersion increases towards the centre. And although the young stars may have an impact in the observed kinematics, their fraction is too small to dominate over the bulge and compensate the increase in dispersion at small radii, so no dispersion drop is seen. Finally, we find no evidence for a difference in the stellar kinematics and nuclear stellar luminosity excess between these active and inactive galaxies.

OGLE-2016-BLG-1190Lb: The First Spitzer Bulge Planet Lies Near the Planet/Brown-dwarf Boundary

NASA Astrophysics Data System (ADS)

Ryu, Y.-H.; Yee, J. C.; Udalski, A.; Bond, I. A.; Shvartzvald, Y.; Zang, W.; Figuera Jaimes, R.; Jørgensen, U. G.; Zhu, W.; Huang, C. X.; Jung, Y. K.; Albrow, M. D.; Chung, S.-J.; Gould, A.; Han, C.; Hwang, K.-H.; Shin, I.-G.; Cha, S.-M.; Kim, D.-J.; Kim, H.-W.; Kim, S.-L.; Lee, C.-U.; Lee, D.-J.; Lee, Y.; Park, B.-G.; Pogge, R. W.; KMTNet Collaboration; Calchi Novati, S.; Carey, S.; Henderson, C. B.; Beichman, C.; Gaudi, B. S.; Spitzer team; Mróz, P.; Poleski, R.; Skowron, J.; Szymański, M. K.; Soszyński, I.; Kozłowski, S.; Pietrukowicz, P.; Ulaczyk, K.; Pawlak, M.; OGLE Collaboration; Abe, F.; Asakura, Y.; Barry, R.; Bennett, D. P.; Bhattacharya, A.; Donachie, M.; Evans, P.; Fukui, A.; Hirao, Y.; Itow, Y.; Kawasaki, K.; Koshimoto, N.; Li, M. C. A.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Miyazaki, S.; Muraki, Y.; Nagakane, M.; Ohnishi, K.; Ranc, C.; Rattenbury, N. J.; Saito, To.; Sharan, A.; Sullivan, D. J.; Sumi, T.; Suzuki, D.; Tristram, P. J.; Yamada, T.; Yamada, T.; Yonehara, A.; MOA Collaboration; Bryden, G.; Howell, S. B.; Jacklin, S.; UKIRT Microlensing Team; Penny, M. T.; Mao, S.; Fouqué, Pascal; Wang, T.; CFHT-K2C9 Microlensing Survey group; Street, R. A.; Tsapras, Y.; Hundertmark, M.; Bachelet, E.; Dominik, M.; Li, Z.; Cross, S.; Cassan, A.; Horne, K.; Schmidt, R.; Wambsganss, J.; Ment, S. K.; Maoz, D.; Snodgrass, C.; Steele, I. A.; RoboNet Team; Bozza, V.; Burgdorf, M. J.; Ciceri, S.; D’Ago, G.; Evans, D. F.; Hinse, T. C.; Kerins, E.; Kokotanekova, R.; Longa, P.; MacKenzie, J.; Popovas, A.; Rabus, M.; Rahvar, S.; Sajadian, S.; Skottfelt, J.; Southworth, J.; von Essen, C.; MiNDSTEp Team

2018-01-01

We report the discovery of OGLE-2016-BLG-1190Lb, which is likely to be the first Spitzer microlensing planet in the Galactic bulge/bar, an assignation that can be confirmed by two epochs of high-resolution imaging of the combined source–lens baseline object. The planet’s mass, M p = 13.4 ± 0.9 M J , places it right at the deuterium-burning limit, i.e., the conventional boundary between “planets” and “brown dwarfs.” Its existence raises the question of whether such objects are really “planets” (formed within the disks of their hosts) or “failed stars” (low-mass objects formed by gas fragmentation). This question may ultimately be addressed by comparing disk and bulge/bar planets, which is a goal of the Spitzer microlens program. The host is a G dwarf, M host = 0.89 ± 0.07 M ⊙, and the planet has a semimajor axis a ∼ 2.0 au. We use Kepler K2 Campaign 9 microlensing data to break the lens-mass degeneracy that generically impacts parallax solutions from Earth–Spitzer observations alone, which is the first successful application of this approach. The microlensing data, derived primarily from near-continuous, ultradense survey observations from OGLE, MOA, and three KMTNet telescopes, contain more orbital information than for any previous microlensing planet, but not quite enough to accurately specify the full orbit. However, these data do permit the first rigorous test of microlensing orbital-motion measurements, which are typically derived from data taken over <1% of an orbital period.

A geometric approach to non-linear correlations with intrinsic scatter

NASA Astrophysics Data System (ADS)

Pihajoki, Pauli

2017-12-01

We propose a new mathematical model for n - k-dimensional non-linear correlations with intrinsic scatter in n-dimensional data. The model is based on Riemannian geometry and is naturally symmetric with respect to the measured variables and invariant under coordinate transformations. We combine the model with a Bayesian approach for estimating the parameters of the correlation relation and the intrinsic scatter. A side benefit of the approach is that censored and truncated data sets and independent, arbitrary measurement errors can be incorporated. We also derive analytic likelihoods for the typical astrophysical use case of linear relations in n-dimensional Euclidean space. We pay particular attention to the case of linear regression in two dimensions and compare our results to existing methods. Finally, we apply our methodology to the well-known MBH-σ correlation between the mass of a supermassive black hole in the centre of a galactic bulge and the corresponding bulge velocity dispersion. The main result of our analysis is that the most likely slope of this correlation is ∼6 for the data sets used, rather than the values in the range of ∼4-5 typically quoted in the literature for these data.

Images in the rocket ultraviolet - The stellar population in the central bulge of M31

NASA Technical Reports Server (NTRS)

Bohlin, R. C.; Cornett, R. H.; Hill, J. K.; Hill, R. S.; Oconnell, R. W.; Stecher, T. P.

1985-01-01

Imagery of the bulge of M31 obtained with a rocket-borne telescope in two broad bands centered at 1460 A and 2380 A is discussed. The UV spatial profiles over a region about 200 arcsec wide are identical with those at visible wavelengths. The absence of detectable point sources indicates that main-sequence stars hotter than B0 V are not present in the bulge. It is suggested that the far-UV flux in old stellar populations originates in post-AGB stars. The UV flux from such stars is extremely sensitive to age and the physics of their previous mass loss.

Differential Targeting of Unpaired Bases within Duplex DNA by the Natural Compound Clerocidin: A Valuable Tool to Dissect DNA Secondary Structure

PubMed Central

Nadai, Matteo; Palù, Giorgio; Palumbo, Manlio; Richter, Sara N.

2012-01-01

Non-canonical DNA structures have been postulated to mediate protein-nucleic acid interactions and to function as intermediates in the generation of frame-shift mutations when errors in DNA replication occur, which result in a variety of diseases and cancers. Compounds capable of binding to non-canonical DNA conformations may thus have significant diagnostic and therapeutic potential. Clerocidin is a natural diterpenoid which has been shown to selectively react with single-stranded bases without targeting the double helix. Here we performed a comprehensive analysis on several non-canonical DNA secondary structures, namely mismatches, nicks, bulges, hairpins, with sequence variations in both the single-stranded region and the double-stranded flanking segment. By analysis of clerocidin reactivity, we were able to identify the exposed reactive residues which provided information on both the secondary structure and the accessibility of the non-paired sites. Mismatches longer than 1 base were necessary to be reached by clerocidin reactive groups, while 1-base nicks were promptly targeted by clerocidin; in hairpins, clerocidin reactivity increased with the length of the hairpin loop, while, interestingly, reactivity towards bulges reached a maximum in 3-base-long bulges and declined in longer bulges. Electrophoretic mobility shift analysis demonstrated that bulges longer than 3 bases (i.e. 5- and 7-bases) folded or stacked on the duplex region therefore being less accessible by the compound. Clerocidin thus represents a new valuable diagnostic tool to dissect DNA secondary structures. PMID:23285245

Differential targeting of unpaired bases within duplex DNA by the natural compound clerocidin: a valuable tool to dissect DNA secondary structure.

PubMed

Nadai, Matteo; Palù, Giorgio; Palumbo, Manlio; Richter, Sara N

2012-01-01

Non-canonical DNA structures have been postulated to mediate protein-nucleic acid interactions and to function as intermediates in the generation of frame-shift mutations when errors in DNA replication occur, which result in a variety of diseases and cancers. Compounds capable of binding to non-canonical DNA conformations may thus have significant diagnostic and therapeutic potential. Clerocidin is a natural diterpenoid which has been shown to selectively react with single-stranded bases without targeting the double helix. Here we performed a comprehensive analysis on several non-canonical DNA secondary structures, namely mismatches, nicks, bulges, hairpins, with sequence variations in both the single-stranded region and the double-stranded flanking segment. By analysis of clerocidin reactivity, we were able to identify the exposed reactive residues which provided information on both the secondary structure and the accessibility of the non-paired sites. Mismatches longer than 1 base were necessary to be reached by clerocidin reactive groups, while 1-base nicks were promptly targeted by clerocidin; in hairpins, clerocidin reactivity increased with the length of the hairpin loop, while, interestingly, reactivity towards bulges reached a maximum in 3-base-long bulges and declined in longer bulges. Electrophoretic mobility shift analysis demonstrated that bulges longer than 3 bases (i.e. 5- and 7-bases) folded or stacked on the duplex region therefore being less accessible by the compound. Clerocidin thus represents a new valuable diagnostic tool to dissect DNA secondary structures.

T box transcription antitermination riboswitch: Influence of nucleotide sequence and orientation on tRNA binding by the antiterminator element

PubMed Central

Fauzi, Hamid; Agyeman, Akwasi; Hines, Jennifer V.

2008-01-01

Many bacteria utilize riboswitch transcription regulation to monitor and appropriately respond to cellular levels of important metabolites or effector molecules. The T box transcription antitermination riboswitch responds to cognate uncharged tRNA by specifically stabilizing an antiterminator element in the 5′-untranslated mRNA leader region and precluding formation of a thermodynamically more stable terminator element. Stabilization occurs when the tRNA acceptor end base pairs with the first four nucleotides in the seven nucleotide bulge of the highly conserved antiterminator element. The significance of the conservation of the antiterminator bulge nucleotides that do not base pair with the tRNA is unknown, but they are required for optimal function. In vitro selection was used to determine if the isolated antiterminator bulge context alone dictates the mode in which the tRNA acceptor end binds the bulge nucleotides. No sequence conservation beyond complementarity was observed and the location was not constrained to the first four bases of the bulge. The results indicate that formation of a structure that recognizes the tRNA acceptor end in isolation is not the determinant driving force for the high phylogenetic sequence conservation observed within the antiterminator bulge. Additional factors or T box leader features more likely influenced the phylogenetic sequence conservation. PMID:19152843

The Galactic Distribution of Planets via Spitzer Microlensing Parallax

NASA Astrophysics Data System (ADS)

Gould, Andrew; Yee, Jennifer; Carey, Sean; Shvartzvald, Yossi

2018-05-01

We will measure the Galactic distribution of planets by obtaining 'microlens parallaxes' of about 200 events, including 3 planetary events, from the comparison of microlens lightcurves observed from Spitzer and Earth, which are separated by >1.5 AU in projection. The proposed observations are part of a campaign that we have conducted with Spitzer since 2014. The planets expected to be identified in this campaign when combined with previous work will yield a first statistically significant measurement of the frequency of planets in the Galactic bulge versus the Galactic disk. As we have demonstrated in three previous programs, the difference in these lightcurves yields both the 'microlens parallax' (ratio of the lens-source relative parallax) to the Einstein radius, and the direction of lens-source relative motion. For planetary events, this measurement directly yields the mass and distance of the planet. This proposal is significantly more sensitive to planets than previous work because it takes advantage of the KMTNet observing strategy that covers >85 sq.deg t >0.4/hr cadence, 24/7 from 3 southern observatories and a alert system KMTNet is implementing for 2019. This same observing program also provides a unique probe of dark objects. It will yield an improved measurement of the isolated-brown-dwarf mass function. Thirteen percent of the observations will specifically target binaries, which will probe systems with dark components (brown dwarfs, neutron stars, black holes) that are difficult or impossible to investigate by other methods. The observations and methods from this work are a test bed for WFIRST microlensing.

NGC 6273: Towards Defining A New Class of Galactic Globular Clusters?

NASA Astrophysics Data System (ADS)

Johnson, Christian I.; Rich, Robert Michael; Pilachowski, Catherine A.; Caldwell, Nelson; Mateo, Mario L.; Ira Bailey, John; Crane, Jeffrey D.

2016-01-01

A growing number of observations have found that several Galactic globular clusters exhibit abundance dispersions beyond the well-known light element (anti-)correlations. These clusters tend to be very massive, have >0.1 dex intrinsic metallicity dispersions, have complex sub-giant branch morphologies, and have correlated [Fe/H] and s-process element enhancements. Interestingly, nearly all of these clusters discovered so far have [Fe/H]~-1.7. In this context, we have examined the chemical composition of 18 red giant branch (RGB) stars in the massive, metal-poor Galactic bulge globular cluster NGC 6273 using high signal-to-noise, high resolution (R~27,000) spectra obtained with the Michigan/Magellan Fiber System (M2FS) and MSpec spectrograph mounted on the Magellan-Clay 6.5m telescope at Las Campanas Observatory. We find that the cluster exhibits a metallicity range from [Fe/H]=-1.80 to -1.30 and is composed of two dominant populations separated in [Fe/H] and [La/Fe] abundance. The increase in [La/Eu] as a function of [La/H] suggests that the increase in [La/Fe] with [Fe/H] is due to almost pure s-process enrichment. The most metal-rich star in our sample is not strongly La-enhanced, but is α-poor and may belong to a third "anomalous" stellar population. The two dominant populations exhibit the same [Na/Fe]-[Al/Fe] correlation found in other "normal" globular clusters. Therefore, NGC 6273 joins ω Centauri, M 22, M 2, and NGC 5286 as a possible new class of Galactic globular clusters.

An optical study of stars and dust in the Andromeda galaxy

NASA Technical Reports Server (NTRS)

Walterbos, R. A. M.; Kennicutt, R. C., Jr.

1988-01-01

The distribution of light in M 31 is characterized on the basis of the UBVR surface photometry reported by Walterbos and Kennicutt (1987). The results of the data analysis are presented in extensive graphs, maps, and tables and discussed in detail, considering the outer disk regions, the decomposition into bulge and disk, the global disk and bulge colors, and dust and gas in two spiral arms. Principal findings examined include: (1) position-angle changes at radial distances beyond about 18 kpc (consistent with SW disk warping); (2) a bulge profile well described by an r exp 1/4 power law; (3) a bulge contribution to total light of about 40 percent; (4) increasing blueness in the outer disk (color gradient 0.02 mag/kpc in B-R); (5) an extinction law similar to that for the Galaxy; and (6) a significant correlation between dust and H I distributions.

A Complete Census of the ~7000 Milky Way HII Regions

NASA Astrophysics Data System (ADS)

Armentrout, William Paul; Anderson, Loren Dean; Wenger, Trey; Bania, Thomas; Balser, Dana; Dame, Thomas; Dickey, John M.; Dawson, Joanne; Jordan, Christopher H.; McClure-Griffiths, Naomi M.; Andersen, Morten

2018-01-01

HII regions are the archetypical tracers of high-mass star formation. Because of their high luminosities, they can be seen across the entire Galactic disk from mid-infrared to radio wavelengths. A uniformly sensitive survey of Galactic HII regions would allow us to constrain the properties of Galactic structure and star formation. We have cataloged over 8000 HII regions and candidates in the WISE Catalog of Galactic HII Regions (astro.phys.wvu.edu/wise), but only 2000 of these are confirmed HII regions to date.To bring us closer to a complete census of high-mass star formation regions in the Milky Way, we have several ongoing observational campaigns. These efforts include (1) Green Bank Telescope radio recombination line (RRL) observations as part of the HII Region Discovery Survey (HRDS); (2) Australia Telescope Compact Array observations of southern HII region candidates in the Southern HII Region Discovery Survey (SHRDS); (3) Green Bank and Gemini North Telescope observations of star formation regions thought to reside at the edge of the star forming disk in the Outer Scutum-Centaurus Arm (OSC); and (4) Very Large Array continuum observations of the faintest HII region candidates in the second and third Galactic quadrants.Together, these observations will detect the RRL emission from all Galactic HII regions with peak cm-wavelength flux densities > 60mJy, establish the outer edge of Galactic high-mass star formation, and determine the number of HII regions in the Galaxy. The HRDS and SHRDS surveys have more than doubled the known population of Galactic HII regions. We use the OSC observations to determine the properties of high-mass star formation in the extreme outer Galaxy and our VLA observations to determine how many of our faint candidates are indeed HII regions. We combine the completeness limits we obtain through these HII region surveys with an HII region population synthesis model to estimate the total number of Galactic HII regions. From this, we predict nearly 7000 HII regions in the Milky Way created by a central star of type B2 or earlier.

The Star Formation History in the M31 Bulge

NASA Astrophysics Data System (ADS)

Dong, Hui; Olsen, Knut; Lauer, Tod; Saha, Abhijit; Li, Zhiyuan; García-Benito, Ruben; Schödel, Rainer

2018-05-01

We present the study of stellar populations in the central 5.5' (˜1.2 kpc) of the M31 bulge by using the optical color magnitude diagram derived from HST ACS WFC/HRC observations. In order to enhance image quality and then obtain deeper photometry, we construct Nyquist-sampled images and use a deconvolution method to detect sources and measure their photometry. We demonstrate that our method performs better than DOLPHOT in the extremely crowded region. The resolved stars in the M31 bulge have been divided into nine annuli and the color magnitude diagram fitting is performed for each of them. We confirm that the majority of stars (>70%) in the M31 bulge are indeed very old (> 5 Gyr) and metal-rich ([Fe/H]˜0.3). At later times, the star formation rate decreased and then experienced a significant rise around 1 Gyr ago, which pervaded the entire M31 bulge. After that, stars formed at less than 500 Myr ago in the central 130" . Through simulation, we find that these intermediate-age stars cannot be the artifacts introduced by the blending effect. Our results suggest that although the majority of the M31 bulge are very old, the secular evolutionary process still continuously builds up the M31 bulge slowly. We compare our star formation history with an older analysis derived from the spectral energy distribution fitting, which suggests that the latter one is still a reasonable tool for the study of stellar populations in remote galaxies.

Spectroscopic decomposition of NGC 3521: unveiling the properties of the bulge and disc

NASA Astrophysics Data System (ADS)

Coccato, Lodovico; Fabricius, Maximilian H.; Saglia, Roberto P.; Bender, Ralf; Erwin, Peter; Drory, Niv; Morelli, Lorenzo

2018-06-01

We study the kinematics and the stellar populations of the bulge and disc of the spiral galaxy NGC 3521. At each position in the field of view, we separate the contributions of the bulge and the disc from the total observed spectrum and study their kinematics, age, and metallicities independently. Their properties are clearly distinct: the bulge rotates more slowly, has a higher velocity dispersion, and is less luminous than the disc. We identify three main populations of stars in NGC 3521: old (≥7 Gyr), intermediate (≈3 Gyr), and young (≤1 Gyr). The mass and light of NGC 3521 are dominated by the intermediate stellar population. The youngest population contributes mostly to the disc component and its contribution increases with radius. We also study the luminosity-weighed properties of the stars in NGC 3521. Along the photometric major axis, we find (i) no age gradient for the stars in the bulge, and a negative age gradient for the stars in the disc; (ii) negative metallicity gradients and subsolar α-enhancement for both the bulge and the disc. We propose the following picture for the formation of NGC 3521: initial formation a long time ago (≥7 Gyr), followed by a second burst of star formation or a merger (≈3 Gyr ago), which contributed predominantly to the mass build-up of the bulge. Recently (≤1 Gyr), the disc of NGC 3521 experienced an additional episode of star formation that started in the innermost regions.

Construction of the Database for Pulsating Variable Stars

NASA Astrophysics Data System (ADS)

Chen, Bing-Qiu; Yang, Ming; Jiang, Bi-Wei

2012-01-01

A database for pulsating variable stars is constructed to favor the study of variable stars in China. The database includes about 230,000 variable stars in the Galactic bulge, LMC and SMC observed in an about 10 yr period by the MACHO(MAssive Compact Halo Objects) and OGLE(Optical Gravitational Lensing Experiment) projects. The software used for the construction is LAMP, i.e., Linux+Apache+MySQL+PHP. A web page is provided for searching the photometric data and light curves in the database through the right ascension and declination of an object. Because of the flexibility of this database, more up-to-date data of variable stars can be incorporated into the database conveniently.

pyLIMA : The first open source microlensing modeling software

NASA Astrophysics Data System (ADS)

Bachelet, Etienne; Street, Rachel; Bozza, Valerio

2018-01-01

Microlensing is highly sensitive to planets beyond the snowline and distributed along the line of sight towards the Galactic Bulge. The WFIRST-AFTA mission should detect about 3000 of these planets and significantly improves our knowledge of planet formation and statistics, complementing results found by transit and radial velocity methods. However, the modeling of microlensing event is challenging on different aspects leading to a highly time consuming analysis. After a quick summarize of these different challenges, I will present pyLIMA, the first open source microlensing modeling software. The aimed goal of this software are to be flexible, powerful and user friendly. This presentation will focus on various case and early results.

Identification on HST Images of Microlensed Stars from the MACHO Project

NASA Astrophysics Data System (ADS)

King, L. J.; Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T. S.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Drake, A. J.; Freeman, K. C.; Griest, K.; Lehner, M. J.; Marshall, S. L.; Minniti, D.; Peterson, B. A.; Popowski, P.; Pratt, M. R.; Quinn, P. J.; Rodgers, A. W.; Stubbs, C. W.; Sutherland, W.; Tomaney, A.; Vandehei, T.; Welch, D. L.; MACHO Collaboration

1998-12-01

The MACHO collaboration has been searching for microlensing events toward the Galactic Bulge and the Magellanic Clouds. We have used the WFPC2/HST to obtain high resolution images of a number of fields centred on stars that have undergone microlensing events. Ground based optical images typically have a resolution in excess of one arcsecond, so that the microlensed star may be blended with other stars. On HST images the star is unblended. We show that microlensed stars can be identified by comparing the HST images with image subtracted ground based images. The unblended intrinsic magnitudes, lensed magnitudes and magnifications of the stars can be determined, providing invaluable constraints on lens models.

The Southern HII Region Discovery Survey: The Bright Catalog

NASA Astrophysics Data System (ADS)

Wenger, Trey V.; Dickey, John M.; Jordan, Christopher H.; Balser, Dana; Armentrout, William Paul; Anderson, Loren; Bania, Thomas; Dawson, Joanne; McClure-Griffiths, Naomi M.; Shea, Jeanine

2018-01-01

HII regions, the zones of ionized gas surrounding recently formed high-mass stars, are the archetypical tracers of Galactic structure. The census of Galactic HII regions in the Southern sky is vastly incomplete due to a lack of sensitive radio recombination line (RRL) surveys. The Southern HII Region Discovery Survey (SHRDS) is a 900-hour Australia Telescope Compact Array cm-wavelength RRL and continuum emission survey of hundreds of third and fourth quadrant Galactic HII region candidates. These candidates are identified in the Widefield Infrared Survey Explorer (WISE) Catalog of Galactic HII Regions based on coincident 10 micron (WISE) and 20 cm (Southern Galactic Plane Survey) emission. The SHRDS is an extension of HII Region Discovery Surveys in the Northern sky with the Green Bank Telescope and Arecibo Telescope which discovered ~800 new HII regions. In the first 500 hours of the SHRDS, we targeted the 249 brightest HII region candidates and 33 previously known HII regions. We discuss the data reduction, analysis, and preliminary results from this first stage of the survey.

Discovering Extrasolar Planets with Microlensing Surveys

NASA Astrophysics Data System (ADS)

Wambsganss, J.

2016-06-01

An astronomical survey is commonly understood as a mapping of a large region of the sky, either photometrically (possibly in various filters/wavelength ranges) or spectroscopically. Often, catalogs of objects are produced/provided as the main product or a by-product. However, with the advent of large CCD cameras and dedicated telescopes with wide-field imaging capabilities, it became possible in the early 1990s, to map the same region of the sky over and over again. In principle, such data sets could be combined to get very deep stacked images of the regions of interest. However, I will report on a completely different use of such repeated maps: Exploring the time domain for particular kinds of stellar variability, namely microlens-induced magnifications in search of exoplanets. Such a time-domain microlensing survey was originally proposed by Bohdan Paczynski in 1986 in order to search for dark matter objects in the Galactic halo. Only a few years later three teams started this endeavour. I will report on the history and current state of gravitational microlensing surveys. By now, routinely 100 million stars in the Galactic Bulge are monitored a few times per week by so-called survey teams. All stars with constant apparent brightness and those following known variability patterns are filtered out in order to detect the roughly 2000 microlensing events per year which are produced by stellar lenses. These microlensing events are identified "online" while still in their early phases and then monitored with much higher cadence by so-called follow-up teams. The most interesting of such events are those produced by a star-plus-planet lens. By now of order 30 exoplanets have been discovered by these combined microlensing surveys. Microlensing searches for extrasolar planets are complementary to other exoplanet search techniques. There are two particular advantages: The microlensing method is sensitive down to Earth-mass planets even with ground-based telecopes, and it can be easily used to determine the global abundance of planets in the Milky Way. Recent results of these microlensing surveys are presented and discussed, e. g. the discovery that on average every Milky Way star has at least one planet of Neptune mass or higher.

A Green Bank Telescope Survey of Large Galactic H II Regions

NASA Astrophysics Data System (ADS)

Anderson, L. D.; Armentrout, W. P.; Luisi, Matteo; Bania, T. M.; Balser, Dana S.; Wenger, Trey V.

2018-02-01

As part of our ongoing H II Region Discovery Survey (HRDS), we report the Green Bank Telescope detection of 148 new angularly large Galactic H II regions in radio recombination line (RRL) emission. Our targets are located at a declination of δ > -45^\\circ , which corresponds to 266^\\circ > {\\ell }> -20^\\circ at b=0^\\circ . All sources were selected from the Wide-field Infrared Survey Explorer Catalog of Galactic H II Regions, and have infrared angular diameters ≥slant 260\\prime\\prime . The Galactic distribution of these “large” H II regions is similar to that of the previously known sample of Galactic H II regions. The large H II region RRL line width and peak line intensity distributions are skewed toward lower values, compared with that of previous HRDS surveys. We discover seven sources with extremely narrow RRLs < 10 {km} {{{s}}}-1. If half the line width is due to turbulence, these seven sources have thermal plasma temperatures < 1100 {{K}}. These temperatures are lower than any measured for Galactic H II regions, and the narrow-line components may arise instead from partially ionized zones in the H II region photodissociation regions. We discover G039.515+00.511, one of the most luminous H II regions in the Galaxy. We also detect the RRL emission from three H II regions with diameters > 100 {pc}, making them some of the physically largest known H II regions in the Galaxy. This survey completes the HRDS H II region census in the Northern sky, where we have discovered 887 H II regions and more than doubled the size of the previously known census of Galactic H II regions.

