The black hole candidate XTE J1752-223 towards and in quiescence: optical and simultaneous X-ray-radio observations

NASA Astrophysics Data System (ADS)

Ratti, E. M.; Jonker, P. G.; Miller-Jones, J. C. A.; Torres, M. A. P.; Homan, J.; Markoff, S.; Tomsick, J. A.; Kaaret, P.; Wijnands, R.; Gallo, E.; Özel, F.; Steeghs, D. T. H.; Fender, R. P.

2012-07-01

We present optical, X-ray and radio observations of the black hole transient (BHT) XTE J1752-223 towards and in quiescence. Optical photometry shows that the quiescent magnitude of XTE J1752-223 is fainter than 24.4 mag in the i' band. A comparison with measurements of the source during its 2009-2010 outburst shows that the outburst amplitude is more than 8 mag in the i' band. Known X-ray properties of the source combined with the faintness of the quiescence optical counterpart and the large outburst optical amplitude point towards a short orbital-period system (Porb≲ 6.8 h) with an M type (or later) mass donor, at a distance of 3.5 ≲d≲ 8 kpc. Simultaneous X-ray and radio data were collected with Chandra and the Expanded Very Large Array (EVLA), allowing constraints to be placed on the quiescent X-ray and radio flux of XTE J1752-223. Furthermore, using data covering the final stage of the outburst decay, we investigated the low-luminosity end of the X-ray-radio correlation for this source and compared it with other BHTs. We found that XTE J1752-223 adds to the number of outliers with respect to the 'standard' X-ray-radio luminosity relation. Furthermore, XTE J1752-223 is the second source, after the BHT H1743-322, that shows a transition from the region of the outliers towards the 'standard' correlation at low luminosity. Finally, we report on a faint, variable X-ray source we discovered with Chandra at an angular distance of ˜2.9 arcsec to XTE J1752-223 and at a position angle consistent with that of the radio jets previously observed from the BHT. We discuss the possibility that we detected X-ray emission associated with a jet from XTE J1752-223.

The effects of correlated noise in phased-array observations of radio sources

NASA Technical Reports Server (NTRS)

Dewey, Rachel J.

1994-01-01

Arrays of radio telescopes are now routinely used to provide increased signal-to-noise when observing faint point sources. However, calculation of the achievable sensitivity is complicated if there are sources in the field of view other than the target source. These additional sources not only increase the system temperatures of the individual antennas, but may also contribute significant 'correlated noise' to the effective system temperature of the array. This problem has been of particular interest in the context of tracking spacecraft in the vicinity of radio-bright planets (e.g., Galileo at Jupiter), but it has broader astronomical relevance as well. This paper presents a general formulation of the problem, for the case of a point-like target source in the presence of an additional radio source of arbitrary brightness distribution. We re-derive the well known result that, in the absence of any background sources, a phased array of N indentical antennas is a factor of N more sensitive than a single antenna. We also show that an unphased array of N identical antennas is, on average, no more sensitive than a single antenna if the signals from the individual antennas are combined prior to detection. In the case where a background source is present we show that the effects of correlated noise are highly geometry dependent, and for some astronomical observations may cause significant fluctuations in the array's effective system temperature.

Infrared Faint Radio Sources in the Extended Chandra Deep Field South

NASA Astrophysics Data System (ADS)

Huynh, Minh T.

2009-01-01

Infrared-Faint Radio Sources (IFRSs) are a class of radio objects found in the Australia Telescope Large Area Survey (ATLAS) which have no observable counterpart in the Spitzer Wide-area Infrared Extragalactic Survey (SWIRE). The extended Chandra Deep Field South now has even deeper Spitzer imaging (3.6 to 70 micron) from a number of Legacy surveys. We report the detections of two IFRS sources in IRAC images. The non-detection of two other IFRSs allows us to constrain the source type. Detailed modeling of the SED of these objects shows that they are consistent with high redshift AGN (z > 2).

A Tale of Two Faint Bursts: GRB 050223 and GRB 050911

NASA Astrophysics Data System (ADS)

Page, K. L.; Barthelmy, S. D.; Beardmore, A. P.; Burrows, D. N.; Campana, S.; Chincharini, G.; Cummings, J. R.; Cusumano, G.; Gehrels, N.; Giommi, P.; Goad, M. R.; Godet, O.; Graham, J.; Kaneko, Y.; Kennea, J. A.; Mangano, V.; Markwardt, C. B.; O'Brien, P. T.; Osborne, J. P.; Reichart, D. E.; Rol, E.; Sakamoto, T.; Tagliaferri, G.; Tanvir, N. R.; Wells, A. A.; Zhang, B.

2006-05-01

GRBs 050223 and 050911 were discovered by the Swift Burst Alert Telescope (BAT) on 23rd February and 11th September 2005 respectively. The observation of GRB 050223 showed a faint, fading X-ray source, which was identified as the afterglow; GRB 050911, however, was not detected, making any X-ray afterglow extremely faint. The faintness of the afterglow of GRB 050223 could be explained by a large opening or viewing angle, or by the burst being at high redshift. The non-detection of GRB 050911 may indicate the burst occurred in a low-density environment, or, alternatively, was due to a compact object merger, in spite of the apparent long duration of the burst.

SELFI: an object-based, Bayesian method for faint emission line source detection in MUSE deep field data cubes

NASA Astrophysics Data System (ADS)

Meillier, Céline; Chatelain, Florent; Michel, Olivier; Bacon, Roland; Piqueras, Laure; Bacher, Raphael; Ayasso, Hacheme

2016-04-01

We present SELFI, the Source Emission Line FInder, a new Bayesian method optimized for detection of faint galaxies in Multi Unit Spectroscopic Explorer (MUSE) deep fields. MUSE is the new panoramic integral field spectrograph at the Very Large Telescope (VLT) that has unique capabilities for spectroscopic investigation of the deep sky. It has provided data cubes with 324 million voxels over a single 1 arcmin2 field of view. To address the challenge of faint-galaxy detection in these large data cubes, we developed a new method that processes 3D data either for modeling or for estimation and extraction of source configurations. This object-based approach yields a natural sparse representation of the sources in massive data fields, such as MUSE data cubes. In the Bayesian framework, the parameters that describe the observed sources are considered random variables. The Bayesian model leads to a general and robust algorithm where the parameters are estimated in a fully data-driven way. This detection algorithm was applied to the MUSE observation of Hubble Deep Field-South. With 27 h total integration time, these observations provide a catalog of 189 sources of various categories and with secured redshift. The algorithm retrieved 91% of the galaxies with only 9% false detection. This method also allowed the discovery of three new Lyα emitters and one [OII] emitter, all without any Hubble Space Telescope counterpart. We analyzed the reasons for failure for some targets, and found that the most important limitation of the method is when faint sources are located in the vicinity of bright spatially resolved galaxies that cannot be approximated by the Sérsic elliptical profile. The software and its documentation are available on the MUSE science web service (muse-vlt.eu/science).

The little Galaxies that could (reionize the universe): predicting faint end slopes & escape fractions at z>4

NASA Astrophysics Data System (ADS)

Anderson, Lauren; Governato, F.; Karcher, M.; Quinn, T.; Wadsley, J.

2017-07-01

The sources that reionized the universe are still unknown, but likely candidates are faint but numerous galaxies. In this paper, we present results from running a high-resolution, uniform volume simulation, the Vulcan, to predict the number densities of undetectable, faint galaxies and their escape fractions of ionizing radiation, fesc, during reionization. Our approach combines a high spatial resolution, a realistic treatment of feedback and hydroprocesses, a strict threshold for minimum number of resolution elements per galaxy, and a converged measurement of fesc. We calibrate our physical model using a novel approach to create realistic galaxies at z = 0, so the simulation is predictive at high redshifts. With this approach, we can (1) robustly predict the evolution of the galaxy UV luminosity function at faint magnitudes down to MUV ˜ -15, two magnitudes fainter than observations, and (2) estimate fesc over a large range of galaxy masses based on the detailed stellar and gas distributions in resolved galaxies. We find steep faint end slopes, implying high number densities of faint galaxies, and the dependence of fesc on the UV magnitude of a galaxy, given by the power law: log fesc = (0.51 ± 0.04)MUV + 7.3 ± 0.8, with the faint population having fesc ˜ 35 per cent. Convolving the UV luminosity function with fesc(MUV), we find an ionizing emissivity that is (1) dominated by the faintest galaxies and (2) reionizes the universe at the appropriate rate, consistent with observational constraints of the ionizing emissivity and the optical depth to the decoupling surface τes, without the need for additional sources of ionizing radiation.

AzTEC/ASTE 1.1 mm Deep Surveys: Number Counts and Clustering of Millimeter-bright Galaxies

NASA Astrophysics Data System (ADS)

Hatsukade, B.; Kohno, K.; Aretxaga, I.; Austermann, J. E.; Ezawa, H.; Hughes, D. H.; Ikarashi, S.; Iono, D.; Kawabe, R.; Matsuo, H.; Matsuura, S.; Nakanishi, K.; Oshima, T.; Perera, T.; Scott, K. S.; Shirahata, M.; Takeuchi, T. T.; Tamura, Y.; Tanaka, K.; Tosaki, T.; Wilson, G. W.; Yun, M. S.

2010-10-01

We present number counts and clustering properties of millimeter-bright galaxies uncovered by the AzTEC camera mounted on the Atacama Submillimeter Telescope Experiment (ASTE). We surveyed the AKARI Deep Field South (ADF-S), the Subaru/XMM Newton Deep Field (SXDF), and the SSA22 fields with an area of ~0.25 deg2 each with an rms noise level of ~0.4-1.0 mJy. We constructed differential and cumulative number counts, which provide currently the tightest constraints on the faint end. The integration of the best-fit number counts in the ADF-S find that the contribution of 1.1 mm sources with fluxes >=1 mJy to the cosmic infrared background (CIB) at 1.1 mm is 12-16%, suggesting that the large fraction of the CIB originates from faint sources of which the number counts are not yet constrained. We estimate the cosmic star-formation rate density contributed by 1.1 mm sources with >=1 mJy using the best-fit number counts in the ADF-S and find that it is lower by about a factor of 5-10 compared to those derived from UV/optically-selected galaxies at z~2-3. The average mass of dark halos hosting bright 1.1 mm sources was calculated to be 1013-1014 Msolar. Comparison of correlation lengths of 1.1 mm sources with other populations and with a bias evolution model suggests that dark halos hosting bright 1.1 mm sources evolve into systems of clusters at present universe and the 1.1 mm sources residing the dark halos evolve into massive elliptical galaxies located in the center of clusters.

Do the enigmatic ``Infrared-Faint Radio Sources'' include pulsars?

NASA Astrophysics Data System (ADS)

Hobbs, George; Middelberg, Enno; Norris, Ray; Keith, Michael; Mao, Minnie; Champion, David

2009-04-01

The Australia Telescope Large Area Survey (ATLAS) team have surveyed seven square degrees of sky at 1.4GHz. During processing some unexpected infrared-faint radio sources (IFRS sources) were discovered. The nature of these sources is not understood, but it is possible that some of these sources may be pulsars within our own galaxy. We propose to observe the IFRS sources with steep spectral indices using standard search techniques to determine whether or not they are pulsars. A pulsar detection would 1) remove a subset of the IFRS sources from the ATLAS sample so they would not need to be observed with large optical/IR telescopes to find their hosts and 2) be intrinsically interesting as the pulsar would be a millisecond pulsar and/or have an extreme spatial velocity.

A high-significance measurement of correlation between unresolved IRAS sources and optically-selected galaxy clusters

NASA Astrophysics Data System (ADS)

Hincks, Adam D.; Hajian, Amir; Addison, Graeme E.

2013-05-01

We cross-correlate the 100 μm Improved Reprocessing of the IRAS Survey (IRIS) map and galaxy clusters at 0.1 < z < 0.3 in the maxBCG catalogue taken from the Sloan Digital Sky Survey, measuring an angular cross-power spectrum over multipole moments 150 < l < 3000 at a total significance of over 40σ. The cross-spectrum, which arises from the spatial correlation between unresolved dusty galaxies that make up the cosmic infrared background (CIB) in the IRIS map and the galaxy clusters, is well-fit by a single power law with an index of -1.28±0.12, similar to the clustering of unresolved galaxies from cross-correlating far-infrared and submillimetre maps at longer wavelengths. Using a recent, phenomenological model for the spectral and clustering properties of the IRIS galaxies, we constrain the large-scale bias of the maxBCG clusters to be 2.6±1.4, consistent with existing analyses of the real-space cluster correlation function. The success of our method suggests that future CIB-optical cross-correlations using Planck and Herschel data will significantly improve our understanding of the clustering and redshift distribution of the faint CIB sources.

Alternative light source (polilight) illumination with digital image analysis does not assist in determining the age of bruises.

PubMed

Hughes, V K; Ellis, P S; Langlois, N E I

2006-05-10

The age of a bruise may be of interest to forensic investigators. Previous research has demonstrated that an alternative light source may assist in the visualisation of faint or non-visible bruises. This project aimed to determine if an alternative light source could be utilised to assist investigators estimate the age of a bruise. Forty braises, sustained from blunt force trauma, were examined from 30 healthy subjects. The age of the bruises ranged from 2 to 231 h (mean = 74.6, median = 69.0). Alternative light source (polilight) illumination at 415 and 450 nm was used. The black and white photographs obtained were assessed using densitometry. A statistical analysis indicated that there was no correlation between time and the mean densitometry values. The alternative light source used in this study was unable to assist in determining the age of a bruise.

OPTICAL–INFRARED PROPERTIES OF FAINT 1.3 mm SOURCES DETECTED WITH ALMA

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

Hatsukade, Bunyo; Yabe, Kiyoto; Ohta, Kouji

2015-09-10

We report optical-infrared (IR) properties of faint 1.3 mm sources (S{sub 1.3mm} = 0.2–1.0 mJy) detected with the Atacama Large Millimeter/submillimeter Array (ALMA) in the Subaru/XMM-Newton Deep Survey field. We searched for optical/IR counterparts of eight ALMA-detected sources (≥4.0σ, the sum of the probability of spurious source contamination is ∼1) in a K-band source catalog. Four ALMA sources have K-band counterpart candidates within a 0.″4 radius. Comparison between ALMA-detected and undetected K-band sources in the same observing fields shows that ALMA-detected sources tend to be brighter, more massive, and more actively forming stars. While many of the ALMA-identified submillimeter-bright galaxiesmore » (SMGs) in previous studies lie above the sequence of star-forming galaxies in the stellar mass–star formation rate plane, our ALMA sources are located in the sequence, suggesting that the ALMA-detected faint sources are more like “normal” star-forming galaxies rather than “classical” SMGs. We found a region where multiple ALMA sources and K-band sources reside in a narrow photometric redshift range (z ∼ 1.3–1.6) within a radius of 5″ (42 kpc if we assume z = 1.45). This is possibly a pre-merging system and we may be witnessing the early phase of formation of a massive elliptical galaxy.« less

Evidence for Infrared-faint Radio Sources as z > 1 Radio-loud Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Huynh, Minh T.; Norris, Ray P.; Siana, Brian; Middelberg, Enno

2010-02-01

Infrared-Faint Radio Sources (IFRSs) are a class of radio objects found in the Australia Telescope Large Area Survey which have no observable mid-infrared counterpart in the Spitzer Wide-area Infrared Extragalactic (SWIRE) survey. The extended Chandra Deep Field South now has even deeper Spitzer imaging (3.6-70 μm) from a number of Legacy surveys. We report the detections of two IFRS sources in IRAC images. The non-detection of two other IFRSs allows us to constrain the source type. Detailed modeling of the spectral energy distribution of these objects shows that they are consistent with high-redshift (z >~ 1) active galactic nuclei.

EVIDENCE FOR INFRARED-FAINT RADIO SOURCES AS z > 1 RADIO-LOUD ACTIVE GALACTIC NUCLEI

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

Huynh, Minh T.; Norris, Ray P.; Siana, Brian

2010-02-10

Infrared-Faint Radio Sources (IFRSs) are a class of radio objects found in the Australia Telescope Large Area Survey which have no observable mid-infrared counterpart in the Spitzer Wide-area Infrared Extragalactic (SWIRE) survey. The extended Chandra Deep Field South now has even deeper Spitzer imaging (3.6-70 {mu}m) from a number of Legacy surveys. We report the detections of two IFRS sources in IRAC images. The non-detection of two other IFRSs allows us to constrain the source type. Detailed modeling of the spectral energy distribution of these objects shows that they are consistent with high-redshift (z {approx}> 1) active galactic nuclei.

The correlation between malaria RDT (Paracheck pf.®) faint test bands and microscopy in the diagnosis of malaria in Malawi.

PubMed

Makuuchi, Ryoko; Jere, Sandy; Hasejima, Nobuchika; Chigeda, Thoms; Gausi, January

2017-05-02

Faint test bands of Paracheck Pf.® are interpreted as malaria positive according to world health organization (WHO) guideline. However if there are conspicuous number of faint test bands, a performance of Paracheck Pf.® could be influenced depending on whether interpreting faint test bands as malaria positive or negative. Finding out the frequency and accurate interpretation of faint test bands are important to prevent the overdiagnosis and drug resistance. A cross-sectional, descriptive study was conducted to find out the frequency of faint test bands and evaluate the performance of Paracheck Pf.® by sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of diagnosis of Paracheck Pf.® using microscopy as the gold standard. 388 suspected patients with malaria in Malawi were recruited in this study. Malaria rapid diagnostic tests (RDTs) and microscopy were used and patients' information which includes age, sex, body temperature and signs or symptoms of malaria were recorded. Among all patients involved in the study, 29.1% (113/388) were found malaria positive by RDT. Overall 5.4% (21/388) of all Paracheck Pf.® tests resulted in a "faint test band" and 85.7% (18/21) corresponded with malaria negative by microscopy. Faint test bands which corresponded with malaria positive by microscopy were lower parasite density and there are no patients who showed definitive symptom of malaria, such as fever. When Paracheck Pf.® "faint test bands" were classified as positive, accuracy of diagnosis was 76.5% (95% CI 72%-80.7%) as compared to 80.4% (95% CI 76.1%-84.2%) when Paracheck Pf.® "faint test bands" were classified as negative. This study shows that frequency of faint test bands is 5.4% in all malaria RDTs. The accuracy of diagnosis was improved when faint test bands were interpreted as malaria negative. However information and data obtained in this study may not be enough and more intensive research including a frequency and property of faint test bands is needed for significant interpretation of faint test bands.

Are the infrared-faint radio sources pulsars?

NASA Astrophysics Data System (ADS)

Cameron, A. D.; Keith, M.; Hobbs, G.; Norris, R. P.; Mao, M. Y.; Middelberg, E.

2011-07-01

Infrared-faint radio sources (IFRS) are objects which are strong at radio wavelengths but undetected in sensitive Spitzer observations at infrared wavelengths. Their nature is uncertain and most have not yet been associated with any known astrophysical object. One possibility is that they are radio pulsars. To test this hypothesis we undertook observations of 16 of these sources with the Parkes Radio Telescope. Our results limit the radio emission to a pulsed flux density of less than 0.21 mJy (assuming a 50 per cent duty cycle). This is well below the flux density of the IFRS. We therefore conclude that these IFRS are not radio pulsars.

A NEW RESULT ON THE ORIGIN OF THE EXTRAGALACTIC GAMMA-RAY BACKGROUND

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

Zhou Ming; Wang Jiancheng, E-mail: mzhou@ynao.ac.cn

2013-06-01

In this paper, we repeatedly use the method of image stacking to study the origin of the extragalactic gamma-ray background (EGB) at GeV bands, and find that the Faint Images of the Radio Sky at Twenty centimeters (FIRST) sources undetected by the Large Area Telescope on the Fermi Gamma-ray Space Telescope can contribute about (56 {+-} 6)% of the EGB. Because FIRST is a flux-limited sample of radio sources with incompleteness at the faint limit, we consider that point sources, including blazars, non-blazar active galactic nuclei, and starburst galaxies, could produce a much larger fraction of the EGB.

Constraining the Milky Way's Faint HMXB Population Using Archival Data

NASA Astrophysics Data System (ADS)

Tomsick, John

2017-09-01

In the first 40 months of sensitive hard X-ray observations with the Nuclear Spectroscopic Telescope Array, nearly 500 sources have been detected serendipitously. While the effort to determine the nature of these sources has been very successful at high Galactic latitudes, identifications close to the Galactic plane have been more difficult because of source crowding and optical extinction. Only six 8-24 keV sources within 5 deg of the plane have been classified, and two of them are High-Mass X-ray Binaries (HMXBs), leaving open the possibility of a large population of faint HMXBs. We propose an archival study of 13 unclassified sources, including obtaining subarcsecond positions, which, along with joint near-IR imaging, will be used to find counterparts and determine their nature.

CROSS-CORRELATION OF NEAR- AND FAR-INFRARED BACKGROUND ANISOTROPIES AS TRACED BY SPITZER AND HERSCHEL

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

Thacker, Cameron; Gong, Yan; Cooray, Asantha

We present the cross-correlation between the far-infrared (far-IR) background fluctuations as measured with the Herschel Space Observatory at 250, 350, and 500 μm and the near-infrared (near-IR) background fluctuations with the Spitzer Space Telescope at 3.6 and 4.5 μm. The cross-correlation between the FIR and NIR background anisotropies is detected such that the correlation coefficient at a few to 10 arcminute angular scale decreases from 0.3 to 0.1 when the FIR wavelength increases from 250 to 500 μm. We model the cross-correlation using a halo model with three components: (a) FIR bright or dusty star-forming galaxies below the masking depth inmore » Herschel maps, (b) NIR faint galaxies below the masking depth, and (c) intra-halo light (IHL), or diffuse stars in dark matter halos, that is likely dominating the large-scale NIR fluctuations. The model is able to reasonably reproduce the auto-correlations at each of the FIR wavelengths and at 3.6 μm and their corresponding cross-correlations. While the FIR and NIR auto-correlations are dominated by faint, dusty, star-forming galaxies and IHL, respectively, we find that roughly half of the cross-correlation between the NIR and FIR backgrounds is due to the same dusty galaxies that remain unmasked at 3.6 μm. The remaining signal in the cross-correlation is due to IHL present in the same dark matter halos as those hosting the same faint and unmasked galaxies.« less

Chandra ACIS Sub-pixel Resolution

NASA Astrophysics Data System (ADS)

Kim, Dong-Woo; Anderson, C. S.; Mossman, A. E.; Allen, G. E.; Fabbiano, G.; Glotfelty, K. J.; Karovska, M.; Kashyap, V. L.; McDowell, J. C.

2011-05-01

We investigate how to achieve the best possible ACIS spatial resolution by binning in ACIS sub-pixel and applying an event repositioning algorithm after removing pixel-randomization from the pipeline data. We quantitatively assess the improvement in spatial resolution by (1) measuring point source sizes and (2) detecting faint point sources. The size of a bright (but no pile-up), on-axis point source can be reduced by about 20-30%. With the improve resolution, we detect 20% more faint sources when embedded on the extended, diffuse emission in a crowded field. We further discuss the false source rate of about 10% among the newly detected sources, using a few ultra-deep observations. We also find that the new algorithm does not introduce a grid structure by an aliasing effect for dithered observations and does not worsen the positional accuracy

Faint submillimeter galaxies revealed by multifield deep ALMA observations: number counts, spatial clustering, and a dark submillimeter line emitter

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

Ono, Yoshiaki; Ouchi, Masami; Momose, Rieko

2014-11-01

We present the statistics of faint submillimeter/millimeter galaxies (SMGs) and serendipitous detections of a submillimeter/millimeter line emitter (SLE) with no multi-wavelength continuum counterpart revealed by the deep ALMA observations. We identify faint SMGs with flux densities of 0.1-1.0 mJy in the deep Band-6 and Band-7 maps of 10 independent fields that reduce cosmic variance effects. The differential number counts at 1.2 mm are found to increase with decreasing flux density down to 0.1 mJy. Our number counts indicate that the faint (0.1-1.0 mJy, or SFR{sub IR} ∼ 30-300 M {sub ☉} yr{sup –1}) SMGs contribute nearly a half of themore » extragalactic background light (EBL), while the remaining half of the EBL is mostly contributed by very faint sources with flux densities of <0.1 mJy (SFR{sub IR} ≲ 30 M {sub ☉} yr{sup –1}). We conduct counts-in-cells analysis with multifield ALMA data for the faint SMGs, and obtain a coarse estimate of galaxy bias, b {sub g} < 4. The galaxy bias suggests that the dark halo masses of the faint SMGs are ≲ 7 × 10{sup 12} M {sub ☉}, which is smaller than those of bright (>1 mJy) SMGs, but consistent with abundant high-z star-forming populations, such as sBzKs, LBGs, and LAEs. Finally, we report the serendipitous detection of SLE-1, which has no continuum counterparts in our 1.2 mm-band or multi-wavelength images, including ultra deep HST/WFC3 and Spitzer data. The SLE has a significant line at 249.9 GHz with a signal-to-noise ratio of 7.1. If the SLE is not a spurious source made by the unknown systematic noise of ALMA, the strong upper limits of our multi-wavelength data suggest that the SLE would be a faint galaxy at z ≳ 6.« less

A LARGE AND FAINT PHOTOMETRIC CATALOG ON THE ECLIPTIC

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

Buie, Marc W.; Trilling, David E.; Wasserman, Lawrence H.

2011-06-01

A photometric catalog, developed for the calibration of the Deep Ecliptic Survey, is presented. The catalog contains 213,272 unique sources that were measured in V and R filters and transformed to the Johnson-Cousins systems using the Landolt standard catalog. All of the sources lie within 6{sup 0} of the ecliptic and cover all longitudes except for the densest stellar regions nearest the galactic center. Seventeen percent of the sources in the catalog are derived from three or more nights of observation. The catalog contains sources as faint as R {approx}19 but the largest fraction fall in the R {approx}15-16 (Vmore » {approx}16-17) mag range. All magnitude bins down to R = 19 have a significant fraction of objects with uncertainties {<=}0.1 mag.« less

Wearable vital parameters monitoring system

NASA Astrophysics Data System (ADS)

Caramaliu, Radu Vadim; Vasile, Alexandru; Bacis, Irina

2015-02-01

The system we propose monitors body temperature, heart rate and beside this, it tracks if the person who wears it suffers a faint. It uses a digital temperature sensor, a pulse sensor and a gravitational acceleration sensor to monitor the eventual faint or small heights free falls. The system continuously tracks the GPS position when available and stores the last valid data. So, when measuring abnormal vital parameters the module will send an SMS, using the GSM cellular network , with the person's social security number, the last valid GPS position for that person, the heart rate, the body temperature and, where applicable, a valid fall alert or non-valid fall alert. Even though such systems exist, they contain only faint detection or heart rate detection. Usually there is a strong correlation between low/high heart rate and an eventual faint. Combining both features into one system results in a more reliable detection device.

Lyman-α emitters in the context of hierarchical galaxy formation: predictions for VLT/MUSE surveys

NASA Astrophysics Data System (ADS)

Garel, T.; Guiderdoni, B.; Blaizot, J.

2016-02-01

The VLT/Multi Unit Spectrograph Explorer (MUSE) integral-field spectrograph can detect Lyα emitters (LAE) in the redshift range 2.8 ≲ z ≲ 6.7 in a homogeneous way. Ongoing MUSE surveys will notably probe faint Lyα sources that are usually missed by current narrow-band surveys. We provide quantitative predictions for a typical wedding-cake observing strategy with MUSE based on mock catalogues generated with a semi-analytic model of galaxy formation coupled to numerical Lyα radiation transfer models in gas outflows. We expect ≈1500 bright LAEs (FLyα ≳ 10-17 erg s-1 cm-2) in a typical shallow field (SF) survey carried over ≈100 arcmin2 , and ≈2000 sources as faint as 10-18 erg s-1 cm-2 in a medium-deep field (MDF) survey over 10 arcmin2 . In a typical deep field (DF) survey of 1 arcmin2 , we predict that ≈500 extremely faint LAEs (FLyα ≳ 4 × 10-19 erg s-1 cm-2) will be found. Our results suggest that faint Lyα sources contribute significantly to the cosmic Lyα luminosity and SFR budget. While the host haloes of bright LAEs at z ≈ 3 and 6 have descendants with median masses of 2 × 1012 and 5 × 1013 M⊙, respectively, the faintest sources detectable by MUSE at these redshifts are predicted to reside in haloes which evolve into typical sub-L* and L* galaxy haloes at z = 0. We expect typical DF and MDF surveys to uncover the building blocks of Milky Way-like objects, even probing the bulk of the stellar mass content of LAEs located in their progenitor haloes at z ≈ 3.

Diffuse Gamma Rays Galactic and Extragalactic Diffuse Emission

NASA Technical Reports Server (NTRS)

Moskalenko, Igor V.; Strong, Andrew W.; Reimer, Olaf

2004-01-01

Diffuse gamma rays consist of several components: truly diffuse emission from the interstellar medium, the extragalactic background, whose origin is not firmly established yet, and the contribution from unresolved and faint Galactic point sources. One approach to unravel these components is to study the diffuse emission from the interstellar medium, which traces the interactions of high energy particles with interstellar gas and radiation fields. Because of its origin such emission is potentially able to reveal much about the sources and propagation of cosmic rays. The extragalactic background, if reliably determined, can be used in cosmological and blazar studies. Studying the derived average spectrum of faint Galactic sources may be able to give a clue to the nature of the emitting objects.

Study on Formulation of Optimum Lighting-system for Purchasing Power at Stores

NASA Astrophysics Data System (ADS)

Fujita, Hiroki; Nakashima, Yoshio; Takamatsu, Mamoru; Oota, Masaaki; Sawa, Kazuhiro

In store lighting, difference in the look-and-feel of foods gives effects on the purchasing power of customers. This study conducted the digitalization and quantification on the effects of the variation of light-source color and illuminance used for lighting foods on image recognition on foods. As a result, it was clarified that when meat was illuminated with the light source of “pink” or “faint pink,” image evaluation on foods became higher. In addition, when illuminance increase was applied to these two light-source colors, image evaluation on “faint pink” became further higher. The reason is supposed to be that the redness of meat increased, which may have enhanced fresher impression. From this study, it has been clarified that the light-source color and illuminance optimum for each food are variant. The results show that lighting foods with the optimum light-source color and illuminance can make foods look better.

A Sneak Peek at the JWST Era: Observing Galaxies Below the Hubble Limit with Gravitational Lensing

NASA Astrophysics Data System (ADS)

Livermore, Rachael C.

2016-01-01

The installation of WFC3 on the Hubble Space Telescope pushed the frontier of high-redshift galaxy studies to only 500 Myr after the Big Bang. However, observations in this epoch remain challenging and are limited to the brightest galaxies; the fainter sources believed to be responsible for reionizing the Universe remain beyond the grasp of Hubble. With gravitational lensing, however, we can benefit from the magnification of faint sources, which brings them within reach of today's telescopes. The Hubble Frontier Fields program is a deep survey of strongly lensing clusters observed in the optical and near-infrared. Unfortunately, detecting highly magnified, intrinsically faint galaxies in these fields has proved challenging due to the bright foregound cluster galaxies and intracluster light. We have developed a technique using wavelet decomposition to overcome these difficulties and detect galaxies at z~7 with intrinsic UV magnitudes as faint as MUV = -13. We present this method and the resulting luminosity functions, which support a steep faint-end slope extending out to the observational limits. Our method has uncovered hundreds of galaxies at z > 6 fainter than any that have been seen before, providing our first insight into the small galaxy population during the epoch of reionization and a preview of the capabilities of JWST.

Strongly lensed gravitational waves from intrinsically faint double compact binaries—prediction for the Einstein Telescope

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

Ding, Xuheng; Biesiada, Marek; Zhu, Zong-Hong, E-mail: dingxuheng@mail.bnu.edu.cn, E-mail: marek.biesiada@us.edu.pl, E-mail: zhuzh@bnu.edu.cn

With a fantastic sensitivity improving significantly over the advanced GW detectors, Einstein Telescope (ET) will be able to observe hundreds of thousand inspiralling double compact objects per year. By virtue of gravitational lensing effect, intrinsically unobservable faint sources can be observed by ET due to the magnification by intervening galaxies. We explore the possibility of observing such faint sources amplified by strong gravitational lensing. Following our previous work, we use the merger rates of DCO (NS-NS,BH-NS,BH-BH systems) as calculated by Dominik et al.(2013). It turns out that tens to hundreds of such (lensed) extra events will be registered by ET.more » This will strongly broaden the ET's distance reach for signals from such coalescences to the redshift range z = 2 − 8. However, with respect to the full inspiral event catalog this magnification bias is at the level of 0.001 and should not affect much cosmological inferences.« less

The first VLBI image of an infrared-faint radio source

NASA Astrophysics Data System (ADS)

Middelberg, E.; Norris, R. P.; Tingay, S.; Mao, M. Y.; Phillips, C. J.; Hotan, A. W.

2008-11-01

Context: We investigate the joint evolution of active galactic nuclei and star formation in the Universe. Aims: In the 1.4 GHz survey with the Australia Telescope Compact Array of the Chandra Deep Field South and the European Large Area ISO Survey - S1 we have identified a class of objects which are strong in the radio but have no detectable infrared and optical counterparts. This class has been called Infrared-Faint Radio Sources, or IFRS. 53 sources out of 2002 have been classified as IFRS. It is not known what these objects are. Methods: To address the many possible explanations as to what the nature of these objects is we have observed four sources with the Australian Long Baseline Array. Results: We have detected and imaged one of the four sources observed. Assuming that the source is at a high redshift, we find its properties in agreement with properties of Compact Steep Spectrum sources. However, due to the lack of optical and infrared data the constraints are not particularly strong.

HIGHLY VARIABLE EXTINCTION AND ACCRETION IN THE JET-DRIVING CLASS I-TYPE YOUNG STAR PTF 10nvg (V2492 Cyg, IRAS 20496+4354)

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

Hillenbrand, Lynne A.; Carpenter, John M.; Muirhead, Philip S.