Finding Distant Galactic HII Regions

NASA Astrophysics Data System (ADS)

Anderson, L. D.; Armentrout, W. P.; Johnstone, B. M.; Bania, T. M.; Balser, Dana S.; Wenger, Trey V.; Cunningham, V.

2015-12-01

The WISE Catalog of Galactic H ii Regions contains ˜2000 H ii region candidates lacking ionized gas spectroscopic observations. All candidates have the characteristic H ii region mid-infrared morphology of WISE 12 μ {{m}} emission surrounding 22 μ {{m}} emission, and additionally have detected radio continuum emission. We here report Green Bank Telescope hydrogen radio recombination line and radio continuum detections in the X-band (9 GHz; 3 cm) of 302 WISE H ii region candidates (out of 324 targets observed) in the zone 225^\\circ ≥slant {\\ell }≥slant -20^\\circ , | {\\text{}}b| ≤slant 6^\\circ . Here we extend the sky coverage of our H ii region Discovery Survey, which now contains nearly 800 H ii regions distributed across the entire northern sky. We provide LSR velocities for the 302 detections and kinematic distances for 131 of these. Of the 302 new detections, 5 have ({\\ell },{\\text{}}b,v) coordinates consistent with the Outer Scutum-Centaurus Arm (OSC), the most distant molecular spiral arm of the Milky Way. Due to the Galactic warp, these nebulae are found at Galactic latitudes >1° in the first Galactic quadrant, and therefore were missed in previous surveys of the Galactic plane. One additional region has a longitude and velocity consistent with the OSC but lies at a negative Galactic latitude (G039.183-01.422 -54.9 {km} {{{s}}}-1). With Heliocentric distances >22 kpc and Galactocentric distances >16 kpc, the OSC H ii regions are the most distant known in the Galaxy. We detect an additional three H ii regions near {\\ell }≃ 150^\\circ whose LSR velocities place them at Galactocentric radii >19 kpc. If their distances are correct, these nebulae may represent the limit to Galactic massive star formation.

LBSizeCleav: improved support vector machine (SVM)-based prediction of Dicer cleavage sites using loop/bulge length.

PubMed

Bao, Yu; Hayashida, Morihiro; Akutsu, Tatsuya

2016-11-25

Dicer is necessary for the process of mature microRNA (miRNA) formation because the Dicer enzyme cleaves pre-miRNA correctly to generate miRNA with correct seed regions. Nonetheless, the mechanism underlying the selection of a Dicer cleavage site is still not fully understood. To date, several studies have been conducted to solve this problem, for example, a recent discovery indicates that the loop/bulge structure plays a central role in the selection of Dicer cleavage sites. In accordance with this breakthrough, a support vector machine (SVM)-based method called PHDCleav was developed to predict Dicer cleavage sites which outperforms other methods based on random forest and naive Bayes. PHDCleav, however, tests only whether a position in the shift window belongs to a loop/bulge structure. In this paper, we used the length of loop/bulge structures (in addition to their presence or absence) to develop an improved method, LBSizeCleav, for predicting Dicer cleavage sites. To evaluate our method, we used 810 empirically validated sequences of human pre-miRNAs and performed fivefold cross-validation. In both 5p and 3p arms of pre-miRNAs, LBSizeCleav showed greater prediction accuracy than PHDCleav did. This result suggests that the length of loop/bulge structures is useful for prediction of Dicer cleavage sites. We developed a novel algorithm for feature space mapping based on the length of a loop/bulge for predicting Dicer cleavage sites. The better performance of our method indicates the usefulness of the length of loop/bulge structures for such predictions.

Reversible and irreversible wrinkling in tube hydroforming process

NASA Astrophysics Data System (ADS)

El-Aty, Ali Abd; Ahmed, Tauseef; Farooq, Ahmed

2017-07-01

The aim of this research is to analyzeandoptimize the hydroforming process parameters in order to achieve a sound bulged tube without failure. Theoretical constitutive model is formulated to develop a working diagram including process window, which represents the optimize region to carry out the hydroforming process and predict the type of tube failure during the process accurately. The model is applied into different bulging ratios for low carbon steel (C1010). From this study, it is concluded that the tubes with bulging ratios up to 50% and 70% are successfully formed without defects. The tubes with bulging ratio of 90% are successfully formed by hydroforming with optimized the loading path (axial feed versus internal pressure) within the process window. The working diagram is modified due to different types of formation of wrinkling during the hydroforming process. The formation of wrinkles with increasing axial feed can be useful in terms of the achievement of higher bulging ratio and/or less thinning and this type of wrinkles can be overcome through the internal pressure in the later stage of the hydroforming process. On the other hand, the formation of wrinkles may be harmful, if it cannot be reversed.

Hubble Space Telescope Observations of Extended [O III]λ 5007 Emission in Nearby QSO2s: New Constraints on AGN Host Galaxy Interaction

NASA Astrophysics Data System (ADS)

Fischer, Travis C.; Kraemer, S. B.; Schmitt, H. R.; Longo Micchi, L. F.; Crenshaw, D. M.; Revalski, M.; Vestergaard, M.; Elvis, M.; Gaskell, C. M.; Hamann, F.; Ho, L. C.; Hutchings, J.; Mushotzky, R.; Netzer, H.; Storchi-Bergmann, T.; Straughn, A.; Turner, T. J.; Ward, M. J.

2018-04-01

We present a Hubble Space Telescope survey of extended [O III] λ5007 emission for a sample of 12 nearby (z < 0.12), luminous Type 2 quasars (QSO2s), which we use to measure the extent and kinematics of their AGN-ionized gas. We find that the size of the observed [O III] regions scale with luminosity in comparison to nearby, less luminous Seyfert galaxies and radially outflowing kinematics to exist in all targets. We report an average maximum outflow radius of ∼600 pc, with gas continuing to be kinematically influenced by the central active galactic nucleus (AGN) out to an average radius of ∼1130 pc. These findings question the effectiveness of AGNs being capable of clearing material from their host bulge in the nearby universe and suggest that disruption of gas by AGN activity may prevent star formation without requiring evacuation. Additionally, we find a dichotomy in our targets when comparing [O III] radial extent and nuclear FWHM, where QSO2s with compact [O III] morphologies typically possess broader nuclear emission lines.

WFIRST: Resolving the Milky Way Galaxy

NASA Astrophysics Data System (ADS)

Kalirai, Jason; Conroy, Charlie; Dressler, Alan; Geha, Marla; Levesque, Emily; Lu, Jessica; Tumlinson, Jason

2018-01-01

WFIRST will yield a transformative impact in measuring and characterizing resolved stellar populations in the Milky Way. The proximity and level of detail that such populations need to be studied at directly map to all three pillars of WFIRST capabilities - sensitivity from a 2.4 meter space based telescope, resolution from 0.1" pixels, and large 0.3 degree field of view from multiple detectors. In this poster, we describe the activities of the WFIRST Science Investigation Team (SIT), "Resolving the Milky Way with WFIRST". Notional programs guiding our analysis include targeting sightlines to establish the first well-resolved large scale maps of the Galactic bulge aand central region, pockets of star formation in the disk, benchmark star clusters, and halo substructure and ultra faint dwarf satellites. As an output of this study, our team is building optimized strategies and tools to maximize stellar population science with WFIRST. This will include: new grids of IR-optimized stellar evolution and synthetic spectroscopic models; pipelines and algorithms for optimal data reduction at the WFIRST sensitivity and pixel scale; wide field simulations of Milky Way environments including new astrometric studies; and strategies and automated algorithms to find substructure and dwarf galaxies in the Milky Way through the WFIRST High Latitude Survey.

Discovery of a Second Millesecond Accreting Pulsar: XTE J1751-305

NASA Technical Reports Server (NTRS)

Markwardt, C. B.; Swank, J. H.; Strohmayer, T. E.; intZand, J. J. M.; Marshall, F. E.; White, Nicholas E. (Technical Monitor)

2002-01-01

We report the discovery by the RXTE PCA of a second transient accreting millisecond pulsar, XTE J1751-305, during regular monitoring observations of the galactic bulge region. The pulsar has a spin frequency of 435 Hz, making it one of the fastest pulsars. The pulsations contain the signature of orbital Doppler modulation, which implies an orbital period of 42 minutes, the shortest orbital period of any known radio or X-ray millisecond pulsar. The mass function, f(sub x) = (1.278 +/- 0.003) x 10 (exp -6) solar mass, yields a minimum mass for the companion of between 0.013 and 0.0017 solar mass depending on the mass of the neutron star. No eclipses were detected. A previous X-ray outburst in June, 1998, was discovered in archival All-Sky Monitor data. Assuming mass transfer in this binary system is driven by gravitational radiation, we constrain the orbital inclination to be in the range 30 deg-85 deg and the companion mass to be 0.013-0.035 solar mass. The companion is most likely a heated helium dwarf. We also present results from the Chandra HRC-S observations which provide the best known position of XTE J1751-305.

Unbound or distant planetary mass population detected by gravitational microlensing.

PubMed

2011-05-19

Since 1995, more than 500 exoplanets have been detected using different techniques, of which 12 were detected with gravitational microlensing. Most of these are gravitationally bound to their host stars. There is some evidence of free-floating planetary-mass objects in young star-forming regions, but these objects are limited to massive objects of 3 to 15 Jupiter masses with large uncertainties in photometric mass estimates and their abundance. Here, we report the discovery of a population of unbound or distant Jupiter-mass objects, which are almost twice (1.8(+1.7)(-0.8)) as common as main-sequence stars, based on two years of gravitational microlensing survey observations towards the Galactic Bulge. These planetary-mass objects have no host stars that can be detected within about ten astronomical units by gravitational microlensing. However, a comparison with constraints from direct imaging suggests that most of these planetary-mass objects are not bound to any host star. An abrupt change in the mass function at about one Jupiter mass favours the idea that their formation process is different from that of stars and brown dwarfs. They may have formed in proto-planetary disks and subsequently scattered into unbound or very distant orbits.

Hubble Sees Galaxy Hiding in the Night Sky

NASA Image and Video Library

2017-12-08

This striking NASA/ESA Hubble Space Telescope image captures the galaxy UGC 477, located just over 110 million light-years away in the constellation of Pisces (The Fish). UGC 477 is a low surface brightness (LSB) galaxy. First proposed in 1976 by Mike Disney, the existence of LSB galaxies was confirmed only in 1986 with the discovery of Malin 1. LSB galaxies like UGC 477 are more diffusely distributed than galaxies such as Andromeda and the Milky Way. With surface brightnesses up to 250 times fainter than the night sky, these galaxies can be incredibly difficult to detect. Most of the matter present in LSB galaxies is in the form of hydrogen gas, rather than stars. Unlike the bulges of normal spiral galaxies, the centers of LSB galaxies do not contain large numbers of stars. Astronomers suspect that this is because LSB galaxies are mainly found in regions devoid of other galaxies, and have therefore experienced fewer galactic interactions and mergers capable of triggering high rates of star formation. LSB galaxies such as UGC 477 instead appear to be dominated by dark matter, making them excellent objects to study to further our understanding of this elusive substance. However, due to an underrepresentation in galactic surveys — caused by their characteristic low brightness — their importance has only been realized relatively recently. Image credit: ESA/Hubble & NASA, Acknowledgement: Judy Schmidt NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

CHANDRA X-RAY AND HUBBLE SPACE TELESCOPE IMAGING OF OPTICALLY SELECTED KILOPARSEC-SCALE BINARY ACTIVE GALACTIC NUCLEI. II. HOST GALAXY MORPHOLOGY AND AGN ACTIVITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shangguan, Jinyi; Ho, Luis C.; Liu, Xin

Binary active galactic nuclei (AGNs) provide clues to how gas-rich mergers trigger and fuel AGNs and how supermassive black hole (SMBH) pairs evolve in a gas-rich environment. While significant effort has been invested in their identification, the detailed properties of binary AGNs and their host galaxies are still poorly constrained. In a companion paper, we examined the nature of ionizing sources in the double nuclei of four kiloparsec-scale binary AGNs with redshifts between 0.1 and 0.2. Here, we present their host galaxy morphology based on F336W ( U -band) and F105W ( Y -band) images taken by the Wide Fieldmore » Camera 3 on board the Hubble Space Telescope . Our targets have double-peaked narrow emission lines and were confirmed to host binary AGNs with follow-up observations. We find that kiloparsec-scale binary AGNs occur in galaxy mergers with diverse morphological types. There are three major mergers with intermediate morphologies and a minor merger with a dominant disk component. We estimate the masses of the SMBHs from their host bulge stellar masses and obtain Eddington ratios for each AGN. Compared with a representative control sample drawn at the same redshift and stellar mass, the AGN luminosities and Eddington ratios of our binary AGNs are similar to those of single AGNs. The U − Y color maps indicate that clumpy star-forming regions could significantly affect the X-ray detection of binary AGNs, e.g., the hardness ratio. Considering the weak X-ray emission in AGNs triggered in merger systems, we suggest that samples of X-ray-selected AGNs may be biased against gas-rich mergers.« less

Black holes in binary stellar systems and galactic nuclei

NASA Astrophysics Data System (ADS)

Cherepashchuk, A. M.

2014-04-01

In the last 40 years, following pioneering papers by Ya B Zeldovich and E E Salpeter, in which a powerful energy release from nonspherical accretion of matter onto a black hole (BH) was predicted, many observational studies of black holes in the Universe have been carried out. To date, the masses of several dozen stellar-mass black holes (M_BH = (4{-}20) M_\\odot) in X-ray binary systems and of several hundred supermassive black holes (M_BH = (10^{6}{-}10^{10}) M_\\odot) in galactic nuclei have been measured. The estimated radii of these massive and compact objects do not exceed several gravitational radii. For about ten stellar-mass black holes and several dozen supermassive black holes, the values of the dimensionless angular momentum a_* have been estimated, which, in agreement with theoretical predictions, do not exceed the limiting value a_* = 0.998. A new field of astrophysics, so-called black hole demography, which studies the birth and growth of black holes and their evolutionary connection to other objects in the Universe, namely stars, galaxies, etc., is rapidly developing. In addition to supermassive black holes, massive stellar clusters are observed in galactic nuclei, and their evolution is distinct from that of supermassive black holes. The evolutionary relations between supermassive black holes in galactic centers and spheroidal stellar components (bulges) of galaxies, as well as dark-matter galactic haloes are brought out. The launch into Earth's orbit of the space radio interferometer RadioAstron opened up the real possibility of finally proving that numerous discovered massive and highly compact objects with properties very similar to those of black holes make up real black holes in the sense of Albert Einstein's General Relativity. Similar proofs of the existence of black holes in the Universe can be obtained by intercontinental radio interferometry at short wavelengths \\lambda \\lesssim 1 mm (the international program, Event Horizon Telescope).

New PARSEC data base of α-enhanced stellar evolutionary tracks and isochrones - I. Calibration with 47 Tuc (NGC 104) and the improvement on RGB bump

NASA Astrophysics Data System (ADS)

Fu, Xiaoting; Bressan, Alessandro; Marigo, Paola; Girardi, Léo; Montalbán, Josefina; Chen, Yang; Nanni, Ambra

2018-05-01

Precise studies on the Galactic bulge, globular cluster, Galactic halo, and Galactic thick disc require stellar models with α enhancement and various values of helium content. These models are also important for extra-Galactic population synthesis studies. For this purpose, we complement the existing PARSEC models, which are based on the solar partition of heavy elements, with α-enhanced partitions. We collect detailed measurements on the metal mixture and helium abundance for the two populations of 47 Tuc (NGC 104) from the literature, and calculate stellar tracks and isochrones with these α-enhanced compositions. By fitting the precise colour-magnitude diagram with HST ACS/WFC data, from low main sequence till horizontal branch (HB), we calibrate some free parameters that are important for the evolution of low mass stars like the mixing at the bottom of the convective envelope. This new calibration significantly improves the prediction of the red giant branch bump (RGBB) brightness. Comparison with the observed RGB and HB luminosity functions also shows that the evolutionary lifetimes are correctly predicted. As a further result of this calibration process, we derive the age, distance modulus, reddening, and the RGB mass-loss for 47 Tuc. We apply the new calibration and α-enhanced mixtures of the two 47 Tuc populations ([α/Fe] ˜ 0.4 and 0.2) to other metallicities. The new models reproduce the RGB bump observations much better than previous models. This new PARSEC data base, with the newly updated α-enhanced stellar evolutionary tracks and isochrones, will also be a part of the new stellar products for Gaia.

ORIGIN OF THE GALACTIC DIFFUSE X-RAY EMISSION: IRON K-SHELL LINE DIAGNOSTICS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nobukawa, Masayoshi; Uchiyama, Hideki; Nobukawa, Kumiko K.

This paper reports detailed K-shell line profiles of iron (Fe) and nickel (Ni) of the Galactic Center X-ray Emission (GCXE), Galactic Bulge X-ray Emission (GBXE), Galactic Ridge X-ray Emission (GRXE), magnetic Cataclysmic Variables (mCVs), non-magnetic Cataclysmic Variables (non-mCVs), and coronally Active Binaries (ABs). For the study of the origin of the GCXE, GBXE, and GRXE, the spectral analysis is focused on equivalent widths of the Fe i-K α , Fe xxv-He α , and Fe xxvi-Ly α  lines. The global spectrum of the GBXE is reproduced by a combination of the mCVs, non-mCVs, and ABs spectra. On the other hand,more » the GRXE spectrum shows significant data excesses at the Fe i-K α and Fe xxv-He α  line energies. This means that additional components other than mCVs, non-mCVs, and ABs are required, which have symbiotic phenomena of cold gas and very high-temperature plasma. The GCXE spectrum shows larger excesses than those found in the GRXE spectrum at all the K-shell lines of iron and nickel. Among them the largest ones are the Fe i-K α , Fe xxv-He α , Fe xxvi-Ly α , and Fe xxvi-Ly β  lines. Together with the fact that the scale heights of the Fe i-K α , Fe xxv-He α , and Fe xxvi-Ly α lines are similar to that of the central molecular zone (CMZ), the excess components would be related to high-energy activity in the extreme envelopment of the CMZ.« less

Taking Measure of the Milky Way

NASA Technical Reports Server (NTRS)

Majewski, Steven R.; Bahcall, John N.; Geisler, Douglas; Gieren, Wolfgang; Grebel, Eva; Grillmair, Carl; Irwin, Michael; Johnston, Kathryn V.; Patterson, Richard J.; Reid, Neill I.

2004-01-01

We intend to use SIM to make definitive measurements of fundamental structural and dynamical parameters of the Milky Way. The important niche in dynamical parameter space afforded by SIM can be exploited to resolve, with unprecedented precision, a number of classical problems of Galactic astronomy. In addition, we have developed new tests of the Galactic mass distribution specifically designed for data with the special properties of SIM products. Our proposed suite of experiments will utilize the SIM Astrometric Grid as well as complementary observations of star clusters and other strategically-selected, distant "test particles" for a definitive characterization of the major components (bulge, disk, halo, satellite system) of the Milky Way. Specifically, our goals will be: 1) The determination of two fundamental parameters that play a central role in virtually every problem in Galactic astronomy, namely (a) the solar distance to the center of the Milky Way, R(sub 0); (b) the solar angular velocity around the Galactic: center, omega(sub 0). 2) The measurement of fundamental dynamical properties of the Milky Way, among them (a) the pattern speed of the central bar (b) the rotation field and velocity-dispersion tensor in the disk (c) the kinematics (mean rotational velocity and velocity dispersion tensor) of the halo as a function of position 3. The definition of the mass distribution of the Galaxy, which is dominated by the presence of dark matter. We intend to measure (a) the relative contribution of the disk and halo to the gravitational potential (b) the local volume and surface mass density of the disk (c) the shape, mass and extent of the dark halo of the Milky Way out to 250 kpc.

Star Formation of Merging Disk Galaxies with AGN Feedback Effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Jongwon; Smith, Rory; Yi, Sukyoung K., E-mail: jw.park@yonsei.ac.kr

2017-08-20

Using a numerical hydrodynamics code, we perform various idealized galaxy merger simulations to study the star formation (SF) of two merging disk galaxies. Our simulations include gas accretion onto supermassive black holes and active galactic nucleus (AGN) feedback. By comparing AGN simulations with those without AGNs, we attempt to understand when the AGN feedback effect is significant. Using ∼70 simulations, we investigate SF with the AGN effect in mergers with a variety of mass ratios, inclinations, orbits, galaxy structures, and morphologies. Using these merger simulations with AGN feedback, we measure merger-driven SF using the burst efficiency parameter introduced by Coxmore » et al. We confirm previous studies which demonstrated that, in galaxy mergers, AGN suppresses SF more efficiently than in isolated galaxies. However, we also find that the effect of AGNs on SF is larger in major than in minor mergers. In minor merger simulations with different primary bulge-to-total ratios, the effect of bulge fraction on the merger-driven SF decreases due to AGN feedback. We create models of Sa-, Sb-, and Sc-type galaxies and compare their SF properties while undergoing mergers. With the current AGN prescriptions, the difference in merger-driven SF is not as pronounced as in the recent observational study of Kaviraj. We discuss the implications of this discrepancy.« less

Hubble Space Telescope Imaging of the Active Dwarf Galaxy RGG 118

NASA Astrophysics Data System (ADS)

Baldassare, Vivienne F.; Reines, Amy E.; Gallo, Elena; Greene, Jenny E.

2017-12-01

RGG 118 (SDSS 1523+1145) is a nearby (z = 0.0243), dwarf disk galaxy ({M}* ≈ 2× {10}9 {M}⊙ ) that is found to host an active ˜50,000 solar mass black hole at its core. RGG 118 is one of a growing collective sample of dwarf galaxies known to contain active galactic nuclei (AGNs)—a group that, until recently, contained only a handful of objects. Here, we report on new Hubble Space Telescope Wide Field Camera 3 UVIS and IR imaging of RGG 118, with the main goal of analyzing its structure. Using 2D parametric modeling, we find that the morphology of RGG 118 is best described by an outer spiral disk, an inner component consistent with a pseudobulge, and a central point-spread function (PSF). The luminosity of the PSF is consistent with the central point source that is being dominated by the AGN. We measure the luminosity and the mass of the “pseudobulge” and confirm that the central black hole in RGG 118 is under-massive, with respect to the {M}{BH}{--}{M}{bulge} and {M}{BH}{--}{L}{bulge} relations. This result is consistent with a picture in which black holes in disk-dominated galaxies grow primarily through secular processes.

Secular Black Hole Growth and Feedback in Merger-Free Galaxies

NASA Astrophysics Data System (ADS)

Simmons, Brooke

2016-10-01

We will measure the merger-free galaxy-black hole mass relation for the first time, using a unique, newly-discovered sample of luminous active galactic nuclei (AGN) hosted in galaxies that have not grown via mergers. Our preliminary study has shown that supermassive black holes (SMBHs) in bulgeless galaxies - i.e., galaxies that have never undergone a significant merger - can have substantial growth: bulges are not required for the formation and growth of SMBHs. The proposed targets are broad-line AGN with black hole masses spanning a wide mass range (1e6 to >1e9 M_Sun) and hosted in strongly disk dominated galaxies (>80% light from a disk). This sample is an ideal laboratory for understanding merger-free black hole growth and its feedback on the host galaxy. HST imaging will allow us to disentangle bright nuclear emission from host galaxy, measure bulge type and strength, and identify bulgeless galaxies that have evolved under purely secular conditions. In addition, we will determine whether merger-free galaxies lie on the same SMBH-galaxy relation as galaxies with substantial past mergers, or whether merger-free growth results in a separate relation. The answer to this question has profound consequences for the role of baryon dynamics in driving black hole-galaxy co-evolution.

OGLE-2003-BLG-262: Finite-Source Effects from a Point-Mass Lens

NASA Astrophysics Data System (ADS)

Yoo, Jaiyul; DePoy, D. L.; Gal-Yam, A.; Gaudi, B. S.; Gould, A.; Han, C.; Lipkin, Y.; Maoz, D.; Ofek, E. O.; Park, B.-G.; Pogge, R. W.; Mu-Fun Collaboration; Udalski, A.; Soszyński, I.; Wyrzykowski, Ł.; Kubiak, M.; Szymański, M.; Pietrzyński, G.; Szewczyk, O.; Żebruń, K.; OGLE Collaboration

2004-03-01

We analyze OGLE-2003-BLG-262, a relatively short (tE=12.5+/-0.1 day) microlensing event generated by a point-mass lens transiting the face of a K giant source in the Galactic bulge. We use the resulting finite-source effects to measure the angular Einstein radius, θE=195+/-17 μas, and so constrain the lens mass to the FWHM interval 0.08

How A Black Hole Lights Up Its Surroundings

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-10-01

How do the supermassive black holes that live at the centers of galaxies influence their environments? New observations of a distant active galaxy offer clues about this interaction.Signs of CoevolutionPlot demonstrating the m-sigma relation, the empirical correlation between the stellar velocity dispersion of a galactic bulge and the mass of the supermassive black hole at its center. [Msigma]We know that the centers of active galaxies host supermassive black holes with masses of millions to billions of suns. One mystery surrounding these beasts is that they are observed to evolve simultaneously with their host galaxies for instance, an empirical relationship is seen between the growth of a black hole and the growth of its host galaxys bulge. This suggests that there must be a feedback mechanism through which the evolution of a black hole is linked to that of its host galaxy.One proposed source of this coupling is the powerful jets emitted from the poles of these supermassive black holes. These jets are thought to be produced as some of the material accreting onto the black hole is flung out, confined by surrounding gas and magnetic fields. Because the jets of hot gas and radiation extend outward through the host galaxy, they provide a means for the black hole to influence the gas and dust of its surroundings.In our current model of a radio-loud active galactic nuclei,a region of hot, ionized gas the narrow-line region lies beyond the sphere of influence of the supermassive black hole. [C.M. Urry and P. Padovani]Clues in the Narrow-Line RegionThe region of gas thought to sit just outside of the black holes sphere of influence (at a distance of perhaps a thousand to a few thousand light-years) is known as the narrow line region so named because we observe narrow emission lines from this gas. Given its hot, ionized state, this gas must somehow be being pummeled with energy. In the canonical picture, radiation from the black hole heats the gas directly in a process called photoionization. But could jets also be involved?In a recent study led by kos Bogdn, a team of scientists at the Harvard-Smithsonian Center for Astrophysics used X-ray observations of a galaxys nucleus to explore the possibility that its narrow-line region is heated and ionized not only by radiation, but also by the shocks produced as radio jets collide with their surrounding environment.Heating from JetsChandra X-ray data for Mrk 3, with radio contours overplotted. Both wavelengths show S-shaped morphology of the jets, with the X-ray emission enveloping the radio emission. A strong shock is present in the west and a weaker shock toward the east. [Bogdn et al. 2017]Bogdn and collaborators analyzed deep Chandra X-ray observations of the center of Mrk 3, an early-type galaxy located roughly 200 million light-years away. Chandras imaging and high-resolution spectroscopy of the galaxys narrow-line region allowed the team to build a detailed picture of the hot gas, demonstrating that it shows similar S-shaped morphology to the gas emitting at radio wavelengths, but its more broadly distributed.The authors demonstrate the presence of shocks in the X-ray gas both toward the west and toward the east of the nucleus. These shocks, combined with the broadening of the X-ray emission and other signs, strongly support the idea that collisions of the jets with the surrounding environment heat the narrow-line-region gas, contributing to its ionization. The authors argue that, given how common small-scale radio jets are in galaxies such as Mrk 3, its likely that collisional ionization plays an important role in how the black holes in these galaxies impart energy to their surrounding environments.Citationkos Bogdn et al 2017 ApJ 848 61. doi:10.3847/1538-4357/aa8c76

IRAS and the Boston University Arecibo Galactic H I Survey: A catalog of cloud properties

NASA Technical Reports Server (NTRS)

Bania, Thomas M.

1992-01-01

The Infrared Astronomy Satellite (IRAS) Galactic Plane Surface Brightness Images were used to identify infrared emission associated with cool, diffuse H I clouds detected by the Boston University-Arecibo Galactic H I Survey. These clouds are associated with galactic star clusters, H II regions, and molecular clouds. Using emission-absorption experiments toward galactic H II regions, we determined the H I properties of cool H I clouds seen in absorption against the thermal continuum, including their kinematic distances. Correlations were then made between IRAS sources and these H II regions, thus some of the spatial confusion associated with the IRAS fields near the galactic plane was resolved since the distances to these sources was known. Because we can also correlate the BU-Arecibo clouds with existing CO surveys, these results will allow us to determine the intrinsic properties of the gas (neutral and ionized atomic as well as molecular) and dust for interstellar clouds in the inner galaxy. For the IRAS-identified H II region sample, we have established the far infrared (FIR) luminosities and galactic distribution of these sources.

Science Questions for the Post-SIRTF and Herschel Era

NASA Technical Reports Server (NTRS)

Werner, Michael

2004-01-01

The contents include the following: 1. SIRTF. Long wavelength surveys planned for SIRTF. Galaxy Discovery Rates for Future Missions. Impact of SIRTF s Improved Resolution at 160um: Resolving the Background. 2. Polarimetry. Submillimeter Polarimetry - The State of Play. Magnetic Vectors Across the Orion Molecular Cloud Core. Neutral and Ionized Molecular Spectral Lines. Variation of Polarization With Wavelength. The Polarization Spectrum. Submillimeter Polarimetry - Looking Ahead. 3.Confusion. Confusion at 500, 600 micron. 4. Extragalactic Science. Do Massive Black Holes and Galaxy Bulges form Together? 5. Galactic Science. Can We See the First Generations of Stars and Metal Formation? The Birth of Planets and the Origins of Life. Spatial Resolution at 100 microns. Far-ir/Sub-mm Transitions of Linear Carbon Clusters. Predicted Spectra of Glycine.

Numerical simulation of the formation of a spiral galaxy

NASA Astrophysics Data System (ADS)

Williams, P. R.; Nelson, A. H.

2001-08-01

A simulation is described in which the numerical galaxy formed compares favourably in every measurable respect with contemporary bright spiral galaxies, including the formation of a distinct stellar bulge and large scale spiral arm shocks in the gas component. This is achieved in spite of the fact that only idealized proto-galactic initial conditions were used, and only simple phenomenological prescriptions for the physics of the interstellar medium (ISM) and star formation were implemented. In light of the emphasis in recent literature on the importance of the link between galaxy formation and models of the universe on cosmological scales, on the details of the physics of the ISM and star formation, and on apparent problems therein, the implications of this result are discussed.

Probing the X-Ray Binary Populations of the Ring Galaxy NGC 1291

NASA Technical Reports Server (NTRS)

Luo, B.; Fabbiano, G.; Fragos, T.; Kim, D. W.; Belczynski, K.; Brassington, N. J.; Pellegrini, S.; Tzanavaris, P.; Wang, J.; Zezas, A.

2012-01-01

We present Chandra studies of the X-ray binary (XRB) populations in the bulge and ring regions of the ring galaxy NGC 1291. We detect 169 X-ray point sources in the galaxy, 75 in the bulge and 71 in the ring, utilizing the four available Chandra observations totaling an effective exposure of 179 ks. We report photometric properties of these sources in a point-source catalog. There are approx. 40% of the bulge sources and approx. 25% of the ring sources showing > 3(sigma) long-term variability in their X-ray count rate. The X-ray colors suggest that a significant fraction of the bulge (approx. 75%) and ring (approx. 65%) sources are likely low-mass X-ray binaries (LMXBs). The spectra of the nuclear source indicate that it is a low-luminosity AGN with moderate obscuration; spectral variability is observed between individual observations. We construct 0.3-8.0 keV X-ray luminosity functions (XLFs) for the bulge and ring XRB populations, taking into account the detection incompleteness and background AGN contamination. We reach 90% completeness limits of approx.1.5 x 10(exp 37) and approx. 2.2 x 10(exp 37) erg/s for the bulge and ring populations, respectively. Both XLFs can be fit with a broken power-law model, and the shapes are consistent with those expected for populations dominated by LMXBs. We perform detailed population synthesis modeling of the XRB populations in NGC 1291 , which suggests that the observed combined XLF is dominated by aD old LMXB population. We compare the bulge and ring XRB populations, and argue that the ring XRBs are associated with a younger stellar population than the bulge sources, based on the relative over-density of X-ray sources in the ring, the generally harder X-ray color of the ring sources, the overabundance of luminous sources in the combined XLF, and the flatter shape of the ring XLF.

Probing the Galactic Structure of the Milky Way with H II Regions

NASA Astrophysics Data System (ADS)

Red, Wesley Alexander; Wenger, Trey V.; Balser, Dana; Anderson, Loren; Bania, Thomas

2018-01-01

Mapping the structure of the Milky Way is challenging since we reside within the Galactic disk and distances are difficult to determine. Elemental abundances provide important constraints on theories of the formation and evolution of the Milky Way. HII regions are the brightest objects in the Galaxy at radio wavelengths and are detected across the entire Galactic disk. We use the Jansky Very Large Array (VLA) to observe the radio recombination line (RRL) and continuum emission of 120 Galactic HII regions located across the Galactic disk. In thermal equilibrium, metal abundances are expected to set the nebular electron temperature with high abundances producing low temperatures. We derive the metallicity of HII regions using an empirical relation between an HII region's radio recombination line-to-continuum ratio and nebular metallicity. Here we focus on a subset of 20 HII regions from our sample that have been well studied with the Green Bank Telescope (GBT) to test our data reduction pipeline and analysis methods. Our goal is to expand this study to the Southern skies with the Australia Telescope Compact Array and create a metallicity map of the entire Galactic disk.

Abundances of disk and bulge giants from high-resolution optical spectra. I. O, Mg, Ca, and Ti in the solar neighborhood and Kepler field samples

NASA Astrophysics Data System (ADS)

Jönsson, H.; Ryde, N.; Nordlander, T.; Pehlivan Rhodin, A.; Hartman, H.; Jönsson, P.; Eriksson, K.

2017-02-01

Context. The Galactic bulge is an intriguing and significant part of our Galaxy, but it is hard to observe because it is both distant and covered by dust in the disk. Therefore, there are not many high-resolution optical spectra of bulge stars with large wavelength coverage, whose determined abundances can be compared with nearby, similarly analyzed stellar samples. Aims: We aim to determine the diagnostically important alpha elements of a sample of bulge giants using high-resolution optical spectra with large wavelength coverage. The abundances found are compared to similarly derived abundances from similar spectra of similar stars in the local thin and thick disks. In this first paper we focus on the solar neighborhood reference sample. Methods: We used spectral synthesis to derive the stellar parameters as well as the elemental abundances of both the local and bulge samples of giants. We took special care to benchmark our method of determining stellar parameters against independent measurements of effective temperatures from angular diameter measurements and surface gravities from asteroseismology. Results: In this first paper we present the method used to determine the stellar parameters and elemental abundances, evaluate them, and present the results for our local disk sample of 291 giants. Conclusions: When comparing our determined spectroscopic temperatures to those derived from angular diameter measurements, we reproduce these with a systematic difference of +10 K and a standard deviation of 53 K. The spectroscopic gravities reproduce those determined from asteroseismology with a systematic offset of +0.10 dex and a standard deviation of 0.12 dex. When it comes to the abundance trends, our sample of local disk giants closely follows trends found in other works analyzing solar neighborhood dwarfs, showing that the much brighter giant stars are as good abundance probes as the often used dwarfs. Based on observations made with the Nordic Optical Telescope (programs 51-018 and 53-002), operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias, and on spectral data retrieved from PolarBase at Observatoire Midi Pyrénées.Full Tables A.1 and A.3 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/598/A100

Formation of the Sun-aligned arc region and the void (polar slot) under the null-separator structure

NASA Astrophysics Data System (ADS)

Tanaka, T.; Obara, T.; Watanabe, M.; Fujita, S.; Ebihara, Y.; Kataoka, R.

2017-04-01

From the global magnetosphere-ionosphere coupling simulation, we examined the formation of the Sun-aligned arc region and the void (polar slot) under the northward interplanetary magnetic field (IMF) with negative By condition. In the magnetospheric null-separator structure, the separatrices generated from two null points and two separators divide the entire space into four types of magnetic region, i.e., the IMF, the northern open magnetic field, the southern open magnetic field, and the closed magnetic field. In the ionosphere, the Sun-aligned arc region and the void are reproduced in the distributions of simulated plasma pressure and field-aligned current. The outermost closed magnetic field lines on the boundary (separatrix) between the northern open magnetic field and the closed magnetic field are projected to the northern ionosphere at the boundary between the Sun-aligned arc region and the void, both on the morning and evening sides. The magnetic field lines at the plasma sheet inner edge are projected to the equatorward boundary of the oval. Therefore, the Sun-aligned arc region is on the closed magnetic field lines of the plasma sheet. In the plasma sheet, an inflated structure (bulge) is generated at the junction of the tilted plasma sheet in the far-to-middle tail and nontilted plasma sheet in the ring current region. In the Northern Hemisphere, the bulge is on the evening side wrapped by the outermost closed magnetic field lines that are connected to the northern evening ionosphere. This inflated structure (bulge) is associated with shear flows that cause the Sun-aligned arc.

UKIRT-2017-BLG-001Lb: A Giant Planet Detected through the Dust

NASA Astrophysics Data System (ADS)

Shvartzvald, Y.; Calchi Novati, S.; Gaudi, B. S.; Bryden, G.; Nataf, D. M.; Penny, M. T.; Beichman, C.; Henderson, C. B.; Jacklin, S.; Schlafly, E. F.; Huston, M. J.

2018-04-01

We report the discovery of a giant planet in event UKIRT-2017-BLG-001, detected by the United Kingdom Infrared Telescope (UKIRT) microlensing survey. The mass ratio between the planet and its host is q={1.50}-0.14+0.17× {10}-3, about 1.5 times the Jupiter/Sun mass ratio. The event lies 0.°35 from the Galactic center and suffers from high extinction of A K = 1.68. Therefore, it could be detected only by a near-infrared (NIR) survey. The field also suffers from large spatial differential extinction, which makes it difficult to estimate the source properties required to derive the angular Einstein radius. Nevertheless, we find evidence suggesting that the source is located in the far disk. If correct, this would be the first source star of a microlensing event to be identified as belonging to the far disk. We estimate the lens mass and distance using a Bayesian analysis to find that the planet’s mass is {1.28}-0.44+0.37 {M}J, and it orbits a {0.81}-0.27+0.21 {M}ȯ star at an instantaneous projected separation of {4.18}-0.88+0.96 au. The system is at a distance of {6.3}-2.1+1.6 kpc, and so likely resides in the Galactic bulge. In addition, we find a non-standard extinction curve in this field, in agreement with previous results toward high-extinction fields near the Galactic center.

Particle Dark Matter constraints: the effect of Galactic uncertainties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benito, Maria; Bernal, Nicolás; Iocco, Fabio

2017-02-01

Collider, space, and Earth based experiments are now able to probe several extensions of the Standard Model of particle physics which provide viable dark matter candidates. Direct and indirect dark matter searches rely on inputs of astrophysical nature, such as the local dark matter density or the shape of the dark matter density profile in the target in object. The determination of these quantities is highly affected by astrophysical uncertainties. The latter, especially those for our own Galaxy, are ill-known, and often not fully accounted for when analyzing the phenomenology of particle physics models. In this paper we present amore » systematic, quantitative estimate of how astrophysical uncertainties on Galactic quantities (such as the local galactocentric distance, circular velocity, or the morphology of the stellar disk and bulge) propagate to the determination of the phenomenology of particle physics models, thus eventually affecting the determination of new physics parameters. We present results in the context of two specific extensions of the Standard Model (the Singlet Scalar and the Inert Doublet) that we adopt as case studies for their simplicity in illustrating the magnitude and impact of such uncertainties on the parameter space of the particle physics model itself. Our findings point toward very relevant effects of current Galactic uncertainties on the determination of particle physics parameters, and urge a systematic estimate of such uncertainties in more complex scenarios, in order to achieve constraints on the determination of new physics that realistically include all known uncertainties.« less

X-raying galaxies: a Chandra legacy.

PubMed

Wang, Q Daniel

2010-04-20

This presentation reviews Chandra's major contribution to the understanding of nearby galaxies. After a brief summary on significant advances in characterizing various types of discrete x-ray sources, the presentation focuses on the global hot gas in and around galaxies, especially normal ones like our own. The hot gas is a product of stellar and active galactic nuclear feedback--the least understood part in theories of galaxy formation and evolution. Chandra observations have led to the first characterization of the spatial, thermal, chemical, and kinetic properties of the gas in our galaxy. The gas is concentrated around the galactic bulge and disk on scales of a few kiloparsec. The column density of chemically enriched hot gas on larger scales is at least an order magnitude smaller, indicating that it may not account for the bulk of the missing baryon matter predicted for the galactic halo according to the standard cosmology. Similar results have also been obtained for other nearby galaxies. The x-ray emission from hot gas is well correlated with the star formation rate and stellar mass, indicating that the heating is primarily due to the stellar feedback. However, the observed x-ray luminosity of the gas is typically less than a few percent of the feedback energy. Thus the bulk of the feedback (including injected heavy elements) is likely lost in galaxy-wide outflows. The results are compared with simulations of the feedback to infer its dynamics and interplay with the circumgalactic medium, hence the evolution of galaxies.

X-raying galaxies: A Chandra legacy

PubMed Central

Wang, Q. Daniel

2010-01-01

This presentation reviews Chandra’s major contribution to the understanding of nearby galaxies. After a brief summary on significant advances in characterizing various types of discrete x-ray sources, the presentation focuses on the global hot gas in and around galaxies, especially normal ones like our own. The hot gas is a product of stellar and active galactic nuclear feedback—the least understood part in theories of galaxy formation and evolution. Chandra observations have led to the first characterization of the spatial, thermal, chemical, and kinetic properties of the gas in our galaxy. The gas is concentrated around the galactic bulge and disk on scales of a few kiloparsec. The column density of chemically enriched hot gas on larger scales is at least an order magnitude smaller, indicating that it may not account for the bulk of the missing baryon matter predicted for the galactic halo according to the standard cosmology. Similar results have also been obtained for other nearby galaxies. The x-ray emission from hot gas is well correlated with the star formation rate and stellar mass, indicating that the heating is primarily due to the stellar feedback. However, the observed x-ray luminosity of the gas is typically less than a few percent of the feedback energy. Thus the bulk of the feedback (including injected heavy elements) is likely lost in galaxy-wide outflows. The results are compared with simulations of the feedback to infer its dynamics and interplay with the circumgalactic medium, hence the evolution of galaxies. PMID:20212160

Gemini spectroscopy of the outer disk star cluster BH176

NASA Astrophysics Data System (ADS)

Sharina, M. E.; Donzelli, C. J.; Davoust, E.; Shimansky, V. V.; Charbonnel, C.

2014-10-01

Context. BH176 is an old metal-rich star cluster. It is spatially and kinematically consistent with belonging to the Monoceros Ring. It is larger in size and more distant from the Galactic plane than typical open clusters, and it does not belong to the Galactic bulge. Aims: Our aim is to determine the origin of this unique object by accurately determining its distance, metallicity, and age. The best way to reach this goal is to combine spectroscopic and photometric methods. Methods: We present medium-resolution observations of red clump and red giant branch stars in BH176 obtained with the Gemini South Multi-Object Spectrograph. We derive radial velocities, metallicities, effective temperatures, and surface gravities of the observed stars and use these parameters to distinguish member stars from field objects. Results: We determine the following parameters for BH176: Vh = 0 ± 15 km s-1, [Fe/H] = -0.1 ± 0.1, age 7 ± 0.5 Gyr, E(V - I) = 0.79 ± 0.03, distance 15.2 ± 0.2 kpc, α-element abundance [α/Fe] ~ 0.25 dex (the mean of [Mg/Fe], and [Ca/Fe]). Conclusions: BH176 is a member of old Galactic open clusters that presumably belong to the thick disk. It may have originated as a massive star cluster after the encounter of the forming thin disk with a high-velocity gas cloud or as a satellite dwarf galaxy. Appendix A is available in electronic form at http://www.aanda.org

RUNAWAY M DWARF CANDIDATES FROM THE SLOAN DIGITAL SKY SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Favia, Andrej; West, Andrew A.; Theissen, Christopher A., E-mail: andrej.favia@umit.maine.edu

2015-11-01

We present a sample of 20 runaway M dwarf candidates (RdMs) within 1 kpc of the Sun whose Galactocentric (GC) velocities exceed 400 km s{sup −1}. The candidates were selected from the Sloan Digital Sky Survey (SDSS) DR7 M Dwarf Catalog of West et al. Our RdMs have SDSS+USNO-B proper motions that are consistent with those recorded in the PPMXL, LSPM, and combined Wide-field Infrared Survey Explorer +SDSS+Two-micron All-sky Survey catalogs. Sixteen RdMs are classified as dwarfs, while the remaining four RdMs are subdwarfs. We model the Galactic potential using a bulge-disk-halo profile. Our fastest RdM, with a GC velocitymore » of 658.5 ± 236.9 km s{sup −1}, is a possible hypervelocity candidate, as it is unbound in 77% of our simulations. About half of our RdMs have kinematics that are consistent with ejection from the Galactic center. Seven of our RdMs have kinematics consistent with an ejection scenario from M31 or M32 to within 2 σ , although our distance-limited survey makes such a realization unlikely. No more than four of our RdMs may have originated from the Leo stream. We propose that to within measurement errors, most of our bound RdMs are likely disk runaways or halo objects, and may have been accelerated through a series of multi-body interactions within the Galactic disk or possibly supernovae explosions.« less

Highly efficient star formation in NGC 5253 possibly from stream-fed accretion.

PubMed

Turner, J L; Beck, S C; Benford, D J; Consiglio, S M; Ho, P T P; Kovács, A; Meier, D S; Zhao, J-H

2015-03-19

Gas clouds in present-day galaxies are inefficient at forming stars. Low star-formation efficiency is a critical parameter in galaxy evolution: it is why stars are still forming nearly 14 billion years after the Big Bang and why star clusters generally do not survive their births, instead dispersing to form galactic disks or bulges. Yet the existence of ancient massive bound star clusters (globular clusters) in the Milky Way suggests that efficiencies were higher when they formed ten billion years ago. A local dwarf galaxy, NGC 5253, has a young star cluster that provides an example of highly efficient star formation. Here we report the detection of the J = 3→2 rotational transition of CO at the location of the massive cluster. The gas cloud is hot, dense, quiescent and extremely dusty. Its gas-to-dust ratio is lower than the Galactic value, which we attribute to dust enrichment by the embedded star cluster. Its star-formation efficiency exceeds 50 per cent, tenfold that of clouds in the Milky Way. We suggest that high efficiency results from the force-feeding of star formation by a streamer of gas falling into the galaxy.

Galactic Distribution of Planets from Spitzer Microlens Parallaxes

NASA Astrophysics Data System (ADS)

Gould, Andrew; Carey, Sean; Yee, Jennifer

2014-12-01

We will measure the 'microlens parallaxes' of about 120 microlensing events that peak during Spitzer's 'bulge window' (2015 Jun 09 - Jul 19), by comparing simultaneous Spitzer and ground-based microlensing lightcurves, making use of Spitzer's location about 1 AU from Earth. These measurements will enable mass and distance measurements of about 4 microlensing planets. The ensemble of planet and non-planet distance measurements will yield the first probe of the Galactic distribution of planets Microlens planet mass measurements are very rare and have proved extremely interesting in every case. Microlensing identifies planets at and beyond the snowline, probing unique parameter space and providing vital information to constrain planet formation and migration theories. But the sample of ground-based microlens-parallax measurements is highly biased toward special systems. Spitzer would provide the first unbiased study. The same survey would provide a unique probe of brown dwarf binaries, and yield the first mass-based (not light-based) measurement of the stellar mass function (i.e., including dark objects such as black holes). A very successful 2014 'Pilot Program' demonstrates that this project is technically and scientifically viable. (As in the previous 'Pilot Program', we request zero day proprietary period.)

Weak deflection gravitational lensing for photons coupled to Weyl tensor in a Schwarzschild black hole

NASA Astrophysics Data System (ADS)

Cao, Wei-Guang; Xie, Yi

2018-03-01

Beyond the Einstein-Maxwell model, electromagnetic field might couple with gravitational field through the Weyl tensor. In order to provide one of the missing puzzles of the whole physical picture, we investigate weak deflection lensing for photons coupled to the Weyl tensor in a Schwarzschild black hole under a unified framework that is valid for its two possible polarizations. We obtain its coordinate-independent expressions for all observables of the geometric optics lensing up to the second order in the terms of ɛ which is the ratio of the angular gravitational radius to angular Einstein radius of the lens. These observables include bending angle, image position, magnification, centroid and time delay. The contributions of such a coupling on some astrophysical scenarios are also studied. We find that, in the cases of weak deflection lensing on a star orbiting the Galactic Center Sgr A*, Galactic microlensing on a star in the bulge and astrometric microlensing by a nearby object, these effects are beyond the current limits of technology. However, measuring the variation of the total flux of two weak deflection lensing images caused by the Sgr A* might be a promising way for testing such a coupling in the future.

Absolute Ages and Distances of 22 GCs Using Monte Carlo Main-sequence Fitting

NASA Astrophysics Data System (ADS)

O'Malley, Erin M.; Gilligan, Christina; Chaboyer, Brian

2017-04-01

The recent Gaia Data Release 1 of stellar parallaxes provides ample opportunity to find metal-poor main-sequence stars with precise parallaxes. We select 21 such stars with parallax uncertainties better than σ π /π ≤ 0.10 and accurate abundance determinations suitable for testing metal-poor stellar evolution models and determining the distance to Galactic globular clusters (GCs). A Monte Carlo analysis was used, taking into account uncertainties in the model construction parameters, to generate stellar models and isochrones to fit to the calibration stars. The isochrones that fit the calibration stars best were then used to determine the distances and ages of 22 GCs with metallicities ranging from -2.4 dex to -0.7 dex. We find distances with an average uncertainty of 0.15 mag and absolute ages ranging from 10.8 to 13.6 Gyr with an average uncertainty of 1.6 Gyr. Using literature proper motion data, we calculate orbits for the clusters, finding six that reside within the Galactic disk/bulge, while the rest are considered halo clusters. We find no strong evidence for a relationship between age and Galactocentric distance, but we do find a decreasing age-[Fe/H] relation.

The simulation of molecular clouds formation in the Milky Way

NASA Astrophysics Data System (ADS)

Khoperskov, S. A.; Vasiliev, E. O.; Sobolev, A. M.; Khoperskov, A. V.

2013-01-01

Using 3D hydrodynamic calculations we simulate formation of molecular clouds in the Galaxy. The simulations take into account molecular hydrogen chemical kinetics, cooling and heating processes. Comprehensive gravitational potential accounts for contributions from the stellar bulge, two- and four-armed spiral structure, stellar disc, dark halo and takes into account self-gravitation of the gaseous component. Gas clouds in our model form in the spiral arms due to shear and wiggle instabilities and turn into molecular clouds after t ≳ 100 Myr. At the times t ˜ 100-300 Myr the clouds form hierarchical structures and agglomerations with the sizes of 100 pc and greater. We analyse physical properties of the simulated clouds and find that synthetic statistical distributions like mass spectrum, `mass-size' relation and velocity dispersion are close to those observed in the Galaxy. The synthetic l-v (galactic longitude-radial velocity) diagram of the simulated molecular gas distribution resembles observed one and displays a structure with appearance similar to molecular ring of the Galaxy. Existence of this structure in our modelling can be explained by superposition of emission from the galactic bar and the spiral arms at ˜3-4 kpc.

The abundance of Galactic planets from OGLE-III 2002 microlensing data

NASA Astrophysics Data System (ADS)

Snodgrass, Colin; Horne, Keith; Tsapras, Yiannis

2004-07-01

From the 389 OGLE-III 2002 observations of Galactic bulge microlensing events, we select 321 that are well described by a point-source point-lens light-curve model. From this sample we identify one event, 2002-BLG-055, that we regard as a strong planetary lensing candidate, and another, 2002-BLG-140, that is a possible candidate. If each of the 321 lens stars has one planet with a mass ratio q = m/M = 10-3 and orbit radius a = RE, the Einstein ring radius, analysis of detection efficiencies indicates that 14 planets should have been detectable with Δχ2 > 25. Assuming our candidate is due to planetary lensing, then the abundance of planets with q = 10-3 and a = RE is np ~ n/14 = 7 per cent. Conversion to physical units (Jupiter masses, MJup, and astronomical units, au) gives the abundance of `cool Jupiters' (m ~ MJup, a ~ 4 au) per lens star as np ~ n/5.5 = 18 per cent. The detection probability scales roughly with q and (Δχ2)-1/2, and drops off from a peak at a ~ 4 au like a Gaussian with a dispersion of 0.4 dex.