2013-03-15

We report extensive new photometry and spectroscopy of the highly variable young stellar object PTF 10nvg (also known as IRAS 20496+4354 and V2492 Cyg), including optical and near-infrared time-series data as well as mid-infrared and millimeter data. Following the previously reported 2010 rise to R{sub PTF} {approx}<13.{sup m}5 and subsequent fade, during 2011 and 2012 the source underwent additional episodes of brightening, followed by several magnitude dimming events including prolonged faint states at R{sub PTF} {approx}> 20{sup m}. The observed high-amplitude variations are largely consistent with extinction changes ({Delta}A{sub V} up to 30 mag) having a {approx}220 day quasi-periodic signal.more » However, photometry measured when the source was near maximum brightness in mid-2010 as well as in late-2012 does not phase well to this period. Spectral evolution includes not only changes in the spectral slope but also correlated variation in the prominence of TiO/VO/CO bands and atomic line emission, as well as anti-correlated variation in forbidden line emission which, along with H{sub 2}, dominates optical and infrared spectra at faint epochs. Notably, night-to-night variations in several forbidden doublet strengths and ratios are observed. High-dispersion spectra were obtained in a variety of photometric states and reveal time-variable line profiles. Neutral and singly ionized atomic species are likely formed in an accretion flow and/or impact while the origin of zero-velocity atomic Li I {lambda}6707 in emission is unknown. Forbidden lines, including several rare species, exhibit blueshifted emission profiles and likely arise from an outflow/jet. Several of these lines are also seen spatially offset from the continuum source position, presumably in a shocked region of an extended jet. Blueshifted absorption components of the Na I D doublet, K I {lambda}{lambda}7665, 7669 doublet, and the O I 7774 triplet, as well as blueshifted absorption components seen against the broad H{alpha} and Ca II triplet emission lines, similarly are formed in the outflow. CARMA maps resolve on larger scales a spatially extended outflow in millimeter-wavelength CO. We attribute the recently observed photometric and spectroscopic behavior to rotating circumstellar disk material located at separation a Almost-Equal-To 0.7(M{sub *}/M{sub Sun }){sup 1/3} AU from the continuum source, causing the semi-periodic dimming. Occultation of the central star as well as the bright inner disk and the accretion/outflow zones renders shocked gas in the inner part of the jet amenable to observation at the faint epochs. We discuss PTF 10nvg as a source exhibiting both accretion-driven (perhaps analogous to V1647 Ori) and extinction-driven (perhaps analogous to UX Ori or GM Cep) high-amplitude variability phenomena.« less

Morphology and astrometry of Infrared-Faint Radio Sources

NASA Astrophysics Data System (ADS)

Middelberg, Enno; Norris, Ray; Randall, Kate; Mao, Minnie; Hales, Christopher

2008-10-01

Infrared-Faint Radio Sources, or IFRS, are an unexpected class of object discovered in the Australia Telescope Large Area Survey, ATLAS. They are compact 1.4GHz radio sources with no visible counterparts in co-located (relatively shallow) Spitzer infrared and optical images. We have detected two of these objects with VLBI, indicating the presence of an AGN. These observations and our ATLAS data indicate that IFRS are extended on scales of arcseconds, and we wish to image their morphologies to obtain clues about their nature. These observations will also help us to select optical counterparts from very deep, and hence crowded, optical images which we have proposed. With these data in hand, we will be able to compare IFRS to known object types and to apply for spectroscopy to obtain their redshifts.

Handling Technique Development of Live Carp, Cyprinus carpio, In Cold Dry Styrofoam Box

NASA Astrophysics Data System (ADS)

Ketut Suwetja, I.; Salindeho, Netty; Gede Prabawa Suwetja, I.

2017-10-01

The study focused on several following aspects: temperature and time optimation for fainting, holding media optimation, temperature and time optimation for recovery, and their correlation with mortality rate of carp, Cyprinus carpio. Fainting occurred at the optimum time of 11 minutes and 03 seconds, temperature of 8°C, and holding time of 6 hours. Holding medium was rice husk. The fastest consciousness of the fish was found in 6 volt-aerated water medium. The fish consciousness after 6 hours of storing in the rice husk at the fainting temperature of 8°C was found faster (p < 0.05), 11 minutes and 15 seconds, than that added with 0.02% of clove oil, 25 minutes and 16 seconds. The fish mortality rate after 6 hours of storage in the rice husk at fainting temperature of 8°C was lower (p < 0.05), 46%, than that with addition of 0.02% of clove oil, 75%.

Time Projection Chamber Polarimeters for X-ray Astrophysics

NASA Astrophysics Data System (ADS)

Hill, Joanne; Black, Kevin; Jahoda, Keith

2015-04-01

Time Projection Chamber (TPC) based X-ray polarimeters achieve the sensitivity required for practical and scientifically significant astronomical observations, both galactic and extragalactic, with a combination of high analyzing power and good quantum efficiency. TPC polarimeters at the focus of an X-ray telescope have low background and large collecting areas providing the ability to measure the polarization properties of faint persistent sources. TPCs based on drifting negative ions rather than electrons permit large detector collecting areas with minimal readout electronics enabling wide field of view polarimeters for observing unpredictable, bright transient sources such as gamma-ray bursts. We described here the design and expected performance of two different TPC polarimeters proposed for small explorer missions: The PRAXyS (Polarimetry of Relativistic X-ray Sources) X-ray Polarimeter Instrument, optimized for observations of faint persistent sources and the POET (Polarimetry of Energetic Transients) Low Energy Polarimeter, designed to detect and measure bright transients. also NASA/GSFC.

FIGGS 2: An HI survey of extremely faint irregular galaxies

NASA Astrophysics Data System (ADS)

Patra, N. N.; Chengalur, J. N.; Karachentsev, I. D.; Sharina, M. E.

2016-10-01

We present observations and first results from the FIGGS2 survey. FIGGS2 is an extension of the earlier Faint Irregular Galaxies GMRT survey (FIGGS) towards faint luminosity end. The sample consists of 20 galaxies, 15 of which were detected in HI 21 cm line using the Giant Meterwave Radio Telescope (GMRT). The median blue band magnitude of our sample is approximately -11.m 6, which is more than one magnitude fainter than earlier FIGGS survey. From our GMRT observations we found that, for many of our sample galaxies, the HI disks are offset from their optical disks. The HI diameters of the FIGGS2 galaxies show a tight correlation with their HI mass. The slope of the correlation is 2.08 ± 0.20 similar to what is found for FIGGS galaxies. We also found that for almost all galaxies, the HI disks are larger than the optical disks which is a common trend for dwarf or spiral galaxies. The mean value of the ratio of HI to optical diameter is about 1.54.

Relation of large-scale coronal X-ray structure and cosmic rays. I - Sources of solar wind streams as defined by X-ray emission and H-alpha absorption features

NASA Technical Reports Server (NTRS)

Krieger, A. S.; Nolte, J. T.; Sullivan, J. D.; Lazarus, A. J.; Mcintosh, P. S.; Gold, R. E.; Roelof, E. C.

1975-01-01

The large-scale structure of the corona and the interplanetary medium during Carrington rotations 1601-1607 is discussed relative to recurrent high-speed solar wind streams and their coronal sources. Only streams A, C, D, and F recur on more than one rotation. Streams A and D are associated with coronal holes, while C and F originate in the high corona (20-50 solar radii) over faint X-ray emissions. The association of the streams with holes is confirmed by earlier findings that there are no large equatorial holes without an associated high-speed stream and that the area of the equatorial region of coronal holes is highly correlated with the maximum velocity observed in the associated stream near 1 AU.

Unidentified point sources in the IRAS minisurvey

NASA Technical Reports Server (NTRS)

Houck, J. R.; Soifer, B. T.; Neugebauer, G.; Beichman, C. A.; Aumann, H. H.; Clegg, P. E.; Gillett, F. C.; Habing, H. J.; Hauser, M. G.; Low, F. J.

1984-01-01

Nine bright, point-like 60 micron sources have been selected from the sample of 8709 sources in the IRAS minisurvey. These sources have no counterparts in a variety of catalogs of nonstellar objects. Four objects have no visible counterparts, while five have faint stellar objects visible in the error ellipse. These sources do not resemble objects previously known to be bright infrared sources.

Spectral Index Properties of millijansky Radio Sources in ATLAS

NASA Astrophysics Data System (ADS)

Randall, Kate; Hopkins, A. M.; Norris, R. P.; Zinn, P.; Middelberg, E.; Mao, M. Y.; Sharp, R. G.

2012-01-01

At the faintest radio flux densities (S1.4GHz < 10 milliJansky (mJy)), the spectral index properties of radio sources are not well constrained. The bright radio source population (S1.4GHz > 10 mJy) is well studied and is predominantly comprised of AGN. At fainter flux densities, particularly into the microJansky regime, star-forming galaxies begin to dominate the radio source population. Understanding these faint radio source populations is essential for understanding galaxy evolution, and the link between AGN and star formation. Conflicting results have recently arisen regarding whether there is a flattening of the average spectral index between a low radio frequency (325 or 610 MHz) and 1.4 GHz at these faint flux densities. To explore this issue, we have investigated the spectral index properties of a new catalogue of 843 MHz radio sources in the ELAIS-S1 (the European Large Area ISO Survey - South 1 Region) field. Our results support previous work showing a tendency towards flatter radio spectra at fainter flux densities. This catalogue is cross-matched to the Australia Telescope Large Area Survey (ATLAS), the widest deep radio survey to date at 1.4 GHz, with complementary 2.3 GHz, optical and infrared Spitzer Wide-area Infra-Red Extragalactic data. The variation of spectral index properties have been explored as a function of redshift, luminosity and flux density. [These new measurements have been used to identify a population of faint Compact Steep Spectrum sources, thought to be one of the earliest stages of the AGN life-cycle. Exploring this population will aid us in understanding the evolution of AGN as a whole.

Infrared-faint radio sources are at high redshifts. Spectroscopic redshift determination of infrared-faint radio sources using the Very Large Telescope

NASA Astrophysics Data System (ADS)

Herzog, A.; Middelberg, E.; Norris, R. P.; Sharp, R.; Spitler, L. R.; Parker, Q. A.

2014-07-01

Context. Infrared-faint radio sources (IFRS) are characterised by relatively high radio flux densities and associated faint or even absent infrared and optical counterparts. The resulting extremely high radio-to-infrared flux density ratios up to several thousands were previously known only for high-redshift radio galaxies (HzRGs), suggesting a link between the two classes of object. However, the optical and infrared faintness of IFRS makes their study difficult. Prior to this work, no redshift was known for any IFRS in the Australia Telescope Large Area Survey (ATLAS) fields which would help to put IFRS in the context of other classes of object, especially of HzRGs. Aims: This work aims at measuring the first redshifts of IFRS in the ATLAS fields. Furthermore, we test the hypothesis that IFRS are similar to HzRGs, that they are higher-redshift or dust-obscured versions of these massive galaxies. Methods: A sample of IFRS was spectroscopically observed using the Focal Reducer and Low Dispersion Spectrograph 2 (FORS2) at the Very Large Telescope (VLT). The data were calibrated based on the Image Reduction and Analysis Facility (IRAF) and redshifts extracted from the final spectra, where possible. This information was then used to calculate rest-frame luminosities, and to perform the first spectral energy distribution modelling of IFRS based on redshifts. Results: We found redshifts of 1.84, 2.13, and 2.76, for three IFRS, confirming the suggested high-redshift character of this class of object. These redshifts and the resulting luminosities show IFRS to be similar to HzRGs, supporting our hypothesis. We found further evidence that fainter IFRS are at even higher redshifts. Conclusions: Considering the similarities between IFRS and HzRGs substantiated in this work, the detection of IFRS, which have a significantly higher sky density than HzRGs, increases the number of active galactic nuclei in the early universe and adds to the problems of explaining the formation of supermassive black holes shortly after the Big Bang.

X-Ray Astronomy--A New View of the Sky From Space

ERIC Educational Resources Information Center

Gursky, Herbert

1973-01-01

Objects and energy sources are detected whose existence was only hinted at a few years ago. The X-Ray sky has a large number of sources along the Milky Way, most of which lie within 30 degrees of the galactic center, plus a number of faint sources associated with external galaxies. (DF)

A search for AGN activity in Infrared-Faint Radio Sources (IFRS)

NASA Astrophysics Data System (ADS)

Lenc, Emil; Middelberg, Enno; Norris, Ray; Mao, Minnie

2009-04-01

We propose to observe a large sample of radio sources from the ATLAS (Australia Telescope Large Area Survey) source catalogue with the LBA, to determine their compactness. The sample consists of 36 sources with no counterpart in the co-located SWIRE survey (3.6 um to 160 um), carried out with the Spitzer Space Telescope. This rare class of sources, dubber Infrared-Faint Radio Sources (IFRS), is inconsistent with current galaxy evolution models. VLBI observations are an essential way to obtain further clues on what these objects are and why they are hidden from infrared observations. We will measure the flux densities on long baselines to determine their compactness. Only five IFRS have been previously targeted with VLBI observations (resulting in two detections). We propose using single baseline (Parkes-ATCA) eVLBI observations with the LBA at 1 Gbps to maximise sensitivity. With the observations proposed here we will increase the number of VLBI-observed IFRS from 5 to 36, allowing us to draw statistical conclusions about this intriguing new class of objects.

A search for AGN activity in Infrared-Faint Radio Sources (IFRS)

NASA Astrophysics Data System (ADS)

Lenc, Emil; Middelberg, Enno; Norris, Ray; Mao, Minnie

2010-04-01

We propose to observe a large sample of radio sources from the ATLAS (Australia Telescope Large Area Survey) source catalogue with the LBA, to determine their compactness. The sample consists of 36 sources with no counterpart in the co-located SWIRE survey (3.6 um to 160 um), carried out with the Spitzer Space Telescope. This rare class of sources, dubber Infrared-Faint Radio Sources (IFRS), is inconsistent with current galaxy evolution models. VLBI observations are an essential way to obtain further clues on what these objects are and why they are hidden from infrared observations. We will measure the flux densities on long baselines to determine their compactness. Only five IFRS have been previously targeted with VLBI observations (resulting in two detections). We propose using single baseline (Parkes-ATCA) eVLBI observations with the LBA at 1 Gbps to maximise sensitivity. With the observations proposed here we will increase the number of VLBI-observed IFRS from 5 to 36, allowing us to draw statistical conclusions about this intriguing new class of objects.

Faint Submillimeter Galaxies Behind Lensing Clusters

NASA Astrophysics Data System (ADS)

Hsu, Li-Yen; Lauchlan Cowie, Lennox; Barger, Amy J.; Desai, Vandana; Murphy, Eric J.

2017-01-01

Faint submillimeter galaxies are the major contributors to the submillimeter extragalactic background light and hence the dominant star-forming population in the dusty universe. Determining how much these galaxies overlap the optically selected samples is critical to fully account for the cosmic star formation history. Observations of massive cluster fields are the best way to explore this faint submillimeter population, thanks to gravitational lensing effects. We have been undertaking a lensing cluster survey with the SCUBA-2 camera on the James Clerk Maxwell Telescope to map nine galaxy clusters, including the northern five clusters in the HST Frontier Fields program. We have also been using the Submillimeter Array and the Very Large Array to determine the accurate positions of our detected sources. Our observations have discovered high-redshift dusty galaxies with far-infrared luminosities similar to that of the Milky Way or luminous infrared galaxies. Some of these galaxies are still undetected in deep optical and near-infrared images. These results suggest that a substantial amount of star formation in even the faint submillimeter population may be hidden from rest-frame optical surveys.

A direct localization of a fast radio burst and its host.

PubMed

Chatterjee, S; Law, C J; Wharton, R S; Burke-Spolaor, S; Hessels, J W T; Bower, G C; Cordes, J M; Tendulkar, S P; Bassa, C G; Demorest, P; Butler, B J; Seymour, A; Scholz, P; Abruzzo, M W; Bogdanov, S; Kaspi, V M; Keimpema, A; Lazio, T J W; Marcote, B; McLaughlin, M A; Paragi, Z; Ransom, S M; Rupen, M; Spitler, L G; van Langevelde, H J

2017-01-04

Fast radio bursts are astronomical radio flashes of unknown physical nature with durations of milliseconds. Their dispersive arrival times suggest an extragalactic origin and imply radio luminosities that are orders of magnitude larger than those of all known short-duration radio transients. So far all fast radio bursts have been detected with large single-dish telescopes with arcminute localizations, and attempts to identify their counterparts (source or host galaxy) have relied on the contemporaneous variability of field sources or the presence of peculiar field stars or galaxies. These attempts have not resulted in an unambiguous association with a host or multi-wavelength counterpart. Here we report the subarcsecond localization of the fast radio burst FRB 121102, the only known repeating burst source, using high-time-resolution radio interferometric observations that directly image the bursts. Our precise localization reveals that FRB 121102 originates within 100 milliarcseconds of a faint 180-microJansky persistent radio source with a continuum spectrum that is consistent with non-thermal emission, and a faint (twenty-fifth magnitude) optical counterpart. The flux density of the persistent radio source varies by around ten per cent on day timescales, and very long baseline radio interferometry yields an angular size of less than 1.7 milliarcseconds. Our observations are inconsistent with the fast radio burst having a Galactic origin or its source being located within a prominent star-forming galaxy. Instead, the source appears to be co-located with a low-luminosity active galactic nucleus or a previously unknown type of extragalactic source. Localization and identification of a host or counterpart has been essential to understanding the origins and physics of other kinds of transient events, including gamma-ray bursts and tidal disruption events. However, if other fast radio bursts have similarly faint radio and optical counterparts, our findings imply that direct subarcsecond localizations may be the only way to provide reliable associations.

VLBI observations of Infrared-Faint Radio Sources

NASA Astrophysics Data System (ADS)

Middelberg, Enno; Phillips, Chris; Norris, Ray; Tingay, Steven

2006-10-01

We propose to observe a small sample of radio sources from the ATLAS project (ATLAS = Australia Telescope Large Area Survey) with the LBA, to determine their compactness and map their structures. The sample consists of three radio sources with no counterpart in the co-located SWIRE survey (3.6 um to 160 um), carried out with the Spitzer Space Telescope. This rare class of sources, dubbed Infrared-Faint Radio Sources, or IFRS, is inconsistent with current galaxy evolution models. VLBI observations are an essential way to obtain further clues on what these objects are and why they are hidden from infrared observations: we will map their structure to test whether they resemble core-jet or double-lobed morphologies, and we will measure the flux densities on long baselines, to determine their compactness. Previous snapshot-style LBA observations of two other IFRS yielded no detections, hence we propose to use disk-based recording with 512 Mbps where possible, for highest sensitivity. With the observations proposed here, we will increase the number of VLBI-observed IFRS from two to five, soon allowing us to draw general conclusions about this intriguing new class of objects.

MOA-2008-BLG-379Lb: A massive planet from a high magnification event with a faint source

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

Suzuki, D.; Sumi, T.; Fukagawa, M.

2014-01-10

We report on the analysis of the high microlensing event MOA-2008-BLG-379, which has a strong microlensing anomaly at its peak due to a massive planet with a mass ratio of q = 6.9 × 10{sup –3}. Because the faint source star crosses the large resonant caustic, the planetary signal dominates the light curve. This is unusual for planetary microlensing events, and as a result, the planetary nature of this light curve was not immediately noticed. The planetary nature of the event was found when the Microlensing Observations in Astrophysics (MOA) Collaboration conducted a systematic study of binary microlensing events previouslymore » identified by the MOA alert system. We have conducted a Bayesian analysis based on a standard Galactic model to estimate the physical parameters of the lens system. This yields a host star mass of M{sub L}=3.3{sub −1.2}{sup +1.7} M{sub ⊙} orbited by a planet of mass m{sub P}=0.56{sub −0.27}{sup +0.24} M{sub Jup} at an orbital separation of a=3.3{sub −1.2}{sup +1.3} AU at a distance of D{sub L}=4.1{sub −1.9}{sup +1.7} kpc. The faint source magnitude of I {sub S} = 21.30 and relatively high lens-source relative proper motion of μ{sub rel} = 7.6 ± 1.6 mas yr{sup –1} imply that high angular resolution adaptive optics or Hubble Space Telescope observations are likely to be able to detect the source star, which would determine the masses and distance of the planet and its host star.« less

Deconvolution of post-adaptive optics images of faint circumstellar environments by means of the inexact Bregman procedure

NASA Astrophysics Data System (ADS)

Benfenati, A.; La Camera, A.; Carbillet, M.

2016-02-01

Aims: High-dynamic range images of astrophysical objects present some difficulties in their restoration because of the presence of very bright point-wise sources surrounded by faint and smooth structures. We propose a method that enables the restoration of this kind of images by taking these kinds of sources into account and, at the same time, improving the contrast enhancement in the final image. Moreover, the proposed approach can help to detect the position of the bright sources. Methods: The classical variational scheme in the presence of Poisson noise aims to find the minimum of a functional compound of the generalized Kullback-Leibler function and a regularization functional: the latter function is employed to preserve some characteristic in the restored image. The inexact Bregman procedure substitutes the regularization function with its inexact Bregman distance. This proposed scheme allows us to take under control the level of inexactness arising in the computed solution and permits us to employ an overestimation of the regularization parameter (which balances the trade-off between the Kullback-Leibler and the Bregman distance). This aspect is fundamental, since the estimation of this kind of parameter is very difficult in the presence of Poisson noise. Results: The inexact Bregman procedure is tested on a bright unresolved binary star with a faint circumstellar environment. When the sources' position is exactly known, this scheme provides us with very satisfactory results. In case of inexact knowledge of the sources' position, it can in addition give some useful information on the true positions. Finally, the inexact Bregman scheme can be also used when information about the binary star's position concerns a connected region instead of isolated pixels.

The faint X-ray sources in and out of omega Centauri: X-ray observations and optical identifications

NASA Technical Reports Server (NTRS)

Cool, Adrienne M.; Grindlay, Jonathan E.; Bailyn, Charles D.; Callanan, Paul J.; Hertz, Paul

1995-01-01

We present the results of an observation of the globular cluster omega Cen (NGC 5139) with the Einstein high-resolution imager (HRI). Of the five low-luminosity X-ray sources toward omega Cen which were first identified with the Einstein imaging proportional counter (IPC) (Hertz and Grindlay 1983a, b), two are detected in the Einstein HRI observation: IPC sources A and D. These detections provide source positions accurate to 3 sec-4 sec; the positions are confirmed in a ROSAT HRI observation reported here. Using CCD photometry and spectroscopy, we have identified both sources as foreground dwarf M stars with emission lines (dMe). The chance projection of two Mde stars within approximately 13 min of the center of omega Cen is not extraordinary, given the space density of these stellar coronal X-ray sources. We discuss the possible nature of the three as yet unidentified IPC sources toward omega Cen, and consider the constraints that the Einstein observations place on the total population of X-ray sources in this cluster. The integrated luminosity from faint X-ray sources in omega Cen appears to be low relative to both the old open cluster M67 and the post-core-collapse globular, NGC 6397.

The Hawaii SCUBA-2 Lensing Cluster Survey: Number Counts and Submillimeter Flux Ratios

NASA Astrophysics Data System (ADS)

Hsu, Li-Yen; Cowie, Lennox L.; Chen, Chian-Chou; Barger, Amy J.; Wang, Wei-Hao

2016-09-01

We present deep number counts at 450 and 850 μm using the SCUBA-2 camera on the James Clerk Maxwell Telescope. We combine data for six lensing cluster fields and three blank fields to measure the counts over a wide flux range at each wavelength. Thanks to the lensing magnification, our measurements extend to fluxes fainter than 1 mJy and 0.2 mJy at 450 μm and 850 μm, respectively. Our combined data highly constrain the faint end of the number counts. Integrating our counts shows that the majority of the extragalactic background light (EBL) at each wavelength is contributed by faint sources with L IR < 1012 L ⊙, corresponding to luminous infrared galaxies (LIRGs) or normal galaxies. By comparing our result with the 500 μm stacking of K-selected sources from the literature, we conclude that the K-selected LIRGs and normal galaxies still cannot fully account for the EBL that originates from sources with L IR < 1012 L ⊙. This suggests that many faint submillimeter galaxies may not be included in the UV star formation history. We also explore the submillimeter flux ratio between the two bands for our 450 μm and 850 μm selected sources. At 850 μm, we find a clear relation between the flux ratio and the observed flux. This relation can be explained by a redshift evolution, where galaxies at higher redshifts have higher luminosities and star formation rates. In contrast, at 450 μm, we do not see a clear relation between the flux ratio and the observed flux.

X-ray-bright optically faint active galactic nuclei in the Subaru Hyper Suprime-Cam wide survey

NASA Astrophysics Data System (ADS)

Terashima, Yuichi; Suganuma, Makoto; Akiyama, Masayuki; Greene, Jenny E.; Kawaguchi, Toshihiro; Iwasawa, Kazushi; Nagao, Tohru; Noda, Hirofumi; Toba, Yoshiki; Ueda, Yoshihiro; Yamashita, Takuji

2018-01-01

We construct a sample of X-ray-bright optically faint active galactic nuclei by combining Subaru Hyper Suprime-Cam, XMM-Newton, and infrared source catalogs. Fifty-three X-ray sources satisfying i-band magnitude fainter than 23.5 mag and X-ray counts with the EPIC-PN detector larger than 70 are selected from 9.1 deg2, and their spectral energy distributions (SEDs) and X-ray spectra are analyzed. Forty-four objects with an X-ray to i-band flux ratio FX/Fi > 10 are classified as extreme X-ray-to-optical flux sources. Spectral energy distributions of 48 among 53 are represented by templates of type 2 AGNs or star-forming galaxies and show the optical signature of stellar emission from host galaxies in the source rest frame. Infrared/optical SEDs indicate a significant contribution of emission from dust to the infrared fluxes, and that the central AGN is dust obscured. The photometric redshifts determined from the SEDs are in the range of 0.6-2.5. The X-ray spectra are fitted by an absorbed power-law model, and the intrinsic absorption column densities are modest (best-fit log NH = 20.5-23.5 cm-2 in most cases). The absorption-corrected X-ray luminosities are in the range of 6 × 1042-2 × 1045 erg s-1. Twenty objects are classified as type 2 quasars based on X-ray luminsosity and NH. The optical faintness is explained by a combination of redshifts (mostly z > 1.0), strong dust extinction, and in part a large ratio of dust/gas.

Discarded candidate companions to low-mass members of Chamaeleon I

NASA Astrophysics Data System (ADS)

Comerón, F.

2012-01-01

Context. Direct detections of brown dwarfs and planetary-mass companions to members of nearby star-forming regions provide important clues about the process of star formation, core fragmentation, and protoplanetary disk evolution. Aims: We study two faint objects at a very small angular distance from the low-mass star ESO-Hα-558 and the possible massive brown dwarf ESO-Hα-566, both of which are members of the Chamaeleon I star-forming region, to establish whether they are physical companions to those sources. If they are, their low luminosities should imply L or T spectral types, which have clearly detectable spectral features. Methods: Adaptive optics-assisted imaging and spectroscopy of both faint candidate companions has been obtained with the NACO instrument at the Very Large Telescope (VLT). Results: Photometry shows that the colors of both objects are compatible with them being moderately reddened, normal stars in the background of the Chamaeleon I clouds. This interpretation is confirmed spectroscopically, as the spectrum between 1.4 and 2.4 μm of both objects has a featureless, monotonic slope lacking the strong H2O absorption features that dominate cool stellar and substellar spectra in that domain. Conclusions: We demonstrate that the two faint sources seen very close to ESO-Hα-558 and ESO-Hα-566 are unrelated background stars, instead of giant planetary-mass companions as might be expected based on their faintness and angular proximity. Based on observations collected with the Very Large Telescope (VLT) at the European Southern Observatory, Paranal, Chile, under observing programmes 075.C-0809(B) and 078.C-0429(C).

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

Zemcov, M.; Cooray, A.; Bock, J.

We have observed four massive galaxy clusters with the SPIRE instrument on the Herschel Space Observatory and measure a deficit of surface brightness within their central region after removing detected sources. We simulate the effects of instrumental sensitivity and resolution, the source population, and the lensing effect of the clusters to estimate the shape and amplitude of the deficit. The amplitude of the central deficit is a strong function of the surface density and flux distribution of the background sources. We find that for the current best fitting faint end number counts, and excellent lensing models, the most likely amplitudemore » of the central deficit is the full intensity of the cosmic infrared background (CIB). Our measurement leads to a lower limit to the integrated total intensity of the CIB of I{sub 250{mu}m}>0.69{sub -0.03}{sup +0.03}(stat.){sub -0.06}{sup +0.11}(sys.) MJy sr{sup -1}, with more CIB possible from both low-redshift sources and from sources within the target clusters. It should be possible to observe this effect in existing high angular resolution data at other wavelengths where the CIB is bright, which would allow tests of models of the faint source component of the CIB.« less

Colliding Neutron Stars as the Source of Heavy Elements

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-09-01

Where do the heavy elements the chemical elements beyond iron in our universe come from? One of the primary candidate sources is the merger of two neutron stars, but recent observations have cast doubt on this model. Can neutron-star mergers really be responsible?Elements from Collisions?Periodic table showing the origin of each chemical element. Those produced by the r-process are shaded orange and attributed to supernovae in this image; though supernovae are one proposed source of r-process elements, an alternative source is the merger of two neutron stars. [Cmglee]When a binary-neutron-star system inspirals and the two neutron stars smash into each other, a shower of neutrons are released. These neutrons are thought to bombard the surrounding atoms, rapidly producing heavy elements in what is known as r-process nucleosynthesis.So could these mergers be responsible for producing the majority of the universes heavy r-process elements? Proponents of this model argue that its supported by observations. The overall amount of heavy r-process material in the Milky Way, for instance, is consistent with the expected ejection amounts from mergers, based both on predicted merger rates for neutron stars in the galaxy, and on the observed rates of soft gamma-ray bursts (which are thought to accompany double-neutron-star mergers).Challenges from Ultra-Faint DwarfsRecently, however, r-process elements have been observed in ultra-faint dwarf satellite galaxies. This discovery raises two major challenges to the merger model for heavy-element production:When neutron stars are born during a core-collapse supernova, mass is ejected, providing the stars with asymmetric natal kicks. During the second collapse in a double-neutron-star binary, wouldnt the kick exceed the low escape velocity of an ultra-faint dwarf, ejecting the binary before it could merge and enrich the galaxy?Ultra-faint dwarfs have very old stellar populations and the observation of r-process elements in these stars requires mergers to have occurred very early in the galaxys history. Can double-neutron-star systems merge quickly enough to account for the observed chemical enrichment?Small Kicks and Fast MergersFraction of double-neutron-star systems that remain bound, vs. the magnitude of the kick they receive. A typical escape velocity for an ultra-faint dwarf is ~15 km/s; roughly 55-65% of binaries receive smaller kicks than that and wouldnt be ejected from an ultra-faint dwarf. [Beniamini et al. 2016]Led by Paz Beniamini, a team of scientists from the Racah Institute of Physics at the Hebrew University of Jerusalem has set out to answer these questions. Using the statistics of our galaxys double-neutron-star population, the team performed Monte Carlo simulations to estimate the distributions of mass ejection and kick velocities for the systems.Beniamini and collaborators find that, for typical initial separations, more than half of neutron star binaries are born with small enough kicks that they remain bound and arent ejected even from small, ultra-faint dwarf galaxies.The team also used their statistics to calculate the time until merger for the population of binaries, finding that ~90% of the double-neutron-star systems merge within 300 Myr, and around 15% merge within 100 Myr quick enough to enrich even the old population of stars.This population of systems that remain confined to the galaxy and merge rapidly can therefore explain the observations of r-process material in ultra-faint dwarf galaxies. Beniamini and collaborators work suggests that the merger of neutron stars is indeed a viable model for the production of heavy elements in our universe.CitationPaz Beniamini et al 2016 ApJ 829 L13. doi:10.3847/2041-8205/829/1/L13

Intracluster light in clusters of galaxies at redshifts 0.4 < z < 0.8

NASA Astrophysics Data System (ADS)

Guennou, L.; Adami, C.; Da Rocha, C.; Durret, F.; Ulmer, M. P.; Allam, S.; Basa, S.; Benoist, C.; Biviano, A.; Clowe, D.; Gavazzi, R.; Halliday, C.; Ilbert, O.; Johnston, D.; Just, D.; Kron, R.; Kubo, J. M.; Le Brun, V.; Marshall, P.; Mazure, A.; Murphy, K. J.; Pereira, D. N. E.; Rabaça, C. R.; Rostagni, F.; Rudnick, G.; Russeil, D.; Schrabback, T.; Slezak, E.; Tucker, D.; Zaritsky, D.

2012-01-01

Context. The study of intracluster light (ICL) can help us to understand the mechanisms taking place in galaxy clusters, and to place constraints on the cluster formation history and physical properties. However, owing to the intrinsic faintness of ICL emission, most searches and detailed studies of ICL have been limited to redshifts z < 0.4. Aims: To help us extend our knowledge of ICL properties to higher redshifts and study the evolution of ICL with redshift, we search for ICL in a subsample of ten clusters detected by the ESO Distant Cluster Survey (EDisCS), at redshifts 0.4 < z < 0.8, that are also part of our DAFT/FADA Survey. Methods: We analyze the ICL by applying the OV WAV package, a wavelet-based technique, to deep HST ACS images in the F814W filter and to V-band VLT/FORS2 images of three clusters. Detection levels are assessed as a function of the diffuse light source surface brightness using simulations. Results: In the F814W filter images, we detect diffuse light sources in all the clusters, with typical sizes of a few tens of kpc (assuming that they are at the cluster redshifts). The ICL detected by stacking the ten F814W images shows an 8σ detection in the source center extending over a ~50 × 50 kpc2 area, with a total absolute magnitude of -21.6 in the F814W filter, equivalent to about two L∗ galaxies per cluster. We find a weak correlation between the total F814W absolute magnitude of the ICL and the cluster velocity dispersion and mass. There is no apparent correlation between the cluster mass-to-light ratio (M/L) and the amount of ICL, and no evidence of any preferential orientation in the ICL source distribution. We find no strong variation in the amount of ICL between z = 0 and z = 0.8. In addition, we find wavelet-detected compact objects (WDCOs) in the three clusters for which data in two bands are available; these objects are probably very faint compact galaxies that in some cases are members of the respective clusters and comparable to the faint dwarf galaxies of the Local Group. Conclusions: We show that the ICL is prevalent in clusters at least up to redshift z = 0.8. In the future, we propose to detect the ICL at even higher redshifts, to determine wether there is a particular stage of cluster evolution where it was stripped from galaxies and spread into the intracluster medium. Based on observations made at ESO Telescopes at the Paranal Observatory under programme ID 082.A-0374. Also based on the use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archives at the Space Telescope European Coordinating Facility and the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Faint source detection in ISOCAM images

NASA Astrophysics Data System (ADS)

Starck, J. L.; Aussel, H.; Elbaz, D.; Fadda, D.; Cesarsky, C.

1999-08-01

We present a tool adapted to the detection of faint mid-infrared sources within ISOCAM mosaics. This tool is based on a wavelet analysis which allows us to discriminate sources from cosmic ray impacts at the very limit of the instrument, four orders of magnitudes below IRAS. It is called PRETI for Pattern REcognition Technique for ISOCAM data, because glitches with transient behaviors are isolated in the wavelet space, i.e. frequency space, where they present peculiar signatures in the form of patterns automatically identified and then reconstructed. We have tested PRETI with Monte-Carlo simulations of fake ISOCAM data. These simulations allowed us to define the fraction of remaining false sources due to cosmic rays, the sensitivity and completeness limits as well as the photometric accuracy as a function of the observation parameters. Although the main scientific applications of this technique have appeared or will appear in separated papers, we present here an application to the ISOCAM-Hubble Deep Field image. This work completes and confirms the results already published (\\cite[Aussel et al. 1999]{starck:aussel99}).

Investigating The Nuclear Activity Of Barred Spirals: The case of NGC 1672

NASA Astrophysics Data System (ADS)

Jenkins, Leigh; Brandt, N.; Colbert, E.; Levan, A.; Roberts, T.; Ward, M.; Zezas, A.

2008-03-01

We present new results from Chandra and XMM-Newton X-ray observations of the nearby barred spiral galaxy NGC1672. It shows dramatic nuclear and extra-nuclear star formation activity, including starburst regions located either end of its prominent bar. Using new X-ray imaging and spectral information, together with supporting multiwavelength data, we show for the first time that NGC1672 possesses a faint, hard, central X-ray source surrounded by a circumnuclear starburst ring that dominates the X-ray emission in the region, presumably triggered and sustained by gas and dust driven inwards along the galactic bar. The faint central source may represent low-level AGN activity, or alternatively emission associated with star-formation in the nucleus. More generally, we present some preliminary results on a Chandra archival search for low-luminosity AGN activity in barred galaxies.

Faints, fits, and fatalities from emotion in Shakespeare's characters: survey of the canon

PubMed Central

2006-01-01

Objectives To determine how often Shakespeare's characters faint, fit, or die from extreme emotion; to assess Shakespeare's uniqueness in this regard; and to examine the plausibility of these dramatised events. Design Line by line search through modern editions of these late 16th and early 17th century works for accounts of characters fainting, fitting, or dying while under strong emotion and for no other apparent reason. Data sources All 39 canonical plays by Shakespeare and his three long narrative poems; 18 similar works by seven of Shakespeare's best known contemporaries. Results 10 deaths from strong emotion are recorded by Shakespeare (three occur on stage); all are due to grief, typically at the loss of a loved one. All but two of the deaths are in the playwright's late works. Some deaths are sudden. Another 29 emotion induced deaths are mentioned as possible, but the likelihood of some can be challenged. Transient loss of consciousness is staged or reported in 18 cases (sounding like epilepsy in two) and near fainting in a further 13. Extreme joy is sometimes depicted as a factor in these events. Emotional death and fainting also occur occasionally in works by Shakespeare's contemporaries. Conclusions These dramatic phenomena are part of the early modern belief system but are also plausible by modern understanding of physiology and disease. They teach us not to underestimate the power of the emotions to disturb bodily functions. PMID:17185734

The population of faint Jupiter family comets near the Earth

NASA Astrophysics Data System (ADS)

Fernández, Julio A.; Morbidelli, Alessandro

2006-11-01

We study the population of faint Jupiter family comets (JFCs) that approach the Earth (perihelion distances q<1.3 AU) by applying a debiasing technique to the observed sample. We found for the debiased cumulative luminosity function (CLF) of absolute total magnitudes H a bimodal distribution in which brighter comets ( H≲9) follow a linear relation with a steep slope α=0.65±0.14, while fainter comets follow a much shallower slope α=0.25±0.06 down to H˜18. The slope can be pushed up to α=0.35±0.09 if a second break in the H distribution to a much shallower slope is introduced at H˜16. We estimate a population of about 10 3 faint JFCs with q<1.3 AU and 10

Sub-percent Photometry: Faint DA White Dwarf Spectrophotometric Standards for Astrophysical Observatories

NASA Astrophysics Data System (ADS)

Narayan, Gautham; Axelrod, Tim; Calamida, Annalisa; Saha, Abhijit; Matheson, Thomas; Olszewski, Edward; Holberg, Jay; Holberg, Jay; Bohlin, Ralph; Stubbs, Christopher W.; Rest, Armin; Deustua, Susana; Sabbi, Elena; MacKenty, John W.; Points, Sean D.; Hubeny, Ivan

2018-01-01

We have established a network of faint (16.5 < V < 19) hot DA white dwarfs as spectrophotometric standards for present and future wide-field observatories. Our standards are accessible from both hemispheres and suitable for ground and space-based covering the UV to the near IR. The network is tied directly to the most precise astrophysical reference presently available - the CALSPEC standards - through a multi-cycle program imaging using the Wide-Field Camera 3 (WFC3) on the Hubble Space Telescope (HST). We have developed two independent analyses to forward model all the observed photometry and ground-based spectroscopy and infer a spectral energy distribution for each source using a non-local-thermodynamic-equilibrium (NLTE) DA white dwarf atmosphere extincted by interstellar dust. The models are in excellent agreement with each other, and agree with the observations to better than 0.01 mag in all passbands, and better than 0.005 mag in the optical. The high-precision of these faint sources, tied directly to the most accurate flux standards presently available, make our network of standards ideally suited for any experiments that have very stringent requirements on absolute flux calibration, such as studies of dark energy using the Large Synoptic Survey Telescope (LSST) and the Wide-Field Infrared Survey Telescope (WFIRST).

The Discovery of Herbig–Haro Objects in LDN 673

NASA Astrophysics Data System (ADS)

Rector, T. A.; Shuping, R. Y.; Prato, L.; Schweiker, H.

2018-01-01

We report the discovery of 12 faint Herbig–Haro (HH) objects in LDN 673 found using a novel color-composite imaging method that reveals faint Hα emission in complex environments. Follow-up observations in [S II] confirmed their classification as HH objects. Potential driving sources are identified from the Spitzer c2d Legacy Program catalog and other infrared observations. The 12 new HH objects can be divided into three groups: four are likely associated with a cluster of eight young stellar object class I/II IR sources that lie between them; five are colinear with the T Tauri multiple star system AS 353, and are likely driven by the same source as HH 32 and HH 332 and three are bisected by a very red source that coincides with an infrared dark cloud. We also provide updated coordinates for the three components of HH 332. Inaccurate numbers were given for this object in the discovery paper. The discovery of HH objects and associated driving sources in this region provides new evidence for star formation in the Aquila clouds, implying a much larger T Tauri population in a seldom-studied region.

Unrecognized astrometric confusion in the Galactic Centre

NASA Astrophysics Data System (ADS)

Plewa, P. M.; Sari, R.

2018-06-01

The Galactic Centre is a crowded stellar field and frequent unrecognized events of source confusion, which involve undetected faint stars, are expected to introduce astrometric noise on a sub-mas level. This confusion noise is the main non-instrumental effect limiting the astrometric accuracy and precision of current near-infrared imaging observations and the long-term monitoring of individual stellar orbits in the vicinity of the central supermassive black hole. We self-consistently simulate the motions of the known and the yet unidentified stars to characterize this noise component and show that a likely consequence of source confusion is a bias in estimates of the stellar orbital elements, as well as the inferred mass and distance of the black hole, in particular if stars are being observed at small projected separations from it, such as the star S2 during pericentre passage. Furthermore, we investigate modelling the effect of source confusion as an additional noise component that is time-correlated, demonstrating a need for improved noise models to obtain trustworthy estimates of the parameters of interest (and their uncertainties) in future astrometric studies.

Source Detection with Bayesian Inference on ROSAT All-Sky Survey Data Sample

NASA Astrophysics Data System (ADS)

Guglielmetti, F.; Voges, W.; Fischer, R.; Boese, G.; Dose, V.

2004-07-01

We employ Bayesian inference for the joint estimation of sources and background on ROSAT All-Sky Survey (RASS) data. The probabilistic method allows for detection improvement of faint extended celestial sources compared to the Standard Analysis Software System (SASS). Background maps were estimated in a single step together with the detection of sources without pixel censoring. Consistent uncertainties of background and sources are provided. The source probability is evaluated for single pixels as well as for pixel domains to enhance source detection of weak and extended sources.

THE HAWAII SCUBA-2 LENSING CLUSTER SURVEY: NUMBER COUNTS AND SUBMILLIMETER FLUX RATIOS

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

Hsu, Li-Yen; Cowie, Lennox L.; Barger, Amy J.

2016-09-20

We present deep number counts at 450 and 850 μ m using the SCUBA-2 camera on the James Clerk Maxwell Telescope. We combine data for six lensing cluster fields and three blank fields to measure the counts over a wide flux range at each wavelength. Thanks to the lensing magnification, our measurements extend to fluxes fainter than 1 mJy and 0.2 mJy at 450 μ m and 850 μ m, respectively. Our combined data highly constrain the faint end of the number counts. Integrating our counts shows that the majority of the extragalactic background light (EBL) at each wavelength ismore » contributed by faint sources with L {sub IR} < 10{sup 12} L {sub ⊙}, corresponding to luminous infrared galaxies (LIRGs) or normal galaxies. By comparing our result with the 500 μ m stacking of K -selected sources from the literature, we conclude that the K -selected LIRGs and normal galaxies still cannot fully account for the EBL that originates from sources with L {sub IR} < 10{sup 12} L {sub ⊙}. This suggests that many faint submillimeter galaxies may not be included in the UV star formation history. We also explore the submillimeter flux ratio between the two bands for our 450 μ m and 850 μ m selected sources. At 850 μ m, we find a clear relation between the flux ratio and the observed flux. This relation can be explained by a redshift evolution, where galaxies at higher redshifts have higher luminosities and star formation rates. In contrast, at 450 μ m, we do not see a clear relation between the flux ratio and the observed flux.« less

Identification of the Infrared Counterpart of SGR 1935+2154 with the Hubble Space Telescope

NASA Astrophysics Data System (ADS)

Levan, Andrew; Kouveliotou, Chryssa; Fruchter, Andrew

2018-02-01

We present deep Hubble Space Telescope observations of a new magnetar source, the soft gamma-repeater SGR 1935+2154, discovered by Swift. We obtained three epochs of observations: while the source was active in 2015 March, during a quiescent period in 2015 August, and during a further active phase in 2016 May. Close to the center of the X-ray error region identified by Chandra, we find a faint (F140W(AB) = 25.3) source, which fades by a factor of ∼2 over the course of 5 months between the first two epochs of observations, before rebrightening during the second active period. If this source is indeed the counterpart to SGR 1935+2154, then it is among the faintest yet located for a magnetar. Our observations are spaced over 1.3 years and enable us to place limits on the source velocity of μ = (60 ± 40) km s‑1 kpc‑1 observations on timescales of a decade can hence probe proper motion limits smaller than the velocities observed for the majority of pulsars. The comparison of the optical/IR and X-ray light curves of the source suggests that emission in the two regimes is associated but not directly correlated, offering support for a magnetospheric versus a fallback disk origin.

Observations of faint comets at McDonald Observatory: 1978-1980

NASA Technical Reports Server (NTRS)

Barker, E. S.; Cochran, A. L.; Rybski, P. M.

1981-01-01

Modern observational techniques, developed for spectroscopy and photometry of faint galaxies and quasars, successfully applied to faint comets on the 2.7 m telescope. The periodic comets Van Biesbrock, Ashbrook-Jackson, Schwassmann-Wachmann 1, Tempel 2, Encke, Forbes, Brooks 2, Stephan-Oterma and the new comets Bradfield (19791), Bowell (1980b), Chernis-Petrauskas (1980k) were observed. The comets ranged in magnitude from 10th to 20th magnitude. For comets fainter than 19th magnitude, reflectance spectra at 100A resolution and area photometry were obtained. On comets of 17th or 18th magnitude, spectrometric scans (6A resolution) of the nucleus or inner coma region. On those comets which are brighter than 16th magnitude spatial spectrophotometric (6A resolution) studies of the inner and extended comae were done. An extensive spatial study of the comae of P/Encke and P/Stephen-Oterma, correlated with heliocentric distance is taking place. The observing process used is described and examples of the results obtained to date are discussed.

One- and two-mode squeezed light in correlated interferometry

NASA Astrophysics Data System (ADS)

Ruo-Berchera, I.; Degiovanni, I. P.; Olivares, S.; Samantaray, N.; Traina, P.; Genovese, M.

2015-11-01

We study in detail a system of two interferometers aimed at detecting extremely faint phase fluctuations. This system can represent a breakthrough for detecting a faint correlated signal that would remain otherwise undetectable even using the most sensitive individual interferometric devices, as in the case of so-called holographic noise. The signature of this kind of noise emerges as a correlation between the output signals of the interferometers. On the other hand, when holographic noise is absent one expects uncorrelated signals since the time-averaged fluctuations due to shot noise and other independent contributions vanish (though limiting the overall sensitivity). We show how injecting quantum light in the free ports of the interferometers can reduce the photon noise of the system beyond the shot noise, enhancing the resolution in the phase-correlation estimation. We analyze the use of both the two-mode squeezed vacuum and two independent squeezed states. Our results confirm the benefit of using squeezed beams together with strong coherent beams in interferometry. We also investigate the possible use of the two-mode squeezed vacuum, discovering interesting and unexplored areas of application of bipartite entanglement, in particular the possibility of reaching in principle a surprising uncertainty reduction.

X-ray and optical observations of four polars

NASA Astrophysics Data System (ADS)

Worpel, H.; Schwope, A. D.; Granzer, T.; Reinsch, K.; Schwarz, R.; Traulsen, I.

2016-08-01

Aims: We investigate the temporal and spectral behaviour of four polar cataclysmic variables from the infrared to X-ray regimes, refine our knowledge of the physical parameters of these systems at different accretion rates, and search for a possible excess of soft X-ray photons. Methods: We obtained and analysed four XMM-Newton X-ray observations of three of the sources, two of them discovered with the SDSS and one in the RASS. The X-ray data were complemented by optical photometric and spectroscopic observations and, for two sources, archival Swift observations. Results: SDSSJ032855.00+052254.2 was X-ray bright in two XMM-Newton and two Swift observations, and shows transitions from high and low accretion states on a timescale of a few months. The source shows no significant soft excess. We measured the magnetic field strength at the main accreting pole to be 39 MG and the inclination to be 45° ≤ I ≤ 77°, and we refined the long-term ephemeris. SDSSJ133309.20+143706.9 was X-ray faint. We measured a faint phase X-ray flux and plasma temperature for this source, which seems to spend almost all of its time accreting at a low level. Its inclination is less than about 76°. 1RXSJ173006.4+033813 was X-ray bright in the XMM-Newton observation. Its spectrum contained a modest soft blackbody component, not luminous enough to be considered a significant soft excess. We inferred a magnetic field strength at the main accreting pole of 20 to 25 MG, and that the inclination is less than 77° and probably less than 63°. V808 Aur, also known as CSS081231:J071126+440405, was X-ray faint in the Swift observation, but there is nonetheless strong evidence for bright and faint phases in X-rays and perhaps in UV. Residual X-ray flux from the faint phase is difficult to explain by thermal emission from the white dwarf surface, or by accretion onto the second pole. We present a revised distance estimate of 250 pc. Conclusions: The three systems we were able to study in detail appear to be normal polars with luminosities and magnetic field strengths typical for this class of accreting binary. None of the four systems studied shows the strong soft excess thought commonplace in polars prior to the XMM-Newton era. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.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).

MORPHOLOGICAL PROPERTIES OF Lyα EMITTERS AT REDSHIFT 4.86 IN THE COSMOS FIELD: CLUMPY STAR FORMATION OR MERGER?

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

Kobayashi, Masakazu A. R.; Taniguchi, Yoshiaki; Kajisawa, Masaru

2016-03-01

We investigate morphological properties of 61 Lyα emitters (LAEs) at z = 4.86 identified in the COSMOS field, based on Hubble Space Telescope Advanced Camera for Surveys (ACS) imaging data in the F814W band. Out of the 61 LAEs, we find the ACS counterparts for 54 LAEs. Eight LAEs show double-component structures with a mean projected separation of 0.″63 (∼4.0 kpc at z = 4.86). Considering the faintness of these ACS sources, we carefully evaluate their morphological properties, that is, size and ellipticity. While some of them are compact and indistinguishable from the point-spread function (PSF) half-light radius of 0.″07 (∼0.45 kpc),more » the others are clearly larger than the PSF size and spatially extended up to 0.″3 (∼1.9 kpc). We find that the ACS sources show a positive correlation between ellipticity and size and that the ACS sources with large size and round shape are absent. Our Monte Carlo simulation suggests that the correlation can be explained by (1) the deformation effects via PSF broadening and shot noise or (2) the source blending in which two or more sources with small separation are blended in our ACS image and detected as a single elongated source. Therefore, the 46 single-component LAEs could contain the sources that consist of double (or multiple) components with small spatial separation (i.e., ≲0.″3 or 1.9 kpc). Further observation with high angular resolution at longer wavelengths (e.g., rest-frame wavelengths of ≳4000 Å) is inevitable to decipher which interpretation is adequate for our LAE sample.« less

Probing cluster potentials through gravitational lensing of background X-ray sources

NASA Technical Reports Server (NTRS)

Refregier, A.; Loeb, A.

1996-01-01

The gravitational lensing effect of a foreground galaxy cluster, on the number count statistics of background X-ray sources, was examined. The lensing produces a deficit in the number of resolved sources in a ring close to the critical radius of the cluster. The cluster lens can be used as a natural telescope to study the faint end of the (log N)-(log S) relation for the sources which account for the X-ray background.

THE CHANDRA COSMOS LEGACY SURVEY: OPTICAL/IR IDENTIFICATIONS

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

Marchesi, S.; Civano, F.; Urry, C. M.

2016-01-20

We present the catalog of optical and infrared counterparts of the Chandra  COSMOS-Legacy  Survey, a 4.6 Ms Chandra  program on the 2.2 deg{sup 2} of the COSMOS field, combination of 56 new overlapping observations obtained in Cycle 14 with the previous C-COSMOS survey. In this Paper we report the i, K, and 3.6 μm identifications of the 2273 X-ray point sources detected in the new Cycle 14 observations. We use the likelihood ratio technique to derive the association of optical/infrared (IR) counterparts for 97% of the X-ray sources. We also update the information for the 1743 sources detected in C-COSMOS,more » using new K and 3.6 μm information not available when the C-COSMOS analysis was performed. The final catalog contains 4016 X-ray sources, 97% of which have an optical/IR counterpart and a photometric redshift, while ≃54% of the sources have a spectroscopic redshift. The full catalog, including spectroscopic and photometric redshifts and optical and X-ray properties described here in detail, is available online. We study several X-ray to optical (X/O) properties: with our large statistics we put better constraints on the X/O flux ratio locus, finding a shift toward faint optical magnitudes in both soft and hard X-ray band. We confirm the existence of a correlation between X/O and the the 2–10 keV luminosity for Type 2 sources. We extend to low luminosities the analysis of the correlation between the fraction of obscured AGNs and the hard band luminosity, finding a different behavior between the optically and X-ray classified obscured fraction.« less

The radio spectral energy distribution of infrared-faint radio sources

NASA Astrophysics Data System (ADS)

Herzog, A.; Norris, R. P.; Middelberg, E.; Seymour, N.; Spitler, L. R.; Emonts, B. H. C.; Franzen, T. M. O.; Hunstead, R.; Intema, H. T.; Marvil, J.; Parker, Q. A.; Sirothia, S. K.; Hurley-Walker, N.; Bell, M.; Bernardi, G.; Bowman, J. D.; Briggs, F.; Cappallo, R. J.; Callingham, J. R.; Deshpande, A. A.; Dwarakanath, K. S.; For, B.-Q.; Greenhill, L. J.; Hancock, P.; Hazelton, B. J.; Hindson, L.; Johnston-Hollitt, M.; Kapińska, A. D.; Kaplan, D. L.; Lenc, E.; Lonsdale, C. J.; McKinley, B.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Morgan, J.; Oberoi, D.; Offringa, A.; Ord, S. M.; Prabu, T.; Procopio, P.; Udaya Shankar, N.; Srivani, K. S.; Staveley-Smith, L.; Subrahmanyan, R.; Tingay, S. J.; Wayth, R. B.; Webster, R. L.; Williams, A.; Williams, C. L.; Wu, C.; Zheng, Q.; Bannister, K. W.; Chippendale, A. P.; Harvey-Smith, L.; Heywood, I.; Indermuehle, B.; Popping, A.; Sault, R. J.; Whiting, M. T.

2016-10-01

Context. Infrared-faint radio sources (IFRS) are a class of radio-loud (RL) active galactic nuclei (AGN) at high redshifts (z ≥ 1.7) that are characterised by their relative infrared faintness, resulting in enormous radio-to-infrared flux density ratios of up to several thousand. Aims: Because of their optical and infrared faintness, it is very challenging to study IFRS at these wavelengths. However, IFRS are relatively bright in the radio regime with 1.4 GHz flux densities of a few to a few tens of mJy. Therefore, the radio regime is the most promising wavelength regime in which to constrain their nature. We aim to test the hypothesis that IFRS are young AGN, particularly GHz peaked-spectrum (GPS) and compact steep-spectrum (CSS) sources that have a low frequency turnover. Methods: We use the rich radio data set available for the Australia Telescope Large Area Survey fields, covering the frequency range between 150 MHz and 34 GHz with up to 19 wavebands from different telescopes, and build radio spectral energy distributions (SEDs) for 34 IFRS. We then study the radio properties of this class of object with respect to turnover, spectral index, and behaviour towards higher frequencies. We also present the highest-frequency radio observations of an IFRS, observed with the Plateau de Bure Interferometer at 105 GHz, and model the multi-wavelength and radio-far-infrared SED of this source. Results: We find IFRS usually follow single power laws down to observed frequencies of around 150 MHz. Mostly, the radio SEDs are steep (α < -0.8; %), but we also find ultra-steep SEDs (α < -1.3; %). In particular, IFRS show statistically significantly steeper radio SEDs than the broader RL AGN population. Our analysis reveals that the fractions of GPS and CSS sources in the population of IFRS are consistent with the fractions in the broader RL AGN population. We find that at least % of IFRS contain young AGN, although the fraction might be significantly higher as suggested by the steep SEDs and the compact morphology of IFRS. The detailed multi-wavelength SED modelling of one IFRS shows that it is different from ordinary AGN, although it is consistent with a composite starburst-AGN model with a star formation rate of 170 M⊙ yr-1. Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).

Galaxy evolution and large-scale structure in the far-infrared. II - The IRAS faint source survey

NASA Astrophysics Data System (ADS)

Lonsdale, Carol J.; Hacking, Perry B.; Conrow, T. P.; Rowan-Robinson, M.

1990-07-01

The new IRAS Faint Source Survey data base is used to confirm the conclusion of Hacking et al. (1987) that the 60 micron source counts fainter than about 0.5 Jy lie in excess of predictions based on nonevolving model populations. The existence of an anisotropy between the northern and southern Galactic caps discovered by Rowan-Robinson et al. (1986) and Needham and Rowan-Robinson (1988) is confirmed, and it is found to extend below their sensitivity limit to about 0.3 Jy in 60 micron flux density. The count anisotropy at f(60) greater than 0.3 can be interpreted reasonably as due to the Local Supercluster; however, no one structure accounting for the fainter anisotropy can be easily identified in either optical or far-IR two-dimensional sky distributions. The far-IR galaxy sky distributions are considerably smoother than distributions from the published optical galaxy catalogs. It is likely that structure of the large size discussed here have been discriminated against in earlier studies due to insufficient volume sampling.

Galaxy evolution and large-scale structure in the far-infrared. II. The IRAS faint source survey

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

Lonsdale, C.J.; Hacking, P.B.; Conrow, T.P.

1990-07-01

The new IRAS Faint Source Survey data base is used to confirm the conclusion of Hacking et al. (1987) that the 60 micron source counts fainter than about 0.5 Jy lie in excess of predictions based on nonevolving model populations. The existence of an anisotropy between the northern and southern Galactic caps discovered by Rowan-Robinson et al. (1986) and Needham and Rowan-Robinson (1988) is confirmed, and it is found to extend below their sensitivity limit to about 0.3 Jy in 60 micron flux density. The count anisotropy at f(60) greater than 0.3 can be interpreted reasonably as due to themore » Local Supercluster; however, no one structure accounting for the fainter anisotropy can be easily identified in either optical or far-IR two-dimensional sky distributions. The far-IR galaxy sky distributions are considerably smoother than distributions from the published optical galaxy catalogs. It is likely that structure of the large size discussed here have been discriminated against in earlier studies due to insufficient volume sampling. 105 refs.« less

Galaxy evolution and large-scale structure in the far-infrared. II - The IRAS faint source survey

NASA Technical Reports Server (NTRS)

Lonsdale, Carol J.; Hacking, Perry B.; Conrow, T. P.; Rowan-Robinson, M.

1990-01-01

The new IRAS Faint Source Survey data base is used to confirm the conclusion of Hacking et al. (1987) that the 60 micron source counts fainter than about 0.5 Jy lie in excess of predictions based on nonevolving model populations. The existence of an anisotropy between the northern and southern Galactic caps discovered by Rowan-Robinson et al. (1986) and Needham and Rowan-Robinson (1988) is confirmed, and it is found to extend below their sensitivity limit to about 0.3 Jy in 60 micron flux density. The count anisotropy at f(60) greater than 0.3 can be interpreted reasonably as due to the Local Supercluster; however, no one structure accounting for the fainter anisotropy can be easily identified in either optical or far-IR two-dimensional sky distributions. The far-IR galaxy sky distributions are considerably smoother than distributions from the published optical galaxy catalogs. It is likely that structure of the large size discussed here have been discriminated against in earlier studies due to insufficient volume sampling.

Gravity Wave Detection through All-sky Imaging of Airglow

NASA Astrophysics Data System (ADS)

Nguyen, T. V.; Martinez, A.; Porat, I.; Hampton, D. L.; Bering, E., III; Wood, L.

2017-12-01

Airglow, the faint glow of the atmosphere, is caused by the interaction of air molecules with radiation from the sun. Similarly, the aurora is created by interactions of air molecules with the solar wind. It has been shown that airglow emissions are altered by gravity waves passing through airglow source region (100-110km), making it possible to study gravity waves and their sources through airglow imaging. University of Houston's USIP - Airglow team designed a compact, inexpensive all-sky imager capable of detecting airglow and auroral emissions using a fisheye lens, a simple optical train, a filter wheel with 4 specific filters, and a CMOS camera. This instrument has been used in USIP's scientific campaign in Alaska throughout March 2017. During this period, the imager captured auroral activity in the Fairbanks region. Due to lunar conditions and auroral activity images from the campaign did not yield visible signs of airglow. Currently, the team is trying to detect gravity wave patterns present in the images through numerical analysis. Detected gravity wave patterns will be compared to local weather data, and may be used to make correlations between gravity waves and weather events. Such correlations could provide more data on the relationship between the mesosphere and lower layers of the atmosphere. Practical applications of this research include weather prediction and detection of air turbulence.

Herschel-PACS photometry of faint stars for sensitivity performance assessment and establishment of faint FIR primary photometric standards

NASA Astrophysics Data System (ADS)

Klaas, U.; Balog, Z.; Nielbock, M.; Müller, T. G.; Linz, H.; Kiss, Cs.

2018-05-01

Aims: Our aims are to determine flux densities and their photometric accuracy for a set of seventeen stars that range in flux from intermediately bright (≲2.5 Jy) to faint (≳5 mJy) in the far-infrared (FIR). We also aim to derive signal-to-noise dependence with flux and time, and compare the results with predictions from the Herschel exposure-time calculation tool. Methods: We obtain aperture photometry from Herschel-PACS high-pass-filtered scan maps and chop/nod observations of the faint stars. The issues of detection limits and sky confusion noise are addressed by comparison of the field-of-view at different wavelengths, by multi-aperture photometry, by special processing of the maps to preserve extended emission, and with the help of large-scale absolute sky brightness maps from AKARI. This photometry is compared with flux-density predictions based on photospheric models for these stars. We obtain a robust noise estimate by fitting the flux distribution per map pixel histogram for the area around the stars, scaling it for the applied aperture size and correcting for noise correlation. Results: For 15 stars we obtain reliable photometry in at least one PACS filter, and for 11 stars we achieve this in all three PACS filters (70, 100, 160 μm). Faintest fluxes, for which the photometry still has good quality, are about 10-20 mJy with scan map photometry. The photometry of seven stars is consistent with models or flux predictions for pure photospheric emission, making them good primary standard candidates. Two stars exhibit source-intrinsic far-infrared excess: β Gem (Pollux), being the host star of a confirmed Jupiter-size exoplanet, due to emission of an associated dust disk, and η Dra due to dust emission in a binary system with a K1 dwarf. The investigation of the 160 μm sky background and environment of four sources reveals significant sky confusion prohibiting the determination of an accurate stellar flux at this wavelength. As a good model approximation, for nine stars we obtain scaling factors of the continuum flux models of four PACS fiducial standards with the same or quite similar spectral type. We can verify a linear dependence of signal-to-noise ratio (S/N) with flux and with square root of time over significant ranges. At 160 μm the latter relation is, however, affected by confusion noise. Conclusions: The PACS faint star sample has allowed a comprehensive sensitivity assessment of the PACS photometer. Accurate photometry allows us to establish a set of five FIR primary standard candidates, namely α Ari, ɛ Lep, ω Cap, HD 41047 and 42 Dra, which are 2-20 times fainter than the faintest PACS fiducial standard (γ Dra) with absolute accuracy of <6%. For three of these primary standard candidates, essential stellar parameters are known, meaning that a dedicated flux model code may be run. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Tables A.3 to A.5 and B.1 to B.3 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/613/A40

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

Murray, S. G.; Trott, C. M.; Jordan, C. H.

We present a sophisticated statistical point-source foreground model for low-frequency radio Epoch of Reionization (EoR) experiments using the 21 cm neutral hydrogen emission line. Motivated by our understanding of the low-frequency radio sky, we enhance the realism of two model components compared with existing models: the source count distributions as a function of flux density and spatial position (source clustering), extending current formalisms for the foreground covariance of 2D power-spectral modes in 21 cm EoR experiments. The former we generalize to an arbitrarily broken power law, and the latter to an arbitrary isotropically correlated field. This paper presents expressions formore » the modified covariance under these extensions, and shows that for a more realistic source spatial distribution, extra covariance arises in the EoR window that was previously unaccounted for. Failure to include this contribution can yield bias in the final power-spectrum and under-estimate uncertainties, potentially leading to a false detection of signal. The extent of this effect is uncertain, owing to ignorance of physical model parameters, but we show that it is dependent on the relative abundance of faint sources, to the effect that our extension will become more important for future deep surveys. Finally, we show that under some parameter choices, ignoring source clustering can lead to false detections on large scales, due to both the induced bias and an artificial reduction in the estimated measurement uncertainty.« less

Ultra faint dwarf galaxies: an arena for testing dark matter versus modified gravity

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

Lin, Weikang; Ishak, Mustapha, E-mail: wxl123830@utdallas.edu, E-mail: mishak@utdallas.edu

2016-10-01

The scenario consistent with a wealth of observations for the missing mass problem is that of weakly interacting dark matter particles. However, arguments or proposals for a Newtonian or relativistic modified gravity scenario continue to be made. A distinguishing characteristic between the two scenarios is that dark matter particles can produce a gravitational effect, in principle, without the need of baryons while this is not the case for the modified gravity scenario where such an effect must be correlated with the amount of baryonic matter. We consider here ultra-faint dwarf (UFD) galaxies as a promising arena to test the twomore » scenarios based on the above assertion. We compare the correlation of the luminosity with the velocity dispersion between samples of UFD and non-UFD galaxies, finding a significant loss of correlation for UFD galaxies. For example, we find for 28 non-UFD galaxies a strong correlation coefficient of −0.688 which drops to −0.077 for the 23 UFD galaxies. Incoming and future data will determine whether the observed stochasticity for UFD galaxies is physical or due to systematics in the data. Such a loss of correlation (if it is to persist) is possible and consistent with the dark matter scenario for UFD galaxies but would constitute a new challenge for the modified gravity scenario.« less

Fainting

MedlinePlus

... pressure. Why Do People Faint? Fainting is pretty common in teens. The good news is that most of the time it's not a sign of something serious. When someone faints, it's usually because ... ventilated setting are common causes of fainting in teens. People can also ...