Surprise: Dwarf Galaxy Harbors Supermassive Black Hole

NASA Astrophysics Data System (ADS)

2011-01-01

The surprising discovery of a supermassive black hole in a small nearby galaxy has given astronomers a tantalizing look at how black holes and galaxies may have grown in the early history of the Universe. Finding a black hole a million times more massive than the Sun in a star-forming dwarf galaxy is a strong indication that supermassive black holes formed before the buildup of galaxies, the astronomers said. The galaxy, called Henize 2-10, 30 million light-years from Earth, has been studied for years, and is forming stars very rapidly. Irregularly shaped and about 3,000 light-years across (compared to 100,000 for our own Milky Way), it resembles what scientists think were some of the first galaxies to form in the early Universe. "This galaxy gives us important clues about a very early phase of galaxy evolution that has not been observed before," said Amy Reines, a Ph.D. candidate at the University of Virginia. Supermassive black holes lie at the cores of all "full-sized" galaxies. In the nearby Universe, there is a direct relationship -- a constant ratio -- between the masses of the black holes and that of the central "bulges" of the galaxies, leading them to conclude that the black holes and bulges affected each others' growth. Two years ago, an international team of astronomers found that black holes in young galaxies in the early Universe were more massive than this ratio would indicate. This, they said, was strong evidence that black holes developed before their surrounding galaxies. "Now, we have found a dwarf galaxy with no bulge at all, yet it has a supermassive black hole. This greatly strengthens the case for the black holes developing first, before the galaxy's bulge is formed," Reines said. Reines, along with Gregory Sivakoff and Kelsey Johnson of the University of Virginia and the National Radio Astronomy Observatory (NRAO), and Crystal Brogan of the NRAO, observed Henize 2-10 with the National Science Foundation's Very Large Array radio telescope and with the Hubble Space Telescope. They found a region near the center of the galaxy that strongly emits radio waves with characteristics of those emitted by super-fast "jets" of material spewed outward from areas close to a black hole. They then searched images from the Chandra X-Ray Observatory that showed this same, radio-bright region to be strongly emitting energetic X-rays. This combination, they said, indicates an active, black-hole-powered, galactic nucleus. "Not many dwarf galaxies are known to have massive black holes," Sivakoff said. While central black holes of roughly the same mass as the one in Henize 2-10 have been found in other galaxies, those galaxies all have much more regular shapes. Henize 2-10 differs not only in its irregular shape and small size but also in its furious star formation, concentrated in numerous, very dense "super star clusters." "This galaxy probably resembles those in the very young Universe, when galaxies were just starting to form and were colliding frequently. All its properties, including the supermassive black hole, are giving us important new clues about how these black holes and galaxies formed at that time," Johnson said. The astronomers reported their findings in the January 9 online edition of Nature, and at the American Astronomical Society's meeting in Seattle, WA.

Molecular diagnostics of Galactic star-formation regions

NASA Astrophysics Data System (ADS)

Loenen, Edo; Baan, Willem; Spaans, Marco

2007-10-01

We propose a sensitive spectral survey of Galactic star-formation regions. Using the broadband correlator at two different frequencies, we expect to detect the (1-0) transition of CO, CN, HNC, HCN, HCO+, and HCO and various of their isotopes lines, as well as the (12-11) and (10-9) transitions of HC3N. The purpose of these observations is to create a consistent (public) database of molecular emission from galactic star-formation regions. The data will be interpreted using extensive physical and chemical modeling of the whole ensemble of lines, in order to get an accurate description of the molecular environment of these regions. In particular, this diagnostic approach will describe the optical depths, the densities, and the radiation fields in the medium and will allow the establishment of dominant temperature gradients. These observations are part of a program to study molecular emission on all scales, going from individual Galactic star-formation regions, through resolved nearby galaxies, to unresolved extra-galactic emission.

The Physical Characteristics of Interstellar Medium in NGC 3665 with Herschel Observations

NASA Astrophysics Data System (ADS)

Xiao, Meng-Yuan; Zhao, Yinghe; Gu, Qiu-Sheng; Shi, Yong

2018-02-01

We present the analysis of the physical properties of the interstellar medium in the nearby early-type galaxy NGC 3665, based on the far-infrared photometric and spectroscopic data as observed by the Herschel Space Observatory. The fit to the spectral energy distribution reveals a high dust content in the galaxy, with a dust-to-stellar mass ratio of {M}dust}/M * ∼ 1.1 × 10‑4 that is nearly three times larger than the mean value of local S0+S0a galaxies. For the ionized regions (H II regions), the electron density (n e ) is around 49.5 ± 11.9 cm‑3 based on the [N II] 122 μm/[N II] 205 μm ratio. For the photodissociation regions, the heating efficiency ranges from 1.26 × 10‑3 to 1.37 × 10‑3 based on the ([C II]+[O I] 63 μm)/{L}TIR}, which is slightly lower than other local galaxies; the hydrogen nucleus density and the strength of the far-UV radiation field are n ∼ 104 cm‑3 and G 0 ∼ 10‑0.25, respectively. The above results are consistent with the presence of weak active galactic nuclei and a low level of star-forming activity in NGC 3665. Our results give strong support to the “morphological quenching” scenario, where a compact, massive bulge can stabilize the amount of cool gas against star formation. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Plasmasphere dynamics in the duskside bulge region: A new look at old topic

NASA Technical Reports Server (NTRS)

Carpenter, D. L.; Giles, B. L.; Chappell, C. R.; Decreau, P. M. E.; Anderson, R. R.; Persoon, A. M.; Smith, A. J.; Corcuff, Y.; Canu, P.

1993-01-01

Data acquired during several multiday periods in 1982 at ground stations Siple, Halley, and Kerguelen and on satellites Dynamics Explorer 1, International Sun Earth Explorer 1, and GEOS 2 have been used to investigate thermal plasma structure and dynamics in the duskside plasmasphere bulge region of the Earth. The distribution of thermal plasma in the dusk bulge sector is difficult to describe realistically, in part because of the time integral manner in which the thermal plasma distribution depends upon on the effects of bulk cross-B flow and interchange plasma flows along B. While relatively simple MHD models can be useful for qualitatively predicting certain effects of enhanced convection on a quiet plasmasphere, such as an initial sunward entrainment of the outer regions, they are of limited value in predicting the duskside thermal plasma structures that are observed. Furthermore, use of such models can be misleading if one fails to realize that they do not address the question of the formation of the steep plasmapause profile or provide for a possible role of instabilities or other irreversible processes in plasmapause formation. Our specific findings, which are based both upon the present case studies and upon earlier work, include the following: (1) during active periods the plasmasphere appears to become divided into two entities, a main plasmasphere and a duskside bulge region. (2) in the aftermath of an increase in convection activity, the main plasmasphere tends (from a statistical point of view) to become roughly circular in equatorial cross section, with only a slight bulge at dusk; (3) the abrupt westward edge of the duskside bulge observed from whistlers represents a state in the evolution of sunward extending streamers; (4) in the aftermath of a weak magnetic storm, 10 to 30% of the plasma 'removed' from the outer plasmasphere appears to remain in the afternoon-dusk sector beyond the main plasmasphere. (5) outlying dense plasma structures may circulate in the outer duskside magetosphere for many days following an increase in convection, unless there is extremely deep quieting; (6) a day-night plasmatrough boundary may be identified in equatorial satellite data; (7) factor-of-2-to-10 density irregularities appear near the plasmatrough from the ionosphere at L = 4.6, predominantly bidirectional field aligned and equatorially trapped light ion pitch angle distributions give away to a predominantly isotropic distribution (as seen by DE 1) when the plasma density reaches a level a factor of about 3 below the satured plasmasphere level; (9) some outlying dense plasma structures are effectively detached from the main plasmasphere, while others appear to be connected to that body.

He bulge revealed: He and CO2 diurnal and seasonal variations in the upper atmosphere of Mars as detected by MAVEN NGIMS

NASA Astrophysics Data System (ADS)

Elrod, M. K.; Bougher, S.; Bell, J.; Mahaffy, P. R.; Benna, M.; Stone, S.; Yelle, R.; Jakosky, B.

2017-02-01

Analysis of the Neutral Gas and Ion Mass Spectrometer (NGIMS) on the Mars Atmosphere Volatiles and EvolutioN (MAVEN) spacecraft closed source data from all orbits with good pointing revealed an enhanced Helium [He] density on the nightside orbits and a depressed He density on the dayside by about a factor of 10-20. He was also found to be larger in the polar regions than in the equatorial regions. The northern polar winter nightside He bulge was approximately twice that of the northern polar summer nightside bulge. The first 6 weeks of the MAVEN prime mission had periapsis at high latitudes on the nightside during northern winter, followed by the midlatitudes on the dayside moving to low latitudes on the nightside returning to the high latitudes during northern summer. In this study we examined the NGIMS data not only in the different latitudes but sorted by solar longitude (Ls) in order to separate the diurnal or local solar time (LST) effects from the seasonal effects. The Mars Global Ionosphere-Thermosphere Model (M-GITM) has predicted the formation of a He bulge in the upper atmosphere of Mars on the nightside early morning hours (Ls = 2-5 h) with more He collecting around the poles. Taking a slice at constant altitude across all orbits indicates corresponding variations in He and CO2 with respect to LST and Ls and a diurnal and seasonal dependence.

The Southern HII Region Discovery Survey

NASA Astrophysics Data System (ADS)

Wenger, Trey; Miller Dickey, John; Jordan, Christopher; Bania, Thomas M.; Balser, Dana S.; Dawson, Joanne; Anderson, Loren D.; Armentrout, William P.; McClure-Griffiths, Naomi

2016-01-01

HII regions are zones of ionized gas surrounding recently formed high-mass (OB-type) stars. They are among the brightest objects in the sky at radio wavelengths. HII regions provide a useful tool in constraining the Galactic morphological structure, chemical structure, and star formation rate. We describe the Southern HII Region Discovery Survey (SHRDS), an Australia Telescope Compact Array (ATCA) survey that discovered ~80 new HII regions (so far) in the Galactic longitude range 230 degrees to 360 degrees. This project is an extension of the Green Bank Telescope HII Region Discovery Survey (GBT HRDS), Arecibo HRDS, and GBT Widefield Infrared Survey Explorer (WISE) HRDS, which together discovered ~800 new HII regions in the Galactic longitude range -20 degrees to 270 degrees. Similar to those surveys, candidate HII regions were chosen from 20 micron emission (from WISE) coincident with 10 micron (WISE) and 20 cm (SGPS) emission. By using the ATCA to detect radio continuum and radio recombination line emission from a subset of these candidates, we have added to the population of known Galactic HII regions.

Structural Insights Into DNA Repair by RNase T—An Exonuclease Processing 3′ End of Structured DNA in Repair Pathways

PubMed Central

Hsiao, Yu-Yuan; Fang, Woei-Horng; Lee, Chia-Chia; Chen, Yi-Ping; Yuan, Hanna S.

2014-01-01

DNA repair mechanisms are essential for preservation of genome integrity. However, it is not clear how DNA are selected and processed at broken ends by exonucleases during repair pathways. Here we show that the DnaQ-like exonuclease RNase T is critical for Escherichia coli resistance to various DNA-damaging agents and UV radiation. RNase T specifically trims the 3′ end of structured DNA, including bulge, bubble, and Y-structured DNA, and it can work with Endonuclease V to restore the deaminated base in an inosine-containing heteroduplex DNA. Crystal structure analyses further reveal how RNase T recognizes the bulge DNA by inserting a phenylalanine into the bulge, and as a result the 3′ end of blunt-end bulge DNA can be digested by RNase T. In contrast, the homodimeric RNase T interacts with the Y-structured DNA by a different binding mode via a single protomer so that the 3′ overhang of the Y-structured DNA can be trimmed closely to the duplex region. Our data suggest that RNase T likely processes bulge and bubble DNA in the Endonuclease V–dependent DNA repair, whereas it processes Y-structured DNA in UV-induced and various other DNA repair pathways. This study thus provides mechanistic insights for RNase T and thousands of DnaQ-like exonucleases in DNA 3′-end processing. PMID:24594808

The Sagittarius Dwarf Galaxy Survey (SDGS) - I. Colour-magnitude diagrams, reddening and population gradients. First evidence of a very metal-poor population

NASA Astrophysics Data System (ADS)

Bellazzini, M.; Ferraro, F. R.; Buonanno, R.

1999-04-01

We present the first results of a large photometric survey devoted to the study of the star formation history of the Sagittarius dwarf spheroidal galaxy (Sgr dSph). Three wide strips (size ~ 9 x 35 arcmin ^2) located at ~ (l deg b deg) = (6.5;-16), (6;-14), (5;-12) have been observed. Each strip is roughly east-west oriented, nearly along the major axis of the galaxy. A control field (size ~ 9 x 24 arcmin ^2), located outside the body of Sgr dSph [~ (l deg b deg) = (354;-14)] has also been observed for statistical decontamination purposes. Accurate and well-calibrated V, I photometry down to V ~ 22 has been obtained for ~ 90 000 stars towards the Sgr dSph and ~ 8000 stars in the control field. This is the largest photometric sample (covering the widest spatial extension) ever observed in the Sgr dSph up to now. The main new results presented in this paper are: (1) the possible discovery of a strong asymmetry in the distribution of stars along the major axis, since the north-western arm of the Sgr galaxy (i.e. the region nearer to the Galactic bulge) apparently shows a significant deficiency of Sgr stars and (2) the first direct detection of a very metal-poor (and presumably old) population in the Sgr stellar content. Hints at a metallicity gradient towards the densest region of the galaxy are also reported.

The Galactic HII Region Luminosity Function at Infrared and Radio Wavelengths

NASA Astrophysics Data System (ADS)

Mascoop, Joshua; Anderson, Loren; Sandor Makai, Zoltan; Armentrout, William Paul

2018-01-01

HII regions are the clearest indicators of ongoing high-mass star formation. The HII region luminosity function (LF) therefore probes present global star formation properties, and its shape has been related to HII region properties and galaxy Hubble types. Most HII region LF studies to date have been conducted in external galaxies; due to observational difficulties, there have been relatively few studies of the Milky Way HII region LF. Using ~600 HII regions from the WISE Catalog of Galactic HII Regions, we examine the Galactic LF in the first quadrant. Our high-resolution view of Galactic star formation regions allows us to separate nearby sources, and our sample is complete for all HII regions ionized by single O9.5 stars.We analyze the Galactic LF at six infrared wavelengths - where the emission is due to dust - and also at 20 cm, where the emission is from ionized gas. All LFs have a similar shape, showing that infrared LFs can be used in place of ionized gas tracers. All LFs can be described by a single power law with an index of approximately -2, in agreement with previous studes. We find no compelling evidence of a break or "knee" in the LF. Moreover, we see no significant variation in the form of the LF as a function of heliocentric distance, HII region size, or Galactocentric radius.

Hubble’s High-Definition Panoramic View of the Andromeda Galaxy

NASA Image and Video Library

2017-12-08

The largest NASA Hubble Space Telescope image ever assembled, this sweeping bird’s-eye view of a portion of the Andromeda galaxy (M31) is the sharpest large composite image ever taken of our galactic next-door neighbor. Though the galaxy is over 2 million light-years away, The Hubble Space Telescope is powerful enough to resolve individual stars in a 61,000-light-year-long stretch of the galaxy’s pancake-shaped disk. It's like photographing a beach and resolving individual grains of sand. And there are lots of stars in this sweeping view -- over 100 million, with some of them in thousands of star clusters seen embedded in the disk. This ambitious photographic cartography of the Andromeda galaxy represents a new benchmark for precision studies of large spiral galaxies that dominate the universe's population of over 100 billion galaxies. Never before have astronomers been able to see individual stars inside an external spiral galaxy over such a large contiguous area. Most of the stars in the universe live inside such majestic star cities, and this is the first data that reveal populations of stars in context to their home galaxy. Hubble traces densely packed stars extending from the innermost hub of the galaxy seen at the left. Moving out from this central galactic bulge, the panorama sweeps from the galaxy's central bulge across lanes of stars and dust to the sparser outer disk. Large groups of young blue stars indicate the locations of star clusters and star-forming regions. The stars bunch up in the blue ring-like feature toward the right side of the image. The dark silhouettes trace out complex dust structures. Underlying the entire galaxy is a smooth distribution of cooler red stars that trace Andromeda’s evolution over billions of years. Because the galaxy is only 2.5 million light-years from Earth, it is a much bigger target in the sky than the myriad galaxies Hubble routinely photographs that are billions of light-years away. This means that the Hubble survey is assembled together into a mosaic image using 7,398 exposures taken over 411 individual pointings. Read more: 1.usa.gov/1y0i3H8 Credit: NASA, ESA, J. Dalcanton, B.F. Williams, and L.C. Johnson (University of Washington), the PHAT team, and R. Gendler NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

VizieR Online Data Catalog: VISTA Variables in the Via Lactea Survey DR1 (Saito+, 2012)

NASA Astrophysics Data System (ADS)

Saito, R. K.; Hempel, M.; Minniti, D.; Lucas, P. W.; Rejkuba, M.; Toledo, I.; Gonzalez, O. A.; Alonso-Garcia, J.; Irwin, M. J.; Gonzalez-Solares, E.; Hodgkin, S. T.; Lewis, J. R.; Cross, N.; Ivanov, V. D.; Kerins, E.; Emerson, J. P.; Soto, M.; Amores, E. B.; Gurovich, S.; Dekany, I.; Angeloni, R.; Beamin, J. C.; Catelan, M.; Padilla, N.; Zoccali, M.; Pietrukowicz, P.; Moni Bidin, C.; Mauro, F.; Geisler, D.; Folkes, S. L.; Sale, S. E.; Borissova, J.; Kurtev, R.; Ahumada, A. V.; Alonso, M. V.; Adamson, A.; Arias, J. I.; Bandyopadhyay, R. M.; Barba, R. H.; Barbuy, B.; Baume, G. L.; Bedin, L. R.; Bellini, A.; Benjamin, R.; Bica, E.; Bonatto, C.; Bronfman, L.; Carraro, G.; Chene, A. N.; Claria, J. J.; Clarke, J. R. A.; Contreras, C.; Corvillon, A.; de Grijs, R.; Dias, B.; Drew, J. E.; Farina, C.; Feinstein, C.; Fernandez-Lajus, E.; Gamen, R. C.; Gieren, W.; Goldman, B.; Gonzalez-Fernandez, C.; Grand, R. J. J.; Gunthardt, G.; Hambly, N. C.; Hanson, M. M.; Helminiak, K. G.; Hoare, M. G.; Huckvale, L.; Jordan, A.; Kinemuchi, K.; Longmore, A.; Lopez-Corredoira, M.; Maccarone, T.; Maja! Ess, D.; M Artin, E. L.; Masetti, N.; Mennickent, R. E.; Mirabel, I. F.; Monaco, L.; Morelli, L.; Motta, V.; Palma, T.; Parisi, M. C.; Parker, Q.; Penaloza, F.; Pietrzynski, G.; Pignata, G.; Popescu, B.; Read, M. A.; Rojas, A.; Roman-Lopes, A.; Ruiz, M. T.; Saviane, I.; Schreiber, M. R.; Schroeder, A. C.; Sharma, S.; Smith, M. D.; Sodre, L. Jr; Stead, J.; Stephens, A. W.; Tamura, M.; Tappert, C.; Thompson, M. A.; Valenti, E.; Vanzi, L.; Walton, N. A.; Weidmann, W.; Zijlstra, A.

2015-01-01

The VVV survey targets the galactic bulge and a piece of the adjacent plane in Z, Y, J, H, and Ks. The total area of this survey is 520 square degrees and contains 355 open and 33 globular clusters. The VVV is multi-epoch in nature in order to detect a large number of variable objects and will provide > 100 carefully spaced observations for each tile. 5-sigma detection limits are Z=21.9, Y=21.2, J=20.2, H=18.2, Ks=18.1. These will be used to create a 3-dimensional map of the Bulge from well-understood distance indicators such as RR Lyrae stars. Other science drivers include the ages of stellar populations, globular cluster evolution, as well as the stellar initial mass function. The VVV Survey data delivered in this part of ESO Data Release 1 (DR1) includes the VISTA/VIRCAM paw-print and tile images that were acquired until September 30, 2010, and processed by the Cambridge Astronomical Survey Unit (CASU). This VVV_CAT data release contains the single-epoch band-merged (Z,Y,J,H,Ks) catalogues associated with the VVV tile images that have already been released in the part of DR1 identified as VVV in the ESO archive. VVV_CAT contains 269 tile catalogues. (1 data file).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feoli, A.; Mancini, L., E-mail: feoli@unisannio.i, E-mail: lmancini@physics.unisa.i

We show that the relation between the mass of supermassive black holes located in the center of the host galaxies and the kinetic energy of random motions of the corresponding bulges is a useful tool to study the evolution of galaxies. In the form log{sub 10}(M-dot)=b+m log{sub 10}(M{sub G}sigma{sup 2}/c{sup 2}), the best-fitting results for a sample of 64 galaxies of various morphological types are the slope m = 0.80 +- 0.03 and the normalization b = 4.53 +- 0.13. We note that, in analogy with the Hertzsprung-Russell diagram for stars, each morphological type of galaxy generally occupies a differentmore » area in the M{sub .}-(M{sub G}sigma{sup 2})/c {sup 2} plane. In particular, we find elliptical galaxies in the upper part of the line of best fit, the lenticular galaxies in the middle part, and the late-type galaxies in the lower part, the mass of the central black hole giving an estimate of the age, whereas the kinetic energy of the stellar bulges is directly connected with the temperature of each galactic system. Finally, the values of the linear correlation coefficient, the intrinsic scatter, and the chi{sup 2} obtained by using the M{sub .}-M{sub G}sigma{sup 2} relation are better than the corresponding ones obtained from the M{sub .}-sigma or the M{sub .}-M {sub G} relation.« less

Resonance Trapping in the Galactic Disc and Halo and its Relation with Moving Groups

NASA Astrophysics Data System (ADS)

Pichardo, Barbara; Moreno, Edmundo; william, schuster B.

2015-08-01

With the use of a detailed Milky Way nonaxisymmetric potential, observationally and dynamically constrained, the eects of the bar and the spiral arms in the Galaxy are studied in the disc and in the stellar halo. Especially the trapping of stars in the disk and Galactic halo by resonances on the Galactic plane created by the Galactic bar has been analysed in detail. To this purpose, a new method is presented to delineate the trapping regions using empirical diagrams of some orbital properties obtained in the Galactic potential. In these diagrams we plot in the inertial Galactic frame a characteristic orbital energy versus a characteristic orbital angular momentum, or versus the orbital Jacobi constant in the reference frame of the bar, when this is the only nonaxisymmetric component in the Galactic potential. With these diagrams some trapping regions are obtained in the disc and halo using a sample of disc stars and halo stars in the solar neighborhood. We compute several families of periodic orbits on the Galactic plane, some associated with this resonant trapping. In particular, we nd that the trapping eect of these resonances on the Galactic plane can extend some kpc from this plane, trapping stars in the Galactic halo. The purpose of our analysis is to investigate if the trapping regions contain some known moving groups in our Galaxy. We have applied our method to the Kapteyn group, a moving group in the halo, and we have found that this group appears not to be associated with a particular resonance on the Galactic plane.

Three-Dimensional MHD Simulation of FTEs Produced by Merging at an Isolated Point in a Sheared Magnetic Field Configuration

NASA Technical Reports Server (NTRS)

Santos, J. C.; Sibeck, D. G.; Buchner, J.; Gonzalez, W. D.; Ferreira, J. L.

2014-01-01

We present predictions for the evolution of FTEs generated by localized bursts of reconnection on a planar magnetopause that separates a magnetosheath region of high densities and weak magnetic field from a magnetospheric region of low densities and strong magnetic field. The magnetic fields present a shear angle of 105 degrees. Reconnection forms a pair of FTEs each crossing the magnetopause in the field reversal region and bulging into the magnetosphere and magnetosheath. At their initial stage they can be characterized as flux tubes since the newly reconnected magnetic field lines are not twisted. Reconnection launches Alfvenic perturbations that propagate along the FTEs generating high-speed jets, which move the pair of FTEs in opposite directions. As the FTE moves, it displaces the ambient magnetic field and plasma producing bipolar magnetic field and plasma velocity signatures normal to the nominal magnetopause in the regions surrounding the FTE. The combination of the ambient plasma with the FTE flows generates a vortical velocity pattern around the reconnected field lines. During its evolution the FTE evolves to a flux rope configuration due to the twist of the magnetic field lines. The alfvenic perturbations propagate faster along the part of the FTE bulging into the magnetosphere than in the magnetosheath, and due to the differences between the plasma and magnetic field properties the perturbations have slightly different signatures in the two regions. As a consequence, the FTEs have different signatures depending on whether the satellite encounters the part bulging into the magnetosphere or into the magnetosheath.

The distribution of cosmic rays in the galaxy and their dynamics as deduced from recent gamma-ray observations. [X-ray intensity variations with galactocentric distance

NASA Technical Reports Server (NTRS)

Puget, J. L.; Stecker, F. W.

1974-01-01

Recent data from SAS-2 on the galactic gamma ray line flux as a function of longitude reveal a broad maximum in the gamma ray intensity in the region absolute value of l approximately smaller than 30 deg. These data imply that the low energy galactic cosmic ray flux varies with galactocentric distance and is about an order of magnitude higher than the local value in a toroidal region between 4 and 5 kpc from the galactic center. This enhancement can be plausibly accounted for by first order Fermi acceleration, compression and trapping of cosmic rays consistent with present ideas of galactic dynamics and galactic structure theory. Calculations indicate that cosmic rays in the 4 to 5 kpc region are trapped and accelerated over a mean time of the order of a few million years or about 2 to 4 times the assumed trapping time in the solar region of the galaxy.

Dynamical constraints on the dark matter distribution in the Milky Way

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pato, Miguel; Iocco, Fabio; Bertone, Gianfranco, E-mail: migpato@gmail.com, E-mail: fabio.iocco.astro@gmail.com, E-mail: g.bertone@uva.nl

2015-12-01

An accurate knowledge of the dark matter distribution in the Milky Way is of crucial importance for galaxy formation studies and current searches for particle dark matter. In this paper we set new dynamical constraints on the Galactic dark matter profile by comparing the observed rotation curve, updated with a comprehensive compilation of kinematic tracers, with that inferred from a wide range of observation-based morphologies of the bulge, disc and gas. The generalised Navarro-Frenk-White (NFW) and Einasto dark matter profiles are fitted to the data in order to determine the favoured ranges of local density, slope and scale radius. Formore » a representative baryonic model, a typical local circular velocity v{sub 0}=230 km/s and a distance of the Sun to the Galactic centre R{sub 0}=8 kpc, we find a local dark matter density ρ{sub 0} = 0.420{sup +0.021}{sub −0.018} (2σ) ± 0.025 GeV/cm{sup 3} (ρ{sub 0} = 0.420{sup +0.019}{sub −0.021} (2σ) ± 0.026 GeV/cm{sup 3}) for NFW (Einasto), where the second error is an estimate of the systematic due to baryonic modelling. Apart from the Galactic parameters, the main sources of uncertainty inside and outside the solar circle are baryonic modelling and rotation curve measurements, respectively. Upcoming astronomical observations are expected to reduce all these uncertainties substantially over the coming years.« less

THE ROLES OF RADIATION AND RAM PRESSURE IN DRIVING GALACTIC WINDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Mahavir; Nath, Biman B., E-mail: mahavir@rri.res.in, E-mail: biman@rri.res.in

We study gaseous outflows from disk galaxies driven by the combined effects of ram pressure on cold gas clouds and radiation pressure on dust grains. Taking into account the gravity due to disk, bulge, and dark matter halo, and assuming continuous star formation in the disk, we show that radiation or ram pressure alone is not sufficient to drive escaping winds from disk galaxies and that both processes contribute. We show that in the parameter space of star formation rate (SFR) and rotation speed of galaxies the wind speed in galaxies with rotation speeds v{sub c} {<=} 200 km s{supmore » -1} and SFR {<=} 100 M{sub Sun} yr{sup -1} has a larger contribution from ram pressure, and that in high-mass galaxies with large SFR radiation from the disk has a greater role in driving galactic winds. The ratio of wind speed to circular speed can be approximated as v{sub w} / v{sub c} {approx} 10{sup 0.7}, [SFR/50{sub Sun }yr{sup -1}]{sup 0.4} [v{sub c}/120 km s{sup -1}]{sup -1.25}. We show that this conclusion is borne out by observations of galactic winds at low and high redshift and also of circumgalactic gas. We also estimate the mass loading factors under the combined effect of ram and radiation pressure, and show that the ratio of mass-loss rate to SFR scales roughly as v{sup -1}{sub c}{Sigma}{sub g}{sup -1}, where {Sigma}{sub g} is the gas column density in the disk.« less

On the origin of the Monoceros Ring - I. Kinematics, proper motions, and the nature of the progenitor

NASA Astrophysics Data System (ADS)

Guglielmo, Magda; Lane, Richard R.; Conn, Blair C.; Ho, Anna Y. Q.; Ibata, Rodrigo A.; Lewis, Geraint F.

2018-03-01

The Monoceros Ring (MRi) structure is an apparent stellar overdensity that has been postulated to entirely encircle the Galactic plane and has been variously described as being due to line-of-sight effects of the Galactic warp and flare or of extragalactic origin (via accretion). Despite being intensely scrutinized in the literature for more than a decade, no studies to date have been able to definitively uncover its origins. Here we use N-body simulations and a genetic algorithm to explore the parameter space for the initial position, orbital parameters, and, for the first time, the final location of a satellite progenitor. We fit our models to the latest Pan-STARRS data to determine whether an accretion scenario is capable of producing an in-plane ring-like structure matching the known parameters of the MRi. Our simulations produce streams that closely match the location, proper motion, and kinematics of the MRi structure. However, we are not able to reproduce the mass estimates from earlier studies based on Pan-STARRS data. Furthermore, in contrast to earlier studies, our best-fitting models are those for progenitors on retrograde orbits. If the MRi was produced by satellite accretion, we find that its progenitor has an initial mass upper limit of ˜1010 M⊙ and the remnant is likely located behind the Galactic bulge, making it difficult to locate observationally. While our models produce realistic MRi-like structures, we cannot definitively conclude that the MRi was produced by the accretion of a satellite galaxy.

Black hole binaries in galactic nuclei and gravitational wave sources

NASA Astrophysics Data System (ADS)

Hong, Jongsuk; Lee, Hyung Mok

2015-03-01

Stellar black hole (BH) binaries are one of the most promising gravitational wave (GW) sources for GW detection by the ground-based detectors. Nuclear star clusters (NCs) located at the centre of galaxies are known to harbour massive black holes (MBHs) and to be bounded by a gravitational potential by other galactic components such as the galactic bulge. Such an environment of NCs provides a favourable conditions for the BH-BH binary formation by the gravitational radiation capture due to the high BH number density and velocity dispersion. We carried out detailed numerical study of the formation of BH binaries in the NCs using a series of N-body simulations for equal-mass cases. There is no mass segregation introduced. We have derived scaling relations of the binary formation rate with the velocity dispersion of the stellar system beyond the radius of influence and made estimates of the rate of formation of BH binaries per unit comoving volume and thus expected detection rate by integrating the binary formation rate over galaxy population within the detection distance of the advanced detectors. We find that the overall formation rates for BH-BH binaries per NC is ˜10-10 yr-1 for the Milky Way-like galaxies and weakly dependent on the mass of MBH as Γ ∝ M_MBH^{3/28}. We estimate the detection rate of 0.02-14 yr-1 for advanced LIGO/Virgo considering several factors such as the dynamical evolution of NCs, the variance of the number density of stars and the mass range of MBH giving uncertainties.

Environmental Effects on Evolution of Cluster Galaxies in a Λ-dominated Cold Dark Matter Universe

NASA Astrophysics Data System (ADS)

Okamoto, Takashi; Nagashima, Masahiro

2003-04-01

We investigate environmental effects on evolution of bright cluster galaxies (L>L*) in a Λ-dominated cold dark matter universe using a combination of dissipationless N-body simulations and a semianalytic galaxy formation model. The N-body simulations enable us to calculate orbits of galaxies in simulated clusters. Therefore, we can incorporate stripping of cold gas from galactic disks by ram pressure (RP) from the intracluster medium into our model. In this paper we study how ram pressure stripping (RPS) and small starburst induced by a minor merger affect colors, star formation rates (SFRs), and morphologies of cluster galaxies. These processes are new ingredients in our model and have not been studied sufficiently. We find that the RPS is not important for colors and SFRs of galaxies in the cluster core if the star formation timescale is properly chosen, because the star formation is sufficiently suppressed by consumption of the cold gas in the disks. Then observed color and SFR gradients can be reproduced without the RPS. The small starburst triggered by a minor merger hardly affects the SFRs and colors of the galaxies as well. We also examine whether these two processes can resolve the known problem that the hierarchical clustering models based on the major merger-driven bulge formation scenario predict too few galaxies of intermediate bulge-to-total luminosity ratio (B/T) in clusters. When the minor burst is taken into account, the intermediate B/T population is increased, and the observed morphology gradients in clusters are successfully reproduced. Without the minor burst, the RPS cannot increase the intermediate B/T population. On the other hand, when the minor burst is considered, the RPS also plays an important role in formation of the intermediate B/T galaxies. We present redshift evolution of morphological fractions predicted by our models. The predicted number ratios of the intermediate B/T galaxies to the bulge-dominated galaxies show nearly flat or slightly increasing trends with increasing redshift. We conclude that these trends are inevitable when bulges are formed through mergers. We discuss whether our results conflict with observationally suggested NS0/NE evolution in clusters, which is a decreasing function of redshift.

Crater Flux Transfer Events: Highroad to the X Line?

NASA Technical Reports Server (NTRS)

Farrugia, C. J.; Chen, Li-Jen; Torbert, R. B.; Southwood, D. J.; Cowley, S. W. H.; Vrublevskis, A.; Mouikis, C.; Vaivads, A.; Andre, M.; Decreau, P.;

Role of conserved nucleotides in building the 16S rRNA binding site of E. coli ribosomal protein S8.

PubMed Central

Allmang, C; Mougel, M; Westhof, E; Ehresmann, B; Ehresmann, C

1994-01-01

Ribosomal protein S8 specifically recognizes a helical and irregular region of 16S rRNA that is highly evolutionary constrained. Despite its restricted size, the precise conformation of this region remains a question of debate. Here, we used chemical probing to analyze the structural consequences of mutations in this RNA region. These data, combined with computer modelling and previously published data on protein binding were used to investigate the conformation of the RNA binding site. The experimental data confirm the model in which adenines A595, A640 and A642 bulge out in the deep groove. In addition to the already proposed non canonical U598-U641 interaction, the structure is stabilized by stacking interactions (between A595 and A640) and an array of hydrogen bonds involving bases and the sugar phosphate backbone. Mutations that alter the ability to form these interdependent interactions result in a local destabilization or reorganization. The specificity of recognition by protein S8 is provided by the irregular and distorted backbone and the two bulged adenines 640 and 642 in the deep groove. The third adenine (A595) is not a direct recognition site but must adopt a bulged position. The U598-U641 pair should not be directly in contact with the protein. Images PMID:7937081

THE X-SHAPED BULGE OF THE MILKY WAY REVEALED BY WISE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ness, Melissa; Lang, Dustin, E-mail: ness@mpia-hd.mpg.de

2016-07-01

The Milky Way bulge has a boxy/peanut morphology and an X-shaped structure. This X-shape has been revealed by the “split in the red clump” from star counts along the line of sight toward the bulge, measured from photometric surveys. This boxy, X-shaped bulge morphology is not unique to the Milky Way and such bulges are observed in other barred spiral galaxies. N -body simulations show that boxy and X-shaped bulges are formed from the disk via dynamical instabilities. It has also been proposed that the Milky Way bulge is not X-shaped, but rather, the apparent split in the red clumpmore » stars is a consequence of different stellar populations, in an old classical spheroidal bulge. We present a Wide-Field Infrared Survey Explorer ( WISE ) image of the Milky Way bulge, produced by downsampling the publicly available “unWISE” coadds. The WISE image of the Milky Way bulge shows that the X-shaped nature of the Milky Way bulge is self-evident and irrefutable. The X-shape morphology of the bulge in itself and the fraction of bulge stars that comprise orbits within this structure has important implications for the formation history of the Milky Way, and, given the ubiquity of boxy X-shaped bulges, spiral galaxies in general.« less

A new photometric model of the Galactic bar using red clump giants

NASA Astrophysics Data System (ADS)

Cao, Liang; Mao, Shude; Nataf, David; Rattenbury, Nicholas J.; Gould, Andrew

2013-09-01

We present a study of the luminosity density distribution of the Galactic bar using number counts of red clump giants from the Optical Gravitational Lensing Experiment (OGLE) III survey. The data were recently published by Nataf et al. for 9019 fields towards the bulge and have 2.94 × 106 RC stars over a viewing area of 90.25 deg^2. The data include the number counts, mean distance modulus (μ), dispersion in μ and full error matrix, from which we fit the data with several triaxial parametric models. We use the Markov Chain Monte Carlo method to explore the parameter space and find that the best-fitting model is the E3 model, with the distance to the GC 8.13 kpc, the ratio of semimajor and semiminor bar axis scalelengths in the Galactic plane x0, y0 and vertical bar scalelength z0 x0: y0: z0 ≈ 1.00: 0.43: 0.40 (close to being prolate). The scalelength of the stellar density profile along the bar's major axis is ˜0.67 kpc and has an angle of 29.4°, slightly larger than the value obtained from a similar study based on OGLE-II data. The number of estimated RC stars within the field of view is 2.78 × 106, which is systematically lower than the observed value. We subtract the smooth parametric model from the observed counts and find that the residuals are consistent with the presence of an X-shaped structure in the Galactic Centre, the excess to the estimated mass content is ˜5.8 per cent. We estimate that the total mass of the bar is ˜1.8 × 1010 M⊙. Our results can be used as a key ingredient to construct new density models of the Milky Way and will have implications on the predictions of the optical depth to gravitational microlensing and the patterns of hydrodynamical gas flow in the Milky Way.

The Size Distribution Of Cluster Galaxies

NASA Astrophysics Data System (ADS)

Kuchner, U.; Ziegler, B.; Bamford, S.; Verdugo, M.; Haeussler, B.

2017-06-01

We establish a sample of 560 spectroscopically confirmed cluster members of MACS J1206.2- 0847 at z = 0.45 and utilize multi-wavelength and multi-component Sersic profile fitting to provide luminosities and sizes for the key structural components bulge and disk. While the difference between field and cluster galaxy properties are mostly due to a preference for cluster members to be early-type (quiescent, bulge-dominated), we see evidence for an outer disk fading and a sharp rise in the number of red disks with smaller effective radii at the tidally active cluster region around R200. Even though red disks are already virialized according to their velocity distribution, they are clearly not part of the old population found in the innermost region; they represent an important population of transitional objects in clusters.

Line formation in the hot spot region of cataclysmic variable accretion disks

NASA Technical Reports Server (NTRS)

Elitzur, Moshe; Clarke, John T.; Kallman, T. R.

1988-01-01

The paper presents a theoretical analysis of the emission lines observed in the cataclysmic variable A0 Psc (=H2252-035), including detailed modeling of the hydrogen Balmer line emission. The analysis makes it possible to deduce the physical conditions in the so called 'hot spot', or 'bulge' region where the accretion column hits the rim of the accretion disk. It is concluded that the bulge is optically thick to the ionizing disk radiation. Consequently, its disk illuminated face is fully ionized whereas the side facing away from the disk is neutral, resulting in modulation of the observed emission lines with the orbital period. The density in the hot spot is about 5 x 10 to the 12th to 10 to the 13th/cu cm.

The GALAH survey: observational overview and Gaia DR1 companion

NASA Astrophysics Data System (ADS)

Martell, S. L.; Sharma, S.; Buder, S.; Duong, L.; Schlesinger, K. J.; Simpson, J.; Lind, K.; Ness, M.; Marshall, J. P.; Asplund, M.; Bland-Hawthorn, J.; Casey, A. R.; De Silva, G.; Freeman, K. C.; Kos, J.; Lin, J.; Zucker, D. B.; Zwitter, T.; Anguiano, B.; Bacigalupo, C.; Carollo, D.; Casagrande, L.; Da Costa, G. S.; Horner, J.; Huber, D.; Hyde, E. A.; Kafle, P. R.; Lewis, G. F.; Nataf, D.; Navin, C. A.; Stello, D.; Tinney, C. G.; Watson, F. G.; Wittenmyer, R.

2017-03-01

The Galactic Archaeology with HERMES (GALAH) survey is a massive observational project to trace the Milky Way's history of star formation, chemical enrichment, stellar migration and minor mergers. Using high-resolution (R ≃ 28 000) spectra, taken with the High Efficiency and Resolution Multi-Element Spectrograph (HERMES) instrument at the Anglo-Australian Telescope, GALAH will determine stellar parameters and abundances of up to 29 elements for up to one million stars. Selecting targets from a colour-unbiased catalogue built from 2MASS, APASS and UCAC4 data, we expect to observe dwarfs at 0.3-3 kpc and giants at 1-10 kpc. This enables a thorough local chemical inventory of the Galactic thin and thick discs, and also captures smaller samples of the bulge and halo. In this paper, we present the plan, process and progress as of early 2016 for GALAH survey observations. In our first two years of survey observing we have accumulated the largest high-quality spectroscopic data set at this resolution, over 200 000 stars. We also present the first public GALAH data catalogue: stellar parameters (Teff, log(g), [Fe/H], [α/Fe]), radial velocity, distance modulus and reddening for 10 680 observations of 9860 Tycho-2 stars, 7894 of which are included in the first Gaia data release.

Campaign 9 of the K2 Mission: Observational Parameters, Scientific Drivers, and Community Involvement for a Simultaneous Space- and Ground-based Microlensing Survey

NASA Technical Reports Server (NTRS)

Henderson, Calen B.; Poleski, Radoslaw; Penny, Matthew; Street, Rachel A.; Bennett, David P.; Hogg, David W.; Gaudi, B. Scott; Zhu, W.; Barclay, T.; Barentsen, G.;

Galactic Shapiro delay to the Crab pulsar and limit on weak equivalence principle violation

NASA Astrophysics Data System (ADS)

Desai, Shantanu; Kahya, Emre

2018-02-01

We calculate the total galactic Shapiro delay to the Crab pulsar by including the contributions from the dark matter as well as baryonic matter along the line of sight. The total delay due to dark matter potential is about 3.4 days. For baryonic matter, we included the contributions from both the bulge and the disk, which are approximately 0.12 and 0.32 days respectively. The total delay from all the matter distribution is therefore 3.84 days. We also calculate the limit on violations of Weak equivalence principle by using observations of "nano-shot" giant pulses from the Crab pulsar with time-delay <0.4 ns, as well as using time differences between radio and optical photons observed from this pulsar. Using the former, we obtain a limit on violation of Weak equivalence principle in terms of the PPN parameter Δ γ < 2.41× 10^{-15}. From the time-difference between simultaneous optical and radio observations, we get Δ γ < 1.54× 10^{-9}. We also point out differences in our calculation of Shapiro delay and that from two recent papers (Yang and Zhang, Phys Rev D 94(10):101501, 2016; Zhang and Gong, Astrophys J 837:134, 2017), which used the same observations to obtain a corresponding limit on Δ γ.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Christian I.; Caldwell, Nelson; Rich, R. Michael

We present radial velocities and chemical abundances for red giant branch stars in the Galactic bulge globular clusters NGC 6342 and NGC 6366. The velocities and abundances are based on measurements of high-resolution ( R ≳ 20,000) spectra obtained with the MMT–Hectochelle and WIYN–Hydra spectrographs. We find that NGC 6342 has a heliocentric radial velocity of +112.5 km s{sup −1} ( σ = 8.6 km s{sup −1}), NGC 6366 has a heliocentric radial velocity of −122.3 km s{sup −1} ( σ = 1.5 km s{sup −1}), and both clusters have nearly identical metallicities ([Fe/H] ≈ −0.55). NGC 6366 shows evidencemore » of a moderately extended O–Na anti-correlation, but more data are needed for NGC 6342 to determine if this cluster also exhibits the typical O–Na relation likely found in all other Galactic globular clusters. The two clusters are distinguished from similar metallicity field stars as having larger [Na/Fe] spreads and enhanced [La/Fe] ratios, but we find that NGC 6342 and NGC 6366 display α and Fe-peak element abundance patterns that are typical of other metal-rich ([Fe/H] > −1) inner Galaxy clusters. However, the median [La/Fe] abundance may vary from cluster-to-cluster.« less

Dual Active Galactic Nuclei in Nearby Galaxies

NASA Astrophysics Data System (ADS)

Das, Mousumi; Rubinur, Khatun; Karb, Preeti; Varghese, Ashlin; Novakkuni, Navyasree; James, Atul

2018-04-01

Galaxy mergers play a crucial role in the formation of massive galaxies and the buildup of their bulges. An important aspect of the merging process is the in-spiral of the supermassive black-holes (SMBHs) to the centre of the merger remnant and the eventual formation of a SMBH binary. If both the SMBHs are accreting they will form a dual or binary active galactic nucleus (DAGN). The final merger remnant is usually very bright and shows enhanced star formation. In this paper we summarise the current sample of DAGN from previous studies and describe methods that can be used to identify strong DAGN candidates from optical and spectroscopic surveys. These methods depend on the Doppler separation of the double peaked AGN emission lines, the nuclear velocity dispersion of the galaxies and their optical/UV colours. We describe two high resolution, radio observations of DAGN candidates that have been selected based on their double peaked optical emission lines (DPAGN). We also examine whether DAGN host galaxies have higher star formation rates (SFRs) compared to merging galaxies that do not appear to have DAGN. We find that the SFR is not higher for DAGN host galaxies. This suggests that the SFRs in DAGN host galaxies is due to the merging process itself and not related to the presence of two AGN in the system.

Galactic plane gamma-radiation

NASA Technical Reports Server (NTRS)

Hartman, R. C.; Kniffen, D. A.; Thompson, D. J.; Fichtel, C. E.; Ogelman, H. B.; Tumer, T.; Ozel, M. E.

1979-01-01

Analysis of the SAS 2 data together with the COS B results shows that the distribution of galactic gamma-radiation has several similarities to that of other large-scale tracers of galactic structure. The radiation is primarily confined to a thin disc which exhibits offsets from b = 0 degrees similar to warping at radio frequencies. The principal distinction of the gamma-radiation is a stronger contrast in intensity between the region from 310 to 45 degrees in longitude and the regions away from the center that can be attributed to a variation in cosmic-ray density as a function of position in Galaxy. The diffuse galactic gamma-ray energy spectrum shows no significant variation in direction, and the spectrum seen along the plane is the same as that for the galactic component of the gamma-radiation at high altitudes. The uniformity of the galactic gamma-ray spectrum, the smooth decrease in intensity as a function of altitude, and the absence of any galactic gamma-ray sources at high altitudes indicate a diffuse origin for bulk of the galactic gamma-radiation rather than a collection of localized sources.

Novae as a Class of Transient X-ray Sources

NASA Technical Reports Server (NTRS)

Mukai, K.; Orio, M.; Valle, M. Della

2007-01-01

Motivated by the recently discovered class of faint (10(exp 34)-10(exp 35) ergs/s) X-ray transients in the Galactic Center region, we investigate the 2-10 keV properties of classical and recurrent novae. Existing data are consistent with the idea that all classical novae are transient X-ray sources with durations of months to years and peak luminosities in the 10(exp 34)-10(exp 35)ergs/s range. This makes classical novae a viable candidate class for the faint Galactic Center transients. We estimate the rate of classical novae within a 15 arcmin radius region centered on the Galactic Center (roughly the field of view of XMM-Newton observations centered on Sgr A*) to be approx.0.1 per year. Therefore, it is plausible that some of the Galactic Center transients that have been announced to date are unrecognized classical novae. The continuing monitoring of the Galactic Center region carried out by Chandra and XMM-Newton may therefore provide a new method to detect classical novae in this crowded and obscured region, an

Einstein@Home discovers a radio-quiet gamma-ray millisecond pulsar

DOE PAGES

Clark, Colin J.; Pletsch, Holger J.; Wu, Jason; ...

2018-02-28

Millisecond pulsars (MSPs) are old neutron stars that spin hundreds of times per second and appear to pulsate as their emission beams cross our line of sight. To date, radio pulsations have been detected from all rotation-powered MSPs. Here, in an attempt to discover radio-quiet gamma-ray MSPs, we used the aggregated power from the computers of tens of thousands of volunteers participating in the Einstein@Home distributed computing project to search for pulsations from unidentified gamma-ray sources in Fermi Large Area Telescope data. This survey discovered two isolated MSPs, one of which is the only known rotation-powered MSP to remain undetectedmore » in radio observations. These gamma-ray MSPs were discovered in completely blind searches without prior constraints from other observations, raising hopes for detecting MSPs from a predicted Galactic bulge population.« less

Einstein@Home discovers a radio-quiet gamma-ray millisecond pulsar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, Colin J.; Pletsch, Holger J.; Wu, Jason

Millisecond pulsars (MSPs) are old neutron stars that spin hundreds of times per second and appear to pulsate as their emission beams cross our line of sight. To date, radio pulsations have been detected from all rotation-powered MSPs. Here, in an attempt to discover radio-quiet gamma-ray MSPs, we used the aggregated power from the computers of tens of thousands of volunteers participating in the Einstein@Home distributed computing project to search for pulsations from unidentified gamma-ray sources in Fermi Large Area Telescope data. This survey discovered two isolated MSPs, one of which is the only known rotation-powered MSP to remain undetectedmore » in radio observations. These gamma-ray MSPs were discovered in completely blind searches without prior constraints from other observations, raising hopes for detecting MSPs from a predicted Galactic bulge population.« less

Challenges in Timeseries Analysis from Microlensing

NASA Astrophysics Data System (ADS)

Street, R. A.

2017-06-01

Despite a flood of discoveries over the last ~ 20 years, our knowledge of the exoplanet population is incomplete owing to a gap between the sensitivities of different detection techniques. However, a census of exoplanets at all separations from their host stars is essential to fully understand planet formation mechanisms. Microlensing offers an effective way to bridge the gap around 1-10 AU and is therefore one of the major science goals of the Wide Field Infrared Survey Telescope (WFIRST) mission. WFIRST's survey of the Galactic Bulge is expected to discover ~ 20,000 microlensing events, including ~ 3000 planets, which represents a substantial data analysis challenge with the modeling software currently available. This paper highlights areas where further work is needed. The community is encouraged to join new software development efforts aimed at making the modeling of microlensing events both more accessible and rigorous.

Einstein@Home discovers a radio-quiet gamma-ray millisecond pulsar

PubMed Central

Clark, Colin J.; Pletsch, Holger J.; Wu, Jason; Guillemot, Lucas; Kerr, Matthew; Johnson, Tyrel J.; Camilo, Fernando; Salvetti, David; Allen, Bruce; Anderson, David; Aulbert, Carsten; Beer, Christian; Bock, Oliver; Cuéllar, Andres; Eggenstein, Heinz-Bernd; Fehrmann, Henning; Kramer, Michael; Kwang, Shawn A.; Machenschalk, Bernd; Nieder, Lars; Ackermann, Markus; Ajello, Marco; Baldini, Luca; Ballet, Jean; Barbiellini, Guido; Bastieri, Denis; Bellazzini, Ronaldo; Bissaldi, Elisabetta; Blandford, Roger D.; Bloom, Elliott D.; Bonino, Raffaella; Bottacini, Eugenio; Brandt, Terri J.; Bregeon, Johan; Bruel, Philippe; Buehler, Rolf; Burnett, Toby H.; Buson, Sara; Cameron, Rob A.; Caputo, Regina; Caraveo, Patrizia A.; Cavazzuti, Elisabetta; Cecchi, Claudia; Charles, Eric; Chekhtman, Alexandre; Ciprini, Stefano; Cominsky, Lynn R.; Costantin, Denise; Cutini, Sara; D’Ammando, Filippo; De Luca, Andrea; Desiante, Rachele; Di Venere, Leonardo; Di Mauro, Mattia; Di Lalla, Niccolò; Digel, Seth W.; Favuzzi, Cecilia; Ferrara, Elizabeth C.; Franckowiak, Anna; Fukazawa, Yasushi; Funk, Stefan; Fusco, Piergiorgio; Gargano, Fabio; Gasparrini, Dario; Giglietto, Nico; Giordano, Francesco; Giroletti, Marcello; Gomez-Vargas, Germán A.; Green, David; Grenier, Isabelle A.; Guiriec, Sylvain; Harding, Alice K.; Hewitt, John W.; Horan, Deirdre; Jóhannesson, Guðlaugur; Kensei, Shiki; Kuss, Michael; La Mura, Giovanni; Larsson, Stefan; Latronico, Luca; Li, Jian; Longo, Francesco; Loparco, Francesco; Lovellette, Michael N.; Lubrano, Pasquale; Magill, Jeffrey D.; Maldera, Simone; Manfreda, Alberto; Mazziotta, Mario N.; McEnery, Julie E.; Michelson, Peter F.; Mirabal, Nestor; Mitthumsiri, Warit; Mizuno, Tsunefumi; Monzani, Maria Elena; Morselli, Aldo; Moskalenko, Igor V.; Nuss, Eric; Ohsugi, Takashi; Omodei, Nicola; Orienti, Monica; Orlando, Elena; Palatiello, Michele; Paliya, Vaidehi S.; de Palma, Francesco; Paneque, David; Perkins, Jeremy S.; Persic, Massimo; Pesce-Rollins, Melissa; Porter, Troy A.; Principe, Giacomo; Rainò, Silvia; Rando, Riccardo; Ray, Paul S.; Razzano, Massimiliano; Reimer, Anita; Reimer, Olaf; Romani, Roger W.; Saz Parkinson, Pablo M.; Sgrò, Carmelo; Siskind, Eric J.; Smith, David A.; Spada, Francesca; Spandre, Gloria; Spinelli, Paolo; Thayer, Jana B.; Thompson, David J.; Torres, Diego F.; Troja, Eleonora; Vianello, Giacomo; Wood, Kent; Wood, Matthew

2018-01-01

Millisecond pulsars (MSPs) are old neutron stars that spin hundreds of times per second and appear to pulsate as their emission beams cross our line of sight. To date, radio pulsations have been detected from all rotation-powered MSPs. In an attempt to discover radio-quiet gamma-ray MSPs, we used the aggregated power from the computers of tens of thousands of volunteers participating in the Einstein@Home distributed computing project to search for pulsations from unidentified gamma-ray sources in Fermi Large Area Telescope data. This survey discovered two isolated MSPs, one of which is the only known rotation-powered MSP to remain undetected in radio observations. These gamma-ray MSPs were discovered in completely blind searches without prior constraints from other observations, raising hopes for detecting MSPs from a predicted Galactic bulge population. PMID:29503868

Einstein@Home discovers a radio-quiet gamma-ray millisecond pulsar.