COMPLETE ELEMENT ABUNDANCES OF NINE STARS IN THE r -PROCESS GALAXY RETICULUM II

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

Ji, Alexander P.; Frebel, Anna; Chiti, Anirudh

We present chemical abundances derived from high-resolution Magellan /Magellan Inamori Kyocera Echelle spectra of the nine brightest known red giant members of the ultra-faint dwarf galaxy Reticulum II (Ret II). These stars span the full metallicity range of Ret II (−3.5 < [Fe/H] < −2). Seven of the nine stars have extremely high levels of r -process material ([Eu/Fe] ∼ 1.7), in contrast to the extremely low neutron-capture element abundances found in every other ultra-faint dwarf galaxy studied to date. The other two stars are the most metal-poor stars in the system ([Fe/H] < −3), and they have neutron-capture elementmore » abundance limits similar to those in other ultra-faint dwarf galaxies. We confirm that the relative abundances of Sr, Y, and Zr in these stars are similar to those found in r -process halo stars, but they are ∼0.5 dex lower than the solar r -process pattern. If the universal r -process pattern extends to those elements, the stars in Ret II display the least contaminated known r -process pattern. The abundances of lighter elements up to the iron peak are otherwise similar to abundances of stars in the halo and in other ultra-faint dwarf galaxies. However, the scatter in abundance ratios is large enough to suggest that inhomogeneous metal mixing is required to explain the chemical evolution of this galaxy. The presence of low amounts of neutron-capture elements in other ultra-faint dwarf galaxies may imply the existence of additional r -process sites besides the source of r -process elements in Ret II. Galaxies like Ret II may be the original birth sites of r -process enhanced stars now found in the halo.« less

Number density distribution of near-infrared sources on a sub-degree scale in the Galactic center: Comparison with the Fe XXV Kα line at 6.7 keV

NASA Astrophysics Data System (ADS)

Yasui, Kazuki; Nishiyama, Shogo; Yoshikawa, Tatsuhito; Nagatomo, Schun; Uchiyama, Hideki; Tsuru, Takeshi Go; Koyama, Katsuji; Tamura, Motohide; Kwon, Jungmi; Sugitani, Koji; Schödel, Rainer; Nagata, Tetsuya

2015-12-01

The stellar distribution derived from an H- and KS-band survey of the central region of our Galaxy is compared with the Fe XXV Kα (6.7 keV) line intensity observed with the Suzaku satellite. The survey is for the galactic coordinates |l| ≲ 3.0° and |b | ≲ 1.0° (equivalent to 0.8 kpc × 0.3 kpc for R⊙ = 8 kpc), and the number-density distribution N(KS,0; l, b) of stars is derived by using the extinction-corrected magnitude KS,0 = 10.5. This is deep enough to probe the old red-giant population and in turn to estimate the (l, b) distribution of faint X-ray point sources such as coronally active binaries and cataclysmic variables. In the Galactic plane (b = 0°), N(10.5; l, b) increases in the direction of the Galactic center as |l|-0.30±0.03 in the range of - 0.1° ≥ l ≥ - 0.7°, but this increase is significantly slower than the increase (|l|-0.44±0.02) of the Fe XXV Kα line intensity. If normalized with the ratios in the outer region 1.5° ≤ |l| ≤ 2.8°, where faint X-ray point sources are argued to dominate the diffuse Galactic X-ray ridge emission, the excess of the Fe XXV Kα line intensity over the stellar number density is at least a factor of two at |l| = 0.1°. This indicates that a significant part of the Galactic-center diffuse emission arises from a truly diffuse optically thin thermal plasma, and not from an unresolved collection of faint X-ray point sources related to the old stellar population.

Infrared-faint radio sources in the SERVS deep fields. Pinpointing AGNs at high redshift

NASA Astrophysics Data System (ADS)

Maini, A.; Prandoni, I.; Norris, R. P.; Spitler, L. R.; Mignano, A.; Lacy, M.; Morganti, R.

2016-12-01

Context. Infrared-faint radio sources (IFRS) represent an unexpected class of objects which are relatively bright at radio wavelength, but unusually faint at infrared (IR) and optical wavelengths. A recent and extensive campaign on the radio-brightest IFRSs (S1.4 GHz≳ 10 mJy) has provided evidence that most of them (if not all) contain an active galactic nuclei (AGN). Still uncertain is the nature of the radio-faintest IFRSs (S1.4 GHz≲ 1 mJy). Aims: The scope of this paper is to assess the nature of the radio-faintest IFRSs, testing their classification and improving the knowledge of their IR properties by making use of the most sensitive IR survey available so far: the Spitzer Extragalactic Representative Volume Survey (SERVS). We also explore how the criteria of IFRSs can be fine-tuned to pinpoint radio-loud AGNs at very high redshift (z > 4). Methods: We analysed a number of IFRS samples identified in SERVS fields, including a new sample (21 sources) extracted from the Lockman Hole. 3.6 and 4.5 μm IR counterparts of the 64 sources located in the SERVS fields were searched for and, when detected, their IR properties were studied. Results: We compared the radio/IR properties of the IR-detected IFRSs with those expected for a number of known classes of objects. We found that IR-detected IFRSs are mostly consistent with a mixture of high-redshift (z ≳ 3) radio-loud AGNs. The faintest ones (S1.4 GHz 100 μJy), however, could be also associated with nearer (z 2) dust-enshrouded star-burst galaxies. We also argue that, while IFRSs with radio-to-IR ratios >500 can very efficiently pinpoint radio-loud AGNs at redshift 2 < z < 4, lower radio-to-IR ratios ( 100-200) are expected for higher redshift radio-loud AGNs.

An IRAS-Based Search for New Dusty Late-Type WC Wolf-Rayet Stars

NASA Technical Reports Server (NTRS)

Cohen, Martin

1995-01-01

I have examined all Infrared Astronomical Satellite (IRAS) data relevant to the 173 Galactic Wolf-Rayet (W-R) stars in an updated catalog, including the 13 stars newly discovered by Shara and coworkers. Using the W-R coordinates in these lists, I have examined the IRAS Point Source Catalog (PSC), the Faint Source Catalog, and the Faint Source Reject Catalog, and have generated one-dimensional spatial profiles, 'ADDSCANs', and two-dimensional full-resolution images, 'FRESCOS'. The goal was to assemble the best set of observed IRAS color indices for different W-R types, in particular for known dusty late-type WC Wolf-Rayet (WCL) objects. I have also unsuccessfully sought differences in IRAS colors and absolute magnitudes between single and binary W-R stars. The color indices for the entire ensemble of W-R stars define zones in the IRAS color-color ([12] - [25], [25] - [60])-plane. By searching the PSC for otherwise unassociated sources that satisfy these colors, I have identified potential new W-R candidates, perhaps too faint to have been recognized in previous optical searches. I have extracted these candidates' IRAS low-resolution spectrometer (LRS) data and compared the spectra with the highly characteristic LRS shape for known dusty WCL stars. The 13 surviving candidates must now be ex amined by optical spectroscopy. This work represents a much more rigorous and exhaustive version of the LRS study that identified IRAS 17380 - 3031 (WR98a) as the first new W-R (WC9) star discovered by IPAS. This search should have detected dusty WCL stars to a distance of 7.0 kpc from the Sun, for l is greater than 30 degrees, and to 2.9 kpc even in the innermost galaxy. For free-free-dominated W-R stars the corresponding distances are 2.5 and 1.0 kpc, respectively.

An IRAS-based search for new Dusty Late-Type WC Wolf-Rayet stars

NASA Technical Reports Server (NTRS)

Cohen, Martin

1995-01-01

I have examined all Infrared Astronomical Satellite (IRAS) data relevant to the 173 Galactic Wolf-Rayet (W-R) stars in an updated catalog, including the 13 stars newly discovered by Shara and coworkers. Using the W-R coordinates in these lists, I have examined the IRAS Point Source Catalog (PSC), the Faint Source Catalog, and the Faint Source Reject Catalog, and have generated one-dimensional spatial profiles ('ADDSCANs') and two-dimensional full-resolution images ('FRESCOs'). The goal was to assemble the best set of observed IRAS color indices for different W-R types, in particular for known dusty late-type WC Wolf-Rayet (WCL) objects. I have also unsuccessfully sought differences in IRAS colors and absolute magnitudes between single and binary W-R stars. The color indices for the entire ensemble of W-R stars define zones in the IRAS color-color plane. By searching the PSC for otherwise unassociated sources that satisfy these colors, I have identified potential new W-R candidates, perhaps too faint to have been recognized in previous optical searches. I have extracted these candidates' IRAS low-resolution spectrometer (LRS) data and compared the spectra with the highly characteristic LRS shape for known dusty WCL stars. The 13 surviving candidates must now be examined by optical spectroscopy. This work represents a much more rigorous and exhaustive version of the LRS study that identified IRAS 17380 - 3031 (WR98a) as the first new W-R (WC9) star discovered by IRAS. This search should have detected dusty WCL stars to a distance of 7.0 kpc from the Sun, for the absolute value of l greater than 30 deg, and to 2.9 kpc even in the innermost Galaxy. For free-free-dominated W-R stars the corresponding distances are 2.5 and 1.0 kpc, respectively.

Adaptive Optics Photometry and Astrometry of Binary Stars. III. A Faint Companion Search of O-Star Systems

DTIC Science & Technology

2008-08-01

Mason et al. (1998) survey. 3.3. 2MASS Data Mining Confirmations Searches were made for Two Micron All Sky Survey ( 2MASS ) (Cutri et al. 2003...the separation/m limits of 2MASS , the point-source catalog was searched for sources in the magnitude range 5.5 J 8.0, corresponding to the...approximate 2MASS J -magnitude range for the AO targets in this project. This yielded 99,656 sources. All sources within 10′′ of these “primaries” were then

ON THE FERMI -GBM EVENT 0.4 s AFTER GW150914

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

Greiner, J.; Yu, H.-F.; Burgess, J. M.

In view of the recent report by Connaughton et al., we analyze continuous time-tagged event (TTE) data of Fermi -gamma-ray burst monitor (GBM) around the time of the gravitational-wave event GW 150914. We find that after proper accounting for low-count statistics, the GBM transient event at 0.4 s after GW 150914 is likely not due to an astrophysical source, but consistent with a background fluctuation, removing the tension between the INTEGRAL /ACS non-detection and GBM. Additionally, reanalysis of other short GRBs shows that without proper statistical modeling the fluence of faint events is over-predicted, as verified for some joint GBM–ACSmore » detections of short GRBs. We detail the statistical procedure to correct these biases. As a result, faint short GRBs, verified by ACS detections, with significances in the broadband light curve even smaller than that of the GBM–GW150914 event are recovered as proper non-zero source, while the GBM–GW150914 event is consistent with zero fluence.« less

Exploring the Hard and Soft X-ray Emission of Magnetic Cataclysmic Variables

NASA Astrophysics Data System (ADS)

de Martino, D.; Anzolin, G.; Bonnet-Bidaud, J.-M.; Falanga, M.; Matt, G.; Mouchet, M.; Mukai, K.; Masetti, N.

2009-05-01

A non-negligible fraction of galactic hard (>20 keV) X-ray sources were identified as CVs of the magnetic Intermediate Polar type in INTEGRAL, SWIFT and RXTE surveys, that suggests a still hidden but potentially important population of faint hard X-ray sources. Simbol-X has the unique potential to simultaneously characterize their variable and complex soft and hard X-ray emission thus allowing to understand their putative role in galactic populations of X-ray sources.

Emission Mechanisms in X-Ray Faint Elliptical Galaxies

NASA Astrophysics Data System (ADS)

Brown, B. A.; Bregman, J. N.

1999-12-01

To understand the X-ray emission in normal elliptical galaxies, it is important to determine the relative contributions of hot interstellar gas and discrete sources to the observed emission. In X-ray luminous ellipticals, a hot gaseous component dominates the emission from X-ray binaries and other discrete sources. It is expected that, as one looks toward lower X-ray luminous galaxies, that the hot gas will contribute less to the overall X-ray emission and that discrete sources will supply most, if not all of, the observed X-ray emission. Here we examine ROSAT HRI and PSPC data for seventeen optically bright (BT < 11.15) elliptical galaxies with log(LX/L_B) < 29.7 ergs s-1/L⊙ . Radial surface brightness profiles are modeled with a modified King beta model and a de Vaucouleurs r1/4 law (similar to a beta = 0.5 beta model). For galaxy profiles where the two models are easily distinguishable, the models are combined, and fit to the data to determine or set upper limits to the discrete source contribution. The modeled data suggest that X-ray faint elliptical galaxies may still retain a sizable fraction of hot gas, but that emission from discrete sources are a significant component of the total observed X-ray emission. Support for this project has been provided by NASA and the National Academy of Sciences.

Photometric Redshift Calibration Strategy for WFIRST Cosmology

NASA Astrophysics Data System (ADS)

Hemmati, Shoubaneh; WFIRST, WFIRST-HLS-COSMOLOGY

2018-01-01

In order for WFIRST and other Stage IV Dark energy experiments (e.g. LSST, Euclid) to infer cosmological parameters not limited by systematic errors, accurate redshift measurements are needed. This accuracy can only be met using spectroscopic subsamples to calibrate the full sample. In this poster, we employ the machine leaning, SOM based spectroscopic sampling technique developed in Masters et al. 2015, using the empirical color-redshift relation among galaxies to find the minimum spectra required for the WFIRST weak lensing calibration. We use galaxies from the CANDELS survey to build the LSST+WFIRST lensing analog sample of ~36k objects and train the LSST+WFIRST SOM. We show that 26% of the WFIRST lensing sample consists of sources fainter than the Euclid depth in the optical, 91% of which live in color cells already occupied by brighter galaxies. We demonstrate the similarity between faint and bright galaxies as well as the feasibility of redshift measurements at different brightness levels. 4% of SOM cells are however only occupied by faint galaxies for which we recommend extra spectroscopy of ~200 new sources. Acquiring the spectra of these sources will enable the comprehensive calibration of the WFIRST color-redshift relation.

Characterisation of a candidate dual AGN

NASA Astrophysics Data System (ADS)

Lena, D.; Panizo-Espinar, G.; Jonker, P. G.; Torres, M.; Heida, M.

2018-05-01

We present Chandra and optical observations of a candidate dual AGN discovered serendipitously while searching for recoiling black holes via a cross-correlation between the serendipitous XMM source catalog (2XMMi) and SDSS-DR7 galaxies with a separation no larger than ten times the sum of their Petrosian radii. The system has a stellar mass ratio M1/M2 ≈ 0.7. One of the galaxies (Source 1) shows clear evidence for AGN activity in the form of hard X-ray emission and optical emission-line diagnostics typical of AGN ionisation. The nucleus of the other galaxy (Source 2) has a soft X-ray spectrum, bluer colours, and optical emission line ratios dominated by stellar photoionisation with a "composite" signature, which might indicate the presence of a weak AGN. When plotted on a diagram with X-ray luminosity vs [OIII] luminosity both nuclei fall within the locus defined by local Seyfert galaxies. From the optical spectrum we estimate the electron densities finding n1 < 27 e- cm-3 and n2 ≈ 200 e- cm-3. From a 2D decomposition of the surface brightness distribution we infer that both galaxies host rotationally supported bulges (Sersic index <1). While the active nature of Source 1 can be established with confidence, whether the nucleus of Source 2 is active remains a matter of debate. Evidence that a faint AGN might reside in its nucleus is, however, tantalising.

An Improved Statistical Point-source Foreground Model for the Epoch of Reionization

NASA Astrophysics Data System (ADS)

Murray, S. G.; Trott, C. M.; Jordan, C. H.

2017-08-01

We present a sophisticated statistical point-source foreground model for low-frequency radio Epoch of Reionization (EoR) experiments using the 21 cm neutral hydrogen emission line. Motivated by our understanding of the low-frequency radio sky, we enhance the realism of two model components compared with existing models: the source count distributions as a function of flux density and spatial position (source clustering), extending current formalisms for the foreground covariance of 2D power-spectral modes in 21 cm EoR experiments. The former we generalize to an arbitrarily broken power law, and the latter to an arbitrary isotropically correlated field. This paper presents expressions for the modified covariance under these extensions, and shows that for a more realistic source spatial distribution, extra covariance arises in the EoR window that was previously unaccounted for. Failure to include this contribution can yield bias in the final power-spectrum and under-estimate uncertainties, potentially leading to a false detection of signal. The extent of this effect is uncertain, owing to ignorance of physical model parameters, but we show that it is dependent on the relative abundance of faint sources, to the effect that our extension will become more important for future deep surveys. Finally, we show that under some parameter choices, ignoring source clustering can lead to false detections on large scales, due to both the induced bias and an artificial reduction in the estimated measurement uncertainty.

Vasovagal syncope in medical students and their first-degree relatives.

PubMed

Serletis, Anna; Rose, Sarah; Sheldon, Aaron G; Sheldon, Robert S

2006-08-01

To determine the effect of family history on the likelihood of vasovagal syncope. Sixty-two medical students and 228 first-degree relatives were studied. Vasovagal syncope was ascertained with the Calgary syncope symptom score. The effects of the sex of the subject and parental syncope history on the likelihood of offspring fainting were described using Kaplan-Meier estimates and analysed using proportional hazards regression. The prevalence of vasovagal syncope was 32% and the median age of first faint in those who fainted was 14 years. More females than males fainted [42 vs. 31%; P=0.02; hazard ratio (HR) 1.34 (95% CI 1.07-1.68)]. An individual with two fainting parents was more likely to faint than one with no fainting parents [P<0.0001; HR 3.4 (95% CI 1.7-7.03)]. In the proportional hazards model, offspring of either sex whose mother faints are more likely to faint than those whose mother does not faint [HR 2.86 (95% CI 1.54-5.31)]. Having a father who faints significantly increases the risk of syncope in sons [HR 4.12 (95%CI 1.39-12.31)], but not in daughters [HR 1.18 (95% CI 0.56-3.34)]. Family history and sex of subject are important predictors of vasovagal syncope in offspring.

High-Redshift Astrophysics Using Every Photon

NASA Astrophysics Data System (ADS)

Breysse, Patrick; Kovetz, Ely; Rahman, Mubdi; Kamionkowski, Marc

2017-01-01

Large galaxy surveys have dramatically improved our understanding of the complex processes which govern gas dynamics and star formation in the nearby universe. However, we know far less about the most distant galaxies, as existing high-redshift observations can only detect the very brightest sources. Intensity mapping surveys provide a promising tool to access this poorly-studied population. By observing emission lines with low angular resolution, these surveys can make use of every photon in a target line to study faint emitters which are inaccessible using traditional techniques. With upcoming carbon monoxide experiments in mind, I will demonstrate how an intensity map can be used to measure the luminosity function of a galaxy population, and in turn how these measurements will allow us to place robust constraints on the cosmic star formation history. I will then show how cross-correlating CO isotopologue lines will make it possible to study gas dynamics within the earliest galaxies in unprecedented detail.

Ionization of the diffuse gas in galaxies: Hot low-mass evolved stars at work

NASA Astrophysics Data System (ADS)

Flores-Fajardo, N.; Morisset, C.; Stasinska, G.; Binette, L.

2011-10-01

The Diffuse Ionized Medium (DIG) is visible through its faint optical line emission outside classical HII regions (Reynolds 1971) and turns out to be a major component of the interstellar medium in galaxies. OB stars in galaxies likely represent the main source of ionizing photons for the DIG. However, an additional source is needed to explain the increase of [NII]/Hα, [SII]/Hα with galactic height.

Investigation of ultraviolet fluxes of normal and peculiar stars

NASA Technical Reports Server (NTRS)

Deutschman, W. A.; Schild, R. E.

1974-01-01

Data from Project Celescope, a program that photographed the ultraviolet sky, in order to study several problems in current astrophysics are analyzed. Two star clusters, the Pleiades and the Hyades, reveal differences between the two that we are unable to explain simply from their differences in chemical abundance, rotation, or reddening. Data for Orion show large scatter, which appears to be in the sense that the Orion stars are too faint for their ground-based photometry. Similarly, many supergiants in the association Sco OB1 are too faint in the ultraviolet, but the ultraviolet brightness appears to be only poorly correlated with spectral type. Ultraviolet Celescope data for several groups of peculiar stars have also been analyzed. The strong He I stars are too faint in the ultraviolet, possibly owing to enhancement of O II continuous opacity due to oxygen overabundance. The Be stars appear to have ultraviolet colors normal for their MK spectral types. The P Cygni stars are considerably fainter than main-sequence stars of comparable spectral type, probably owing, at least in part, to line blocking by resonance lines of multiply ionized light metals. The Wolf-Rayet stars have ultraviolet color temperatures of O stars.

The red-sequence of 72 WINGS local galaxy clusters

NASA Astrophysics Data System (ADS)

Valentinuzzi, T.; Poggianti, B. M.; Fasano, G.; D'Onofrio, M.; Moretti, A.; Ramella, M.; Biviano, A.; Fritz, J.; Varela, J.; Bettoni, D.; Vulcani, B.; Moles, M.; Couch, W. J.; Dressler, A.; Kjærgaard, P.; Omizzolo, A.; Cava, A.

2011-12-01

We study the color - magnitude red sequence and blue fraction of 72 X-ray selected galaxy clusters at z = 0.04-0.07 from the WINGS survey, searching for correlations between the characteristics of the red sequence (RS) and the environment. We consider the slope and scatter of the red sequence, the number ratio of red luminous-to-faint galaxies, the blue fraction, and the fractions of ellipticals, S0s, and spirals that compose the RS. None of these quantities correlate with the cluster velocity dispersion, X-ray luminosity, number of cluster substructures, BCG prevalence over next brightest galaxies, and the spatial concentration of ellipticals. The properties of the RS, instead, depend strongly on local galaxy density. Higher density regions have a smaller RS scatter, a higher luminous-to-faint ratio, a lower blue fraction, and a lower spiral fraction on the RS. Our results clearly illustrate the prominent effect of the local density in setting the epoch when galaxies become passive and join the red sequence, as opposed to the mass of the galaxy host structure.

An extended galactic population of low-luminosity x-ray sources (CVs?) and the diffuse x-ray background

NASA Technical Reports Server (NTRS)

Maoz, Eyal; Grindlay, Jonathan E.

1995-01-01

The incompatibility of the properties of the X-ray background (XRB) with active galactic nuclei (AGNs) contributing approximately greater than 60% at energies of a few keV has often been interpreted as being due to a substantial contribution of a new population of yet unrecognized X-ray sources. The existence of such population has been recently suggested also by an analysis of very deep ROSAT observations which revealed a considerable excess of faint X-ray sources over that expected from QSO evolution models, and that the average spectrum of the resolved sources becomes harder with decreasing flux limit. These sources could be extragalactic in origin, but if they make a substantial contribution to the XRB then they must exhibit much weaker clustering than galaxies or QSOs in order to be consistent with the stringent constraints on source clustering imposed by autocorrelation analyses of the unresolved XRB. We investigate the possibility that the indicated new population of X-ray sources is Galactic in origin. Examining spherical halo and thick disk distributions, we derive the allowed properties of such populations which would resolve the discrepancy found in the number counts of faint sources and be consistent with observational constraints on the total background intensity, the XRB anisotropy, the number of unidentified bright sources, the Galaxy's total X-ray luminosity, and with the results of fluctuation analyses of the unresolved XRB. We find that a flattened Galactic halo (or a thick disk) distribution with a scale height of a few kpc is consistent with all the above requirements. The typical X-ray luminosity of the sources is approximately equal to 10(exp 30-31)ergs/s in the 0.5-2 keV band, the number density of sources in the solar vicinity is approximately 10(exp -4.5)pc(exp -3), their total number in the Galaxy is approximately 10(exp 8.5), and their total contribution to the Galaxy's X-ray luminosity is approximately 10(exp 39) ergs/s. We discuss the possible nature of these soures, including their being subdwarfs, low mass x-ray binaries (LMXBs), massive black holes, and old neutron stars. We argue that the inferred X-ray and optical luminosities of these sources, the slope of their energy spectrum, and the derived local number density and spatial distribution are all consistent with their being intrinsically faint cataclysmic variables with low accretion rates. We suggest a few possibilities for the origin of such population, including an origin from disrupted globular clusters or dark clusters. We make predictions and suggest tests that could either confirm or rule out our proposal in the near future.

Possible new VY Scl-type variable 1RXS J075330.1+044606

NASA Astrophysics Data System (ADS)

Sokolovsky, K.; Denisenko, D.; Mescheryakov, A.; Tkachenko, A.; Korotkiy, S.; Gerke, V.

2012-02-01

We report the discovery of a possible new VY Scl-type cataclysmic variable associated with previously unidentified X-ray source 1RXS J075330.1+044606. The variable optical object USNO-B1.0 0947-0148659 (07:53:30.78 +04:45:56.3, J2000) located 15" from the X-ray source listed in the ROSAT All Sky Survey Faint Source Catalog (Voges et al., 2000, IAUC, 7432) was identified from information listed in the USNO-B1.0 catalog (Monet et al.

Space telescope scientific instruments

NASA Technical Reports Server (NTRS)

Leckrone, D. S.

1979-01-01

The paper describes the Space Telescope (ST) observatory, the design concepts of the five scientific instruments which will conduct the initial observatory observations, and summarizes their astronomical capabilities. The instruments are the wide-field and planetary camera (WFPC) which will receive the highest quality images, the faint-object camera (FOC) which will penetrate to the faintest limiting magnitudes and achieve the finest angular resolution possible, and the faint-object spectrograph (FOS), which will perform photon noise-limited spectroscopy and spectropolarimetry on objects substantially fainter than those accessible to ground-based spectrographs. In addition, the high resolution spectrograph (HRS) will provide higher spectral resolution with greater photometric accuracy than previously possible in ultraviolet astronomical spectroscopy, and the high-speed photometer will achieve precise time-resolved photometric observations of rapidly varying astronomical sources on short time scales.

Globular clusters in high-redshift dwarf galaxies: a case study from the Local Group

NASA Astrophysics Data System (ADS)

Zick, Tom O.; Weisz, Daniel R.; Boylan-Kolchin, Michael

2018-06-01

We present the reconstructed evolution of rest-frame ultraviolet (UV) luminosities of the most massive Milky Way dwarf spheroidal satellite galaxy, Fornax, and its five globular clusters (GCs) across redshift, based on analysis of the stellar fossil record and stellar population synthesis modelling. We find that (1) Fornax's (proto-)GCs can generate 10-100 times more UV flux than the field population, despite comprising <˜{5} per cent of the stellar mass at the relevant redshifts; (2) due to their respective surface brightnesses, it is more likely that faint, compact sources in the Hubble Frontier Fields (HFFs) are GCs hosted by faint galaxies, than faint galaxies themselves. This may significantly complicate the construction of a galaxy UV luminosity function at z > 3. (3) GC formation can introduce order-of-magnitude errors in abundance matching. We also find that some compact HFF objects are consistent with the reconstructed properties of Fornax's GCs at the same redshifts (e.g. surface brightness, star formation rate), suggesting we may have already detected proto-GCs in the early Universe. Finally, we discuss the prospects for improving the connections between local GCs and proto-GCs detected in the early Universe.

Astronomical Data Center Bulletin, volume 1, number 3

NASA Technical Reports Server (NTRS)

Mead, J. M.; Warren, W. H., Jr.; Nagy, T. A.

1983-01-01

A catalog of galactic O-type stars, a machine-readable version of the bright star catalog, a two-micron sky survey, sky survey sources with problematical Durchmusterung identifications, data retrieval for visual binary stars, faint blue objects, the sixth catalog of galactic Wolf-Rayet stars, declination versus magnitude distribution, the SAO-HD-GC-DM cross index catalog, star cross-identification tables, astronomical sources, bibliographical star index search updates, DO-HD and HD-DO cross indices, and catalogs, are reviewed.

HUBBLE FRONTIER FIELDS FIRST COMPLETE CLUSTER DATA: FAINT GALAXIES AT z ∼ 5-10 FOR UV LUMINOSITY FUNCTIONS AND COSMIC REIONIZATION

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

Ishigaki, Masafumi; Ouchi, Masami; Ono, Yoshiaki

2015-01-20

We present comprehensive analyses of faint dropout galaxies up to z ∼ 10 with the first full-depth data set of the A2744 lensing cluster and parallel fields observed by the Hubble Frontier Fields (HFF) program. We identify 54 dropouts at z ∼ 5-10 in the HFF fields and enlarge the size of the z ∼ 9 galaxy sample obtained to date. Although the number of highly magnified (μ ∼ 10) galaxies is small because of the tiny survey volume of strong lensing, our study reaches the galaxies' intrinsic luminosities comparable to the deepest-field HUDF studies. We derive UV luminosity functionsmore » with these faint dropouts, carefully evaluating by intensive simulations the combination of observational incompleteness and lensing effects in the image plane, including magnification, distortion, and multiplication of images, with the evaluation of mass model dependencies. Our results confirm that the faint-end slope, α, is as steep as –2 at z ∼ 6-8 and strengthen the evidence for the rapid decrease of UV luminosity densities, ρ{sub UV}, at z > 8 from the large z ∼ 9 sample. We examine whether the rapid ρ{sub UV} decrease trend can be reconciled with the large Thomson scattering optical depth, τ{sub e}, measured by cosmic microwave background experiments, allowing a large space of free parameters, such as an average ionizing photon escape fraction and a stellar-population-dependent conversion factor. No parameter set can reproduce both the rapid ρ{sub UV} decrease and the large τ {sub e}. It is possible that the ρ{sub UV} decrease moderates at z ≳ 11, that the free parameters significantly evolve toward high z, or that there exist additional sources of reionization such as X-ray binaries and faint active galactic nuclei.« less

Experiment S030: Dim sky photography/orthicon

NASA Technical Reports Server (NTRS)

Dunkelman, L.; Mercer, R. D.; Ney, E. P.; Hemenway, C. L.

1971-01-01

During Gemini missions, the image orthicon system was used to obtain photographic data on faint and diffuse astronomical phenomena. Results show that the photographs may be used to determine the airglow geometry. Although it was sensitive, the original photographic system was unsuitable for use in the study of dim and diffuse astronomical light 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

Discovery of low-redshift X-ray selected quasars - New clues to the QSO phenomenon

NASA Technical Reports Server (NTRS)

Grindlay, J. E.; Forman, W. R.; Steiner, J. E.; Canizares, C. R.; Mcclintock, J. E.

1980-01-01

The identification of six X-ray sources discovered by the Einstein Observatory with X-ray quasars is reported, and the properties of these X-ray selected quasars are discussed. The four high-latitude fields of 1 sq deg each in which the Einstein imaging proportional counter detected serendipitous X-ray sources at intermediate exposures of 10,000 sec were observed by 4-m and 1.5-m telescopes, and optical sources with uv excesses and emission line spectra typical of many low-redshift quasars and Seyfert 1 galaxies were found within the 1-arcsec error boxes of the X-ray sources. All six quasars identified were found to be radio quiet, with low redshift and relatively faint optical magnitudes, and to be similar in space density, colors and magnitude versus redshift relation to an optically selected sample at the same mean magnitude. X-ray luminosity was found to be well correlated with both continuum and broad-line emission luminosities for the known radio-quiet quasars and Seyfert 1 galaxies, and it was observed that the five objects with the lowest redshifts have very similar X-ray/optical luminosity ratios despite tenfold variations in X-ray luminosity. It is concluded that photoionization by a continuum extending to X-ray energies is the dominant excitation mechanism in radio-quiet quasars.

The SCUBA HAlf Degree Extragalactic Survey (SHADES) - V. Submillimetre properties of near-infrared-selected galaxies in the Subaru/XMM -Newton deep field

NASA Astrophysics Data System (ADS)

Takagi, T.; Mortier, A. M. J.; Shimasaku, K.; Coppin, K.; Pope, A.; Ivison, R. J.; Hanami, H.; Serjeant, S.; Clements, D. L.; Priddey, R. S.; Dunlop, J. S.; Takata, T.; Aretxaga, I.; Chapman, S. C.; Eales, S. A.; Farrah, D.; Granato, G. L.; Halpern, M.; Hughes, D. H.; van Kampen, E.; Scott, D.; Sekiguchi, K.; Smail, I.; Vaccari, M.

2007-11-01

We have studied the submillimetre (submm) properties of the following classes of near-infrared-selected (NIR-selected) massive galaxies at high redshifts: BzK-selected star-forming galaxies (BzKs); distant red galaxies (DRGs); and extremely red objects (EROs). We used the SCUBA HAlf Degree Extragalactic Survey (SHADES), the largest uniform submm survey to date. Partial overlap of SIRIUS/NIR images and SHADES in Subaru/XMM-Newton deep field has allowed us to identify four submm-bright NIR-selected galaxies, which are detected in the mid-IR, 24μ m, and the radio, 1.4GHz. We find that all of our submm-bright NIR-selected galaxies satisfy the BzK selection criteria, i.e. BzK ≡ (z - K)AB - (B - z)AB >= -0.2, except for one galaxy whose B - z and z - K colours are however close to the BzK colour boundary. Two of the submm-bright NIR-selected galaxies satisfy all of the selection criteria we considered, i.e. they belong to the BzK-DRG-ERO overlapping population, or `extremely red' BzKs. Although these extremely red BzKs are rare (0.25 arcmin-2), up to 20 per cent of this population could be submm galaxies. This fraction is significantly higher than that found for other galaxy populations studied here. Via a stacking analysis, we have detected the 850-μ m flux of submm-faint BzKs and EROs in our SCUBA maps. While the contribution of z ~ 2 BzKs to the submm background is about 10-15 per cent and similar to that from EROs typically at z ~ 1, BzKs have a higher fraction (~30 per cent) of submm flux in resolved sources compared with EROs and submm sources as a whole. From the spectral energy distribution (SED) fitting analysis for both submm-bright and submm-faint BzKs, we found no clear signature that submm-bright BzKs are experiencing a specifically luminous evolutionary phase, compared with submm-faint BzKs. An alternative explanation might be that submm-bright BzKs are more massive than submm-faint ones.

First Results from the ISO-IRAS Faint Galaxy Survey

NASA Astrophysics Data System (ADS)

Levine, Deborah A.; Lonsdale, Carol J.; Hurt, Robert L.; Smith, Harding E.; Helou, George; Beichman, Charles; Cesarsky, Catherine; Elbaz, David; Klaas, Ulrich; Laureijs, Rene; Lemke, Detrich; Lord, Steven; McMahon, Richard; Moshir, Mehrdad; Neugebauer, Gerry; Soifer, B. T.; Van Buren, Dave; Wehrle, Ann; Wolstencroft, Ray

1998-09-01

We present the first results from the ISO-IRAS Faint Galaxy Survey (IIFGS), a program designed to obtain ISO observations of the most distant and luminous galaxies in the IRAS Faint Source Survey by filling short gaps in the ISO observing schedule with pairs of 12 μm ISOCAM and 90 μm ISOPHOT observations. As of 1997 October, over 500 sources have been observed, with an ISOCAM detection rate over 80%, covering over 1.25 deg2 of sky to an 11.5 μm point-source completeness limit of approximately 1.0 mJy (corresponding to a ~10 σ detection sensitivity). Observations are presented for nine sources detected by ISOPHOT and ISOCAM early in the survey for which we have ground-based G- and I-band images and optical spectroscopy. The ground-based data confirm that the IIFGS strategy efficiently detects moderate-redshift (z = 0.11-0.38 for this small sample) strong emission line galaxies with L60 μm >~ 1011 L⊙ one of our sample has L60 μm > 1012 L⊙ (H0 = 75 km s-1 Mpc-1, Ω = 1). The infrared-optical spectral energy distributions are comparable to those of nearby luminous infrared galaxies, which span the range from pure starburst (e.g., Arp 220) to infrared QSO (Mrk 231). Two of the systems show signs of strong interaction, and four show active galactic nucleus (AGN)-like excitation; one of the AGNs, F15390+6038, which shows a high excitation Seyfert 2 spectrum, has an unusually warm far- to mid-infrared color and may be an obscured QSO. The IIFGS sample is one of the largest and deepest samples of infrared-luminous galaxies available, promising to be a rich sample for studying infrared-luminous galaxies up to z ~ 1 and for understanding the evolution of infrared galaxies and the star formation rate in the universe. ISO is an ESA project with instruments funded by ESA member states (especially the PI countries: France, Germany, the Netherlands, and the United Kingdom) and with the participation of ISAS and NASA.