PubMed

Clark, Colin J; Pletsch, Holger J; Wu, Jason; Guillemot, Lucas; Kerr, Matthew; Johnson, Tyrel J; Camilo, Fernando; Salvetti, David; Allen, Bruce; Anderson, David; Aulbert, Carsten; Beer, Christian; Bock, Oliver; Cuéllar, Andres; Eggenstein, Heinz-Bernd; Fehrmann, Henning; Kramer, Michael; Kwang, Shawn A; Machenschalk, Bernd; Nieder, Lars; Ackermann, Markus; Ajello, Marco; Baldini, Luca; Ballet, Jean; Barbiellini, Guido; Bastieri, Denis; Bellazzini, Ronaldo; Bissaldi, Elisabetta; Blandford, Roger D; Bloom, Elliott D; Bonino, Raffaella; Bottacini, Eugenio; Brandt, Terri J; Bregeon, Johan; Bruel, Philippe; Buehler, Rolf; Burnett, Toby H; Buson, Sara; Cameron, Rob A; Caputo, Regina; Caraveo, Patrizia A; Cavazzuti, Elisabetta; Cecchi, Claudia; Charles, Eric; Chekhtman, Alexandre; Ciprini, Stefano; Cominsky, Lynn R; Costantin, Denise; Cutini, Sara; D'Ammando, Filippo; De Luca, Andrea; Desiante, Rachele; Di Venere, Leonardo; Di Mauro, Mattia; Di Lalla, Niccolò; Digel, Seth W; Favuzzi, Cecilia; Ferrara, Elizabeth C; Franckowiak, Anna; Fukazawa, Yasushi; Funk, Stefan; Fusco, Piergiorgio; Gargano, Fabio; Gasparrini, Dario; Giglietto, Nico; Giordano, Francesco; Giroletti, Marcello; Gomez-Vargas, Germán A; Green, David; Grenier, Isabelle A; Guiriec, Sylvain; Harding, Alice K; Hewitt, John W; Horan, Deirdre; Jóhannesson, Guðlaugur; Kensei, Shiki; Kuss, Michael; La Mura, Giovanni; Larsson, Stefan; Latronico, Luca; Li, Jian; Longo, Francesco; Loparco, Francesco; Lovellette, Michael N; Lubrano, Pasquale; Magill, Jeffrey D; Maldera, Simone; Manfreda, Alberto; Mazziotta, Mario N; McEnery, Julie E; Michelson, Peter F; Mirabal, Nestor; Mitthumsiri, Warit; Mizuno, Tsunefumi; Monzani, Maria Elena; Morselli, Aldo; Moskalenko, Igor V; Nuss, Eric; Ohsugi, Takashi; Omodei, Nicola; Orienti, Monica; Orlando, Elena; Palatiello, Michele; Paliya, Vaidehi S; de Palma, Francesco; Paneque, David; Perkins, Jeremy S; Persic, Massimo; Pesce-Rollins, Melissa; Porter, Troy A; Principe, Giacomo; Rainò, Silvia; Rando, Riccardo; Ray, Paul S; Razzano, Massimiliano; Reimer, Anita; Reimer, Olaf; Romani, Roger W; Saz Parkinson, Pablo M; Sgrò, Carmelo; Siskind, Eric J; Smith, David A; Spada, Francesca; Spandre, Gloria; Spinelli, Paolo; Thayer, Jana B; Thompson, David J; Torres, Diego F; Troja, Eleonora; Vianello, Giacomo; Wood, Kent; Wood, Matthew

2018-02-01

Millisecond pulsars (MSPs) are old neutron stars that spin hundreds of times per second and appear to pulsate as their emission beams cross our line of sight. To date, radio pulsations have been detected from all rotation-powered MSPs. In an attempt to discover radio-quiet gamma-ray MSPs, we used the aggregated power from the computers of tens of thousands of volunteers participating in the Einstein@Home distributed computing project to search for pulsations from unidentified gamma-ray sources in Fermi Large Area Telescope data. This survey discovered two isolated MSPs, one of which is the only known rotation-powered MSP to remain undetected in radio observations. These gamma-ray MSPs were discovered in completely blind searches without prior constraints from other observations, raising hopes for detecting MSPs from a predicted Galactic bulge population.

The evolution of high-metallicity horizontal-branch stars and the origin of the ultraviolet light in elliptical galaxies

NASA Technical Reports Server (NTRS)

Horch, E.; Demarque, P.; Pinsonneault, M.

1992-01-01

Evolutionary calculations of high-metallicity horizontal-branch stars show that for the relevant masses and helium abundances, post-HB evolution in the HR diagram does not proceed toward and along the AGB, but rather toward a 'slow blue phase' in the vicinity of the helium-burning main sequence, following the extinction of the hydrogen shell energy source. For solar and twice solar metallicity, the blue phase begins during the helium shell-burning phase (in agreement with the work of Brocato and Castellani and Tornambe); for 3 times solar metallicity, it begins earlier, during the helium core-burning phase. This behavior differs from what takes place at lower metallicities. The implications for high-metallicity old stellar populations in the Galactic bulge and for the integrated colors of elliptical galaxies are discussed.

Diffuse ionized gas in galaxies across the Hubble sequence at the CALIFA resolution

NASA Astrophysics Data System (ADS)

Lacerda, E. A. D.; Cid Fernandes, R.; Couto, G. S.; Stasińska, G.; García-Benito, R.; Vale Asari, N.; Pérez, E.; González Delgado, R. M.; Sánchez, S. F.; de Amorim, A. L.

2018-03-01

We use spatially resolved spectroscopy from the Calar Alto Legacy Integral Field Area (CALIFA) survey to study the nature of the line emitting gas in galaxies of different Hubble types, focusing on the separation of star-forming (SF) regions from those better characterized as diffuse ionized gas (DIG). The diagnosis is carried out in terms of the equivalent width of H α (WH α). Three nebular regimes are identified. Regions where WH α < 3 Å define what we call the hDIG, the component of the DIG where photoionization is dominated by hot, low-mass, evolved stars. Regions where WH α > 14 Å trace SF complexes. WH α values in the intermediate 3-14 Å range reflect a mixed regime (mDIG) where more than one process contributes. This three-tier scheme is inspired both by theoretical and empirical considerations. Its application to CALIFA galaxies of different types and inclinations leads to the following results: (i) the hDIG component is prevalent throughout ellipticals and S0's as well as in bulges, and explains the strongly bimodal distribution of WH α both among and within galaxies. (ii) Early-type spirals have some hDIG in their discs, but this component becomes progressively less relevant for later Hubble types. (iii) hDIG emission is also present above and below galactic discs, as seen in several edge-on spirals in our sample. (iv) The SF/mDIG proportion grows steadily from early- to late-type spirals, and from inner to outer radii. (v) Besides circumventing basic inconsistencies in conventional DIG/SF separation criteria based on the H α surface brightness, our WH α-based method produces results in agreement with a classical excitation diagram analysis.

Diffuse ionized gas in galaxies across the Hubble sequence at the CALIFA resolution

NASA Astrophysics Data System (ADS)

Lacerda, E. A. D.; Cid Fernandes, R.; Couto, G. S.; Stasińska, G.; García-Benito, R.; Vale Asari, N.; Pérez, E.; Gonzalez Delgado, R. M.; Sánchez, S. F.; de Amorim, A. L.

2017-11-01

We use spatially resolved spectroscopy from the CALIFA survey to study the nature of the line emitting gas in galaxies of different Hubble types, focusing on the separation of star-forming (SF) regions from those better characterized as diffuse ionized gas (DIG). The diagnosis is carried out in terms of the equivalent width of Hα (W_{Hα}). Three nebular regimes are identified: Regions where W_{Hα} < 3 Å define what we call the hDIG, the component of the DIG where photoionization is dominated by hot, low mass, evolved stars. Regions where W_{Hα} > 14 Å trace SF complexes. W_{Hα} values in the intermediate 3-14 Å range reflect a mixed regime (mDIG) where more than one process contributes.This three-tier scheme is inspired both by theoretical and empirical considerations. Its application to CALIFA galaxies of different types and inclinations leads to the following results: (i) The hDIG component is prevalent throughout ellipticals and S0's as well as in bulges, and explains the strongly bimodal distribution of W_{{Hα} both among and within galaxies. (ii) Early type spirals have some hDIG in their disks, but this component becomes progressively less relevant for later Hubble types. (iii) hDIG emission is also present above and below galactic disks, as seen in several edge-on spirals in our sample. (iv) The SF/mDIG proportion grows steadily from early to late types spirals, and from inner to outer radii. (v) Besides circumventing basic inconsistencies in conventional DIG/SF separation criteria based on the &Hα surface brightness, our W_{Hα}-based method produces results in agreement with a classical excitation diagram analysis.

Why are classical bulges more common in S0 galaxies than in spiral galaxies?

NASA Astrophysics Data System (ADS)

Mishra, Preetish K.; Wadadekar, Yogesh; Barway, Sudhanshu

2018-07-01

In this paper, we try to understand why the classical bulge fraction observed in S0 galaxies is significantly higher than that in spiral galaxies. We carry out a comparative study of the bulge and global properties of a sample of spiral and S0 galaxies in a fixed environment. Our sample is flux limited and contains 262 spiral and 155 S0 galaxies drawn from the Sloan Digital Sky Survey. We have classified bulges into classical and pseudo-bulge categories based on their position on the Kormendy diagram. Dividing our sample into bins of galaxy stellar mass, we find that the fraction of S0 galaxies hosting a classical bulge is significantly higher than the classical bulge fraction seen in spirals even at fixed stellar mass. We have compared the bulge and the global properties of spirals and S0 galaxies in our sample and find indications that spiral galaxies which host a classical bulge, preferentially get converted into S0 population as compared to pseudo-bulge hosting spirals. By studying the star formation properties of our galaxies in the NUV-r colour-mass diagram, we find that the pseudo-bulge hosting spirals are mostly star forming while the majority of classical bulge host spirals are in the green valley or in the passive sequence. We suggest that some internal process, such as AGN feedback or morphological quenching due to the massive bulge, quenches these classical bulge hosting spirals and transforms them into S0 galaxies, thus resulting in the observed predominance of the classical bulge in S0 galaxies.

Chandra X-Ray and Hubble Space Telescope Imaging of Optically Selected Kiloparsec-scale Binary Active Galactic Nuclei. II. Host Galaxy Morphology and AGN Activity

NASA Astrophysics Data System (ADS)

Shangguan, Jinyi; Liu, Xin; Ho, Luis C.; Shen, Yue; Peng, Chien Y.; Greene, Jenny E.; Strauss, Michael A.

2016-05-01

Binary active galactic nuclei (AGNs) provide clues to how gas-rich mergers trigger and fuel AGNs and how supermassive black hole (SMBH) pairs evolve in a gas-rich environment. While significant effort has been invested in their identification, the detailed properties of binary AGNs and their host galaxies are still poorly constrained. In a companion paper, we examined the nature of ionizing sources in the double nuclei of four kiloparsec-scale binary AGNs with redshifts between 0.1 and 0.2. Here, we present their host galaxy morphology based on F336W (U-band) and F105W (Y-band) images taken by the Wide Field Camera 3 on board the Hubble Space Telescope. Our targets have double-peaked narrow emission lines and were confirmed to host binary AGNs with follow-up observations. We find that kiloparsec-scale binary AGNs occur in galaxy mergers with diverse morphological types. There are three major mergers with intermediate morphologies and a minor merger with a dominant disk component. We estimate the masses of the SMBHs from their host bulge stellar masses and obtain Eddington ratios for each AGN. Compared with a representative control sample drawn at the same redshift and stellar mass, the AGN luminosities and Eddington ratios of our binary AGNs are similar to those of single AGNs. The U - Y color maps indicate that clumpy star-forming regions could significantly affect the X-ray detection of binary AGNs, e.g., the hardness ratio. Considering the weak X-ray emission in AGNs triggered in merger systems, we suggest that samples of X-ray-selected AGNs may be biased against gas-rich mergers. Based, in part, on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program number GO 12363.

The Surface Density Profile of the Galactic Disk from the Terminal Velocity Curve

NASA Astrophysics Data System (ADS)

McGaugh, Stacy S.

2016-01-01

The mass distribution of the Galactic disk is constructed from the terminal velocity curve and the mass discrepancy-acceleration relation. Mass models numerically quantifying the detailed surface density profiles are tabulated. For R0 = 8 kpc, the models have stellar mass 5 < M* < 6 × 1010 {M}⊙ , scale length 2.0 ≤ Rd ≤ 2.9 kpc, LSR circular velocity 222 ≤ Θ0 ≤ 233 {km} {{{s}}}-1, and solar circle stellar surface density 34 ≤ Σd(R0) ≤ 61 {M}⊙ {{pc}}-2. The present interarm location of the solar neighborhood may have a somewhat lower stellar surface density than average for the solar circle. The Milky Way appears to be a normal spiral galaxy that obeys scaling relations like the Tully-Fisher relation, the size-mass relation, and the disk maximality-surface brightness relation. The stellar disk is maximal, and the spiral arms are massive. The bumps and wiggles in the terminal velocity curve correspond to known spiral features (e.g., the Centaurus arm is a ˜50% overdensity). The rotation curve switches between positive and negative over scales of hundreds of parsecs. The rms amplitude {< {| {dV}/{dR}| }2> }1/2≈ 14 {km} {{{s}}}-1 {{kpc}}-1, implying that commonly neglected terms in the Jeans equations may be nonnegligible. The spherically averaged local dark matter density is ρ0,DM ≈ 0.009 {M}⊙ {{pc}}-3 (0.34 {GeV} {{cm}}-3). Adiabatic compression of the dark matter halo may help reconcile the Milky Way with the c-V200 relation expected in ΛCDM while also helping to mitigate the too-big-to-fail problem, but it remains difficult to reconcile the inner bulge/bar-dominated region with a cuspy halo. We note that NGC 3521 is a near twin to the Milky Way, having a similar luminosity, scale length, and rotation curve.

Solving the Mystery of Galaxy Bulges and Bulge Substructure

NASA Astrophysics Data System (ADS)

Erwin, Peter

2017-08-01

Understanding galaxy bulges is crucial for understanding galaxy evolution and the growth of supermassive black holes (SMBHs). Recent studies have shown that at least some - perhaps most - disk-galaxy bulges are actually composite structures, with both classical-bulge (spheroid) and pseudobulge (disky) components; this calls into question the standard practice of using simple, low-resolution bulge/disk decompositions to determine spheroid and SMBH mass functions. We propose WFC3 optical and near-IR imaging of a volume- and mass-limited sample of local disk galaxies to determine the full range of pure-classical, pure-pseudobulge, and composite-bulge frequencies and parameters, including stellar masses for classical bulges, disky pseudobulges, and boxy/peanut-shaped bulges. We will combine this with ground-based spectroscopy to determine the stellar-kinematic and population characteristics of the different substructures revealed by our WFC3 imaging. This will help resolve growing uncertainties about the status and nature of bulges and their relation to SMBH masses, and will provide an essential local-universe reference for understanding bulge (and SMBH) formation and evolution.

SDSS-IV MaNGA-resolved Star Formation and Molecular Gas Properties of Green Valley Galaxies: A First Look with ALMA and MaNGA

NASA Astrophysics Data System (ADS)

Lin, Lihwai; Belfiore, Francesco; Pan, Hsi-An; Bothwell, M. S.; Hsieh, Pei-Ying; Huang, Shan; Xiao, Ting; Sánchez, Sebastián F.; Hsieh, Bau-Ching; Masters, Karen; Ramya, S.; Lin, Jing-Hua; Hsu, Chin-Hao; Li, Cheng; Maiolino, Roberto; Bundy, Kevin; Bizyaev, Dmitry; Drory, Niv; Ibarra-Medel, Héctor; Lacerna, Ivan; Haines, Tim; Smethurst, Rebecca; Stark, David V.; Thomas, Daniel

2017-12-01

We study the role of cold gas in quenching star formation in the green valley by analyzing ALMA 12CO (1-0) observations of three galaxies with resolved optical spectroscopy from the MaNGA survey. We present resolution-matched maps of the star formation rate and molecular gas mass. These data are used to calculate the star formation efficiency (SFE) and gas fraction ({f}{gas}) for these galaxies separately in the central “bulge” regions and outer disks. We find that, for the two galaxies whose global specific star formation rate (sSFR) deviates most from the star formation main sequence, the gas fraction in the bulges is significantly lower than that in their disks, supporting an “inside-out” model of galaxy quenching. For the two galaxies where SFE can be reliably determined in the central regions, the bulges and disks share similar SFEs. This suggests that a decline in {f}{gas} is the main driver of lowered sSFR in bulges compared to disks in green valley galaxies. Within the disks, there exist common correlations between the sSFR and SFE and between sSFR and {f}{gas} on kiloparsec scales—the local SFE or {f}{gas} in the disks declines with local sSFR. Our results support a picture in which the sSFR in bulges is primarily controlled by {f}{gas}, whereas both SFE and {f}{gas} play a role in lowering the sSFR in disks. A larger sample is required to confirm if the trend established in this work is representative of the green valley as a whole.

Analysis of reworked sediments as a basis of the Palaeogene-Neogene palaeogeography reinterpretation: Case study of the Roztocze region (SE Poland)

NASA Astrophysics Data System (ADS)

Margielewski, Włodzimierz; Jankowski, Leszek; Krąpiec, Marek; Garecka, Małgorzata; Hałas, Stanisław; Urban, Jan

2017-05-01

Radiometric K/Ar dating of glauconite and nanno- and micropaleontologic analyses of calcareous nannoplankton, foraminifers and dinoflagellates isolated from the Miocene rocks in the Polish part of the Roztocze region, a northeastern part of the fore-bulge of the Carpathian Foreland Basin System - CFBS), SE Poland, reveal that these strata contain numerous microfossils and glauconite grains of the Upper Eocene and Lower Oligocene age. Such occurrences clearly indicate that these materials were redeposited from the Upper Eocene and Lower Oligocene marine rocks that must have originally covered most of the Roztocze and the surrounding area. It is therefore proposed herein that the geographical extent of the boreal, epi-continental basin during the Eocene-Oligocene was much greater than previously considered. Moreover, it appears that this basin was connected with the back-bulge zone of the warm Carpathian Basin (originally a northern part of the Tethys Basin which since Eocene/Oligocene boundary remained isolated as the Paratethys Basin). Hence, it is unlikely that the Roztocze region was uplifted during the Palaeogene as part of the Meta-Carpathian Swell, as it was earlied hypothesized. Instead, the Roztocze Swell formed during the Sarmatian, in the last stage of the development of the fore-bulge structure in the foreland of the up-thrust Carpathian orogenic belt. Multiple redeposition of sediments is the reason that the absolute dating (K/Ar) of glauconite, as well as incomprehensive palaeontological analysis could result in erroneous stratigraphic and palaeogeographic interpretations.

WISE TF: A MID-INFRARED, 3.4 {mu}m EXTENSION OF THE TULLY-FISHER RELATION USING WISE PHOTOMETRY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lagattuta, David J.; Mould, Jeremy R.; Staveley-Smith, Lister

2013-07-10

We present a mid-infrared Tully-Fisher (TF) relation using photometry from the 3.4 {mu}m W1 band of the Wide-field Infrared Survey Explorer (WISE) satellite. The WISE TF relation is formed from 568 galaxies taken from the all-sky 2MASS Tully-Fisher (2MTF) galaxy catalog, spanning a range of environments including field, group, and cluster galaxies. This constitutes the largest mid-infrared TF relation constructed to date. After applying a number of corrections to galaxy magnitudes and line widths, we measure a master TF relation given by M{sub corr} = -22.24 - 10.05[log (W{sub corr}) - 2.5], with an average dispersion of {sigma}{sub WISE} =more » 0.686 mag. There is some tension between WISE TF and a preliminary 3.6 {mu}m relation, which has a shallower slope and almost no intrinsic dispersion. However, our results agree well with a more recent relation constructed from a large sample of cluster galaxies. We additionally compare WISE TF to the near-infrared 2MTF template relations, finding a good agreement between the TF parameters and total dispersions of WISE TF and the 2MTF K-band template. This fact, coupled with typical galaxy colors of (K - W1) {approx} 0, suggests that these two bands are tracing similar stellar populations, including the older, centrally-located stars in the galactic bulge which can (for galaxies with a prominent bulge) dominate the light profile.« less

A NEW METHOD FOR DERIVING THE STELLAR BIRTH FUNCTION OF RESOLVED STELLAR POPULATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gennaro, M.; Brown, T. M.; Gordon, K. D.

We present a new method for deriving the stellar birth function (SBF) of resolved stellar populations. The SBF (stars born per unit mass, time, and metallicity) is the combination of the initial mass function (IMF), the star formation history (SFH), and the metallicity distribution function (MDF). The framework of our analysis is that of Poisson Point Processes (PPPs), a class of statistical models suitable when dealing with points (stars) in a multidimensional space (the measurement space of multiple photometric bands). The theory of PPPs easily accommodates the modeling of measurement errors as well as that of incompleteness. Our method avoidsmore » binning stars in the color–magnitude diagram and uses the whole likelihood function for each data point; combining the individual likelihoods allows the computation of the posterior probability for the population's SBF. Within the proposed framework it is possible to include nuisance parameters, such as distance and extinction, by specifying their prior distributions and marginalizing over them. The aim of this paper is to assess the validity of this new approach under a range of assumptions, using only simulated data. Forthcoming work will show applications to real data. Although it has a broad scope of possible applications, we have developed this method to study multi-band Hubble Space Telescope observations of the Milky Way Bulge. Therefore we will focus on simulations with characteristics similar to those of the Galactic Bulge.« less

Large Magellanic Cloud Near-infrared Synoptic Survey. IV. Leavitt Laws for Type II Cepheid Variables

NASA Astrophysics Data System (ADS)

Bhardwaj, Anupam; Macri, Lucas M.; Rejkuba, Marina; Kanbur, Shashi M.; Ngeow, Chow-Choong; Singh, Harinder P.

2017-04-01

We present time-series observations of Population II Cepheids in the Large Magellanic Cloud at near-infrared (JHK s ) wavelengths. Our sample consists of 81 variables with accurate periods and optical (VI) magnitudes from the OGLE survey, covering various subtypes of pulsators (BL Herculis, W Virginis, and RV Tauri). We generate light-curve templates using high-quality I-band data in the LMC from OGLE and K s -band data in the Galactic bulge from VISTA Variables in Via Láctea survey and use them to obtain robust mean magnitudes. We derive period-luminosity (P-L) relations in the near-infrared and Period-Wesenheit (P-W) relations by combining optical and near-infrared data. Our P-L and P-W relations are consistent with published work when excluding long-period RV Tauris. We find that Pop II Cepheids and RR Lyraes follow the same P-L relations in the LMC. Therefore, we use trigonometric parallax from the Gaia DR1 for VY Pyx and the Hubble Space Telescope parallaxes for k Pav and 5 RR Lyrae variables to obtain an absolute calibration of the Galactic K s -band P-L relation, resulting in a distance modulus to the LMC of {μ }{LMC}=18.54+/- 0.08 mag. We update the mean magnitudes of Pop II Cepheids in Galactic globular clusters using our light-curve templates and obtain distance estimates to those systems, anchored to a precise late-type eclipsing binary distance to the LMC. We find that the distances to these globular clusters based on Pop II Cepheids are consistent (within 2σ ) with estimates based on the {M}V-[{Fe}/{{H}}] relation for horizontal branch stars.

Testing the Caustic Ring Dark Matter Halo Model Against Observations in the Milky Way

NASA Astrophysics Data System (ADS)

Dumas, Julie; Newberg, Heidi Jo; Niedzielski, Bethany; Susser, Adam; Thompson, Jeffery M.; Weiss, Jake; Lewis, Kim M.

2016-06-01

One prediction of axion dark matter models is they can form Bose-Einstein condensates and rigid caustic rings as a halo collapses in the non-linear regime. In this thesis, we undertake the first study of a caustic ring model for the Milky Way halo (Duffy & Sikivie 2008), paying particular attention to observational consequences. We first present the formalism for calculating the gravitational acceleration of a caustic ring halo. The caustic ring dark matter theory reproduces a roughly logarithmic halo, with large perturbations near the rings. We show that this halo can reasonably match the known Galactic rotation curve. We are not able to confirm or rule out an association between the positions of the caustic rings and oscillations in the observed rotation curve, due to insufficient rotation curve data. We explore the effects of dark matter caustic rings on dwarf galaxy tidal disruption with N-body simulations. Simulations of the Sagittarius (Sgr) dwarf galaxy in a caustic ring halo potential, with disk and bulge parameters that are tuned to match the Galactic rotation curve, match observations of the Sgr trailing tidal tails as far as 90 kpc from the Galactic center. Like the Navarro-Frenk-White (NFW) halo, they are, however, unable to match the leading tidal tail. None of the caustic, NFW, or triaxial logarithmic halos are able to simultaneously match observations of the leading and trailing arms of the Sagittarius stream. We further show that simulations of dwarf galaxies that move through caustic rings are qualitatively similar to those moving in a logarithmic halo. This research was funded by NSF grant AST 10-09670, the NASA-NY Space Grant, and the American Fellowship from AAUW.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruiter, Ashley J.; Belczynski, Krzysztof; Benacquista, Matthew

Double white dwarfs (WDs) are expected to be a source of confusion-limited noise for the future gravitational wave observatory LISA. In a specific frequency range, this 'foreground noise' is predicted to rise above the instrumental noise and hinder the detection of other types of signals, e.g., gravitational waves arising from stellar-mass objects inspiraling into massive black holes. In many previous studies, only detached populations of compact object binaries have been considered in estimating the LISA gravitational wave foreground signal. Here, we investigate the influence of compact object detached and Roche-Lobe overflow (RLOF) Galactic binaries on the shape and strength ofmore » the LISA signal. Since >99% of remnant binaries that have orbital periods within the LISA sensitivity range are WD binaries, we consider only these binaries when calculating the LISA signal. We find that the contribution of RLOF binaries to the foreground noise is negligible at low frequencies, but becomes significant at higher frequencies, pushing the frequency at which the foreground noise drops below the instrumental noise to >6 mHz. We find that it is important to consider the population of mass-transferring binaries in order to obtain an accurate assessment of the foreground noise on the LISA data stream. However, we estimate that there still exists a sizeable number ({approx}11,300) of Galactic double WD binaries that will have a signal-to-noise ratio >5, and thus will be potentially resolvable with LISA. We present the LISA gravitational wave signal from the Galactic population of WD binaries, show the most important formation channels contributing to the LISA disk and bulge populations, and discuss the implications of these new findings.« less

BULGES OF NEARBY GALAXIES WITH SPITZER: SCALING RELATIONS IN PSEUDOBULGES AND CLASSICAL BULGES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fisher, David B.; Drory, Niv, E-mail: dbfisher@astro.as.utexas.ed

2010-06-20

We investigate scaling relations of bulges using bulge-disk decompositions at 3.6 {mu}m and present bulge classifications for 173 E-Sd galaxies within 20 Mpc. Pseudobulges and classical bulges are identified using Sersic index, Hubble Space Telescope morphology, and star formation activity (traced by 8 {mu}m emission). In the near-IR pseudobulges have n{sub b} < 2 and classical bulges have n{sub b} >2, as found in the optical. Sersic index and morphology are essentially equivalent properties for bulge classification purposes. We confirm, using a much more robust sample, that the Sersic index of pseudobulges is uncorrelated with other bulge structural properties, unlikemore » for classical bulges and elliptical galaxies. Also, the half-light radius of pseudobulges is not correlated with any other bulge property. We also find a new correlation between surface brightness and pseudobulge luminosity; pseudobulges become more luminous as they become more dense. Classical bulges follow the well-known scaling relations between surface brightness, luminosity, and half-light radius that are established by elliptical galaxies. We show that those pseudobulges (as indicated by Sersic index and nuclear morphology) that have low specific star formation rates are very similar to models of galaxies in which both a pseudobulge and classical bulge exist. Therefore, pseudobulge identification that relies only on structural indicators is incomplete. Our results, especially those on scaling relations, imply that pseudobulges are very different types of objects than elliptical galaxies.« less

The interaction between the yeast telomerase RNA and the Est1 protein requires three structural elements.

PubMed

Lubin, Johnathan W; Tucey, Timothy M; Lundblad, Victoria

2012-09-01

In the budding yeast Saccharomyces cerevisiae, the telomerase enzyme is composed of a 1.3-kb TLC1 RNA that forms a complex with Est2 (the catalytic subunit) and two regulatory proteins, Est1 and Est3. Previous work has identified a conserved 5-nt bulge, present in a long helical arm of TLC1, which mediates binding of Est1 to TLC1. However, increased expression of Est1 can bypass the consequences of removal of this RNA bulge, indicating that there are additional binding site(s) for Est1 on TLC1. We report here that a conserved single-stranded internal loop immediately adjacent to the bulge is also required for the Est1-RNA interaction; furthermore, a TLC1 variant that lacks this internal loop but retains the bulge cannot be suppressed by Est1 overexpression, arguing that the internal loop may be a more critical element for Est1 binding. An additional structural feature consisting of a single-stranded region at the base of the helix containing the bulge and internal loop also contributes to recognition of TLC1 by Est1, potentially by providing flexibility to this helical arm. Association of Est1 with each of these TLC1 motifs was assessed using a highly sensitive biochemical assay that simultaneously monitors the relative levels of the Est1 and Est2 proteins in the telomerase complex. The identification of three elements of TLC1 that are required for Est1 association provides a detailed view of this particular protein-RNA interaction.

The orbital motion of the quintuplet cluster—a common origin for the arches and quintuplet clusters?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stolte, A.; Hußmann, B.; Habibi, M.

2014-07-10

We investigate the orbital motion of the Quintuplet cluster near the Galactic center with the aim of constraining formation scenarios of young, massive star clusters in nuclear environments. Three epochs of adaptive optics high-angular resolution imaging with the Keck/NIRC2 and Very Large Telescope/NAOS-CONICA systems were obtained over a time baseline of 5.8 yr, delivering an astrometric accuracy of 0.5-1 mas yr{sup –1}. Proper motions were derived in the cluster reference frame and were used to distinguish cluster members from the majority of the dense field star population toward the inner bulge. Fitting the cluster and field proper motion distributions withmore » two-dimensional (2D) Gaussian models, we derive the orbital motion of the cluster for the first time. The Quintuplet is moving with a 2D velocity of 132 ± 15 km s{sup –1} with respect to the field along the Galactic plane, which yields a three-dimensional orbital velocity of 167 ± 15 km s{sup –1} when combined with the previously known radial velocity. From a sample of 119 stars measured in three epochs, we derive an upper limit to the velocity dispersion of σ{sub 1D} < 10 km s{sup –1} in the core of the Quintuplet cluster. Knowledge of the three velocity components of the Quintuplet allows us to model the cluster orbit in the potential of the inner Galaxy. Under the assumption that the Quintuplet is located in the central 200 pc at the present time, these simulations exclude the possibility that the cluster is moving on a circular orbit. Comparing the Quintuplet's orbit with our earlier measurements of the Arches' orbit, we discuss the possibility that both clusters originated in the same area of the central molecular zone (CMZ). According to the model of Binney et al., two families of stable cloud orbits are located along the major and minor axes of the Galactic bar, named x1 and x2 orbits, respectively. The formation locus of these clusters is consistent with the outermost x2 orbit and might hint at cloud collisions at the transition region between the x1 and x2 orbital families located at the tip of the minor axis of the Galactic bar. The formation of young, massive star clusters in circumnuclear rings is discussed in the framework of the channeling in of dense gas by the bar potential. We conclude that the existence of a large-scale bar plays a major role in supporting ongoing star and cluster formation, not only in nearby spiral galaxies with circumnuclear rings, but also in the Milky Way's CMZ.« less

A numerical study of circulation in the Gulf of Riga, Baltic Sea. Part II: Mesoscale features and freshwater transport pathways

NASA Astrophysics Data System (ADS)

Lips, Urmas; Zhurbas, Victor; Skudra, Maris; Väli, Germo

2016-03-01

A regional eddy-resolving model is developed to study mesoscale processes in the Gulf of Riga in relation to river runoff, saltwater inflow, and atmospheric forcing. A number of mesoscale phenomena are simulated and discussed, such as meandering of coastal buoyant plume/current of riverine waters and formation and splitting of cyclonic eddies related to the saltwater inflow. It is shown that the Daugava River discharge forms a surface-advected plume (Yankovsky and Chapman, 1997) consisting of an anticyclonic bulge and coastal buoyant jet. In case of no saltwater inflow and no atmospheric forcing, the river runoff is distributed between the growing anticyclonic bulge and the coastal current in proportion of about 7:6. In the summer season, a substantial fraction of freshwater from the anticyclonic bulge can be transported to the north by the anticyclonic whole-basin circulation gyre leading to the bimodal transport pathways of the Daugava River plume.

The distribution of cosmic rays in the galaxy and their dynamics as deduced from recent gamma ray observations. [noting maximum in toroidal region between 4 and 5 kpc from galactic center

NASA Technical Reports Server (NTRS)

Puget, J. L.; Stecker, F. W.

1974-01-01

Data from SAS-2 on the galactic gamma ray line flux as a function of longitude is examined. It is shown that the gamma ray emissivity varies with galactocentric distance and is about an order of magnitude higher than the local value in a toroidal region between 4 and 5 kpc from the galactic center. This enhancement is accounted for in part by first-order Fermi acceleration, compression, and trapping of cosmic rays consistent with present ideas of galactic dynamics and galactic structure theory. Calculations indicate that cosmic rays in the 4 to 5 kpc region are trapped and accelerated over a mean time of the order of a few million years or about 2 to 4 times the assumed trapping time in the solar region of the galaxy on the assumption that only an increased cosmic ray flux is responsible for the observed emission. Cosmic ray nucleons, cosmic ray electrons, and ionized hydrogen gas were found to have a strikingly similar distribution in the galaxy according to both the observational data and the theoretical model discussed.

Recognition of DNA bulges by dinuclear iron(II) metallosupramolecular helicates.

PubMed

Malina, Jaroslav; Hannon, Michael J; Brabec, Viktor

2014-02-01

Bulged DNA structures are of general biological significance because of their important roles in a number of biochemical processes. Compounds capable of targeting bulged DNA sequences can be used as probes for studying their role in nucleic acid function, or could even have significant therapeutic potential. The interaction of [Fe(2)L(3)](4+) metallosupramolecular helicates (L = C(25)H(20)N(4)) with DNA duplexes containing bulges has been studied by measurement of the DNA melting temperature and gel electrophoresis. This study was aimed at exploring binding affinities of the helicates for DNA bulges of various sizes and nucleotide sequences. The studies reported herein reveal that both enantiomers of [Fe(2)L(3)](4+) bind to DNA bulges containing at least two unpaired nucleotides. In addition, these helicates show considerably enhanced affinity for duplexes containing unpaired pyrimidines in the bulge and/or pyrimidines flanking the bulge on both sides. We suggest that the bulge creates the structural motif, such as the triangular prismatic pocket formed by the unpaired bulge bases, to accommodate the [Fe(2)L(3)](4+) helicate molecule, and is probably responsible for the affinity for duplexes with a varying number of bulge bases. Our results reveal that DNA bulges represent another example of unusual DNA structures recognized by dinuclear iron(II) ([Fe(2)L(3)](4+)) supramolecular helicates. © 2013 FEBS.

BULGES OF NEARBY GALAXIES WITH SPITZER: THE GROWTH OF PSEUDOBULGES IN DISK GALAXIES AND ITS CONNECTION TO OUTER DISKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fisher, David B.; Drory, Niv; Fabricius, Maximilian H.

2009-05-20

We study star formation rates (SFRs) and stellar masses in bulges of nearby disk galaxies. For this we construct a new SFR indicator that linearly combines data from the Spitzer Space Telescope and the Galaxy Evolution Explorer. All bulges are found to be forming stars irrespective of bulge type (pseudobulge or classical bulge). At present-day SFR the median pseudobulge could have grown the present-day stellar mass in 8 Gyr. Classical bulges have the lowest specific SFR implying a growth times that are longer than a Hubble time, and thus the present-day SFR does not likely play a major role inmore » the evolution of classical bulges. In almost all galaxies in our sample the specific SFR (SFR per unit stellar mass) of the bulge is higher than that of the outer disk. This suggests that almost all galaxies are increasing their B/T through internal star formation. The SFR in pseudobulges correlates with their structure. More massive pseudobulges have higher SFR density, this is consistent with that stellar mass being formed by moderate, extended star formation. Bulges in late-type galaxies have similar SFRs as pseudobulges in intermediate-type galaxies, and are similar in radial size. However, they are deficient in mass; thus, they have much shorter growth times, {approx}2 Gyr. We identify a class of bulges that have nuclear morphology similar to pseudobulges, significantly lower specific SFR than pseudobulges, and are closer to classical bulges in structural parameter correlations. These are possibly composite objects, evolved pseudobulges or classical bulges experiencing transient, enhanced nuclear star formation. Our results are consistent with a scenario in which bulge growth via internal star formation is a natural, and near ubiquitous phenomenon in disk galaxies. Those galaxies with large classical bulges are not affected by the in situ bulge growth, likely because the majority of their stellar mass comes from some other phenomenon. Yet, those galaxies without a classical bulge, over long periods of extended star formation are able to growth a pseudobulge. Though cold accretion is not ruled out, for pseudobulge galaxies an addition of stellar mass from mergers or accretion is not required to explain the bulge mass. In this sense, galaxies with pseudobulges may very well be bulgeless (or 'quasi-bulgeless') galaxies, and galaxies with classical bulges are galaxies in which both internal evolution and hierarchical merging are responsible for the bulge mass by fractions that vary from galaxy to galaxy.« less

The galactic gamma-ray distribution: Implications for galactic structure and the radial cosmic ray gradient

NASA Technical Reports Server (NTRS)

Harding, A. K.; Stecker, F. W.

1984-01-01

The radial distribution of gamma ray emissivity in the Galaxy was derived from flux longitude profiles, using both the final SAS-2 results and the recently corrected COS-B results and analyzing the northern and southern galactic regions separately. The recent CO surveys of the Southern Hemisphere, were used in conjunction with the Northern Hemisphere data, to derive the radial distribution of cosmic rays on both sides of the galactic plane. In addition to the 5 kpc ring, there is evidence from the radial asymmetry for spiral features which are consistent with those derived from the distribution of bright HII regions. Positive evidence was also found for a strong increase in the cosmic ray flux in the inner Galaxy, particularly in the 5 kpc region in both halves of the plane.

The low-metallicity QSO HE 2158 - 0107: a massive galaxy growing by accretion of nearly pristine gas from its environment?

NASA Astrophysics Data System (ADS)

Husemann, B.; Wisotzki, L.; Jahnke, K.; Sánchez, S. F.

2011-11-01

The metallicities of active galactic nuclei (AGN) are usually well above solar in their narrow-line regions, often reaching up to several times solar in their broad-line regions independent of redshift. Low-metallicity AGN are rare objects that have so far always been associated with low-mass galaxies hosting low-mass black holes (MBH106M⊙). We present integral field spectroscopy data of the low-redshift (z = 0.212) quasi-stellar object (QSO) HE 2158 - 0107 for which we find strong evidence of sub-solar NLR metallicities associated with a massive black hole (MBH ~ 3 × 108M⊙). The QSO is surrounded by a large extended emission-line region reaching out to 30 kpc from the QSO in a tail-like geometry. We present optical and near-infrared images and investigate the properties of the host galaxy. The host of HE 2158 - 0107 is most likely a very compact bulge-dominated galaxy with a size of re ~ 1.4 kpc. The multi-colour spectral energy distribution (SED) of the host is quite blue, indicative of a significant young age stellar population formed within the last 1 Gyr. A 3σ upper limit of Lbulge,H < 4.5 × 1010L ⊙ ,H for the H-band luminosity and a corresponding stellar mass upper limit of Mbulge < 3.4 × 1010M⊙ show that the host is offset from the local black hole-bulge relations. This is independently supported by the kinematics of the gas. Although the stellar mass of the host galaxy is lower than expected, it cannot explain the exceptionally low metallicity of the gas. We suggest that the extended emission-line region and the galaxy growth are caused by the infall of nearly pristine gas from the environment of the QSO host. Minor mergers of low-metallicity dwarf galaxies or the theoretically predicted smooth accretion of cold (~ 104 K) gas are both potential drivers behind that process. Because the metallicity of the gas in the QSO narrow-line region is much lower than expected, we suspect that the external gas has already reached the galaxy centre and may even contribute to the current feeding of the black hole. HE 2158 - 0107 appears to represent a particular phase of substantial black hole and galaxy growth that can be observationally linked with the accretion of external material from its environment. Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck-Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC) and on observations collected at the European Organisation for Astronomical Reasearch in the Southern Hemisphere, Chile (program 070.B-0418).

The Frequency of Snowline-Region Planets from Four Years of OGLE-MOA-Wise Second-Generation Microlensing

NASA Technical Reports Server (NTRS)

Shvartzvald, Y.; Maoz, D.; Udalski, A.; Sumi, T.; Friedmann, M.; Kaspi, S.; Poleski, R.; Szymanski, M. K.; Skowron, J.; Kozlowski, S.;

Physical Properties of Sub-galactic Clumps at 0.5 ≤ Z ≤ 1.5 in the UVUDF

NASA Astrophysics Data System (ADS)

Soto, Emmaris; de Mello, Duilia F.; Rafelski, Marc; Gardner, Jonathan P.; Teplitz, Harry I.; Koekemoer, Anton M.; Ravindranath, Swara; Grogin, Norman A.; Scarlata, Claudia; Kurczynski, Peter; Gawiser, Eric

2017-03-01

We present an investigation of clumpy galaxies in the Hubble Ultra Deep Field at 0.5≤slant z≤slant 1.5 in the rest-frame far-ultraviolet (FUV) using Hubble Space Telescope Wide Field Camera 3 broadband imaging in F225W, F275W, and F336W. An analysis of 1404 galaxies yields 209 galaxies that host 403 kpc scale clumps. These host galaxies appear to be typical star-forming galaxies, with an average of 2 clumps per galaxy and reaching a maximum of 8 clumps. We measure the photometry of the clumps and determine the mass, age, and star formation rates (SFR) using the spectral energy distribution fitting code FAST. We find that clumps make an average contribution of 19% to the total rest-frame FUV flux of their host galaxy. Individually, clumps contribute a median of 5% to the host galaxy SFR and an average of ˜4% to the host galaxy mass, with total clump contributions to the host galaxy stellar mass ranging widely from lower than 1% up to 93%. Clumps in the outskirts of galaxies are typically younger, with higher SFRs, than clumps in the inner regions. The results are consistent with clump migration theories in which clumps form through violent gravitational instabilities in gas-rich turbulent disks, eventually migrate toward the center of the galaxies, and coalesce into the bulge.

Structural basis for bifunctional zinc(II) macrocyclic complex recognition of thymine bulges in DNA.

PubMed

del Mundo, Imee Marie A; Siters, Kevin E; Fountain, Matthew A; Morrow, Janet R

2012-05-07

The zinc(II) complex of 1-(4-quinoylyl)methyl-1,4,7,10-tetraazacyclododecane (cy4q) binds selectively to thymine bulges in DNA and to a uracil bulge in RNA. Binding constants are in the low-micromolar range for thymine bulges in the stems of hairpins, for a thymine bulge in a DNA duplex, and for a uracil bulge in an RNA hairpin. Binding studies of Zn(cy4q) to a series of hairpins containing thymine bulges with different flanking bases showed that the complex had a moderate selectivity for thymine bulges with neighboring purines. The dissociation constants of the most strongly bound Zn(cy4q)-DNA thymine bulge adducts were 100-fold tighter than similar sequences with fully complementary stems or than bulges containing cytosine, guanine, or adenine. In order to probe the role of the pendent group, three additional zinc(II) complexes containing 1,4,7,10-tetraazacyclododecane (cyclen) with aromatic pendent groups were studied for binding to DNA including 1-(2-quinolyl)methyl-1,4,7,10-tetraazacyclododecane (cy2q), 1-(4-biphenyl)methyl-1,4,7,10-tetraazacyclododecane (cybp), and 5-(1,4,7,10-tetraazacyclododecan-1-ylsulfonyl)-N,N-dimethylnaphthalen-1-amine (dsc). The Zn(cybp) complex binds with moderate affinity but little selectivity to DNA hairpins with thymine bulges and to DNA lacking bulges. Similarly, Zn(dsc) binds weakly both to thymine bulges and hairpins with fully complementary stems. The zinc(II) complex of cy2q has the 2-quinolyl moiety bound to the Zn(II) center, as shown by (1)H NMR spectroscopy and pH-potentiometric titrations. As a consequence, only weak (500 μM) binding is observed to DNA with no appreciable selectivity. An NMR structure of a thymine-bulge-containing hairpin shows that the thymine is extrahelical but rotated toward the major groove. NMR data for Zn(cy4q) bound to DNA containing a thymine bulge is consistent with binding of the zinc(II) complex to the thymine N3(-) and stacking of the quinoline on top of the thymine. The thymine-bulge bound zinc(II) complex is pointed into the major groove, and there are interactions with the guanine positioned 5' to the thymine bulge.

The Southern HII Region Discovery Survey: Preliminary Results

NASA Astrophysics Data System (ADS)

Shea, Jeanine; Wenger, Trey; Balser, Dana S.; Anderson, Loren D.; Armentrout, William P.; Bania, Thomas M.; Dawson, Joanne; Miller Dickey, John; Jordan, Christopher; McClure-Griffiths, Naomi M.

2017-01-01

HII regions are some of the brightest sources at radio frequencies in the Milky Way and are the sites of massive O and B-type star formation. They have relatively short (< 10 Myr) lifetimes compared to other Galactic objects and therefore reveal information about spiral structure and the chemical evolution of the Galaxy. The HII Region Discovery Surveys (HRDS) discovered about 800 new HII regions in the Galactic longitude range -20 degrees to 270 degrees using primarily the Green Bank Telescope. Candidate HII regions were selected from mid-infrared emission coincident with radio continuum emission, and confirmed as HII regions by the detection of radio recombination lines. Here we discuss the Southern HII Region Discovery Survey (SHRDS), a continuation of the HRDS using the Australia Telescope Compact Array over the Galactic longitude range 230 to 360 degrees. We have reduced and analyzed a small sub-set of the SHRDS sources and discuss preliminary results, including kinematic distances and metallicities.

VizieR Online Data Catalog: RR Lyrae in SDSS Stripe 82 (Suveges+, 2012)

NASA Astrophysics Data System (ADS)

Suveges, M.; Sesar, B.; Varadi, M.; Mowlavi, N.; Becker, A. C.; Ivezic, Z.; Beck, M.; Nienartowicz, K.; Rimoldini, L.; Dubath, P.; Bartholdi, P.; Eyer, L.

2013-05-01

We propose a robust principal component analysis framework for the exploitation of multiband photometric measurements in large surveys. Period search results are improved using the time-series of the first principal component due to its optimized signal-to-noise ratio. The presence of correlated excess variations in the multivariate time-series enables the detection of weaker variability. Furthermore, the direction of the largest variance differs for certain types of variable stars. This can be used as an efficient attribute for classification. The application of the method to a subsample of Sloan Digital Sky Survey Stripe 82 data yielded 132 high-amplitude delta Scuti variables. We also found 129 new RR Lyrae variables, complementary to the catalogue of Sesar et al., extending the halo area mapped by Stripe 82 RR Lyrae stars towards the Galactic bulge. The sample also comprises 25 multiperiodic or Blazhko RR Lyrae stars. (8 data files).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gould, Andrew; Yee, Jennifer C., E-mail: gould@astronomy.ohio-state.edu, E-mail: jyee@astronomy.ohio-state.edu

While of order of a million asteroids have been discovered, the number in rigorously controlled samples that have precise orbits and rotation periods, as well as well-measured colors, is relatively small. In particular, less than a dozen main-belt asteroids with estimated diameters D < 3 km have excellent rotation periods. We show how existing and soon-to-be-acquired microlensing data can yield a large asteroid sample with precise orbits and rotation periods, which will include roughly 6% of all asteroids with maximum brightness I < 18.1 and lying within 10 Degree-Sign of the ecliptic. This sample will be dominated by small andmore » very small asteroids, down to D {approx} 1 km. We also show how asteroid astrometry could turn current narrow-angle OGLE proper motions of bulge stars into wide-angle proper motions. This would enable one to measure the proper-motion gradient across the Galactic bar.« less

An Isolated Microlens Observed from K2, Spitzer, and Earth

NASA Astrophysics Data System (ADS)

Zhu, Wei; Udalski, A.; Huang, C. X.; Calchi Novati, S.; Sumi, T.; Poleski, R.; Skowron, J.; Mróz, P.; Szymański, M. K.; Soszyński, I.; Pietrukowicz, P.; Kozłowski, S.; Ulaczyk, K.; Pawlak, M.; OGLE Collaboration; Beichman, C.; Bryden, G.; Carey, S.; Gaudi, B. S.; Gould, A.; Henderson, C. B.; Shvartzvald, Y.; Yee, J. C.; Spitzer Team; Bond, I. A.; Bennett, D. P.; Suzuki, D.; Rattenbury, N. J.; Koshimoto, N.; Abe, F.; Asakura, Y.; Barry, R. K.; Bhattacharya, A.; Donachie, M.; Evans, P.; Fukui, A.; Hirao, Y.; Itow, Y.; Kawasaki, K.; Li, M. C. A.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Miyazaki, S.; Munakata, H.; Muraki, Y.; Nagakane, M.; Ohnishi, K.; Ranc, C.; Saito, To.; Sharan, A.; Sullivan, D. J.; Tristram, P. J.; Yamada, T.; Yonehara, A.; MOA Collaboration

2017-11-01

We present the result of microlensing event MOA-2016-BLG-290, which received observations from the two-wheel Kepler (K2), Spitzer, as well as ground-based observatories. A joint analysis of data from K2 and the ground leads to two degenerate solutions of the lens mass and distance. This degeneracy is effectively broken once the (partial) Spitzer light curve is included. Altogether, the lens is found to be an extremely low-mass star or brown dwarf ({77}-23+34 {M}{{J}}) located in the Galactic bulge (6.8+/- 0.4 kpc). MOA-2016-BLG-290 is the first microlensing event for which we have signals from three well-separated (∼1 au) locations. It demonstrates the power of two-satellite microlensing experiment in reducing the ambiguity of lens properties, as pointed out independently by S. Refsdal and A. Gould several decades ago.

Galacti chemical evolution: Hygrogen through zinc

NASA Technical Reports Server (NTRS)

Timmes, F. X.; Woosley, S. E.; Weaver, Thomas A.

1995-01-01

Using the output from a grid of 60 Type II supernova models (Woosley & Weaver 1995) of varying mass (11 approx. less than (M/solar mass) approx. less than 40) and metallicity (0, 10(exp -4), 0.01, and 1 solar metallicity), the chemical evolution of 76 stable isotopes, from hydrogen to zinc, is calculated. The chemical evolution calculation employs a simple dynamical model for the Galaxy (infall with a 4 Gyr e-folding timescale onto a exponential dsk and 1/r(exp 2) bulge), and standard evolution parameters, such as a Salpeter initial mass function and a quadratic Schmidt star formation rate. The theoretical results are compared in detail with observed stellar abundances in stars with metallicities in the range -3.0 approx. less than (Fe/H) approx. less than 0.0 dex. While our discussion focuses on the solar neighborhood where there are the most observations, the supernova rates, an intrinsically Galactic quality, are also discussed.

Nuclear starburst activity induced by elongated bulges in spiral galaxies

NASA Astrophysics Data System (ADS)

Kim, Eunbin; Kim, Sungsoo S.; Choi, Yun-Young; Lee, Gwang-Ho; de Grijs, Richard; Lee, Myung Gyoon; Hwang, Ho Seong

2018-06-01

We study the effects of bulge elongation on the star formation activity in the centres of spiral galaxies using the data from the Sloan Digital Sky Survey Data Release 7. We construct a volume-limited sample of face-on spiral galaxies with Mr < -19.5 mag at 0.02 ≤z< 0.055 by excluding barred galaxies, where the aperture of the SDSS spectroscopic fibre covers the bulges of the galaxies. We adopt the ellipticity of bulges measured by Simard et al. (2011) who performed two-dimensional bulge+disc decompositions using the SDSS images of galaxies, and identify nuclear starbursts using the fibre specific star formation rates derived from the SDSS spectra. We find a statistically significant correlation between bulge elongation and nuclear starbursts in the sense that the fraction of nuclear starbursts increases with bulge elongation. This correlation is more prominent for fainter and redder galaxies, which exhibit higher ratios of elongated bulges. We find no significant environmental dependence of the correlation between bulge elongation and nuclear starbursts. These results suggest that non-axisymmetric bulges can efficiently feed the gas into the centre of galaxies to trigger nuclear starburst activity.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanna, A.; Menten, K. M.; Brunthaler, A.