Faint Coronal Hard X-rays From Accelerated Electrons in Solar Flares

NASA Astrophysics Data System (ADS)

Glesener, Lindsay Erin

Solar flares are huge explosions on the Sun that release a tremendous amount of energy from the coronal magnetic field, up to 1033 ergs, in a short time (100--1000 seconds), with much of the energy going into accelerated electrons and ions. An efficient acceleration mechanism is needed, but the details of this mechanism remain relatively unknown. A fraction of this explosive energy reaches the Earth in the form of energetic particles, producing geomagnetic storms and posing dangers to spaceborne instruments, astronauts, and Earthbound power grids. There are thus practical reasons, as well as intellectual ones, for wishing to understand this extraordinary form of energy release. Through imaging spectroscopy of the hard X-ray (HXR) emission from solar flares, the behavior of flare-accelerated electrons can be studied. The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI ) spacecraft launched in 2002 with the goal of better understanding flare particle acceleration. Using rotation modulation collimators, RHESSI is able to cover a wide energy range (3 keV--17 MeV) with fine angular and energy resolutions. RHESSI's success in the last 10 years in investigating the relationship between energetic electrons and ions, the nature of faint sources in the corona, the energy distribution of flares, and several other topics have significantly advanced the understanding of flares. But along with the wealth of information revealed by RHESSI come some clear observational challenges. Very few, if any, RHESSI observations have come close to imaging the electron acceleration region itself. This is undoubtedly due to a lack of both sensitivity (HXRs from electron beams in the tenuous corona are faint) and dynamic range (HXR sources at chromospheric flare footpoints are much brighter and tend to obscure faint coronal sources). Greater sensitivity is also required to investigate the role that small flares in the quiet Sun could play in heating the corona. The Focusing Optics X-ray Solar Imager (FOXSI ) is a developing project to address these observational difficulties. FOXSI is a sounding rocket payload developed under NASA's Low Cost Access to Space program. The project spearheads a shift to using direct imaging via focusing grazing-incidence HXR optics rather than the indirect Fourier techniques used by RHESSI and its predecessors. Such optics can attain higher sensitivity since photons are focused onto a small detector volume and have significantly better dynamic range than Fourier methods do. On November 2, 2012 the FOXSI rocket payload was flown for a 6-minute observation and successfully imaged a solar flare, providing the first focused HXR spectroscopic images of the Sun above 5 keV. The motivation, construction, testing, and flight of FOXSI will be described in this text, along with case studies on the use of RHESSI to analyze unique coronal HXR sources from two solar flares.

XMM-Newton observations of the Lockman Hole IV: spectra of the brightest AGN

NASA Astrophysics Data System (ADS)

Mateos, S.; Barcons, X.; Carrera, F. J.; Ceballos, M. T.; Hasinger, G.; Lehmann, I.; Fabian, A. C.; Streblyanska, A.

2005-12-01

This paper presents the results of a detailed X-ray spectral analysis of a sample of 123 X-ray sources detected with XMM-Newton in the Lockman Hole field. This is the deepest observation carried out with XMM-Newton with more that 600 ks of good EPIC-pn data. We have spectra with good signal to noise (>500 source counts) for all objects down to 0.2-12 keV fluxes of 5×10-15 erg cm-2 s-1 (flux limit of 6×10-16 erg cm-2 s-1 in the 0.5-2 and 2-10 keV bands). At the time of the analysis, we had optical spectroscopic identifications for 60% of the sources, 46 being optical type-1 AGN and 28 optical type-2 AGN. Using a single power law model our sources' average spectral slope hardens at faint 0.5-2 keV fluxes but not at faint 2-10 keV fluxes. We have been able to explain this effect in terms of an increase in X-ray absorption at faint fluxes. We did not find in our data any evidence for the existence of a population of faint intrinsically harder sources. The average spectral slope of our sources is 1.9, with an intrinsic dispersion of 0.28. We detected X-ray absorption (F-test significance ≥95%) in 37% of the sources, 10% in type-1 AGN (rest-frame {NH ˜ 1.6 × 1021{-}1.2 × 1022 cm-2}) and 77% (rest-frame {NH ˜ 1.5 ×1021{-}4× 1023 cm-2}) in type-2 AGN. Using X-ray fluxes corrected for absorption, the fraction of absorbed objects and the absorbing column density distribution did not vary with X-ray flux. Our type-1 and type-2 AGN do not appear to have different continuum shapes, but the distribution of intrinsic (rest-frame) absorbing column densities is different among both classes. A significant fraction of our type-2 AGN (5 out of 28) were found to display no substantial absorption ({NH<1021 cm-2}). We discuss possible interpretations to this in terms of Compton-thick AGN and intrinsic Broad Line Region properties. An emission line compatible with Fe Kα was detected in 8 sources (1 type-1 AGN, 5 type-2 AGN and 2 unidentified) with rest frame equivalent widths 120-1000 eV. However weak broad components can be easily missed in other sources by the relatively noisy data. The AGN continuum or intrinsic absorption did not depend on X-ray luminosity and/or redshift. Soft excess emission was detected in 18 objects, but only in 9 (including 4 type-1 AGN and 4 type-2 AGN) could we fit this spectral component with a black body model. The measured 0.5-2 keV luminosities of the fitted black body were not significantly different in type-1 and type-2 AGN, although the temperatures of the black body were slightly higher in type-2 AGN (< {kT}>=0.26±0.08) than in type-1 AGN (< {kT}>=0.09±0.01). For 9 sources (including 1 type-1 AGN and 3 type-2 AGN) a scattering model provided a better fit of the soft excess emission. We found that the integrated contribution from our sources to the X-ray background in the 2-7 keV band is softer (Γ=1.5{-}1.6) than the background itself, implying that fainter sources need to be more absorbed.

Characterization of a candidate dual AGN

NASA Astrophysics Data System (ADS)

Lena, D.; Panizo-Espinar, G.; Jonker, P. G.; Torres, M. A. P.; Heida, M.

2018-07-01

We present Chandra and optical observations of a candidate dual active galactic nucleus (AGN) discovered serendipitously while searching for recoiling black holes via a cross-correlation between the serendipitous XMM source catalogue (2XMMi) and SDSS-DR7 galaxies with a separation no larger than 10 times the sum of their Petrosian radii. The system has a stellar mass ratio M1/M2 ≈ 0.7. One of the galaxies (Source 1) shows clear evidence for AGN activity in the form of hard X-ray emission and optical emission-line diagnostics typical of AGN ionization. The nucleus of the other galaxy (Source 2) has a soft X-ray spectrum, bluer colours, and optical emission-line ratios dominated by stellar photoionization with a `composite' signature, which might indicate the presence of a weak AGN. When plotted on a diagram with X-ray luminosity versus [OIII] luminosity, both nuclei fall within the locus defined by local Seyfert galaxies. From the optical spectrum, we estimate the electron densities finding n1 < 27 e- cm-3 and n2 ≈ 200 e- cm-3. From a 2D decomposition of the surface brightness distribution, we infer that both galaxies host rotationally supported bulges (Sérsic index <1). While the active nature of Source 1 can be established with confidence, whether the nucleus of Source 2 is active remains a matter of debate. Evidence that a faint AGN might reside in its nucleus is, however, tantalizing.

Evidence for a New Class of Extreme Ultraviolet Sources

NASA Technical Reports Server (NTRS)

Maoz, Dan; Ofek, Eran O.; Shemi, Amotz

1997-01-01

Most of the sources detected in the extreme ultraviolet (EUV; 100-600 A) by the ROSAT/WFC and EUVE all-sky surveys have been identified with active late-type stars and hot white dwarfs that are near enough to the Earth to escape absorption by interstellar gas. However, about 15 per cent of EUV sources are as yet unidentified with any optical counterparts. We examine whether the unidentified EUV sources may consist of the same population of late-type stars and white dwarfs. We present B and R photometry of stars in the fields of seven of the unidentified EUV sources. We detect in the optical the entire main-sequence and white dwarf population out to the greatest distances where they could still avoid absorption. We use color-magnitude diagrams to demonstrate that, in most of the fields, none of the observed stars has the colours and magnitudes of late-type dwarfs at distances less than 100 pc. Similarly, none of the observed stars is a white dwarf within 500 pc that is hot enough to be a EUV emitter. The unidentified EUV sources we study are not detected in X-rays, while cataclysmic variables, X-ray binaries, and active galactic nuclei generally are. We conclude that some of the EUV sources may be a new class of nearby objects, which are either very faint at optical bands or which mimic the colours and magnitudes of distant late-type stars or cool white dwarfs. One candidate for optically faint objects is isolated old neutron stars, slowly accreting interstellar matter. Such neutron stars are expected to be abundant in the Galaxy, and have not been unambiguously detected.

Chandra studies of the globular cluster 47 Tucanae: A deeper X-ray source catalogue, five new X-ray counterparts to millisecond radio pulsars, and new constraints to r-mode instability window

NASA Astrophysics Data System (ADS)

Bhattacharya, Souradeep; Heinke, Craig O.; Chugunov, Andrey I.; Freire, Paulo C. C.; Ridolfi, Alessandro; Bogdanov, Slavko

2017-12-01

We combined Chandra ACIS observations of the globular cluster 47 Tucanae (47 Tuc) from 2000, 2002 and 2014-2015 to create a deeper X-ray source list, and study some of the faint radio millisecond pulsars (MSPs) present in this cluster. We have detected 370 X-ray sources within the half-mass radius (2.79 arcsec) of the cluster, 81 of which are newly identified, by including new data and using improved source detection techniques. The majority of the newly identified sources are in the crowded core region, indicating cluster membership. We associate five of the new X-ray sources with chromospherically active BY Dra or W UMa variables identified by Albrow et al. We present alternative positions derived from two methods, centroiding and image reconstruction, for faint, crowded sources. We are able to extract X-ray spectra of the recently discovered MSPs 47 Tuc aa, 47 Tuc ab, the newly timed MSP 47 Tuc Z, and the newly resolved MSPs 47 Tuc S and 47 Tuc F. Generally, they are well fitted by blackbody or neutron star atmosphere models, with temperatures, luminosities and emitting radii similar to those of other known MSPs in 47 Tuc, though 47 Tuc aa and 47 Tuc ab reach lower X-ray luminosities. We limit X-ray emission from the full surface of the rapidly spinning (542 Hz) MSP 47 Tuc aa, and use this limit to put an upper bound for amplitude of r-mode oscillations in this pulsar as α < 2.5 × 10-9 and constrain the shape of the r-mode instability window.

Unveiling high redshift structures with Planck

NASA Astrophysics Data System (ADS)

Welikala, Niraj

2012-07-01

The Planck satellite, with its large wavelength coverage and all-sky survey, has a unique potential of systematically detecting the brightest and rarest submillimetre sources on the sky. We present an original method based on a combination of Planck and IRAS data which we use to select the most luminous submillimetre high-redshift (z>1-2) cold sources over the sky. The majority of these sources are either individual, strongly lensed galaxies, or represent the combined emission of several submillimetre galaxies within the large beam of Planck. The latter includes, in particular, rapidly growing galaxy groups and clusters. We demonstrate our selection method on the first 5 confirmations that include a newly discovered over-density of 5 submillimetre-bright sources which has been confirmed with Herschel/SPIRE observations and followed up with ground-based observations including VLT/XSHOOTER spectroscopy. Using Planck, we also unveil the nature of 107 high-redshift dusty, lensed submillimetre galaxies that have been previously observed over 940 square degrees by the South Pole Telescope (SPT). We stack these galaxies in the Planck maps, obtaining mean SEDs for both the bright (SPT flux F _{220 GHz} > 20 mJy) and faint (F _{220 GHz} < 20 mJy) galaxy populations. These SEDs and the derived mean redshifts suggest that the bright and faint sources belong to the same population of submillimetre galaxies. Stacking the lensed submillimetre galaxies in Planck also enables us to probe the z~1 environments around the foreground lenses and we obtain estimates of their clustering. Finally, we use the stacks to extrapolate SPT source counts to the Planck HFI frequencies, thereby estimating the contribution of the SPT sources at 220 GHz to the galaxy number counts at 353 and 545 GHz.

DISSECTING PHOTOMETRIC REDSHIFT FOR ACTIVE GALACTIC NUCLEUS USING XMM- AND CHANDRA-COSMOS SAMPLES

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

Salvato, M.; Hasinger, G.; Ilbert, O.

2011-12-01

In this paper, we release accurate photometric redshifts for 1692 counterparts to Chandra sources in the central square degree of the Cosmic Evolution Survey (COSMOS) field. The availability of a large training set of spectroscopic redshifts that extends to faint magnitudes enabled photometric redshifts comparable to the highest quality results presently available for normal galaxies. We demonstrate that morphologically extended, faint X-ray sources without optical variability are more accurately described by a library of normal galaxies (corrected for emission lines) than by active galactic nucleus (AGN) dominated templates, even if these sources have AGN-like X-ray luminosities. Preselecting the library onmore » the bases of the source properties allowed us to reach an accuracy {sigma}{sub {Delta}z/(1+z{sub s{sub p{sub e{sub c)}}}}}{approx}0.015 with a fraction of outliers of 5.8% for the entire Chandra-COSMOS sample. In addition, we release revised photometric redshifts for the 1735 optical counterparts of the XMM-detected sources over the entire 2 deg{sup 2} of COSMOS. For 248 sources, our updated photometric redshift differs from the previous release by {Delta}z > 0.2. These changes are predominantly due to the inclusion of newly available deep H-band photometry (H{sub AB} = 24 mag). We illustrate once again the importance of a spectroscopic training sample and how an assumption about the nature of a source together, with the number and the depth of the available bands, influences the accuracy of the photometric redshifts determined for AGN. These considerations should be kept in mind when defining the observational strategies of upcoming large surveys targeting AGNs, such as eROSITA at X-ray energies and the Australian Square Kilometre Array Pathfinder Evolutionary Map of the Universe in the radio band.« less

THE ORIGIN OF LOW [α/Fe] RATIOS IN EXTREMELY METAL-POOR STARS

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

Kobayashi, Chiaki; Ishigaki, Miho N.; Tominaga, Nozomu

2014-04-10

We show that the low ratios of α elements (Mg, Si, and Ca) to Fe recently found for a small fraction of extremely metal-poor stars can be naturally explained with the nucleosynthesis yields of core-collapse supernovae, i.e., 13-25 M {sub ☉} supernovae, or hypernovae. For the case without carbon enhancement, the ejected iron mass is normal, consistent with observed light curves and spectra of nearby supernovae. On the other hand, the carbon enhancement requires much smaller iron production, and the low [α/Fe] of carbon-enhanced metal-poor stars can also be reproduced with 13-25 M {sub ☉} faint supernovae or faint hypernovae.more » Iron-peak element abundances, in particular Zn abundances, are important to put further constraints on the enrichment sources from galactic archaeology surveys.« less

The duration of reionization constrains the ionizing sources

NASA Astrophysics Data System (ADS)

Sharma, Mahavir; Theuns, Tom; Frenk, Carlos

2018-06-01

We investigate how the nature of the galaxies that reionized the Universe affects the duration of reionization. We contrast two sets of models: one in which galaxies on the faint side of the luminosity function dominate the ionizing emissivity, and a second in which the galaxies on the bright side of the luminosity function dominate. The faint end of the luminosity function evolves slowly, therefore the transition from mostly neutral to mostly ionized state takes a much longer time in the first set of models compared to the second. Existing observational constraints on the duration of this transition are relatively weak, but taken at face value prefer the model in which galaxies on the bright side play a major role. Measurements of the kinetic Sunyaev-Zeldovich effect in the cosmic microwave background from the epoch of reionization also point in the same direction.

What's Going on Around BN

NASA Technical Reports Server (NTRS)

Erickson, Edwin; Colgan, S. W. J.; Schultz, A. S. B.; Simpson, J. P.; Burton, M. G.; Kaufman, M. J.; Young, E. T.; Stolovy, S.

2005-01-01

The Becklin-Neugebauer object, discovered in observations made by Eric Becklin as a graduate student, is the brightest mid-infrared source outside the solar system, and a beacon in the nearest region of massive star formation. Using NICMOS on HST, we have obtained near infrared photometric, spectroscopic, and polarimetric images of the region immediately around BN. These images, with resolutions < -0.2", reveal remarkable morphologies, shock details, new young stellar objects, faint stars with variable intensities, and outflow features. We will summarize these results and inferences regarding the shock properties, illuminating sources of the nebulosity, and IRc sources near BN.

The Infrared Properties of Sources Matched in the Wise All-Sky and Herschel ATLAS Surveys

NASA Technical Reports Server (NTRS)

Bond, Nicholas A.; Benford, Dominic J.; Gardner, Jonathan P.; Amblard, Alexandre; Fleuren, Simone; Blain, Andrew W.; Dunne, Loretta; Smith, Daniel J. B.; Maddox, Steve J.; Hoyos, Carlos;

The Infrared Properties of Sources Matched in the WISE All-Sky and Herschel Atlas Surveys

NASA Technical Reports Server (NTRS)

Bond, Nicholas A.; Benford, Dominic J.; Gardner, Jonathan P.; Eisenhardt, Peter; Amblard, Alexandre; Temi, Pasquale; Fleuren, Simone; Blain, Andrew W.; Dunne, Loretta; Smith, Daniel J.;

The Low-Mass Stellar Initial Mass Function: Ultra-Faint Dwarf Galaxies Revisited

NASA Astrophysics Data System (ADS)

Platais, Imants

2017-08-01

The stellar Initial Mass Function plays a critical role in the evolution of the baryonic content of the Universe. The form of the low-mass IMF - stars of mass less than the solar mass - determines the fraction of baryons locked up for a Hubble time, and thus indicates how gas and metals are cycled through galaxies. Inferences from resolved stellar populations, where the low-mass luminosity function and associated IMF can be derived from direct star counts, generally favor an invariant and universal IMF. However, a recent study of ultra-faint dwarf galaxies Hercules and Leo IV indicates a bottom-lite IMF, over a narrow range of stellar mass (only 0.55-0.75 M_sun), correlated with the internal velocity dispersion and/or metallicity. We propose to obtain ultra-deep imaging for a significantly closer ultra-faint dwarf, Bootes I, which will allow us to construct the luminosity function down to M_v=+10 (equivalent to 0.35 solar mass). We will also re-analyze the HST archival observations for the Hercules and Leo IV dwarfs using the same updated techniques as for Bootes I. The combined datasets should provide a reliable answer to the question of how variable is the low-mass stellar IMF.

The Distribution of Fixation Durations during Reading: Effects of Stimulus Quality

ERIC Educational Resources Information Center

White, Sarah J.; Staub, Adrian

2012-01-01

Participants' eye movements were recorded as they read single sentences presented normally, presented entirely in faint text, or presented normally except for a single faint word. Fixations were longer when the entire sentence was faint than when the sentence was presented normally. In addition, fixations were much longer on a single faint word…

Fainting

MedlinePlus

... in older people. Some causes of fainting include Heat or dehydration Emotional distress Standing up too quickly Certain medicines Drop in blood sugar Heart problems When someone faints, make sure that the ...

Detection and Characterization of Exoplanets using Projections on Karhunen-Loeve Eigenimages: Forward Modeling

NASA Astrophysics Data System (ADS)

Pueyo, Laurent

2016-01-01

A new class of high-contrast image analysis algorithms, that empirically fit and subtract systematic noise has lead to recent discoveries of faint exoplanet /substellar companions and scattered light images of circumstellar disks. The consensus emerging in the community is that these methods are extremely efficient at enhancing the detectability of faint astrophysical signal, but do generally create systematic biases in their observed properties. This poster provides a solution this outstanding problem. We present an analytical derivation of a linear expansion that captures the impact of astrophysical over/self-subtraction in current image analysis techniques. We examine the general case for which the reference images of the astrophysical scene moves azimuthally and/or radially across the field of view as a result of the observation strategy. Our new method method is based on perturbing the covariance matrix underlying any least-squares speckles problem and propagating this perturbation through the data analysis algorithm. This work is presented in the framework of Karhunen-Loeve Image Processing (KLIP) but it can be easily generalized to methods relying on linear combination of images (instead of eigen-modes). Based on this linear expansion, obtained in the most general case, we then demonstrate practical applications of this new algorithm. We first consider the case of the spectral extraction of faint point sources in IFS data and illustrate, using public Gemini Planet Imager commissioning data, that our novel perturbation based Forward Modeling (which we named KLIP-FM) can indeed alleviate algorithmic biases. We then apply KLIP-FM to the detection of point sources and show how it decreases the rate of false negatives while keeping the rate of false positives unchanged when compared to classical KLIP. This can potentially have important consequences on the design of follow-up strategies of ongoing direct imaging surveys.

Characterizing the Cosmic Infrared Background Fluctuations

NASA Astrophysics Data System (ADS)

Li, Yanxia

2015-08-01

A salient feature of the Cosmic Infrared Background (CIB) fluctuations is that their spatial power spectrum rises a factor of ~10 above the expected contribution from all known sources at angular scales >20‧‧. A tantalizing large-scale correlation signal between the residual Cosmic X-ray Background (CXB) and CIB found in the Extended Groth Strip (EGS) further suggests that at least 20% of the CIB fluctuations are associated with accreting X-ray sources, with efficient energy production similar to black holes. However, there is still a controversy about the sources that produce the excess flux. They could be faint, local populations with different spatial distribution from other known galaxies, e.g., intra-halo light (emitted from stars in the outskirts of local galaxies), or really high-z populations at the epoch of reionization that we know little of. Constraining the origin of the CIB fluctuations will help to establish our understanding of the overall cosmic energy budget.In this talk, we will present our plan to break down this controversy, current state of data collection and analysis.(1) We will combine the archival Spitzer/IRAC and Herschel/PACS data, with the Chandra data of the Cosmic Evolution Survey (COSMOS), to accurately measure the source-subtracted CIB and CXB fluctuations to the largest angular scale (~1-2 deg) to date. The newly discovered link between CIB and CXB fluctuations found in the EGS will be revisited in the COSMOS, which provides better photon statistics. (2) We have been working on cross-correlating the unresolved background with the discrete sources detected at shorter wavelengths (1- 2μm), using ground-based multi-wavelength observations. In addition to exploring the Pan-STARRS 3PI and Medium Deep Survey database, we have also been awarded the telescope time of CFHT/WIRCam and Subaru/Hyper-Suprime-Cam for this purpose. The preliminary data analysis will be presented.

The Population of Optically Faint GEO Debris

NASA Technical Reports Server (NTRS)

Seitzer, Patrick; Barker, Ed; Buckalew, Brent; Burkhardt, Andrew; Cowardin, Heather; Frith, James; Gomez, Juan; Kaleida, Catherine; Lederer, Susan M.; Lee, Chris H.

2016-01-01

The 6.5-m Magellan telescope 'Walter Baade' at the Las Campanas Observatory in Chile has been used for spot surveys of the GEO orbital regime to study the population of optically faint GEO debris. The goal is to estimate the size of the population of GEO debris at sizes much smaller than can be studied with 1-meter class telescopes. Despite the small size of the field of view of the Magellan instrument (diameter 0.5-degree), a significant population of objects fainter than R = 19th magnitude have been found with angular rates consistent with circular orbits at GEO. We compare the size of this population with the numbers of GEO objects found at brighter magnitudes by smaller telescopes. The observed detections have a wide range in characteristics starting with those appearing as short uniform streaks. But there are a substantial number of detections with variations in brightness, flashers, during the 5-second exposure. The duration of each of these flashes can be extremely brief: sometimes less than half a second. This is characteristic of a rapidly tumbling object with a quite variable projected size times albedo. If the albedo is of the order of 0.2, then the largest projected size of these objects is around 10-cm. The data in this paper was collected over the last several years using Magellan's IMACS camera in f/2 mode. The analysis shows the brightness bins for the observed GEO population as well as the periodicity of the flashers. All objects presented are correlated with the catalog: the focus of the paper will be on the uncorrelated, optically faint, objects. The goal of this project is to better characterize the faint debris population in GEO that access to a 6.5-m optical telescope in a superb site can provide.

The nature of radio emission from distant galaxies

NASA Astrophysics Data System (ADS)

Richards, Eric A.

I describe an observational program aimed at understanding the radio emission from distant, rapidly evolving galaxy populations. These observations were carried out at 1.4 and 8.5 GHz with the VLA centered on the Hubble Deep Field. Further MERLIN observations of the HDF region at 1.4 GHz provided an angular resolution of 0.2'' and when combined with the VLA data produced an image with an unprecedented rms noise of 4 μJy. All radio sources detected in the VLA complete sample are resolved with a median angular size of 1-2''. The differential count of the radio sources is marginally sub-Euclidean (γ = -2.4 +/- 0.1) and fluctuation analysis suggests nearly 60 sources per armin2 are present at the 1 μJy level. A correlation analysis indicates spatial clustering among the 371 radio sources on angular scales of 1-40 arcmin. Optical identifications are made primarily with bright (I = 22) disk systems composed of irregulars, peculiars, interacting/merging galaxies, and a few isolated field spirals. Available redshifts span the range 0.2-3. These clues coupled with the steep spectral index of the 1.4 GHz selected sample are indicative of diffuse synchrotron radiation in distant galactic disks. Thus the evolution in the microjansky radio population is driven principally by star-formation. I have isolated a number of optically faint radio sources (about 25% of the overall sample) which remain unidentified to I = 26-28 in the HDF and flanking optical fields. Several of these objects have extremely red counterparts and constitute a new class of radio sources which are candidate high redshift dusty protogalaxies.

Faint Object Detection in Multi-Epoch Observations via Catalog Data Fusion

NASA Astrophysics Data System (ADS)

Budavári, Tamás; Szalay, Alexander S.; Loredo, Thomas J.

2017-03-01

Astronomy in the time-domain era faces several new challenges. One of them is the efficient use of observations obtained at multiple epochs. The work presented here addresses faint object detection and describes an incremental strategy for separating real objects from artifacts in ongoing surveys. The idea is to produce low-threshold single-epoch catalogs and to accumulate information across epochs. This is in contrast to more conventional strategies based on co-added or stacked images. We adopt a Bayesian approach, addressing object detection by calculating the marginal likelihoods for hypotheses asserting that there is no object or one object in a small image patch containing at most one cataloged source at each epoch. The object-present hypothesis interprets the sources in a patch at different epochs as arising from a genuine object; the no-object hypothesis interprets candidate sources as spurious, arising from noise peaks. We study the detection probability for constant-flux objects in a Gaussian noise setting, comparing results based on single and stacked exposures to results based on a series of single-epoch catalog summaries. Our procedure amounts to generalized cross-matching: it is the product of a factor accounting for the matching of the estimated fluxes of the candidate sources and a factor accounting for the matching of their estimated directions. We find that probabilistic fusion of multi-epoch catalogs can detect sources with similar sensitivity and selectivity compared to stacking. The probabilistic cross-matching framework underlying our approach plays an important role in maintaining detection sensitivity and points toward generalizations that could accommodate variability and complex object structure.

Faint blue counts from formation of dwarf galaxies at z approximately equals 1

NASA Technical Reports Server (NTRS)

Babul, Arif; Rees, Martin J.

1993-01-01

The nature of faint blue objects (FBO's) has been a source of much speculation since their detection in deep CCD images of the sky. Their high surface density argues against them being progenitors of present-day bright galaxies and since they are only weakly clustered on small scales, they cannot be entities that merged together to form present-day galaxies. Babul & Rees (1992) have suggested that the observed faint blue counts may be due to dwarf elliptical galaxies undergoing their initial starburst at z is approximately equal to 1. In generic hierarchical clustering scenarios, however, dwarf galaxy halos (M is approximately 10(exp 9) solar mass) are expected to form at an earlier epoch; for example, typical 10(exp 9) solar mass halos will virialize at z is approximately equal to 2.3 if the power-spectrum for the density fluctuations is that of the standard b = 2 cold dark matter (CDM) model. Under 'ordinary conditions' the gas would rapidly cool, collect in the cores, and undergo star-formation. Conditions at high redshifts are far from 'ordinary'. The intense UV background will prevent the gas in the dwarf halos from cooling, the halos being released from their suspended state only when the UV flux has diminished sufficiently.

A Tool for Optimizing Observation Planning for Faint Moving Objects

NASA Astrophysics Data System (ADS)

Arredondo, Anicia; Bosh, Amanda S.; Levine, Stephen

2016-10-01

Observations of small solar system bodies such as trans-Neptunian objects and Centaurs are vital for understanding the basic properties of these small members of our solar system. Because these objects are often very faint, large telescopes and long exposures may be necessary, which can result in crowded fields in which the target of interest may be blended with a field star. For accurate photometry and astrometry, observations must be planned to occur when the target is free of background stars; this restriction results in limited observing windows. We have created a tool that can be used to plan observations of faint moving objects. Features of the tool include estimates of best times to observe (when the object is not too near another object), a finder chart output, a list of possible astrometric and photometric reference stars, and an exposure time calculator. This work makes use of the USNOFS Image and Catalogue Archive operated by the United States Naval Observatory, Flagstaff Station (S.E. Levine and D.G. Monet 2000), the JPL Horizons online ephemeris service (Giorgini et al. 1996), the Minor Planet Center's MPChecker (http://cgi.minorplanetcenter.net/cgi-bin/checkmp.cgi), and source extraction software SExtractor (Bertin & Arnouts 1996). Support for this work was provided by NASA SSO grant NNX15AJ82G.

Spectroscopic confirmation of an ultra-faint galaxy at the epoch of reionization

NASA Astrophysics Data System (ADS)

Hoag, Austin; Bradač, Maruša; Trenti, Michele; Treu, Tommaso; Schmidt, Kasper B.; Huang, Kuang-Han; Lemaux, Brian C.; He, Julie; Bernard, Stephanie R.; Abramson, Louis E.; Mason, Charlotte A.; Morishita, Takahiro; Pentericci, Laura; Schrabback, Tim

2017-04-01

Within one billion years of the Big Bang, intergalactic hydrogen was ionized by sources emitting ultraviolet and higher energy photons. This was the final phenomenon to globally affect all the baryons (visible matter) in the Universe. It is referred to as cosmic reionization and is an integral component of cosmology. It is broadly expected that intrinsically faint galaxies were the primary ionizing sources due to their abundance in this epoch1,2. However, at the highest redshifts (z > 7.5 lookback time 13.1 Gyr), all galaxies with spectroscopic confirmations to date are intrinsically bright and, therefore, not necessarily representative of the general population3. Here, we report the unequivocal spectroscopic detection of a low luminosity galaxy at z > 7.5. We detected the Lyman-α emission line at ˜10,504 Å in two separate observations with MOSFIRE4 on the Keck I Telescope and independently with the Hubble Space Telescope's slitless grism spectrograph, implying a source redshift of z = 7.640 ± 0.001. The galaxy is gravitationally magnified by the massive galaxy cluster MACS J1423.8+2404 (z = 0.545), with an estimated intrinsic luminosity of MAB = -19.6 ± 0.2 mag and a stellar mass of M⊙=3.0-0.8+1.5×108 solar masses. Both are an order of magnitude lower than the four other Lyman-α emitters currently known at z > 7.5, making it probably the most distant representative source of reionization found to date.

DEEP WIDEBAND SINGLE POINTINGS AND MOSAICS IN RADIO INTERFEROMETRY: HOW ACCURATELY DO WE RECONSTRUCT INTENSITIES AND SPECTRAL INDICES OF FAINT SOURCES?

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

Rau, U.; Bhatnagar, S.; Owen, F. N., E-mail: rurvashi@nrao.edu

Many deep wideband wide-field radio interferometric surveys are being designed to accurately measure intensities, spectral indices, and polarization properties of faint source populations. In this paper, we compare various wideband imaging methods to evaluate the accuracy to which intensities and spectral indices of sources close to the confusion limit can be reconstructed. We simulated a wideband single-pointing (C-array, L-Band (1–2 GHz)) and 46-pointing mosaic (D-array, C-Band (4–8 GHz)) JVLA observation using a realistic brightness distribution ranging from 1 μ Jy to 100 mJy and time-, frequency-, polarization-, and direction-dependent instrumental effects. The main results from these comparisons are (a) errors in themore » reconstructed intensities and spectral indices are larger for weaker sources even in the absence of simulated noise, (b) errors are systematically lower for joint reconstruction methods (such as Multi-Term Multi-Frequency-Synthesis (MT-MFS)) along with A-Projection for accurate primary beam correction, and (c) use of MT-MFS for image reconstruction eliminates Clean-bias (which is present otherwise). Auxiliary tests include solutions for deficiencies of data partitioning methods (e.g., the use of masks to remove clean bias and hybrid methods to remove sidelobes from sources left un-deconvolved), the effect of sources not at pixel centers, and the consequences of various other numerical approximations within software implementations. This paper also demonstrates the level of detail at which such simulations must be done in order to reflect reality, enable one to systematically identify specific reasons for every trend that is observed, and to estimate scientifically defensible imaging performance metrics and the associated computational complexity of the algorithms/analysis procedures.« less

HRI observations of the Pleiades

NASA Technical Reports Server (NTRS)

Harnden, F. R., Jr.; Caillault, J.-P.; Damiani, F.; Kashyap, V.; Micela, G.; Prosser, C.; Rosner, R.; Sciortino, S.; Stauffer, J.

1996-01-01

The preliminary analysis of the data from the first four Rosat high resolution imager (HRI) pointings provided many new faint Pleiades detections. The completion of the high resolution survey of the most source-confused regions of this open cluster will lead to the construction of proper X-ray luminosity functions and will yield a definitive assessment of the coronal emission of the Pleiades members.

2MASS extended sources in the zone of avoidance

NASA Technical Reports Server (NTRS)

Jarrett, T.; Chester, T.; Cutri, R.; Schneider, S.; Rosenberg, J.; Huchra, J.; Mader, J.

2000-01-01

A new high-resolution near-infrared mapping effort, the Two Micron All Sky Survey (2MASS), is now underway and will provide a complete census of galaxies as faint as 13.5 mag (3 mJy) at 2.2 mu m for most of the sky, and similar to 12.1 mag (10 mJy) for regions veiled by the Milky Way.

ARACHNID: A prototype object-oriented database tool for distributed systems

NASA Technical Reports Server (NTRS)

Younger, Herbert; Oreilly, John; Frogner, Bjorn

1994-01-01

This paper discusses the results of a Phase 2 SBIR project sponsored by NASA and performed by MIMD Systems, Inc. A major objective of this project was to develop specific concepts for improved performance in accessing large databases. An object-oriented and distributed approach was used for the general design, while a geographical decomposition was used as a specific solution. The resulting software framework is called ARACHNID. The Faint Source Catalog developed by NASA was the initial database testbed. This is a database of many giga-bytes, where an order of magnitude improvement in query speed is being sought. This database contains faint infrared point sources obtained from telescope measurements of the sky. A geographical decomposition of this database is an attractive approach to dividing it into pieces. Each piece can then be searched on individual processors with only a weak data linkage between the processors being required. As a further demonstration of the concepts implemented in ARACHNID, a tourist information system is discussed. This version of ARACHNID is the commercial result of the project. It is a distributed, networked, database application where speed, maintenance, and reliability are important considerations. This paper focuses on the design concepts and technologies that form the basis for ARACHNID.

Hydrogen production rate from comet Austin 1982g

NASA Technical Reports Server (NTRS)

Shih, P.; Scherb, F.; Roesler, F. L.

1984-01-01

Meaningful measurements with respect to the cometary Balmer-alpha (H-alpha) emission are difficult and require the use of special equipment. The first ground-based observations of H-alpha emission from a cometary hydrogen corona were conducted on comet Kohoutek 1973 XII with a large-aperture Fabry-Perot spectrometer installed at the McMath solar telescope at Kitt Peak National Observatory. The present investigation is concerned with the second ground-based observations of cometary H-alpha emission carried out during the apparition of comet Austin 1982g. A 150 mm dual-etalon Fabry-Perot spectrometer was employed in the experiment. Use was made of an observatory which is designed for the high spectral resolution study of faint extended sources such as interstellar and geocoronal emission lines. The investigation demonstrates that hydrogen production rates from comets as faint as about 7th magnitude can be routinely measured from the ground at minimal cost.

Faint warm debris disks around nearby bright stars explored by AKARI and IRSF

NASA Astrophysics Data System (ADS)

Ishihara, Daisuke; Takeuchi, Nami; Kobayashi, Hiroshi; Nagayama, Takahiro; Kaneda, Hidehiro; Inutsuka, Shu-ichiro; Fujiwara, Hideaki; Onaka, Takashi

2017-05-01

Context. Debris disks are important observational clues for understanding planetary-system formation process. In particular, faint warm debris disks may be related to late planet formation near 1 au. A systematic search of faint warm debris disks is necessary to reveal terrestrial planet formation. Aims: Faint warm debris disks show excess emission that peaks at mid-IR wavelengths. Thus we explore debris disks using the AKARI mid-IR all-sky point source catalog (PSC), a product of the second generation unbiased IR all-sky survey. Methods: We investigate IR excess emission for 678 isolated main-sequence stars for which there are 18 μm detections in the AKARI mid-IR all-sky catalog by comparing their fluxes with the predicted fluxes of the photospheres based on optical to near-IR fluxes and model spectra. The near-IR fluxes are first taken from the 2MASS PSC. However, 286 stars with Ks < 4.5 in our sample have large flux errors in the 2MASS photometry due to saturation. Thus we have measured accurate J, H, and Ks band fluxes, applying neutral density (ND) filters for Simultaneous InfraRed Imager for Unbiased Survey (SIRIUS) on IRSF, the φ1.4 m near-IR telescope in South Africa, and improved the flux accuracy from 14% to 1.8% on average. Results: We identified 53 debris-disk candidates including eight new detections from our sample of 678 main-sequence stars. The detection rate of debris disks for this work is 8%, which is comparable with those in previous works by Spitzer and Herschel. Conclusions: The importance of this study is the detection of faint warm debris disks around nearby field stars. At least nine objects have a large amount of dust for their ages, which cannot be explained by the conventional steady-state collisional cascade model. The full version of Table 2 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/601/A72

The contribution of faint AGNs to the ionizing background at z 4

NASA Astrophysics Data System (ADS)

Grazian, A.; Giallongo, E.; Boutsia, K.; Cristiani, S.; Vanzella, E.; Scarlata, C.; Santini, P.; Pentericci, L.; Merlin, E.; Menci, N.; Fontanot, F.; Fontana, A.; Fiore, F.; Civano, F.; Castellano, M.; Brusa, M.; Bonchi, A.; Carini, R.; Cusano, F.; Faccini, M.; Garilli, B.; Marchetti, A.; Rossi, A.; Speziali, R.

2018-05-01

Context. Finding the sources responsible for the hydrogen reionization is one of the most pressing issues in observational cosmology. Bright quasi-stellar objects (QSOs) are known to ionize their surrounding neighborhood, but they are too few to ensure the required HI ionizing background. A significant contribution by faint active galactic nuclei (AGNs), however, could solve the problem, as recently advocated on the basis of a relatively large space density of faint active nuclei at z > 4. Aims: This work is part of a long-term project aimed at measuring the Lyman Continuum escape fraction for a large sample of AGNs at z 4 down to an absolute magnitude of M1450 -23. We have carried out an exploratory spectroscopic program to measure the HI ionizing emission of 16 faint AGNs spanning a broad U - I color interval, with I 21-23, and 3.6 < z < 4.2. These AGNs are three magnitudes fainter than the typical SDSS QSOs (M1450 ≲-26) which are known to ionize their surrounding IGM at z ≳ 4. Methods: We acquired deep spectra of these faint AGNs with spectrographs available at the VLT, LBT, and Magellan telescopes, that is, FORS2, MODS1-2, and LDSS3, respectively. The emission in the Lyman Continuum region, close to 900 Å rest frame, has been detected with a signal to noise ratio of 10-120 for all 16 AGNs. The flux ratio between the 900 Å rest-frame region and 930 Å provides a robust estimate of the escape fraction of HI ionizing photons. Results: We have found that the Lyman Continuum escape fraction is between 44 and 100% for all the observed faint AGNs, with a mean value of 74% at 3.6 < z < 4.2 and - 25.1 ≲ M1450 ≲-23.3, in agreement with the value found in the literature for much brighter QSOs (M1450 ≲-26) at the same redshifts. The Lyman Continuum escape fraction of our faint AGNs does not show any dependence on the absolute luminosities or on the observed U - I colors of the objects. Assuming that the Lyman Continuum escape fraction remains close to 75% down to M1450 - 18, we find that the AGN population can provide between 16 and 73% (depending on the adopted luminosity function) of the whole ionizing UV background at z 4, measured through the Lyman forest. This contribution increases to 25-100% if other determinations of the ionizing UV background are adopted from the recent literature. Conclusions: Extrapolating these results to z 5-7, there are possible indications that bright QSOs and faint AGNs can provide a significant contribution to the reionization of the Universe, if their space density is high at M1450 -23. Based on observations made at the Large Binocular Telescope (LBT) at Mt. Graham (Arizona, USA). Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 098.A-0862. This paper includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile.

Symbiotic Stars in X-rays. II. Faint Sources Detected with XMM-Newton and Chandra

NASA Technical Reports Server (NTRS)

Nunez, N. E.; Luna, G. J. M.; Pillitteri, I.; Mukai, K.

2014-01-01

We report the detection from four symbiotic stars that were not known to be X-ray sources. These four object show a ß-type X-ray spectrum, that is, their spectra can be modeled with an absorbed optically thin thermal emission with temperatures of a few million degrees. Photometric series obtained with the Optical Monitor on board XMM-Newton from V2416 Sgr and NSV 25735 support the proposed scenario where the X-ray emission is produced in a shock-heated region inside the symbiotic nebulae.

The Large Quasar Reference Frame (LQRF). An Optical Representation of the ICRS

DTIC Science & Technology

2009-10-01

faint regimes, both the 2MASS and the preliminary northernmost UCAC2 positions are shown of astrometry consistent with the UCAC2 main catalog, and the...is used. 2.7. 2MASS The Two Micron All-Sky Survey point source catalog (Cutri et al. 2003), hereafter 2MASS , derives from an uniform scan of the...17.1, H = 16.4, and K = 15.3. The 2MASS contains the position of 470 992 970 sources, but no proper motions. The astrometry is referred to the

Measurement of visible and UV emission from Energetic Neutral Atom Precipitation (ENAP), on Spacelab

NASA Technical Reports Server (NTRS)

Tinsley, B. A.

1980-01-01

The charge exchange of plasmaspheric ions and exospheric H and O and of solar wind ions with exospheric and interplanetary H are sources of precipitating neutrals whose faint emission may be observed by the imaging spectrometric observatory during dark periods of the SL-1 orbit. Measurements of the interactions of these precipitating atoms with the thermosphere are needed to evaluate the heating and ionization effects on the atmosphere as well as the selective loss of i energetic ions from the sources (predominantly the ring current).

Astrophysical interpretation of the anisotropies in the unresolved gamma-ray background

NASA Astrophysics Data System (ADS)

Ando, Shin'ichiro; Fornasa, Mattia; Fornengo, Nicolao; Regis, Marco; Zechlin, Hannes-S.

2017-06-01

Recently, a new measurement of the auto- and cross-correlation angular power spectrum (APS) of the isotropic gamma-ray background was performed, based on 81 months of data of the Fermi Large-Area Telescope (LAT). Here, we fit, for the first time, the new APS data with a model describing the emission of unresolved blazars. These sources are expected to dominate the anisotropy signal. The model we employ in our analysis reproduces well the blazars resolved by Fermi LAT. When considering the APS obtained by masking the sources listed in the 3FGL catalog, we find that unresolved blazars underproduce the measured APS below ˜1 GeV . Contrary to past results, this suggests the presence of a new contribution to the low-energy APS, with a significance of, at least, 5 σ . The excess can be ascribed to a new class of faint gamma-ray emitters. If we consider the APS obtained by masking the sources in the 2FGL catalog, there is no underproduction of the APS below 1 GeV, but the new source class is still preferred over the blazars-only scenario (with a significance larger than 10 σ ). The properties of the new source class and the level of anisotropies induced in the isotropic gamma-ray background are the same, independent of the APS data used. In particular, the new gamma-ray emitters must have a soft energy spectrum, with a spectral index ranging, approximately, from 2.7 to 3.2. This complicates their interpretation in terms of known sources, since, normally, star-forming and radio galaxies are observed with a harder spectrum. The new source class identified here is also expected to contribute significantly to the intensity of the isotropic gamma-ray background.

Galaxy and Mass Assembly (GAMA): Exploring the WISE Web in G12

NASA Astrophysics Data System (ADS)

Jarrett, T. H.; Cluver, M. E.; Magoulas, C.; Bilicki, M.; Alpaslan, M.; Bland-Hawthorn, J.; Brough, S.; Brown, M. J. I.; Croom, S.; Driver, S.; Holwerda, B. W.; Hopkins, A. M.; Loveday, J.; Norberg, P.; Peacock, J. A.; Popescu, C. C.; Sadler, E. M.; Taylor, E. N.; Tuffs, R. J.; Wang, L.

2017-02-01

We present an analysis of the mid-infrared Wide-field Infrared Survey Explorer (WISE) sources seen within the equatorial GAMA G12 field, located in the North Galactic Cap. Our motivation is to study and characterize the behavior of WISE source populations in anticipation of the deep multiwavelength surveys that will define the next decade, with the principal science goal of mapping the 3D large-scale structures and determining the global physical attributes of the host galaxies. In combination with cosmological redshifts, we identify galaxies from their WISE W1 (3.4 μm) resolved emission, and we also perform a star-galaxy separation using apparent magnitude, colors, and statistical modeling of star counts. The resulting galaxy catalog has ≃590,000 sources in 60 deg2, reaching a W1 5σ depth of 31 μJy. At the faint end, where redshifts are not available, we employ a luminosity function analysis to show that approximately 27% of all WISE extragalactic sources to a limit of 17.5 mag (31 μJy) are at high redshift, z> 1. The spatial distribution is investigated using two-point correlation functions and a 3D source density characterization at 5 Mpc and 20 Mpc scales. For angular distributions, we find that brighter and more massive sources are strongly clustered relative to fainter sources with lower mass; likewise, based on WISE colors, spheroidal galaxies have the strongest clustering, while late-type disk galaxies have the lowest clustering amplitudes. In three dimensions, we find a number of distinct groupings, often bridged by filaments and superstructures. Using special visualization tools, we map these structures, exploring how clustering may play a role with stellar mass and galaxy type.

Early-type galaxies: Automated reduction and analysis of ROSAT PSPC data

NASA Technical Reports Server (NTRS)

Mackie, G.; Fabbiano, G.; Harnden, F. R., Jr.; Kim, D.-W.; Maggio, A.; Micela, G.; Sciortino, S.; Ciliegi, P.

1996-01-01

Preliminary results of early-type galaxies that will be part of a galaxy catalog to be derived from the complete Rosat data base are presented. The stored data were reduced and analyzed by an automatic pipeline. This pipeline is based on a command language scrip. The important features of the pipeline include new data time screening in order to maximize the signal to noise ratio of faint point-like sources, source detection via a wavelet algorithm, and the identification of sources with objects from existing catalogs. The pipeline outputs include reduced images, contour maps, surface brightness profiles, spectra, color and hardness ratios.

Fainting

MedlinePlus

... fainted one time and you are otherwise in good health. Fainting is common and usually not serious. However, if you have serious health problems, you probably should see your doctor. This is ... your overall, good health. It helps maintain your temperature, remove waste ...

Studying The Spectral Shape And The X-ray/uv Variability Of Active Galactic Nuclei With Data From Swift And Xmm Archives

NASA Astrophysics Data System (ADS)

Turriziani, Sara

2011-01-01

Many efforts have been made in understanding the underlying origin of variability in Active Galactic Nuclei (AGN), but at present they could give still no conclusive answers. Since a deeper knowledge of variability will enable to understand better the accretion process onto supermassive black holes, I built the first ensemble struction function analysis of the X-ray variability of samples of quasars with data from Swift and XMM-Newton archives in order to study the average properties of their variability. Moreover, it is known that UV and X-ray luminosities of quasars are correlated and recent studies quantified this relation across 5 orders of magnitude. In this context, I presents results on the X-ray/UV ratio from simultaneous observations in UV and X-ray bands of a sample of quasars with data from XMM-Newton archive. Lastly, I will present a complete sample of Swift/SDSS faint blazars and other non-thermal dominated AGNs. I used this sample to calculate the general statistical properties of faint blazars and radio galaxies and in particular their Radio LogN-LogS with fluxes down to 10 mJy, in order to gain knowledge on the contribution to Cosmic Microwave Background (CMB) and gamma-ray background radiation from the faint tail of the radio population. I acknowledge financial support through Grant ASI I/088/06/0.

The Coma Cluster Luminosity Function from Ultraviolet to Near-Infrared

NASA Astrophysics Data System (ADS)

Andreon, S.; Cuillandre, J.-C.; Pello, R.

The Coma cluster luminosity function (LF) from ultraviolet (2000 AA ) to the near-infrared (H band) is summarized. In the UV the LF is very steep, much steeper than in the optical. The steep Coma UV LF implies that faint and bright galaxies give similar contributions to the total UV flux and to the total metal production rate. The ComaUV LF is dominated in number and luminosity by blue galaxies, which are often faint in the optical. Therefore the Coma UV LF is dominated by star forming galaxies, not by massive and large galaxies. The optical Coma LF is relatively steep (alpha=-1.4) over the 11 magnitudes sampled, but its slope and shape depend on considered filter and magnitude. We found a clear steeping of the FL going from B to R bands, indicative of the presence of a large number of red dwarfs, as faint as three bright globular clusters. Furthermore, using Hubble Space Telescope images, we discover that blends of globular clusters, not resolved in individual components due to seeing, look like dwarf galaxies when observed from the ground and are numerous and bright. The existence of these fake extended sources increases the steepness of the LF at faint magnitudes, if not deal on. This concern affects previous deep probing of the luminosity function, but not the present work. The near-infrared LF wa s computed on a near-infrared selected sample of galaxies which photometry is complete down to the typical dwarf (M* +5) luminosity. The Coma LF can be described by a Schechter function with intermediate slope (alpha sim-1.3), plus a dip at MH~-22 mag. The shape of the Coma LF in H band is quite similar to th e one found in the B band. The similarity of the LF in the optical and H bands implies that in the central region of Coma there is no new population of galaxies which is too faint to be observed in the optical band (because dust enshrouded, for instance), down to the magnitudes of dwarfs. The exponential cut of the LF at the bright end is in good agreement with the one derived from shallower near-infrared samples o f galaxies, both in clusters and in the field. The faint end of the LF, reaching MH~-19 mag (roughly MB~ -15), is steep, but less than previously suggested from shallower near-infrared observations of an adjacent region in the Coma cluster.

Using Deep Learning for Gamma Ray Source Detection at the First G-APD Cherenkov Telescope (FACT)

NASA Astrophysics Data System (ADS)

Bieker, Jacob

2018-06-01

Finding gamma-ray sources is of paramount importance for Imaging Air Cherenkov Telescopes (IACT). This study looks at using deep neural networks on data from the First G-APD Cherenkov Telescope (FACT) as a proof-of-concept of finding gamma-ray sources with deep learning for the upcoming Cherenkov Telescope Array (CTA). In this study, FACT’s individual photon level observation data from the last 5 years was used with convolutional neural networks to determine if one or more sources were present. The neural networks used various architectures to determine which architectures were most successful in finding sources. Neural networks offer a promising method for finding faint and extended gamma-ray sources for IACTs. With further improvement and modifications, they offer a compelling method for source detection for the next generation of IACTs.

A NAIVE BAYES SOURCE CLASSIFIER FOR X-RAY SOURCES

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

Broos, Patrick S.; Getman, Konstantin V.; Townsley, Leisa K.

2011-05-01

The Chandra Carina Complex Project (CCCP) provides a sensitive X-ray survey of a nearby starburst region over >1 deg{sup 2} in extent. Thousands of faint X-ray sources are found, many concentrated into rich young stellar clusters. However, significant contamination from unrelated Galactic and extragalactic sources is present in the X-ray catalog. We describe the use of a naive Bayes classifier to assign membership probabilities to individual sources, based on source location, X-ray properties, and visual/infrared properties. For the particular membership decision rule adopted, 75% of CCCP sources are classified as members, 11% are classified as contaminants, and 14% remain unclassified.more » The resulting sample of stars likely to be Carina members is used in several other studies, which appear in this special issue devoted to the CCCP.« less

Faint Object Detection in Multi-Epoch Observations via Catalog Data Fusion

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

Budavári, Tamás; Szalay, Alexander S.; Loredo, Thomas J.

Astronomy in the time-domain era faces several new challenges. One of them is the efficient use of observations obtained at multiple epochs. The work presented here addresses faint object detection and describes an incremental strategy for separating real objects from artifacts in ongoing surveys. The idea is to produce low-threshold single-epoch catalogs and to accumulate information across epochs. This is in contrast to more conventional strategies based on co-added or stacked images. We adopt a Bayesian approach, addressing object detection by calculating the marginal likelihoods for hypotheses asserting that there is no object or one object in a small imagemore » patch containing at most one cataloged source at each epoch. The object-present hypothesis interprets the sources in a patch at different epochs as arising from a genuine object; the no-object hypothesis interprets candidate sources as spurious, arising from noise peaks. We study the detection probability for constant-flux objects in a Gaussian noise setting, comparing results based on single and stacked exposures to results based on a series of single-epoch catalog summaries. Our procedure amounts to generalized cross-matching: it is the product of a factor accounting for the matching of the estimated fluxes of the candidate sources and a factor accounting for the matching of their estimated directions. We find that probabilistic fusion of multi-epoch catalogs can detect sources with similar sensitivity and selectivity compared to stacking. The probabilistic cross-matching framework underlying our approach plays an important role in maintaining detection sensitivity and points toward generalizations that could accommodate variability and complex object structure.« less

SPHEREx: Understanding the Origin and Evolution of Galaxies Through the Extragalactic Background Light

NASA Astrophysics Data System (ADS)

Zemcov, Michael; SPHEREx Science Team

2018-01-01

The near IR extragalactic background light (EBL) encodes the integrated light production over cosmic history, so traces the total emission from all galaxies along the line of sight up to the ancient first-light objects responsible for the epoch of reionization (EOR). The EBL can be constrained through measurements of anisotropies, taking advantage of the fact that extragalactic populations produce fluctuations with distinct spatial and spectral characteristics from local foregrounds. In particular, EBL anisotropies trace the underlying clustering of faint emission sources, such as stars, galaxies and accreting black holes present during the EOR, dwarf galaxies, and intra-halo light (IHL), all of which are components not readily detected in point source surveys. The fluctuation amplitude observed independently by a number of recent measurements exceeds that expected from the large-scale clustering of known galaxy populations, indicating the presence of a large integrated brightness from these faint and diffuse components. Improved large-area measurements covering the entire near-IR are required to constrain the possible models for the history of emission from stars back to the EOR.SPHEREx brings new capabilities to EBL fluctuation measurements, employing 96 spectral channels covering 0.75 to 5 microns with spectral resolving power R = 41 to 135 that enable SPHEREx to carry out a multi-frequency separation of the integrated light from galaxies, IHL, and EOR components using the rich auto- and cross-correlation information available from two 45 square degree surveys of the ecliptic poles. SPHEREx is an ideal intensity mapping machine, and has the sensitivity to disentangle the history of light production associated with EBL fluctuations. SPHEREx will search for an EOR component its to minimum required level through component separation and spectral fitting techniques optimized for the near-IR. In addition to broad-band intensity mapping that enhances and extends the Euclid survey, uniquely SPHEREx will enable tomography of cosmic large scale structure using line tracers such as Lya, Ha, Hb, O[II] and O[III], as highlighted in community workshops and AAS special sessions over the past several years.

The very faint X-ray binary IGR J17062-6143: a truncated disc, no pulsations, and a possible outflow

NASA Astrophysics Data System (ADS)

van den Eijnden, J.; Degenaar, N.; Pinto, C.; Patruno, A.; Wette, K.; Messenger, C.; Hernández Santisteban, J. V.; Wijnands, R.; Miller, J. M.; Altamirano, D.; Paerels, F.; Chakrabarty, D.; Fabian, A. C.

2018-04-01

We present a comprehensive X-ray study of the neutron star low-mass X-ray binary IGR J17062-6143, which has been accreting at low luminosities since its discovery in 2006. Analysing NuSTAR, XMM-Newton, and Swift observations, we investigate the very faint nature of this source through three approaches: modelling the relativistic reflection spectrum to constrain the accretion geometry, performing high-resolution X-ray spectroscopy to search for an outflow, and searching for the recently reported millisecond X-ray pulsations. We find a strongly truncated accretion disc at 77^{+22}_{-18} gravitational radii (˜164 km) assuming a high inclination, although a low inclination and a disc extending to the neutron star cannot be excluded. The high-resolution spectroscopy reveals evidence for oxygen-rich circumbinary material, possibly resulting from a blueshifted, collisionally ionized outflow. Finally, we do not detect any pulsations. We discuss these results in the broader context of possible explanations for the persistent faint nature of weakly accreting neutron stars. The results are consistent with both an ultra-compact binary orbit and a magnetically truncated accretion flow, although both cannot be unambiguously inferred. We also discuss the nature of the donor star and conclude that it is likely a CO or O-Ne-Mg white dwarf, consistent with recent multiwavelength modelling.

CHEMICAL DIVERSITY IN THE ULTRA-FAINT DWARF GALAXY TUCANA II

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

Ji, Alexander P.; Frebel, Anna; Ezzeddine, Rana

We present the first detailed chemical abundance study of the ultra-faint dwarf galaxy Tucana II, based on high-resolution Magellan/MIKE spectra of four red giant stars. The metallicities of these stars range from [Fe/H] = −3.2 to −2.6, and all stars are low in neutron-capture abundances ([Sr/Fe] and [Ba/Fe] < −1). However, a number of anomalous chemical signatures are present. One star is relatively metal-rich ([Fe/H] = −2.6) and shows [Na, α , Sc/Fe] < 0, suggesting an extended star formation history with contributions from AGB stars and SNe Ia. Two stars with [Fe/H] < −3 are mildly carbon-enhanced ([C/Fe] ∼more » 0.7) and may be consistent with enrichment by faint supernovae, if such supernovae can produce neutron-capture elements. A fourth star with [Fe/H] = −3 is carbon-normal, and exhibits distinct light element abundance ratios from the carbon-enhanced stars. This carbon-normal star implies that at least two distinct nucleosynthesis sources, both possibly associated with Population III stars, contributed to the early chemical enrichment of this galaxy. Despite its very low luminosity, Tucana II shows a diversity of chemical signatures that preclude it from being a simple “one-shot” first galaxy yet still provide a window into star and galaxy formation in the early universe.« less

Uncovering extreme AGN variability in serendipitous X-ray source surveys

NASA Astrophysics Data System (ADS)

Moran, Edward C.; Garcia Soto, Aylin; LaMassa, Stephanie; Urry, Meg

2018-01-01

Constraints on the duty cycle and duration of accretion episodes in active galactic nuclei (AGNs) are vital for establishing how most AGNs are fueled, which is essential for a complete picture of black hole/galaxy co-evolution. Perhaps the best handle we have on these activity parameters is provided by AGNs that have displayed dramatic changes in their bolometric luminosities and, in some cases, spectroscopic classifications. Given that X-ray emission is directly linked to black-hole accretion, X-ray surveys should provide a straightforward means of identifying AGNs that have undergone dramatic changes in their accretion states. However, it appears that such events are very rare, so wide-area surveys separated in time by many years are needed to maximize discovery rates. We have cross-correlated the Einstein IPC Two-Sigma Catalog with the ROSAT All-Sky Survey Faint Source Catalog to identify a sample of soft X-ray sources that varied by factors ranging from 7 to more than 100 over a ten year timescale. When possible, we have constructed long-term X-ray light curves for the sources by combining the Einstein and RASS fluxes with those obtained from serendipitous pointed observations by ROSAT, Chandra,XMM, and Swift. Optical follow-up observations indicate that many of the extremely variable sources in our sample are indeed radio-quiet AGNs. Interestingly, the majority of objects that dimmed between ~1980 and ~1990 are still (or are again) broad-line AGNs rather than“changing-look” candidates that have more subtle AGN signatures in their spectra — despite the fact that none of the sources examined thus far has returned to its highest observed luminosity. Future X-ray observations will provide the opportunity to characterize the X-ray behavior of these anonymous, extreme AGNs over a four decade span.

Clustering of High-Redshift Quasars

NASA Astrophysics Data System (ADS)

Timlin, John D., III

In this work, we investigate the clustering of faint quasars in the early Universe and use the clustering strength to gain a better understanding of quasar feedback mechanisms and the growth of central supermassive black holes at early times in the history of the Universe. It has long been understood (e.g., Hopkins et al. 2007a) that the clustering of distant quasars can be used as a probe of different feedback models; however, until now, there was no sample of faint, high-redshift quasars with sufficient density to accurately measure the clustering strength. Therefore we conducted a new survey to increase the number density of these objects. Here, we describe the Spitzer -IRAC Equatorial Survey (SpIES) which is a moderately deep, large-area Spitzer survey which was designed to discover faint, high-redshift (2.9 ≤ z ≤ 5.1) quasars. SpIES spans 115 deg 2 in the equatorial "Stripe 82" region of the Sloan Digital Sky Survey (SDSS) and probes to 5sigma depths of 6.13 microJy (21.93 AB magnitude) and 5.75 microJy (22.0 AB magnitude) at 3.6 and 4.5 microns. At these depths, SpIES is able to observe faint quasars, and we show that SpIES recovers 94% of the high-redshift (z ≥ 3.5), spectroscopically-confirmed quasars that lie within its footprint. SpIES is also ideally located on Stripe 82 for two reasons: It surrounds existing infrared data from the Spitzer-HETDEX Exploratory Large-area (SHELA) survey which increases the area of infrared coverage, and there is a wide range of multi-wavelength, multi-epoch ancillary data on Stripe 82 which we can use together to select high-redshift quasar candidates. To photometrically identify quasar candidates, we combined the optical data from the Sloan Digital Sky Survey and the infrared data from SpIES and SHELA and employed three machine learning algorithms. These algorithms were trained on the optical/infrared colors of known, high-redshift quasars. Using this method, we generate a sample of 1378 objects that are both faint (i ≥ 20.2) and high-redshift (2.9 ≤ z ≤ 5.1) which we use to compute the angular two-point correlation function. We fit a single power-law model with an index of delta = 1.39 +/- 0.618 and amplitude of theta0 = 0.71 +/- 0.546 arcmin to the correlation function, as well as a dark matter model with a bias of b = 6.78 +/- 1.79. The bias in our investigation suggests a model of quasar feedback that considers quasar activity as an intermittent phase in galaxy evolution. If this model is correct, quasar feedback is strong enough to periodically halt the accretion of gas onto the central supermassive black hole of the quasar, which shuts down quasar activity and causes the black hole to stop growing, however it is not strong enough to completely shut down the quasar in the early Universe.

Fast-growing SMBHs in Fast-growing Galaxies, at High Redshifts: the Role of Major Mergers as Revealed by ALMA

NASA Astrophysics Data System (ADS)

Trakhtenbrot, Benny; Lira, Paulina; Netzer, Hagai; Cicone, Claudia; Maiolino, Roberto; Shemmer, Ohad

2017-11-01

We present a long-term, multi-wavelength project to understand the epoch of fastest growth of the most massive black holes by using a sample of 40 luminous quasars at z 4.8. These quasars have rather uniform properties, with typical accretion rates and black hole masses of L/L_Edd 0.7 and M_BH 10^9 M_sun. The sample consists of ``FIR-bright'' sources with a previous Herschel/SPIRE detection, suggesting SFR>1000 M_sun/yr, as well as of ``FIR-faint'' sources for which Herschel stacking analysis implies a typical SFR of 400 M_sun/yr. Six of the quasars have been observed by ALMA in [C II] 157.74 micron line emission and adjacent rest-frame 150 □micron continuum, to study the dusty cold ISM. ALMA detected companion, spectroscopically confirmed sub-mm galaxies (SMGs) for three sources – one FIR-bright and two FIR-faint. The companions are separated by 14-45 kpc from the quasar hosts, and we interpret them as major galaxy interactions. Our ALMA data therefore clearly support the idea that major mergers may be important drivers for rapid, early SMBH growth. However, the fact that not all high-SFR quasar hosts are accompanied by interacting SMGs, and their ordered gas kinematics observed by ALMA, suggest that other processes may be fueling these systems. Our analysis thus demonstrates the diversity of host galaxy properties and gas accretion mechanisms associated with early and rapid SMBH growth.

Variability of faint ROSAT field sources

NASA Astrophysics Data System (ADS)

Nicholson, K. L.; Mittaz, J. P. D.; Mason, K. O.

1997-03-01

We describe a technique to search for variability in faint X-ray sources, based on Poisson statistics. This is applied to data in the field of the detached white dwarf binary RE J1629+781 which has been observed repeatedly with the ROSAT Position Sensitive Proportional Counter (PSPC) over a period of 2.5yr as part of the calibration programme of the co-aligned extreme ultraviolet (EUV) sensitive Wide Field Camera. The field contains eight other identified sources comprising four active galactic nuclei (AGN), a LINER, a probable cluster of galaxies and two stars. Variability is detected in three of the AGN, which all have redshifts between 0.35 and 0.38. The amplitude of variability ranges between one and three times the mean count rate, but is only detected on time-scales of less than 3-5 months. No variability is found in the fourth AGN which is at a redshift of 1.1, nor in the LINER galaxy, Arp 185. The X-ray emission from Arp 185 is relatively bright, and the upper limit to flux variations is 27 per cent of the mean flux. This result is consistent with a non-AGN origin for the X-ray emission from this galaxy. Variability is detected from one of the identified stars in the field, of spectral type dM5.5e. No variations were seen in the flux of the other star (spectral type G) or from the probable cluster of galaxies.

Prospects for Inflationary B-Mode Detection

NASA Technical Reports Server (NTRS)

Kogut, Alan J.

2011-01-01

Measurements of the linear polarization of the cosmic microwave background provide a direct window into the physics of inflation. The experimental challenges are daunting: not only is the predicted signal faint compared to the photon noise limit, but it is hidden behind competing foregrounds from both local and cosmic sources. I will discuss the experimental response to these challenges and the prospects for eventual detection and characterization of the inflationary signal.

A new network of faint calibration stars from the near infrared spectrometer (NIRS) on the IRTS

NASA Technical Reports Server (NTRS)

Freund, Minoru M.; Matsuura, Mikako; Murakami, Hiroshi; Cohen, Martin; Noda, Manabu; Matsuura, Shuji; Matsumoto, Toshio

1997-01-01

The point source extraction and calibration of the near infrared spectrometer (NIRS) onboard the Infrared Telescope in Space (IRTS) is described. About 7 percent of the sky was observed during a one month mission in the range of 1.4 micrometers to 4 micrometers. The accuracy of the spectral shape and absolute values of calibration stars provided by the NIRS/IRTS were validated.

DEEP NEAR-IR OBSERVATIONS OF THE GLOBULAR CLUSTER M4: HUNTING FOR BROWN DWARFS

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

Dieball, A.; Bedin, L. R.; Knigge, C.