We report a trigonometric parallax measurement with the Very Long Baseline Array for the water maser in the distant high-mass star-forming region G75.30+1.32. This source has a heliocentric distance of 9.25{sup +0.45}{sub -0.40} kpc, which places it in the Outer arm in the first Galactic quadrant. It lies 200 pc above the Galactic plane and is associated with a substantial H I enhancement at the border of a large molecular cloud. At a Galactocentric radius of 10.7 kpc, G75.30+1.32 is in a region of the Galaxy where the disk is significantly warped toward the North Galactic Pole. While the star-formingmore » region has an instantaneous Galactic orbit that is nearly circular, it displays a significant motion of 18 km s{sup -1} toward the Galactic plane. The present results, when combined with two previous maser studies in the Outer arm, yield a pitch angle of about 12 Degree-Sign for a large section of the arm extending from the first quadrant to the third.« less

A combined photometric and kinematic recipe for evaluating the nature of bulges using the CALIFA sample

NASA Astrophysics Data System (ADS)

Neumann, J.; Wisotzki, L.; Choudhury, O. S.; Gadotti, D. A.; Walcher, C. J.; Bland-Hawthorn, J.; García-Benito, R.; González Delgado, R. M.; Husemann, B.; Marino, R. A.; Márquez, I.; Sánchez, S. F.; Ziegler, B.; Califa Collaboration

2017-07-01

Understanding the nature of bulges in disc galaxies can provide important insights into the formation and evolution of galaxies. For instance, the presence of a classical bulge suggests a relatively violent history. In contrast, the presence of an inner disc instead (also referred to as a "pseudobulge") indicates the occurrence of secular evolution processes in the main disc. However, we still lack criteria to effectively categorise bulges, limiting our ability to study their impact on the evolution of the host galaxies. Here we present a recipe to separate inner discs from classical bulges by combining four different parameters from photometric and kinematic analyses: the bulge Sérsic index nb, the concentration index C20,50, the Kormendy (1977, ApJ, 217, 406) relation and the inner slope of the radial velocity dispersion profile ∇σ. With that recipe we provide a detailed bulge classification for a sample of 45 galaxies from the integral-field spectroscopic survey CALIFA. To aid in categorising bulges within these galaxies, we perform 2D image decomposition to determine bulge Sérsic index, bulge-to-total light ratio, surface brightness and effective radius of the bulge and use growth curve analysis to derive a new concentration index, C20,50. We further extract the stellar kinematics from CALIFA data cubes and analyse the radial velocity dispersion profile. The results of the different approaches are in good agreement and allow a safe classification for approximately 95% of the galaxies. In particular, we show that our new "inner" concentration index performs considerably better than the traditionally used C50,90 when yielding the nature of bulges. We also found that a combined use of this index and the Kormendy relation gives a very robust indication of the physical nature of the bulge.

Effects of De-spinning and Lithosphere Thickening on the Lunar Fossil Bulge

NASA Astrophysics Data System (ADS)

Zhong, S.; Qin, C.; Phillips, R. J.

2016-12-01

The Moon has abnormally large degree-2 anomalies in gravity and shape (or bulge). The degree-2 gravity coefficients C20 and C22 are, respectively, 22 and 7 times greater than expected from the Moon's current orbital and rotational states. One prevalent hypothesis, called the fossil bulge hypothesis, interprets the current degree-2 shape as a remnant of the bulge that froze in when the Moon was closer to the Earth with stronger tidal and rotational potentials. However, the dynamic feasibility of the freeze-in process has never been quantitatively examined. In this study, we explore, using numerical models of viscoelastic deformation with time-dependent rotational potential and lithospheric rheology, how the degree-2 bulge would evolve with time as the early Moon cools and migrates away from the Earth. Our model includes two competing effects: 1) a thickening lithosphere with time through cooling, which helps maintain the bulge, and 2) de-spinning through tidal locking, which tends to reduce the bulge. In our model, a strong lithosphere is represented by the topmost layer that is orders of magnitude more viscous than the mantle. The benchmark results show that our numerical model can compute the bulge size accurately. Our calculations start with a bulge size that is in hydrostatic equilibrium with the initial rotational rate. The bulge reduces with time as the Moon spins down, while the lithosphere can support certain amount of bulge as it thickens. We find that the final size of the bulge is controlled by the relative time scales of the two processes. At limiting cases, if the time scale of de-spinning were much larger than that of lithosphere thickening, the bulge size would be largely maintained. Conversely, the bulge size would be reduced significantly. We will consider more realistic time scales for these two processes, as well as effects of other subsequent processes after lunar magma ocean crystallization, such as large impacts and mare volcanism.

A Detailed Analysis of the Physical Conditions in the Infrared Dark Clouds in the Region IGGC 16/23

NASA Astrophysics Data System (ADS)

Scibelli, Samantha; Tolls, Volker

2017-01-01

There is an ongoing debate about why the star formation rate is low in the Galactic Center and Galactic Bar region of the Milky Way. Clump 2 is located at a distance of ~400 pc from the Galactic Center in the Galactic Bar region near the edge of the Central Molecular Zone (CMZ). Molecular clouds in this region are too distant to be influenced by the central black hole. However, despite of its location, Clump 2 is comprised of molecular clouds that show the same low star formation rate as those in the Galactic Center. Using Herschel PACS and SPIRE and APEX dust continuum emission data, our measurements indicate that cores in the IGGC 16/23 region have dust masses and densities comparable to those of more typical star-forming molecular clouds in the solar neighborhood. In addition, we analyzed Herschel HIFI high-J 12CO emission line observations supplemented by MOPRA molecular line observations. We find that the IGGC 16/23 region is composed of many smaller cores with different systemic velocities in the same line of sight advocating that additional analysis should be done to provide better constraints on the core sizes and masses to confirm that the core masses are below their virial masses and, thus, are not collapsing.The SAO REU program is funded in part by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant no. 1262851, and by the Smithsonian Institution.

Surprise: Dwarf Galaxy Harbors Supermassive Black Hole

NASA Astrophysics Data System (ADS)

2011-01-01

The surprising discovery of a supermassive black hole in a small nearby galaxy has given astronomers a tantalizing look at how black holes and galaxies may have grown in the early history of the Universe. Finding a black hole a million times more massive than the Sun in a star-forming dwarf galaxy is a strong indication that supermassive black holes formed before the buildup of galaxies, the astronomers said. The galaxy, called Henize 2-10, 30 million light-years from Earth, has been studied for years, and is forming stars very rapidly. Irregularly shaped and about 3,000 light-years across (compared to 100,000 for our own Milky Way), it resembles what scientists think were some of the first galaxies to form in the early Universe. "This galaxy gives us important clues about a very early phase of galaxy evolution that has not been observed before," said Amy Reines, a Ph.D. candidate at the University of Virginia. Supermassive black holes lie at the cores of all "full-sized" galaxies. In the nearby Universe, there is a direct relationship -- a constant ratio -- between the masses of the black holes and that of the central "bulges" of the galaxies, leading them to conclude that the black holes and bulges affected each others' growth. Two years ago, an international team of astronomers found that black holes in young galaxies in the early Universe were more massive than this ratio would indicate. This, they said, was strong evidence that black holes developed before their surrounding galaxies. "Now, we have found a dwarf galaxy with no bulge at all, yet it has a supermassive black hole. This greatly strengthens the case for the black holes developing first, before the galaxy's bulge is formed," Reines said. Reines, along with Gregory Sivakoff and Kelsey Johnson of the University of Virginia and the National Radio Astronomy Observatory (NRAO), and Crystal Brogan of the NRAO, observed Henize 2-10 with the National Science Foundation's Very Large Array radio telescope and with the Hubble Space Telescope. They found a region near the center of the galaxy that strongly emits radio waves with characteristics of those emitted by super-fast "jets" of material spewed outward from areas close to a black hole. They then searched images from the Chandra X-Ray Observatory that showed this same, radio-bright region to be strongly emitting energetic X-rays. This combination, they said, indicates an active, black-hole-powered, galactic nucleus. "Not many dwarf galaxies are known to have massive black holes," Sivakoff said. While central black holes of roughly the same mass as the one in Henize 2-10 have been found in other galaxies, those galaxies all have much more regular shapes. Henize 2-10 differs not only in its irregular shape and small size but also in its furious star formation, concentrated in numerous, very dense "super star clusters." "This galaxy probably resembles those in the very young Universe, when galaxies were just starting to form and were colliding frequently. All its properties, including the supermassive black hole, are giving us important new clues about how these black holes and galaxies formed at that time," Johnson said. The astronomers reported their findings in the January 9 online edition of Nature, and at the American Astronomical Society's meeting in Seattle, WA. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. More information, including images and other multimedia, can be found at: http://chandra.harvard.edu and http://chandra.nasa.gov

YOUNG STARS IN AN OLD BULGE: A NATURAL OUTCOME OF INTERNAL EVOLUTION IN THE MILKY WAY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ness, M.; Debattista, Victor P.; Cole, D. R.

2014-06-01

The center of our disk galaxy, the Milky Way, is dominated by a boxy/peanut-shaped bulge. Numerous studies of the bulge based on stellar photometry have concluded that the bulge stars are exclusively old. The perceived lack of young stars in the bulge strongly constrains its likely formation scenarios, providing evidence that the bulge is a unique population that formed early and separately from the disk. However, recent studies of individual bulge stars using the microlensing technique have reported that they span a range of ages, emphasizing that the bulge may not be a monolithic structure. In this Letter we demonstratemore » that the presence of young stars that are located predominantly nearer to the plane is expected for a bulge that has formed from the disk via dynamical instabilities. Using an N-body+ smoothed particle hydrodynamics simulation of a disk galaxy forming out of gas cooling inside a dark matter halo and forming stars, we find a qualitative agreement between our model and the observations of younger metal-rich stars in the bulge. We are also able to partially resolve the apparent contradiction in the literature between results that argue for a purely old bulge population and those that show a population comprised of a range in ages; the key is where to look.« less

A Pipeline for the Analysis of APOGEE Spectra Based on Equivalent Widths

NASA Astrophysics Data System (ADS)

Arfon Williams, Rob; Bosley, Corinne; Jones, Hayden; Schiavon, Ricardo P.; Allende-Prieto, Carlos; Bizyaev, Dmitry; Carrera, Ricardo; Cunha, Katia M. L.; Nguyen, Duy; Feuillet, Diane; Frinchaboy, Peter M.; García Pérez, Ana; Hasselquist, Sten; Hayden, Michael R.; Hearty, Fred R.; Holtzman, Jon A.; Johnson, Jennifer; Majewski, Steven R.; Meszaros, Szabolcs; Nidever, David L.; Shetrone, Matthew D.; Smith, Verne V.; Sobeck, Jennifer; Troup, Nicholas William; Wilson, John C.; Zasowski, Gail

2015-01-01

The Apache Point Galactic Evolution Experiment (APOGEE) forms part of the third Sloan Digital Sky Survey and has obtained high resolution, high signal-to-noise infrared spectra for ~1.3 x 105 stars across the galactic bulge, disc and halo. From these, stellar parameters are derived together with abundances for various elements using the APOGEE Stellar Parameters and Chemical Abundance Pipeline (ASPCAP). In this poster we report preliminary results from application of an alternative stellar parameters and abundances pipeline, based on measurements of equivalent widths of absorption lines in APOGEE spectra. The method is based on a sequential grid inversion algorithm, originally designed for the derivation of ages and elemental abundances of stellar populations from line indices in their integrated spectra. It allows for the rapid processing of large spectroscopic data sets from both current and future surveys, such as APOGEE and APOGEE 2, and it is easily adaptable for application to other very large data sets that are being/will be generated by other massive surveys of the stellar populations of the Galaxy. It will also allow the cross checking of ASPCAP results using an independent method. In this poster we present preliminary results showing estimates of effective temperature and iron abundance [Fe/H] for a subset of the APOGEE sample, comparing with DR12 numbers produced by the ASPCAP pipeline.

False-color image of the near-infrared sky as seen by the DIRBE

NASA Technical Reports Server (NTRS)

2002-01-01

False-color image of the near-infrared sky as seen by the DIRBE. Data at 1.25, 2.2, and 3.5 Aum wavelengths are represented respectively as blue, green and red colors. The image is presented in Galactic coordinates, with the plane of the Milky Way Galaxy horizontal across the middle and the Galactic center at the center. The dominant sources of light at these wavelengths are stars within our Galaxy. The image shows both the thin disk and central bulge populations of stars in our spiral galaxy. Our Sun, much closer to us than any other star, lies in the disk (which is why the disk appears edge-on to us) at a distance of about 28,000 light years from the center. The image is redder in directions where there is more dust between the stars absorbing starlight from distant stars. This absorption is so strong at visible wavelengths that the central part of the Milky Way cannot be seen. DIRBE data will facilitate studies of the content, energetics and large scale structure of the Galaxy, as well as the nature and distribution of dust within the Solar System. The data also will be studied for evidence of a faint, uniform infrared background, the residual radiation from the first stars and galaxies formed following the Big Bang.

Tiled Array of Pixelated CZT Imaging Detectors for ProtoEXIST2 and MIRAX-HXI

NASA Astrophysics Data System (ADS)

Hong, Jaesub; Allen, Branden; Grindlay, Jonathan; Rodrigues, Barbara; Ellis, Jon Robert; Baker, Robert; Barthelmy, Scott; Mao, Peter; Miyasaka, Hiromasa; Apple, Jeff

2013-12-01

We have assembled a tiled array (220 cm2) of fine pixel (0.6 mm) imaging CZT detectors for a balloon borne wide-field hard X-ray telescope, ProtoEXIST2. ProtoEXIST2 is a prototype experiment for a next generation hard X-ray imager MIRAX-HXI on board Lattes, a spacecraft from the Agencia Espacial Brasilieira. MIRAX will survey the 5 to 200 keV sky of Galactic bulge, adjoining southern Galactic plane and the extragalactic sky with 6 ' angular resolution. This survey will open a vast discovery space in timing studies of accretion neutron stars and black holes. The ProtoEXIST2 CZT detector plane consists of 64 of 5 mm thick 2 cm × 2 cm CZT crystals tiled with a minimal gap. MIRAX will consist of 4 such detector planes, each of which will be imaged with its own coded-aperture mask. We present the packaging architecture and assembly procedure of the ProtoEXIST2 detector. On 2012, Oct 10, we conducted a successful high altitude balloon experiment of the ProtoEXIST1 and 2 telescopes, which demonstrates their technology readiness for space application. During the flight both telescopes performed as well as on the ground. We report the results of ground calibration and the initial results for the detector performance in the balloon flight.

Spitzer Opens New Path to Break Classic Degeneracy for Jupiter-mass Microlensing Planet OGLE-2017-BLG-1140Lb

NASA Astrophysics Data System (ADS)

Calchi Novati, S.; Skowron, J.; Jung, Y. K.; Beichman, C.; Bryden, G.; Carey, S.; Gaudi, B. S.; Henderson, C. B.; Shvartzvald, Y.; Yee, J. C.; Zhu, W.; Spitzer Team; Udalski, A.; Szymański, M. K.; Mróz, P.; Poleski, R.; Soszyński, I.; Kozłowski, S.; Pietrukowicz, P.; Ulaczyk, K.; Pawlak, M.; Rybicki, K.; Iwanek, P.; OGLE Collaboration; Albrow, M. D.; Chung, S.-J.; Gould, A.; Han, C.; Hwang, K.-H.; Ryu, Y.-H.; Shin, I.-G.; Zang, W.; Cha, S.-M.; Kim, D.-J.; Kim, H.-W.; Kim, S.-L.; Lee, C.-U.; Lee, D.-J.; Lee, Y.; Park, B.-G.; Pogge, R. W.; KMTNet Collaboration

2018-06-01

We analyze the combined Spitzer and ground-based data for OGLE-2017-BLG-1140 and show that the event was generated by a Jupiter-class ({m}p≃ 1.6 {M}{{J}{{u}}{{p}}}) planet orbiting a mid-late M dwarf (M≃ 0.2 {M}ȯ ) that lies {D}LS}≃ 1.0 {kpc} in the foreground of the microlensed Galactic-bar source star. The planet–host projected separation is {a}\\perp ≃ 1.0 {au}, i.e., well beyond the snow line. By measuring the source proper motion {{\\boldsymbol{μ }}}s from ongoing long-term OGLE imaging and combining this with the lens-source relative proper motion {{\\boldsymbol{μ }}}rel} derived from the microlensing solution, we show that the lens proper motion {{\\boldsymbol{μ }}}l={{\\boldsymbol{μ }}}rel}+{{\\boldsymbol{μ }}}s is consistent with the lens lying in the Galactic disk, although a bulge lens is not ruled out. We show that while the Spitzer and ground-based data are comparably well fitted by planetary (i.e., binary-lens (2L1S)) and binary-source (1L2S) models, the combination of Spitzer and ground-based data decisively favors the planetary model. This is a new channel to resolve the 2L1S/1L2S degeneracy, which can be difficult to break in some cases.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gaggero, Daniele; Urbano, Alfredo; Valli, Mauro

We compute the γ-ray and neutrino diffuse emission of the Galaxy on the basis of a recently proposed phenomenological model characterized by radially dependent cosmic-ray (CR) transport properties. We show how this model, designed to reproduce both Fermi-LAT γ-ray data and local CR observables, naturally reproduces the anomalous TeV diffuse emission observed by Milagro in the inner Galactic plane. Above 100 TeV our picture predicts a neutrino flux that is about five (two) times larger than the neutrino flux computed with conventional models in the Galactic Center region (full-sky). Explaining in that way up to ∼25% of the flux measuredmore » by IceCube, we reproduce the full-sky IceCube spectrum adding an extra-Galactic component derived from the muonic neutrinos flux in the northern hemisphere. We also present precise predictions for the Galactic plane region where the flux is dominated by the Galactic emission.« less

Why are classical bulges more common in S0 galaxies than in spiral galaxies?

NASA Astrophysics Data System (ADS)

Mishra, Preetish K.; Wadadekar, Yogesh; Barway, Sudhanshu

2018-05-01

In this paper, we try to understand why the classical bulge fraction observed in S0 galaxies is significantly higher than that in spiral galaxies. We carry out a comparative study of the bulge and global properties of a sample of spiral and S0 galaxies in a fixed environment. Our sample is flux limited and contains 262 spiral and 155 S0 galaxies drawn from the Sloan Digital Sky Survey. We have classified bulges into classical and pseudobulge categories based on their position on the Kormendy diagram. Dividing our sample into bins of galaxy stellar mass, we find that the fraction of S0 galaxies hosting a classical bulge is significantly higher than the classical bulge fraction seen in spirals even at fixed stellar mass. We have compared the bulge and the global properties of spirals and S0 galaxies in our sample and find indications that spiral galaxies which host a classical bulge, preferentially get converted into S0 population as compared to pseudobulge hosting spirals. By studying the star formation properties of our galaxies in the NUV - r color-mass diagram, we find that the pseudobulge hosting spirals are mostly star forming while the majority of classical bulge host spirals are in the green valley or in the passive sequence. We suggest that some internal process, such as AGN feedback or morphological quenching due to the massive bulge, quenches these classical bulge hosting spirals and transforms them into S0 galaxies, thus resulting in the observed predominance of the classical bulge in S0 galaxies.

Bright Compact Bulges (BCBs) at intermediate redshifts

NASA Astrophysics Data System (ADS)

Sachdeva, Sonali; Saha, Kanak

2018-04-01

Studying bright (MB < -20), intermediate-redshift (0.4 < z < 1.0), disc dominated (nB < 2.5) galaxies from HST/ACS and WFC3 in Chandra Deep Field South, in rest-frame B and I-band, we found a new class of bulges which is brighter and more compact than ellipticals. We refer to them as "Bright, Compact Bulges" (BCBs) - they resemble neither classical nor pseudo-bulges and constitute ˜12% of the total bulge population at these redshifts. Examining free-bulge + disc decomposition sample and elliptical galaxy sample from Simard et al. (2011), we find that only ˜0.2% of the bulges can be classified as BCBs in the local Universe. Bulge to total ratio (B/T) of disc galaxies with BCBs is (at ˜0.4) a factor of ˜2 and ˜4 larger than for those with classical and pseudo bulges. BCBs are ˜2.5 and ˜6 times more massive than classical and pseudo bulges. Although disc galaxies with BCBs host the most massive and dominant bulge type, their specific star formation rate is 1.5-2 times higher than other disc galaxies. This is contrary to the expectations that a massive compact bulge would lead to lower star formation rates. We speculate that our BCB host disc galaxies are descendant of massive, compact and passive elliptical galaxies observed at higher redshifts. Those high redshift ellipticals lack local counterparts and possibly evolved by acquiring a compact disc around them. The overall properties of BCBs supports a picture of galaxy assembly in which younger discs are being accreted around massive pre-existing spheroids.

A study of the effect of bulges on bar formation in disc galaxies

NASA Astrophysics Data System (ADS)

Kataria, Sandeep Kumar; Das, Mousumi

2018-04-01

We use N-body simulations of bar formation in isolated galaxies to study the effect of bulge mass and bulge concentration on bar formation. Bars are global disc instabilities that evolve by transferring angular momentum from the inner to outer discs and to the dark matter halo. It is well known that a massive spherical component such as halo in a disc galaxy can make it bar stable. In this study, we explore the effect of another spherical component, the bulge, on bar formation in disc galaxies. In our models, we vary both the bulge mass and concentration. We have used two sets of models: one that has a dense bulge and high surface density disc, and the other model has a less concentrated bulge and a lighter disc. In both models, we vary the bulge to disc mass fraction from 0 to 0.7. Simulations of both the models show that there is an upper cut-off in bulge-to-disc mass ratio Mb/Md above which bars cannot form; the cut-off is smaller for denser bulges (Mb/Md = 0.2) compared to less denser ones (Mb/Md = 0.5). We define a new criterion for bar formation in terms of the ratio of bulge to total radial force (Fb/Ftot) at the disc scale lengths above which bars cannot form. We find that if Fb/Ftot > 0.35, a disc is stable and a bar cannot form. Our results indicate that early-type disc galaxies can still form strong bars in spite of having massive bulges.

From a structural average to the conformational ensemble of a DNA bulge

PubMed Central

Shi, Xuesong; Beauchamp, Kyle A.; Harbury, Pehr B.; Herschlag, Daniel

2014-01-01

Direct experimental measurements of conformational ensembles are critical for understanding macromolecular function, but traditional biophysical methods do not directly report the solution ensemble of a macromolecule. Small-angle X-ray scattering interferometry has the potential to overcome this limitation by providing the instantaneous distance distribution between pairs of gold-nanocrystal probes conjugated to a macromolecule in solution. Our X-ray interferometry experiments reveal an increasing bend angle of DNA duplexes with bulges of one, three, and five adenosine residues, consistent with previous FRET measurements, and further reveal an increasingly broad conformational ensemble with increasing bulge length. The distance distributions for the AAA bulge duplex (3A-DNA) with six different Au-Au pairs provide strong evidence against a simple elastic model in which fluctuations occur about a single conformational state. Instead, the measured distance distributions suggest a 3A-DNA ensemble with multiple conformational states predominantly across a region of conformational space with bend angles between 24 and 85 degrees and characteristic bend directions and helical twists and displacements. Additional X-ray interferometry experiments revealed perturbations to the ensemble from changes in ionic conditions and the bulge sequence, effects that can be understood in terms of electrostatic and stacking contributions to the ensemble and that demonstrate the sensitivity of X-ray interferometry. Combining X-ray interferometry ensemble data with molecular dynamics simulations gave atomic-level models of representative conformational states and of the molecular interactions that may shape the ensemble, and fluorescence measurements with 2-aminopurine-substituted 3A-DNA provided initial tests of these atomistic models. More generally, X-ray interferometry will provide powerful benchmarks for testing and developing computational methods. PMID:24706812

Alba Patera

NASA Image and Video Library

1998-06-08

A color image of the Alba Patera region of Mars; north toward top. The scene shows a central circular depression surrounded by splays of fractures, named Alba Fossae (west of Alba Patera) and Tantalus Fossae (east of Alba Patera). A patera (Latin for shallow dish or saucer) is a volcano of broad areal extent with little vertical relief; a fossa is a linear depression. This image is a composite of Viking medium-resolution images in black and white and low-resolution images in color. The image extends from latitude 30 degrees N. to 50 degrees N. and from longitude 95 degrees to 125 degrees; Lambert projection. Alba Patera has a 100-km-diameter caldera at its center surrounded by a fracture ring. In total, the approximately 1,200- km-diameter Alba Patera far exceeds any other known volcano in areal extent; it covers eight times the area of Olympus Mons (the highest volcano in the Solar System) but reaches only about 6 km in height. The patera lies directly north of the Tharsis bulge, which encompasses the most intensely and most recently active volcanic region of the planet. The fossae of the Alba area are fault-bound graben that can be traced south through the Tharsis bulge and therefore likely formed by upwarping of the Tharsis bulge as well as the coeval upwelling of Alba Pateria magma. http://photojournal.jpl.nasa.gov/catalog/PIA00409

Detection of sulfur in the galactic center

NASA Technical Reports Server (NTRS)

Herter, T.; Briotta, D. A., Jr.; Gull, G. E.; Shure, M. A.; Houck, J. R.

1983-01-01

A strong detection at the S III forbidden 18.71 micron line is reported for the galactic center region, Sgr A West. A line flux of 1.7 + or - 0.2 x 10 to the -17th W/sq cm is found for a 20 inch beam size measurement centered on IRS 1. A preliminary analysis indicates that the S III abundance relative to hydrogen is consistent with the cosmic abundance of sulfur, 0.000016, if a filling factor of unity within the known clumps is assumed. However, the sulfur abundance in the galactic center may be as much as a factor of 3 overabundant if a filling factor of 0.03 is adopted, a value found to hold for some galactic H II regions.

An Infrared Survey of the Diffuse Emission within 5 deg of the Galactic Plane.

DTIC Science & Technology

1980-06-05

t O ±60. Over the region of 100 to 3 0 oi longitude along the galactic equator, this emission can be fit by 500( K black -body emission with a dilution...from the AFGL catalog, which they classify as stars. The assumed background is, therefore, composed of black -body radiators with a characteristic...SUPPLEMENTARY NOTES 19 KEY WORDS (c-nIIl, ,l IY ,I. AIIId-1, hI MI’< A III-15SI, Infra red Diffuse emission Galactic structure 1111 regions yI 40