2016-01-20

We present an analysis of deep Hubble Space Telescope (HST)/Wide Field Camera 3 near-IR (NIR) imaging data of the globular cluster (GC) M4. The best-photometry NIR color–magnitude diagram (CMD) clearly shows the main sequence extending toward the expected end of the hydrogen-burning limit and going beyond this point toward fainter sources. The white dwarf (WD) sequence can be identified. As such, this is the deepest NIR CMD of a GC to date. Archival HST optical data were used for proper-motion cleaning of the CMD and for distinguishing the WDs from brown dwarf (BD) candidates. Detection limits in the NIR aremore » around F110W ≈ 26.5 mag and F160W ≈ 27 mag, and in the optical around F775W ≈ 28 mag. Comparing our observed CMDs with theoretical models, we conclude that we have reached beyond the H-burning limit in our NIR CMD and are probably just above or around this limit in our optical–NIR CMDs. Thus, any faint NIR sources that have no optical counterpart are potential BD candidates, since the optical data are not deep enough to detect them. We visually inspected the positions of NIR sources that are fainter than the H-burning limit in F110W and for which the optical photometry did not return a counterpart. We found in total five sources for which we did not get an optical measurement. For four of these five sources, a faint optical counterpart could be visually identified, and an upper optical magnitude was estimated. Based on these upper optical magnitude limits, we conclude that one source is likely a WD, one source could be either a WD or BD candidate, and the remaining two sources agree with being BD candidates. No optical counterpart could be detected for just one source, which makes this source a good BD candidate. We conclude that we found in total four good BD candidates.« less

The Cambridge-Cambridge X-ray Serendipity Survey: I X-ray luminous galaxies

NASA Technical Reports Server (NTRS)

Boyle, B. J.; Mcmahon, R. G.; Wilkes, B. J.; Elvis, M.

1994-01-01

We report on the first results obtained from a new optical identification program of 123 faint X-ray sources with S(0.5-2 keV) greater than 2 x 10(exp -14) erg/s/sq cm serendipitously detected in ROSAT PSPC pointed observations. We have spectroscopically identified the optical counterparts to more than 100 sources in this survey. Although the majority of the sample (68 objects) are QSO's, we have also identified 12 narrow emission line galaxies which have extreme X-ray luminosities (10(exp 42) less than L(sub X) less than 10(exp 43.5) erg/s). Subsequent spectroscopy reveals them to be a mixture of star-burst galaxies and Seyfert 2 galaxies in approximately equal numbers. Combined with potentially similar objects identified in the Einstein Extended Medium Sensitivity Survey, these X-ray luminous galaxies exhibit a rate of cosmological evolution, L(sub X) varies as (1 + z)(exp 2.5 +/- 1.0), consistent with that derived for X-ray QSO's. This evolution, coupled with the steep slope determined for the faint end of the X-ray luminosity function (Phi(L(sub X)) varies as L(sub X)(exp -1.9)), implies that such objects could comprise 15-35% of the soft (1-2 keV) X-ray background.

Discovery of a faint, star-forming, multiply lensed, Lyman-α blob

NASA Astrophysics Data System (ADS)

Caminha, G. B.; Karman, W.; Rosati, P.; Caputi, K. I.; Arrigoni Battaia, F.; Balestra, I.; Grillo, C.; Mercurio, A.; Nonino, M.; Vanzella, E.

2016-11-01

We report the discovery of a multiply lensed Lyman-α blob (LAB) behind the galaxy cluster AS1063 using the Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT). The background source is at z = 3.117 and is intrinsically faint compared to almost all previously reported LABs. We used our highly precise strong lensing model to reconstruct the source properties, and we find an intrinsic luminosity of LLyα = 1.9 × 1042 erg s-1, extending to 33 kpc. We find that the LAB is associated with a group of galaxies, and possibly a protocluster, in agreement with previous studies that find LABs in overdensities. In addition to Lyman-α (Lyα) emission, we find C iv, He II, and O III] ultraviolet (UV) emission lines arising from the centre of the nebula. We used the compactness of these lines in combination with the line ratios to conclude that the Lyα nebula is likely powered by embedded star formation. Resonant scattering of the Lyα photons then produces the extended shape of the emission. Thanks to the combined power of MUSE and strong gravitational lensing, we are now able to probe the circumgalatic medium of sub-L∗ galaxies at z ≈ 3.

Lyman-break Galaxies at z ˜ 3 in the Subaru Deep Field: Luminosity Function, Clustering, and [O III] Emission

NASA Astrophysics Data System (ADS)

Malkan, Matthew A.; Cohen, Daniel P.; Maruyama, Miyoko; Kashikawa, Nobunari; Ly, Chun; Ishikawa, Shogo; Shimasaku, Kazuhiro; Hayashi, Masao; Motohara, Kentaro

2017-11-01

We combined deep U-band and optical/near-infrared imaging, in order to select Lyman Break Galaxies (LBGs) at z˜ 3 using U - V and V-{R}c colors in the Subaru Deep Field. The resulting sample of 5161 LBGs gives a UV luminosity function (LF) down to {M}{UV}=-18, with a steep faint-end slope of α =-1.78+/- 0.05. We analyze UV-to-NIR energy distributions (SEDs) from optical photometry and photometry on IR median-stacked images. In the stacks, we find a systematic background depression centered on the LBGs. This results from the difficulty of finding faint galaxies in regions with higher-than-average surface densities of foreground galaxies, so we corrected for this deficit. Best-fit stellar population models for the LBG SEDs indicate stellar masses and star formation rates of {{log}}10({M}* /{M}⊙ )≃ 10 and ≃ 50 M ⊙ yr-1 at < {i}{AB}{\\prime }> =24, down to {{log}}10({M}* /{M}⊙ )≃ 8 and ≃ 3 {M}⊙ yr-1 at < {i}{AB}{\\prime }> =27. The faint LBGs show a ˜1 mag excess over the stellar continuum in K-band. We interpret this excess flux as redshifted [O III]λ λ {4959,5007} lines. The observed excesses imply equivalent widths that increase with decreasing mass, reaching {{EW}}0([{{O}} {{iii}}]4959,5007+{{H}}β )≳ 1500 Å (rest-frame). Such strong [O III] emission is seen only in a miniscule fraction of local emission-line galaxies, but is probably universal in the faint galaxies that reionized the universe. Our halo occupation distribution analysis of the angular correlation function gives a halo mass of {{log}}10(< {M}{{h}}> /{h}-1{M}⊙ )=11.29+/- 0.12 for the full sample of LBGs, and {{log}}10(< {M}{{h}}> /{h}-1{M}⊙ )=11.49+/- 0.1 for the brightest half of the sample.

Europe's space camera unmasks a cosmic gamma-ray machine

NASA Astrophysics Data System (ADS)

1996-11-01

The new-found neutron star is the visible counterpart of a pulsating radio source, Pulsar 1055-52. It is a mere 20 kilometres wide. Although the neutron star is very hot, at about a million degrees C, very little of its radiant energy takes the form of visible light. It emits mainly gamma-rays, an extremely energetic form of radiation. By examining it at visible wavelengths, astronomers hope to figure out why Pulsar 1055-52 is the most efficient generator of gamma-rays known so far, anywhere the Universe. The Faint Object Camera found Pulsar 1055-52 in near ultraviolet light at 3400 angstroms, a little shorter in wavelength than the violet light at the extremity of the human visual range. Roberto Mignani, Patrizia Caraveo and Giovanni Bignami of the Istituto di Fisica Cosmica in Milan, Italy, report its optical identification in a forthcoming issue of Astrophysical Journal Letters (1 January 1997). The formal name of the object is PSR 1055-52. Evading the glare of an adjacent star The Italian team had tried since 1988 to spot Pulsar 1055-52 with two of the most powerful ground-based optical telescopes in the Southern Hemisphere. These were the 3.6-metre Telescope and the 3.5-metre New Technology Telescope of the European Southern Observatory at La Silla, Chile. Unfortunately an ordinary star 100,000 times brighter lay in almost the same direction in the sky, separated from the neutron star by only a thousandth of a degree. The Earth's atmosphere defocused the star's light sufficiently to mask the glimmer from Pulsar 1055-52. The astronomers therefore needed an instrument in space. The Faint Object Camera offered the best precision and sensitivity to continue the hunt. Devised by European astronomers to complement the American wide field camera in the Hubble Space Telescope, the Faint Object Camera has a relatively narrow field of view. It intensifies the image of a faint object by repeatedly accelerating electrons from photo-electric films, so as to produce brighter flashes when the electrons hit a phosphor screen. Since Hubble's launch in 1990, the Faint Object Camera has examined many different kinds of cosmic objects, from the moons of Jupiter to remote galaxies and quasars. When the space telescope's optics were corrected at the end of 1993 the Faint Object Camera immediately celebrated the event with the discovery of primeval helium in intergalactic gas. In their search for Pulsar 1055-52, the astronomers chose a near-ultraviolet filter to sharpen the Faint Object Camera's vision and reduce the adjacent star's huge advantage in intensity. In May 1996, the Hubble Space Telescope operators aimed at the spot which radio astronomers had indicated, as the source of the radio pulsations of Pulsar 1055-52. The neutron star appeared precisely in the centre of the field of view, and it was clearly separated from the glare of the adjacent star. At magnitude 24.9, Pulsar 1055-52 was comfortably within the power of the Faint Object Camera, which can see stars 20 times fainter still. "The Faint Object Camera is the instrument of choice for looking for neutron stars," says Giovanni Bignami, speaking on behalf of the Italian team. "Whenever it points to a judiciously selected neutron star it detects the corresponding visible or ultraviolet light. The Faint Object Camera has now identified three neutron stars in that way, including Pulsar 1055-52, and it has examined a few that were first detected by other instruments." Mysteries of the neutron stars The importance of the new result can be gauged by the tally of only eight neutron stars seen so far at optical wavelengths, compared with about 760 known from their radio pulsations, and about 21 seen emitting X-rays. Since the first pulsar was detected by radio astronomers in Cambridge, England, nearly 30 years ago, theorists have come to recognize neutron stars as fantastic objects. They are veritable cosmic laboratories in which Nature reveals the behaviour of matter under extreme stress, just one step short of a black hole. A neutron star is created by the force of a supernova explosion in a large star, which crushes the star's core to an unimaginable density. A mass greater than the Sun's is squeezed into a ball no wider than a city. The gravity and magnetic fields are billions of times stronger than the Earth's. The neutron star revolves rapidly, which causes it to wink like a cosmic lighthouse as it swivels its magnetic poles towards and away from the Earth. Pulsar 1055-52 spins at five revolutions per second. At its formation in a supernova explosion, a neutron star is endowed with two main forms of energy. One is heat, at temperatures of millions of degrees, which the neutron star radiates mainly as X-rays, with only a small proportion emerging as visible light. The other power supply for the neutron star comes from its high rate of spin and a gradual slowing of the rotation. By a variety of processes involving the magnetic field and accelerated particles in the neutron star's vicinity, the spin energy of the neutron star is converted into radiation at many different wavelengths, from radio waves to gamma-rays. The exceptional gamma-ray intensity of Pulsar 1055-52 was first appreciated in observations by NASA's Compton Gamma Ray Observatory. The team in Milan recently used the Hubble Space Telescope to find the distance of the peculiar neutron star Geminga, which is not detectable by radio pulses but is a strong source of gamma-rays (see ESA Information Note 04-96, 28 March 1996). Pulsar 1055-52 is even more powerful in that respect. About 50 per cent of its radiant energy is gamma-rays, compared with 15 per cent from Geminga and 0.1 per cent from the famous Crab Pulsar, the first neutron star seen by visible light. Making the gamma-rays requires the acceleration of electrons through billions of volts. The magnetic environment of Pulsar 1055-52 fashions a natural gamma-ray machine of amazing power. The orientation of the neutron star's magnetic field with respect to the Earth may contribute to its brightness in gamma-rays. Geminga, Pulsar 1055-52 and another object, Pulsar 0656+14, make a trio that the Milanese astronomers call the Three Musketeers. All have been observed with the Faint Object Camera. They are isolated, elderly neutron stars, some hundreds of thousands of years old, contrasting with the 942 year-old Crab Pulsar which is still surrounded by dispersing debris of a supernova seen by Chinese astronomers in the 11th Century. The mysteries of the neutron stars will keep astronomers busy for years to come, and the Faint Object Camera in the Hubble Space Telescope will remain the best instrument for spotting their faint visible light. The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency (ESA). The Space Telescope Science Institute is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) for NASA, under contract with the Goddard Space Flight Center, Greenbelt, Maryland. Note to editors: An image is available of (i) PSR 1055-52 seen by ESA's Faint Object Camera in the Hubble Space Telescope, and (ii) the same region of the sky seen by the European Southern Observatory's New Technology Telescope, with the position of PSR 1055-52 indicated. The image is available on the World Wide Web at http://ecf.hq.eso.org/stecf-pubrel.html http://www.estec.esa.nl/spdwww/h2000/html/snlmain.htm

How Faint Can You Go?

NASA Astrophysics Data System (ADS)

Henden, Arne

2017-06-01

For many scientific projects, knowledge of the faint limit of your exposure can be extremely important. In addition, it can be just plain fun to know how faint your equipment can go under varying circumstances. This paper describes the concept and gives some guidance as to how to increase the scientific value of your reports.

How Faint Can You Go? (Abstract)

NASA Astrophysics Data System (ADS)

Henden, A.

2017-12-01

(Abstract only) For many scientific projects, knowledge of the faint limit of your exposure can be extremely important. In addition, it can be just plain fun to know how faint your equipment can go under varying circumstances. This paper describes the concept and gives some guidance as to how to increase the scientific value of your reports.

Deep SOAR follow-up photometry of two Milky Way outer-halo companions discovered with Dark Energy Survey

NASA Astrophysics Data System (ADS)

Luque, E.; Santiago, B.; Pieres, A.; Marshall, J. L.; Pace, A. B.; Kron, R.; Drlica-Wagner, A.; Queiroz, A.; Balbinot, E.; Ponte, M. dal; Neto, A. Fausti; da Costa, L. N.; Maia, M. A. G.; Walker, A. R.; Abdalla, F. B.; Allam, S.; Annis, J.; Bechtol, K.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Rosell, A. Carnero; Kind, M. Carrasco; Carretero, J.; Crocce, M.; Davis, C.; Doel, P.; Eifler, T. F.; Flaugher, B.; García-Bellido, J.; Gerdes, D. W.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Kuehn, K.; Kuropatkin, N.; Miquel, R.; Nichol, R. C.; Plazas, A. A.; Sanchez, E.; Scarpine, V.; Schindler, R.; Sevilla-Noarbe, I.; Smith, M.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Tarle, G.; Thomas, D.

2018-04-01

We report the discovery of a new star cluster, DES 3, in the constellation of Indus, and deeper observations of the previously identified satellite DES J0222.7-5217 (Eridanus III). DES 3 was detected as a stellar overdensity in first-year Dark Energy Survey data, and confirmed with deeper photometry from the 4.1 metre Southern Astrophysical Research (SOAR) telescope. The new system was detected with a relatively high significance and appears in the DES images as a compact concentration of faint blue point sources. We determine that DES 3 is located at a heliocentric distance of ≃ 76.2 kpc and it is dominated by an old (≃ 9.8 Gyr) and metal-poor ([Fe/H] ≃ -1.84) population. While the age and metallicity values of DES 3 are comparable to typical globular clusters (objects with a high stellar density, stellar mass of ˜105M⊙ and luminosity MV ˜ -7.3), its half-light radius (rh ˜ 6.87 pc) and luminosity (MV ˜ -1.7) are more indicative of faint star cluster. Based on the angular size, DES 3, with a value of rh ˜ 0{^'.}31, is among the smallest faint star clusters known to date. Furthermore, using deeper imaging of DES J0222.7-5217 taken with the SOAR telescope, we update structural parameters and perform the first isochrone modeling. Our analysis yields the first age (≃ 12.6 Gyr) and metallicity ([Fe/H] ≃ -2.01) estimates for this object. The half-light radius (rh ≃ 11.24 pc) and luminosity (MV ≃ -2.4) of DES J0222.7-5217 suggest that it is likely a faint star cluster. The discovery of DES 3 indicates that the census of stellar systems in the Milky Way is still far from complete, and demonstrates the power of modern wide-field imaging surveys to improve our knowledge of the Galaxy's satellite population.

NEW CONSTRAINTS ON THE FAINT END OF THE UV LUMINOSITY FUNCTION AT z ∼ 7-8 USING THE GRAVITATIONAL LENSING OF THE HUBBLE FRONTIER FIELDS CLUSTER A2744

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

Atek, Hakim; Kneib, Jean-Paul; Richard, Johan

2015-02-10

Exploiting the power of gravitational lensing, the Hubble Frontier Fields (HFF) program aims at observing six massive galaxy clusters to explore the distant universe far beyond the limits of blank field surveys. Using the complete Hubble Space Telescope observations of the first HFF cluster A2744, we report the detection of 50 galaxy candidates at z ∼ 7 and eight candidates at z ∼ 8 in a total survey area of 0.96 arcmin{sup 2} in the source plane. Three of these galaxies are multiply imaged by the lensing cluster. Using an updated model of the mass distribution in the cluster we weremore » able to calculate the magnification factor and the effective survey volume for each galaxy in order to compute the ultraviolet galaxy luminosity function (LF) at both redshifts 7 and 8. Our new measurements reliably extend the z ∼ 7 UV LF down to an absolute magnitude of M {sub UV} ∼ –15.5. We find a characteristic magnitude of M{sub UV}{sup ⋆}=−20.90{sub −0.73}{sup +0.90} mag and a faint-end slope α=−2.01{sub −0.28}{sup +0.20}, close to previous determinations in blank fields. We show here for the first time that this slope remains steep down to very faint luminosities of 0.01 L {sup *}. Although prone to large uncertainties, our results at z ∼ 8 also seem to confirm a steep faint-end slope below 0.1 L {sup *}. The HFF program is therefore providing an extremely efficient way to study the faintest galaxy populations at z > 7 that would otherwise be inaccessible with current instrumentation. The full sample of six galaxy clusters will provide even better constraints on the buildup of galaxies at early epochs and their contribution to cosmic reionization.« less

Accounting for Cosmic Variance in Studies of Gravitationally Lensed High-redshift Galaxies in the Hubble Frontier Field Clusters

NASA Astrophysics Data System (ADS)

Robertson, Brant E.; Ellis, Richard S.; Dunlop, James S.; McLure, Ross J.; Stark, Dan P.; McLeod, Derek

2014-12-01

Strong gravitational lensing provides a powerful means for studying faint galaxies in the distant universe. By magnifying the apparent brightness of background sources, massive clusters enable the detection of galaxies fainter than the usual sensitivity limit for blank fields. However, this gain in effective sensitivity comes at the cost of a reduced survey volume and, in this Letter, we demonstrate that there is an associated increase in the cosmic variance uncertainty. As an example, we show that the cosmic variance uncertainty of the high-redshift population viewed through the Hubble Space Telescope Frontier Field cluster Abell 2744 increases from ~35% at redshift z ~ 7 to >~ 65% at z ~ 10. Previous studies of high-redshift galaxies identified in the Frontier Fields have underestimated the cosmic variance uncertainty that will affect the ultimate constraints on both the faint-end slope of the high-redshift luminosity function and the cosmic star formation rate density, key goals of the Frontier Field program.

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

Geng, J. J.; Huang, Y. F., E-mail: hyf@nju.edu.cn

Fast radio bursts (FRBs) are newly discovered radio transient sources. Their high dispersion measures indicate an extragalactic origin. However, due to the lack of observational data in other wavelengths, their progenitors still remain unclear. Here we suggest that the collisions between neutron stars (NSs) and asteroids/comets are promising mechanisms for FRBs. During the impact process, a hot plasma fireball forms after the material of the small body penetrates into the NS surface. The ionized matter inside the fireball then expands along the magnetic field lines. Coherent radiation from the thin shell at the top of the fireball will account formore » the observed FRBs. Our scenario can reasonably explain the main features of FRBs, such as their durations, luminosities, and the event rate. We argue that for a single NS, FRBs are not likely to happen repeatedly in a forseeable timespan since such impacts are of low probability. We predict that faint remnant X-ray emissions should be associated with FRBs, but it may be too faint to be detected by detectors at work.« less

Evolution of the Blue and Far-Infrared Galaxy Luminosity Functions

NASA Technical Reports Server (NTRS)

Lonsdale, Carol J.; Chokshi, Arati

1993-01-01

The space density of blue-selected galaxies at moderate redshifts is determined here directly by deriving the luminosity function. Evidence is found for density evolution for moderate luminosity galaxies at a rate of (1+z) exp delta, with a best fit of delta + 4 +/- 2, between the current epoch and Z greater than about 0.1. At M(b) less than -22 evidence is found for about 0.5-1.5 mag of luminosity evolution in addition to the density evolution, corresponding to an evolutionary rate of about (1+z) exp gamma, with gamma = 0.5-2.5, but a redshift of about 0.4. Assuming a steeper faint end slope of alpha = -1.3 similar to that observed in the Virgo cluster, could explain the data with a luminosity evolution rate of gamma = 1-2, without need for any density evolution. Acceptable fits are found by comparing composite density and luminosity evolution models to faint IRAS 60 micron source counts, implying that the blue and far-IR evolutionary rates may be similar.

Deep Wideband Single Pointings and Mosaics in Radio Interferometry: How Accurately Do We Reconstruct Intensities and Spectral Indices of Faint Sources?

NASA Astrophysics Data System (ADS)

Rau, U.; Bhatnagar, S.; Owen, F. N.

2016-11-01

Many deep wideband wide-field radio interferometric surveys are being designed to accurately measure intensities, spectral indices, and polarization properties of faint source populations. In this paper, we compare various wideband imaging methods to evaluate the accuracy to which intensities and spectral indices of sources close to the confusion limit can be reconstructed. We simulated a wideband single-pointing (C-array, L-Band (1-2 GHz)) and 46-pointing mosaic (D-array, C-Band (4-8 GHz)) JVLA observation using a realistic brightness distribution ranging from 1 μJy to 100 mJy and time-, frequency-, polarization-, and direction-dependent instrumental effects. The main results from these comparisons are (a) errors in the reconstructed intensities and spectral indices are larger for weaker sources even in the absence of simulated noise, (b) errors are systematically lower for joint reconstruction methods (such as Multi-Term Multi-Frequency-Synthesis (MT-MFS)) along with A-Projection for accurate primary beam correction, and (c) use of MT-MFS for image reconstruction eliminates Clean-bias (which is present otherwise). Auxiliary tests include solutions for deficiencies of data partitioning methods (e.g., the use of masks to remove clean bias and hybrid methods to remove sidelobes from sources left un-deconvolved), the effect of sources not at pixel centers, and the consequences of various other numerical approximations within software implementations. This paper also demonstrates the level of detail at which such simulations must be done in order to reflect reality, enable one to systematically identify specific reasons for every trend that is observed, and to estimate scientifically defensible imaging performance metrics and the associated computational complexity of the algorithms/analysis procedures. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

What are single photons good for?

NASA Astrophysics Data System (ADS)

Sangouard, Nicolas; Zbinden, Hugo

2012-10-01

In a long-held preconception, photons play a central role in present-day quantum technologies. But what are sources producing photons one by one good for precisely? Well, in opposition to what many suggest, we show that single-photon sources are not helpful for point to point quantum key distribution because faint laser pulses do the job comfortably. However, there is no doubt about the usefulness of sources producing single photons for future quantum technologies. In particular, we show how single-photon sources could become the seed of a revolution in the framework of quantum communication, making the security of quantum key distribution device-independent or extending quantum communication over many hundreds of kilometers. Hopefully, these promising applications will provide a guideline for researchers to develop more and more efficient sources, producing narrowband, pure and indistinguishable photons at appropriate wavelengths.

The X-Ray Polarimeter Instrument on Board the Polarimeter for Relativistic Astrophysical X-Ray Sources (PRAXyS) Mission

NASA Technical Reports Server (NTRS)

Hill, J. E.; Black, J. K.; Jahoda, K.; Tamagawa, T.; Iwakiri, W.; Kitaguchi, T.; Kubota, M.; Kaaret, P.; Mccurdy, R.; Miles, D. M.;

The First Hyper-Luminous Infrared Galaxy Discovered by WISE

NASA Technical Reports Server (NTRS)

Eisenhardt, Peter R.; Wu, Jingwen; Tsai, Chao-Wei; Assef, Roberto; Benford, Dominic; Blain, Andrew; Bridge, Carrie; Condon, J. J.; Cushing, Michael C.; Cutri, Roc;

Minimal spanning tree algorithm for γ-ray source detection in sparse photon images: cluster parameters and selection strategies

DOE PAGES

Campana, R.; Bernieri, E.; Massaro, E.; ...

2013-05-22

We present that the minimal spanning tree (MST) algorithm is a graph-theoretical cluster-finding method. We previously applied it to γ-ray bidimensional images, showing that it is quite sensitive in finding faint sources. Possible sources are associated with the regions where the photon arrival directions clusterize. MST selects clusters starting from a particular “tree” connecting all the point of the image and performing a cut based on the angular distance between photons, with a number of events higher than a given threshold. In this paper, we show how a further filtering, based on some parameters linked to the cluster properties, canmore » be applied to reduce spurious detections. We find that the most efficient parameter for this secondary selection is the magnitudeM of a cluster, defined as the product of its number of events by its clustering degree. We test the sensitivity of the method by means of simulated and real Fermi-Large Area Telescope (LAT) fields. Our results show that √M is strongly correlated with other statistical significance parameters, derived from a wavelet based algorithm and maximum likelihood (ML) analysis, and that it can be used as a good estimator of statistical significance of MST detections. Finally, we apply the method to a 2-year LAT image at energies higher than 3 GeV, and we show the presence of new clusters, likely associated with BL Lac objects.« less

The radio properties of infrared-faint radio sources

NASA Astrophysics Data System (ADS)

Middelberg, E.; Norris, R. P.; Hales, C. A.; Seymour, N.; Johnston-Hollitt, M.; Huynh, M. T.; Lenc, E.; Mao, M. Y.

2011-02-01

Context. Infrared-faint radio sources (IFRS) are objects that have flux densities of several mJy at 1.4 GHz, but that are invisible at 3.6 μm when using sensitive Spitzer observations with μJy sensitivities. Their nature is unclear and difficult to investigate since they are only visible in the radio. Aims: High-resolution radio images and comprehensive spectral coverage can yield constraints on the emission mechanisms of IFRS and can give hints to similarities with known objects. Methods: We imaged a sample of 17 IFRS at 4.8 GHz and 8.6 GHz with the Australia Telescope Compact Array to determine the structures on arcsecond scales. We added radio data from other observing projects and from the literature to obtain broad-band radio spectra. Results: We find that the sources in our sample are either resolved out at the higher frequencies or are compact at resolutions of a few arcsec, which implies that they are smaller than a typical galaxy. The spectra of IFRS are remarkably steep, with a median spectral index of -1.4 and a prominent lack of spectral indices larger than -0.7. We also find that, given the IR non-detections, the ratio of 1.4 GHz flux density to 3.6 μm flux density is very high, and this puts them into the same regime as high-redshift radio galaxies. Conclusions: The evidence that IFRS are predominantly high-redshift sources driven by active galactic nuclei (AGN) is strong, even though not all IFRS may be caused by the same phenomenon. Compared to the rare and painstakingly collected high-redshift radio galaxies, IFRS appear to be much more abundant, but less luminous, AGN-driven galaxies at similar cosmological distances.

Evidence for biasing in the CfA survey

NASA Technical Reports Server (NTRS)

Hamilton, A. J. S.

1988-01-01

Intrinsically bright galaxies appear systematically more correlated than faint galaxies in the Center for Astrophysics redshift survey. The amplification of the two-point correlation function behaves exponentially with luminosity, being essentially flat up to the knee of the luminosity function, then increasing markedly. The amplification reaches a factor of 3.5e + or - 0.4 in the very brightest galaxies. The effect is dominated by spirals rather than ellipticals, so that the correlation function of bright spirals becomes comparable to that of normal ellipticals. Similar results are obtained whether the correlation function is measured in two or three dimensions. The effect persists to separations of a correlation length or more, and is not confined to the cores of the Virgo, Coma, and Abell 1367 clusters, suggesting that the effect is caused by biasing, that is, galaxies kindle preferentially in more clustered regions, rather than by gravitational relaxation.

Global transients in ultraviolet and red-infrared ranges from data of Universitetsky-Tatiana-2 satellite

NASA Astrophysics Data System (ADS)

Garipov, G. K.; Khrenov, B. A.; Klimov, P. A.; Klimenko, V. V.; Mareev, E. A.; Martines, O.; Mendoza, E.; Morozenko, V. S.; Panasyuk, M. I.; Park, I. H.; Ponce, E.; Rivera, L.; Salazar, H.; Tulupov, V. I.; Vedenkin, N. N.; Yashin, I. V.

2013-01-01

Light detectors sensitive to wavelength ranges 240-400 nm and beyond 610 nm (which we refer to, for simplicity, as the UV and Red bands) on board Universitetsky-Tatiana-2 satellite have detected transient flashes in the atmosphere of duration 1-128 ms. Measured ratio of the number of Red photons to the number of UV photons indicates that source of transient radiation is at high atmosphere altitude (>50 km). Distribution of events with various photon numbers Qa in the atmosphere found to be different for "luminous" events Qa = 1023 - 1026 (with exponent of differential distribution -2.2) and for "faint" events Qa = 1021 - 1023 (with exponent - 0.97). Luminous event parameters (atmosphere altitude, energy released to radiation, and temporal profiles) are similar to observed elsewhere parameters of transient luminous events (TLE) of elves, sprites, halo, and gigantic blue jets types. Global map of luminous events demonstrates concentration to equatorial zones (latitudes 30°N to 30°S) above continents. Faint events (with number of photons Qa = 1020 - 5ṡ 1021) are distributed more uniformly over latitudes and longitudes. Phenomenon of series of transients registered every minute along satellite orbit (from 3 to 16 transients in one series) was observed. Most TLE-type events belonged to series. Single transients are in average fainter than serial ones. Some transients belonging to series occurs far away of thunderstorm regions. Origin of faint single transients is not clear; several hypothetical models of their production are discussed.

Adaptive Optics Imaging Survey of Luminous Infrared Galaxies

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

Laag, E A; Canalizo, G; van Breugel, W

2006-03-13

We present high resolution imaging observations of a sample of previously unidentified far-infrared galaxies at z < 0.3. The objects were selected by cross-correlating the IRAS Faint Source Catalog with the VLA FIRST catalog and the HST Guide Star Catalog to allow for adaptive optics observations. We found two new ULIGs (with L{sub FIR} {ge} 10{sup 12} L{sub {circle_dot}}) and 19 new LIGs (with L{sub FIR} {ge} 10{sup 11} L{sub {circle_dot}}). Twenty of the galaxies in the sample were imaged with either the Lick or Keck adaptive optics systems in H or K{prime}. Galaxy morphologies were determined using the twomore » dimensional fitting program GALFIT and the residuals examined to look for interesting structure. The morphologies reveal that at least 30% are involved in tidal interactions, with 20% being clear mergers. An additional 50% show signs of possible interaction. Line ratios were used to determine powering mechanism; of the 17 objects in the sample showing clear emission lines--four are active galactic nuclei and seven are starburst galaxies. The rest exhibit a combination of both phenomena.« less

THE DISTRIBUTION OF FAINT SATELLITES AROUND CENTRAL GALAXIES IN THE CANADA-FRANCE-HAWAII TELESCOPE LEGACY SURVEY

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

Jiang, C. Y.; Jing, Y. P.; Li, Cheng

2012-11-20

We investigate the radial number density profile and the abundance distribution of faint satellites around central galaxies in the low-redshift universe using the Canada-France-Hawaii Telescope (CFHT) Legacy Survey. We consider three samples of central galaxies with magnitudes of M {sub r} = -21, -22, and -23 selected from the Sloan Digital Sky Survey group catalog of Yang et al. The satellite distribution around these central galaxies is obtained by cross-correlating these galaxies with the photometric catalog of the CFHT Legacy Survey. The projected radial number density of the satellites obeys a power-law form with the best-fit logarithmic slope of -1.05,more » independent of both the central galaxy luminosity and the satellite luminosity. The projected cross-correlation function between central and satellite galaxies exhibits a non-monotonic trend with satellite luminosity. It is most pronounced for central galaxies with M {sub r} = -21, where the decreasing trend of clustering amplitude with satellite luminosity is reversed when satellites are fainter than central galaxies by more than 2 mag. A comparison with the satellite luminosity functions in the Milky Way (MW) and M31 shows that the MW/M31 system has about twice as many satellites as around a typical central galaxy of similar luminosity. The implications for theoretical models are briefly discussed.« less

Evolution of X-ray astronomy

NASA Technical Reports Server (NTRS)

Rossj, B.

1981-01-01

The evolution of X-ray astronomy up to the launching of the Einstein observatory is presented. The evaluation proceeded through the following major steps: (1) discovery of an extrasolar X-ray source, Sco X-1, orders of magnitude stronger than astronomers believed might exist; (2) identification of a strong X-ray source with the Crab Nebula; (3) identification of Sco X-1 with a faint, peculiar optical object; (4) demonstration that X-ray stars are binary systems, each consisting of a collapsed object accreting matter from an ordinary star; (5) discovery of X-ray bursts; (6) discovery of exceedingly strong X-ray emission from active galaxies, quasars and clusters of galaxies; (7) demonstration that the principal X-ray source is a hot gas filling the space between galaxies.

Infrared-faint radio sources remain undetected at far-infrared wavelengths. Deep photometric observations using the Herschel Space Observatory

NASA Astrophysics Data System (ADS)

Herzog, A.; Norris, R. P.; Middelberg, E.; Spitler, L. R.; Leipski, C.; Parker, Q. A.

2015-08-01

Context. Showing 1.4 GHz flux densities in the range of a few to a few tens of mJy, infrared-faint radio sources (IFRS) are a type of galaxy characterised by faint or absent near-infrared counterparts and consequently extreme radio-to-infrared flux density ratios up to several thousand. Recent studies showed that IFRS are radio-loud active galactic nuclei (AGNs) at redshifts ≳2, potentially linked to high-redshift radio galaxies (HzRGs). Aims: This work explores the far-infrared emission of IFRS, providing crucial information on the star forming and AGN activity of IFRS. Furthermore, the data enable examining the putative relationship between IFRS and HzRGs and testing whether IFRS are more distant or fainter siblings of these massive galaxies. Methods: A sample of six IFRS was observed with the Herschel Space Observatory between 100 μm and 500 μm. Using these results, we constrained the nature of IFRS by modelling their broad-band spectral energy distribution (SED). Furthermore, we set an upper limit on their infrared SED and decomposed their emission into contributions from an AGN and from star forming activity. Results: All six observed IFRS were undetected in all five Herschel far-infrared channels (stacking limits: σ = 0.74 mJy at 100 μm, σ = 3.45 mJy at 500 μm). Based on our SED modelling, we ruled out the following objects to explain the photometric characteristics of IFRS: (a) known radio-loud quasars and compact steep-spectrum sources at any redshift; (b) starburst galaxies with and without an AGN and Seyfert galaxies at any redshift, even if the templates were modified; and (c) known HzRGs at z ≲ 10.5. We find that the IFRS analysed in this work can only be explained by objects that fulfil the selection criteria of HzRGs. More precisely, IFRS could be (a) known HzRGs at very high redshifts (z ≳ 10.5); (b) low-luminosity siblings of HzRGs with additional dust obscuration at lower redshifts; (c) scaled or unscaled versions of Cygnus A at any redshift; and (d) scaled and dust-obscured radio-loud quasars or compact steep spectrum sources. We estimated upper limits on the infrared luminosity, the black hole accretion rate, and the star formation rate of IFRS, which all agreed with corresponding numbers of HzRGs. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

RS Ophiuchi in Quiescence: Why Is It X-ray Faint?

NASA Technical Reports Server (NTRS)

Mukai, Koji

2007-01-01

The short interval between successive outbursts of RS Oph strongly suggests that it has a high mass white dwarf accreting at a high rate. This, in turn, suggests the possibility of prominent X-ray emission from RS Oph in quiescence. However, archival quiescent X-ray observations of RS Oph show it to be a modest soft X-ray source but not a strong 2-10 keV X-ray source. In this aspect, RS Oph differs markedly from T CrB. We speculate on the possible mechanisms that could significantly suppress the 2-10 keV X-ray emission in RS Oph.

THE ROLE OF STAR FORMATION AND AN AGN IN DUST HEATING OF z = 0.3–2.8 GALAXIES. I. EVOLUTION WITH REDSHIFT AND LUMINOSITY

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

Kirkpatrick, Allison; Pope, Alexandra; Sajina, Anna

2015-11-20

We characterize infrared spectral energy distributions of 343 (ultra)luminous infrared galaxies from z = 0.3–2.8. We diagnose the presence of an active galactic nucleus (AGN) by decomposing individual Spitzer mid-IR spectroscopy into emission from star formation and an AGN-powered continuum; we classify sources as star-forming galaxies (SFGs), AGNs, or composites. Composites comprise 30% of our sample and are prevalent at faint and bright S{sub 24}, making them an important source of IR AGN emission. We combine spectroscopy with multiwavelength photometry, including Herschel imaging, to create three libraries of publicly available templates (2–1000 μm). We fit the far-IR emission using amore » two-temperature modified blackbody to measure cold and warm dust temperatures (T{sub c} and T{sub w}). We find that T{sub c} does not depend on mid-IR classification, while T{sub w} shows a notable increase as the AGN grows more luminous. We measure a quadratic relationship between mid-IR AGN emission and total AGN contribution to L{sub IR}. AGNs, composites, and SFGs separate in S{sub 8}/S{sub 3.6} and S{sub 250}/S{sub 24}, providing a useful diagnostic for estimating relative amounts of these sources. We estimate that >40% of IR-selected samples host an AGN, even at faint selection thresholds (S{sub 24} > 100 μJy). Our decomposition technique and color diagnostics are relevant given upcoming observations with the James Webb Space Telescope.« less

Outreach syncope clinic managed by a nurse practitioner: Outcome and cost effectiveness.

PubMed

Hamdan, Mohamed H; Walsh, Kathleen E; Brignole, Michele; Key, Jamie

2017-01-01

Introduction The purpose of this study was to assess the clinical and financial outcomes of a novel outreach syncope clinic. Methods We compared the clinical outcome of the Faint and Fall Clinic at the American Center (January-June 2016) with that of the University of Wisconsin Health and Clinics Faint and Fall Clinic (January 2013-December 2014). The American Center-Faint and Fall Clinic is run solely by a nurse practitioner, assisted by online faint-decision software and consultancy of a faint specialist through video-conferencing. Results Five hundred and twenty-eight consecutive patients were seen at the University of Wisconsin Hospital and Clinics-Faint and Fall Clinic and 68 patients at the American Center-Faint and Fall Clinic. The patients' clinical characteristics were similar except for a lower age in the American Center patients (45 ± 18 vs 51 ± 22, p = 0.03). Overall, a diagnosis was made within 45 days in 70% (95% confidence interval 66-74%) of the University of Wisconsin Hospital and Clinics patients and 69% (95% confidence interval 58-80%) of the American Center patients, ( p = 0.9). A mean of 3.0 ± 1.6 tests per patient was used in the University of Wisconsin Hospital and Clinics group compared to 1.5 ± 0.8 tests per patient in the American Center group, p = 0.001. Over the six-month study period, the total revenue at the American Center was US$152,597 (contribution margin of US$122,393 plus professional revenue of US$30,204). The total cost of the nurse practitioner including benefits was US$66,662 ((US$98,466 salary/year + 35.4% benefits)/2). Total revenue minus expenses resulted in a net profit of US$85,935. Discussion A nurse practitioner-run outreach syncope-clinic equipped with online faint-decision software and consultancy of a faint specialist through vedio-conferencing is feasible and financially self-sustainable. It allows the dissemination of standardized high-quality syncope care to patients who have no immediate access to a tertiary teaching hospital.

EMITTING ELECTRONS AND SOURCE ACTIVITY IN MARKARIAN 501

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

Mankuzhiyil, Nijil; Ansoldi, Stefano; Persic, Massimo

2012-07-10

We study the variation of the broadband spectral energy distribution (SED) of the BL Lac object Mrk 501 as a function of source activity, from quiescent to flaring. Through {chi}{sup 2}-minimization we model eight simultaneous SED data sets with a one-zone synchrotron self-Compton (SSC) model, and examine how model parameters vary with source activity. The emerging variability pattern of Mrk 501 is complex, with the Compton component arising from {gamma}-e scatterings that sometimes are (mostly) Thomson and sometimes (mostly) extreme Klein-Nishina. This can be seen from the variation of the Compton to synchrotron peak distance according to source state. Themore » underlying electron spectra are faint/soft in quiescent states and bright/hard in flaring states. A comparison with Mrk 421 suggests that the typical values of the SSC parameters are different in the two sources: however, in both jets the energy density is particle-dominated in all states.« less

Discovery of the candidate Kuiper belt object 1992 QB1

NASA Astrophysics Data System (ADS)

Jewitt, D.; Luu, J.

1993-04-01

The discovery of a new faint object in the outer solar system, 1992 QB1, moving beyond the orbit of Neptune is reported. It is suggested that the 1992 QB1 may represent the first detection of a member of the Kuiper belt (Edgworth, 1949; Kuiper, 1951), the hypothesized population of objects beyond Neptune and a possible source of the short-period comets, as suggested by Whipple (1964), Fernandez (1980), and Duncan et al. (1988).

A Novel Approach to model EPIC variable background

NASA Astrophysics Data System (ADS)

Marelli, M.; De Luca, A.; Salvetti, D.; Belfiore, A.

2017-10-01

One of the main aim of the EXTraS (Exploring the X-ray Transient and variable Sky) project is to characterise the variability of serendipitous XMM-Newton sources within each single observation. Unfortunately, 164 Ms out of the 774 Ms of cumulative exposure considered (21%) are badly affected by soft proton flares, hampering any classical analysis of field sources. De facto, the latest releases of the 3XMM catalog, as well as most of the analysis in literature, simply exclude these 'high background' periods from analysis. We implemented a novel SAS-indipendent approach to produce background-subtracted light curves, which allows to treat the case of very faint sources and very bright proton flares. EXTraS light curves of 3XMM-DR5 sources will be soon released to the community, together with new tools we are developing.

Detection of a Compact Radio Source near the Center of a Gravitational Lens: Quasar Image or Galactic Core?

PubMed

Gorenstein, M V; Shapiro, I I; Cohen, N L; Corey, B E; Falco, E E; Marcaide, J M; Rogers, A E; Whitney, A R; Porcas, R W; Preston, R A; Rius, A

1983-01-07

By use of a new, very sensitive interferometric system, a faint, compact radio source has been detected near the center of the galaxy that acts as the main part of a gravitational lens. This lens forms two previously discovered images of the quasar Q09S7+561, which lies in the direction of the constellation Ursa Major. The newly detected source has a core smaller than 0.002 arc second in diameter with a flux density of 0.6 +/- 0.1 millijansky at the 13-centimeter wavelength of the radio observations. This source could be the predicted third image of the transparent gravitational lens, the central core of the galaxy, or some combination of the two. It is not yet possible to choose reliably between these alternatives.

Luminous Obscured AGN Unveiled in the Stripe 82 X-ray Survey

NASA Astrophysics Data System (ADS)

LaMassa, Stephanie; Glikman, Eilat; Brusa, Marcella; Rigby, Jane; Tasnim Ananna, Tonima; Stern, Daniel; Lira, Paulina; Urry, Meg; Salvato, Mara; Alexandroff, Rachael; Allevato, Viola; Cardamone, Carolin; Civano, Francesca Maria; Coppi, Paolo; Farrah, Duncan; Komossa, S.; Lanzuisi, Giorgio; Marchesi, Stefano; Richards, Gordon; Trakhtenbrot, Benny; Treister, Ezequiel

2018-01-01

Stripe 82X is a wide-area (30 deg2) X-ray survey overlapping the legacy Sloan Digital Sky Survey (SDSS) Stripe 82 field, designed to uncover rare, high luminosity active galactic nuclei (AGN). We report on the results of an on-going near-infrared (NIR) spectroscopic campaign to follow-up reddened AGN candidates with Palomar TripleSpec, Keck NIRSPEC, and Gemini GNIRS. We identified 8 AGN in our bright NIR sample (K < 16, Vega), selected to have red R-K colors (> 4, Vega); four of these sources had existing optical spectra in SDSS. We targeted four out of 34 obscured AGN candidates in our faint NIR sample (K > 17, Vega), all of which are undetected in the single-epoch SDSS imaging, making them the best candidates for the most obscured and/or the most distant reddend AGN in Stripe 82X. All twelve sources are Type 1 AGN, with the FWHM of at least one permitted emission line exceeding 1300 km/s. We find that our nearly complete bright NIR sample (12/13 obscured AGN candidates have spectroscopic redshifts) is more distant (z > 0.5) than a matched sample of blue Type 1 AGN from Stripe 82X; these AGN tend to be more luminous than their blue, unobscured counterparts. Results from our pilot program of faint NIR-selected obscured AGN candidates demonstrate that our selection recovers reddened quasars missed by SDSS.

Near-infrared counterparts of three transient very faint neutron star X-ray binaries

NASA Astrophysics Data System (ADS)

Shaw, A. W.; Heinke, C. O.; Degenaar, N.; Wijnands, R.; Kaur, R.; Forestell, L. M.

2017-10-01

We present near-infrared (NIR) imaging observations of three transient neutron star X-ray binaries, SAX J1753.5-2349, SAX J1806.5-2215 and AX J1754.2-2754. All three sources are members of the class of 'very faint' X-ray transients which exhibit X-ray luminosities LX ≲ 1036 erg s-1. The nature of this class of sources is still poorly understood. We detect NIR counterparts for all three systems and perform multiband photometry for both SAX J1753.5-2349 and SAX J1806.5-2215, including narrow-band Br γ photometry for SAX J1806.5-2215. We find that SAX J1753.5-2349 is significantly redder than the field population, indicating that there may be absorption intrinsic to the system, or perhaps a jet is contributing to the infrared emission. SAX J1806.5-2215 appears to exhibit absorption in Br γ, providing evidence for hydrogen in the system. Our observations of AX J1754.2-2754 represent the first detection of an NIR counterpart for this system. We find that none of the measured magnitudes are consistent with the expected quiescent magnitudes of these systems. Assuming that the infrared radiation is dominated by either the disc or the companion star, the observed magnitudes argue against an ultracompact nature for all three systems.

A Chandra-Swift View of Point Sources in Hickson Compact Groups: High AGN Fraction but a Dearth of Strong AGNs

NASA Technical Reports Server (NTRS)

Tzanavaris, P.; Gallagher, S. C.; Hornschemeier, A. E.; Fedotov, K.; Eracleous, M.; Brandt, W. N.; Desjardins, T. D.; Charlton, J. C.; Gronwall, C.

2014-01-01

We present Chandra X-ray point source catalogs for 9 Hickson Compact Groups (HCGs, 37 galaxies) at distances of 34-89 Mpc. We perform detailed X-ray point source detection and photometry and interpret the point source population by means of simulated hardness ratios. We thus estimate X-ray luminosities (L(sub x)) for all sources, most of which are too weak for reliable spectral fitting. For all sources, we provide catalogs with counts, count rates, power-law indices (gamma), hardness ratios, and L(sub X), in the full (0.5-8.0 keV), soft (0.5-2.0 keV), and hard (2.0-8.0 keV) bands. We use optical emission-line ratios from the literature to re-classify 24 galaxies as star-forming, accreting onto a supermassive black hole (AGNs), transition objects, or low-ionization nuclear emission regions. Two-thirds of our galaxies have nuclear X-ray sources with Swift/UVOT counterparts. Two nuclei have L(sub X),0.5-8.0 keV > 10(exp 42) erg s-1, are strong multi-wavelength active galactic nuclei (AGNs), and follow the known alpha OX-?L? (nearUV) correlation for strong AGNs. Otherwise, most nuclei are X-ray faint, consistent with either a low-luminosity AGN or a nuclear X-ray binary population, and fall in the 'non-AGN locus' in alpha OX-?L? (nearUV) space, which also hosts other normal galaxies. Our results suggest that HCG X-ray nuclei in high specific star formation rate spiral galaxies are likely dominated by star formation, while those with low specific star formation rates in earlier types likely harbor a weak AGN. The AGN fraction in HCG galaxies with MR (is) less than -20 and L(sub X),0.5-8.0 keV (is) greater than 10(exp 41) erg s-1 is 0.08+0.35 -0.01, somewhat higher than the 5% fraction in galaxy clusters.

A Chandra-Swift View of Point Sources in Hickson Compact Groups: High AGN Fraction but a Dearth of Strong AGNs

NASA Astrophysics Data System (ADS)

Tzanavaris, P.; Gallagher, S. C.; Hornschemeier, A. E.; Fedotov, K.; Eracleous, M.; Brandt, W. N.; Desjardins, T. D.; Charlton, J. C.; Gronwall, C.

2014-05-01

We present Chandra X-ray point source catalogs for 9 Hickson Compact Groups (HCGs, 37 galaxies) at distances of 34-89 Mpc. We perform detailed X-ray point source detection and photometry and interpret the point source population by means of simulated hardness ratios. We thus estimate X-ray luminosities (LX ) for all sources, most of which are too weak for reliable spectral fitting. For all sources, we provide catalogs with counts, count rates, power-law indices (Γ), hardness ratios, and LX , in the full (0.5-8.0 keV), soft (0.5-2.0 keV), and hard (2.0-8.0 keV) bands. We use optical emission-line ratios from the literature to re-classify 24 galaxies as star-forming, accreting onto a supermassive black hole (AGNs), transition objects, or low-ionization nuclear emission regions. Two-thirds of our galaxies have nuclear X-ray sources with Swift/UVOT counterparts. Two nuclei have L X, 0.5-8.0 keV >1042 erg s-1, are strong multi-wavelength active galactic nuclei (AGNs), and follow the known αOX-νL ν (nearUV) correlation for strong AGNs. Otherwise, most nuclei are X-ray faint, consistent with either a low-luminosity AGN or a nuclear X-ray binary population, and fall in the "non-AGN locus" in αOX-νL ν (nearUV) space, which also hosts other normal galaxies. Our results suggest that HCG X-ray nuclei in high specific star formation rate spiral galaxies are likely dominated by star formation, while those with low specific star formation rates in earlier types likely harbor a weak AGN. The AGN fraction in HCG galaxies with MR <= -20 and L X, 0.5-8.0 keV >=1041 erg s-1 is 0.08^{+0.35}_{-0.01}, somewhat higher than the ~5% fraction in galaxy clusters.

VizieR Online Data Catalog: SFiNCs: X-ray, IR and membership catalogs (Getman+, 2017)

NASA Astrophysics Data System (ADS)

Getman, K. V.; Broos, P. S.; Kuhn, M. A.; Feigelson, E. D.; Richert, A. J. W.; Ota, Y.; Bate, M. R.; Garmire, G. P.

2017-06-01

Sixty five X-ray observations for the 22 Star Formation in Nearby Clouds (SFiNCs) star-forming regions (SFRs) (see tables 1 and 2), made with the imaging array on the Advanced CCD Imaging Spectrometer (ACIS), were pulled from the Chandra archive (spanning 2000 Jan to 2015 Apr; see table 2). Our final Chandra-ACIS catalog for the 22 SFiNCs SFRs comprises 15364 X-ray sources (Tables 3 and 4 and section 3.2). To obtain MIR photometry for X-ray objects and to identify and measure MIR photometry for additional non-Chandra disky stars that were missed in previous studies of the SFiNCs regions (typically faint YSOs), we have reduced the archived Spitzer-IRAC data by homogeneously applying the MYStIX-based Spitzer-IRAC data reduction methods of Kuhn+ (2013, J/ApJS/209/29) to the 423 Astronomical Object Request (AORs) data sets for the 22 SFiNCs SFRs (Table 5). As in MYStIX, here the SFiNCs IRAC source catalog retains all point sources with the photometric signal-to-noise ratio >5 in both [3.6] and [4.5] channels. This catalog covers the 22 SFiNCs SFRs and their vicinities on the sky and comprises 1638654 IRAC sources with available photometric measurements for 100%, 100%, 29%, and 23% of these sources in the 3.6, 4.5, 5.8, and 8.0um bands, respectively (see table 6 and section 3.4). Source position cross correlations between the SFiNCs Chandra X-ray source catalog and an IR catalog, either the "cut-out" IRAC or 2MASS, were made using the steps described in section 3.5. Tables 7 and 8 provide the list of 8492 SFiNCs probable cluster members (SPCMs) and their main IR and X-ray properties (see section 4). (9 data files).

The Radio Luminosity Function and Galaxy Evolution in the Coma Cluster

NASA Technical Reports Server (NTRS)

Miller, Neal A.; Hornschemeier, Ann E.; Mabasher, Bahram; Brudgesm Terrry J.; Hudson, Michael J.; Marzke, Ronald O.; Smith, Russell J.

2008-01-01

We investigate the radio luminosity function and radio source population for two fields within the Coma cluster of galaxies, with the fields centered on the cluster core and southwest infall region and each covering about half a square degree. Using VLA data with a typical rms sensitivity of 28 (mu)Jy per 4.4" beam, we identify 249 radio sources with optical counterparts brighter than r = 22 (equivalent to M(sub r) = -13 for cluster member galaxies). Comprehensive optical spectroscopy identifies 38 of these as members of the Coma cluster, evenly split between sources powered by an active nucleus and sources powered by active star formation. The radio-detected star-forming galaxies are restricted to radio luminosities between about 10(exp 21) and 10(exp 22) W/Hz, an interesting result given that star formation dominates field radio luminosity functions below about 10(exp 23) W/Hz. The majority of the radio-detected star-forming galaxies have characteristics of starbursts, including high specific star formation rates and optical spectra with strong emission lines. In conjunction with prior studies on post-starburst galaxies within the Coma cluster, this is consistent with a picture in which late-type galaxies entering Coma undergo a starburst prior to a rapid cessation of star formation. Optically bright elliptical galaxies (Mr less than or equals -20.5) make the largest contribution to the radio luminosity function at both the high (> approx. 3x10(exp 22) W/Hz) and low (< approx. 10(exp 21) W/Hz) ends. Through a stacking analysis of these optically-bright ellipticals we find that they continue to harbor radio sources down to luminosities as faint as 3x10(exp 19) W/Hz. However, contrary to published results for the Virgo cluster we find no evidence for the existence of a population of optically faint (M(sub r) approx. equals -14) dwarf ellipticals hosting strong radio AGN.

Small-scale Conformity of the Virgo Cluster Galaxies

NASA Astrophysics Data System (ADS)

Lee, Hye-Ran; Lee, Joon Hyeop; Jeong, Hyunjin; Park, Byeong-Gon

2016-06-01

We investigate the small-scale conformity in color between bright galaxies and their faint companions in the Virgo Cluster. Cluster member galaxies are spectroscopically determined using the Extended Virgo Cluster Catalog and the Sloan Digital Sky Survey Data Release 12. We find that the luminosity-weighted mean color of faint galaxies depends on the color of adjacent bright galaxy as well as on the cluster-scale environment (gravitational potential index). From this result for the entire area of the Virgo Cluster, it is not distinguishable whether the small-scale conformity is genuine or if it is artificially produced due to cluster-scale variation of galaxy color. To disentangle this degeneracy, we divide the Virgo Cluster area into three sub-areas so that the cluster-scale environmental dependence is minimized: A1 (central), A2 (intermediate), and A3 (outermost). We find conformity in color between bright galaxies and their faint companions (color-color slope significance S ˜ 2.73σ and correlation coefficient {cc}˜ 0.50) in A2, where the cluster-scale environmental dependence is almost negligible. On the other hand, the conformity is not significant or very marginal (S ˜ 1.75σ and {cc}˜ 0.27) in A1. The conformity is not significant either in A3 (S ˜ 1.59σ and {cc}˜ 0.44), but the sample size is too small in this area. These results are consistent with a scenario in which the small-scale conformity in a cluster is a vestige of infallen groups and these groups lose conformity as they come closer to the cluster center.

A FOURTH H I 21 cm ABSORPTION SYSTEM IN THE SIGHT LINE OF MG J0414+0534: A RECORD FOR INTERVENING ABSORBERS

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

Tanna, A.; Webb, J. K.; Curran, S. J.

2013-08-01

We report the detection of a strong H I 21 cm absorption system at z = 0.5344, as well as a candidate system at z = 0.3389, in the sight line toward the z = 2.64 quasar MG J0414+0534. This, in addition to the absorption at the host redshift and the other two intervening absorbers, takes the total to four (possibly five). The previous maximum number of 21 cm absorbers detected along a single sight line is two and so we suspect that this number of gas-rich absorbers is in some way related to the very red color of themore » background source. Despite this, no molecular gas (through OH absorption) has yet been detected at any of the 21 cm redshifts, although, from the population of 21 cm absorbers as a whole, there is evidence for a weak correlation between the atomic line strength and the optical-near-infrared color. In either case, the fact that so many gas-rich galaxies (likely to be damped Ly{alpha} absorption systems) have been found along a single sight line toward a highly obscured source may have far-reaching implications for the population of faint galaxies not detected in optical surveys, a possibility which could be addressed through future wide-field absorption line surveys with the Square Kilometer Array.« less

OVERDENSITIES OF Y-DROPOUT GALAXIES FROM THE BRIGHTEST-OF-REIONIZING GALAXIES SURVEY: A CANDIDATE PROTOCLUSTER AT REDSHIFT z Almost-Equal-To 8

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

Trenti, Michele; Shull, J. M.; Bradley, L. D.

Theoretical and numerical modeling of the assembly of dark-matter halos predicts that the most massive and luminous galaxies at high redshift are surrounded by overdensities of fainter companions. We test this prediction with Hubble Space Telescope observations acquired by our Brightest-of-Reionizing Galaxies (BoRG) survey, which identified four very bright z {approx} 8 candidates as Y{sub 098}-dropout sources in four of the 23 non-contiguous Wide Field Camera 3 fields observed. We extend here the search for Y{sub 098}-dropouts to fainter luminosities (M{sub *} galaxies with M{sub AB} {approx} -20), with detections at {>=}5{sigma} confidence (compared to the 8{sigma} confidence threshold adoptedmore » earlier) identifying 17 new candidates. We demonstrate that there is a correlation between number counts of faint and bright Y{sub 098}-dropouts at {>=}99.84% confidence. Field BoRG58, which contains the best bright z {approx} 8 candidate (M{sub AB} = -21.3), has the most significant overdensity of faint Y{sub 098}-dropouts. Four new sources are located within 70'' (corresponding to 3.1 comoving Mpc at z = 8) from the previously known brighter z {approx} 8 candidate. The overdensity of Y{sub 098}-dropouts in this field has a physical origin to very high confidence (p > 99.975%), independent of completeness and contamination rate of the Y{sub 098}-dropout selection. We modeled the overdensity by means of cosmological simulations and estimate that the principal dark-matter halo has mass M{sub h} Almost-Equal-To (4-7) Multiplication-Sign 10{sup 11} M{sub Sun} ({approx}5{sigma} density peak) and is surrounded by several M{sub h} Almost-Equal-To 10{sup 11} M{sub Sun} halos which could host the fainter dropouts. In this scenario, we predict that all halos will eventually merge into a M{sub h} > 2 Multiplication-Sign 10{sup 14} M{sub Sun} galaxy cluster by z = 0. Follow-up observations with ground- and space-based telescopes are required to secure the z {approx} 8 nature of the overdensity, discover new members, and measure their precise redshift.« less

THE CHANDRA COSMOS SURVEY. III. OPTICAL AND INFRARED IDENTIFICATION OF X-RAY POINT SOURCES

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

Civano, F.; Elvis, M.; Aldcroft, T.

2012-08-01

The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8 Ms, Chandra program that has imaged the central 0.9 deg{sup 2} of the COSMOS field down to limiting depths of 1.9 Multiplication-Sign 10{sup -16} erg cm{sup -2} s{sup -1} in the soft (0.5-2 keV) band, 7.3 Multiplication-Sign 10{sup -16} erg cm{sup -2} s{sup -1} in the hard (2-10 keV) band, and 5.7 Multiplication-Sign 10{sup -16} erg cm{sup -2} s{sup -1} in the full (0.5-10 keV) band. In this paper we report the i, K, and 3.6 {mu}m identifications of the 1761 X-ray point sources. We use the likelihood ratio technique tomore » derive the association of optical/infrared counterparts for 97% of the X-ray sources. For most of the remaining 3%, the presence of multiple counterparts or the faintness of the possible counterpart prevented a unique association. For only 10 X-ray sources we were not able to associate a counterpart, mostly due to the presence of a very bright field source close by. Only two sources are truly empty fields. The full catalog, including spectroscopic and photometric redshifts and classification described here in detail, is available online. Making use of the large number of X-ray sources, we update the 'classic locus' of active galactic nuclei (AGNs) defined 20 years ago in soft X-ray surveys and define a new locus containing 90% of the AGNs in the survey with full-band luminosity >10{sup 42} erg s{sup -1}. We present the linear fit between the total i-band magnitude and the X-ray flux in the soft and hard bands, drawn over two orders of magnitude in X-ray flux, obtained using the combined C-COSMOS and XMM-COSMOS samples. We focus on the X-ray to optical flux ratio (X/O) and we test its known correlation with redshift and luminosity, and a recently introduced anti-correlation with the concentration index (C). We find a strong anti-correlation (though the dispersion is of the order of 0.5 dex) between X/O computed in the hard band and C and that 90% of the obscured AGNs in the sample with morphological information live in galaxies with regular morphology (bulgy and disky/spiral), suggesting that secular processes govern a significant fraction of the black hole growth at X-ray luminosities of 10{sup 43}-10{sup 44.5} erg s{sup -1}. We also investigate the degree of obscuration of the sample using the hardness ratio, and we compare the X-ray color with the near-infrared to optical color.« less

Antimyosin imaging in acute transmural myocardial infarctions: results of a multicenter clinical trial.

PubMed

Johnson, L L; Seldin, D W; Becker, L C; LaFrance, N D; Liberman, H A; James, C; Mattis, J A; Dean, R T; Brown, J; Reiter, A

1989-01-01

Murine monoclonal antimyosin antibody has been shown experimentally to bind selectively to irreversibly damaged myocytes. To evaluate the safety and efficacy of monoclonal antimyosin for identifying acute transmural infarction, 50 patients with acute Q wave myocardial infarction were entered into a phase I/II multicenter trial involving three clinical sites. Indium-111 antimyosin was prepared from an instant kit formulation containing 0.5 mg of diethylene triamine pentaacetic acid (DTPA)-coupled Fab fragment (R11D10) and 1.2 to 2.4 mCi of indium-111. Average labeling efficiency was 92%. Antimyosin was injected 27 +/- 16 h after the onset of chest pain. Planar or tomographic imaging was performed 27 +/- 9 h after injection in all patients, and repeat imaging was done 24 h later in 39 patients. Of the 50 patients entered, 46 showed myocardial uptake of antimyosin (sensitivity 92%). Thirty-one of 39 planar scans performed at 24 h were diagnostic; 8 showed persistent blood pool activity that cleared by 48 h. Focal myocardial uptake of antimyosin corresponded to electrocardiographic infarct localization. No patient had an adverse reaction to antimyosin. In addition, 125 serum samples, including 21 collected greater than 42 days after injection, were tested for human antimouse antibodies, and all samples were assessed as having undetectable titers. Intensity of antimyosin uptake was correlated with infarct location and the presence or absence of collateral vessels. There was a significant correlation between faint uptake and inferoposterior infarct location. In 21 patients who had coronary angiography close to the time of antimyosin injection, there was a significant correlation between faint tracer uptake and closed infarct-related vessel with absent collateral flow.(ABSTRACT TRUNCATED AT 250 WORDS)

X-ray detections of submillimetre galaxies: active galactic nuclei versus starburst contribution

NASA Astrophysics Data System (ADS)

Johnson, S. P.; Wilson, G. W.; Wang, Q. D.; Williams, C. C.; Scott, K. S.; Yun, M. S.; Pope, A.; Lowenthal, J.; Aretxaga, I.; Hughes, D.; Kim, M. J.; Kim, S.; Tamura, Y.; Kohno, K.; Ezawa, H.; Kawabe, R.; Oshima, T.

2013-05-01

We present a large-scale study of the X-ray properties and near-IR-to-radio spectral energy distributions (SEDs) of submillimetre galaxies (SMGs) detected at 1.1 mm with the AzTEC instrument across a ˜1.2 square degree area of the sky. Combining deep 2-4 Ms Chandra data with Spitzer IRAC/MIPS and Very Large Array data within the Great Observatories Origins Deep Survey North (GOODS-N), GOODS-S and COSMOS fields, we find evidence for active galactic nucleus (AGN) activity in ˜14 per cent of 271 AzTEC SMGs, ˜28 per cent considering only the two GOODS fields. Through X-ray spectral modelling and multiwavelength SED fitting using Monte Carlo Markov chain techniques to Siebenmorgen et al. (AGN) and Efstathiou, Rowan-Robinson & Siebenmorgen (starburst) templates, we find that while star formation dominates the IR emission, with star formation rates (SFRs) ˜100-1000 M⊙ yr-1, the X-ray emission for most sources is almost exclusively from obscured AGNs, with column densities in excess of 1023 cm-2. Only for ˜6 per cent of our sources do we find an X-ray-derived SFR consistent with NIR-to-radio SED derived SFRs. Inclusion of the X-ray luminosities as a prior to the NIR-to-radio SED effectively sets the AGN luminosity and SFR, preventing significant contribution from the AGN template. Our SED modelling further shows that the AGN and starburst templates typically lack the required 1.1 mm emission necessary to match observations, arguing for an extended, cool dust component. The cross-correlation function between the full samples of X-ray sources and SMGs in these fields does not indicate a strong correlation between the two populations at large scales, suggesting that SMGs and AGNs do not necessarily trace the same underlying large-scale structure. Combined with the remaining X-ray-dim SMGs, this suggests that sub-mm-bright sources may evolve along multiple tracks, with X-ray-detected SMGs representing transitionary objects between periods of high star formation and AGN activity, while X-ray-faint SMGs represent a brief starburst phase of more normal galaxies.

New insights into the X-ray properties of nearby barred spiral galaxy NGC 1672

NASA Astrophysics Data System (ADS)

Jenkins, L. P.; Brnadt, W. N.; Colbert, E. J. M.; Levan, A. J.; Roberts, T. P.; Ward, M. J.; Zezas, A.

2008-02-01

We present some preliminary results from new Chandra and XMM-Newton X-ray observations of the nearby barred spiral galaxy NGC1672. It shows dramatic nuclear and extra-nuclear star formation activity, including starburst regions located near each end of its strong bar, both of which host ultraluminous X-ray sources (ULXs). With the new high-spatial-resolution Chandra imaging, we show for the first time that NGC1672 possesses a faint ($L(X)~10^39 erg/s), hard central X-ray source surrounded by an X-ray bright circumnuclear starburst ring that dominates the X-ray emission in the region. The central source may represent low-level AGN activity, or alternatively the emission from X-ray binaries associated with star-formation in the nucleus.

ACCOUNTING FOR COSMIC VARIANCE IN STUDIES OF GRAVITATIONALLY LENSED HIGH-REDSHIFT GALAXIES IN THE HUBBLE FRONTIER FIELD CLUSTERS

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

Robertson, Brant E.; Stark, Dan P.; Ellis, Richard S.

Strong gravitational lensing provides a powerful means for studying faint galaxies in the distant universe. By magnifying the apparent brightness of background sources, massive clusters enable the detection of galaxies fainter than the usual sensitivity limit for blank fields. However, this gain in effective sensitivity comes at the cost of a reduced survey volume and, in this Letter, we demonstrate that there is an associated increase in the cosmic variance uncertainty. As an example, we show that the cosmic variance uncertainty of the high-redshift population viewed through the Hubble Space Telescope Frontier Field cluster Abell 2744 increases from ∼35% atmore » redshift z ∼ 7 to ≳ 65% at z ∼ 10. Previous studies of high-redshift galaxies identified in the Frontier Fields have underestimated the cosmic variance uncertainty that will affect the ultimate constraints on both the faint-end slope of the high-redshift luminosity function and the cosmic star formation rate density, key goals of the Frontier Field program.« less

RELICS: Reionization Lensing Cluster Survey

NASA Astrophysics Data System (ADS)

Coe, Dan A.; RELICS Team

2017-01-01

Hubble and Spitzer imaging programs observing galaxy cluster lenses have delivered some of the highest redshift galaxy candidates to date (z ~ 9 - 11, or 540 - 410 Myr after the Big Bang). These magnified galaxies are intrinsically faint, and thus more representative of the sources believed to be primarily responsible for reionization. Magnified galaxies are also observed brightly enough to be prime targets for detailed follow-up study with current and future observatories, including JWST. Building on the successes of CLASH and the Frontier Fields, we have begun RELICS, the Reionization Lensing Cluster Survey. By observing 41 massive clusters for the first time at infrared wavelengths, RELICS will deliver more of the best and brightest high-redshift candidates to the community in time for the November 2017 JWST GO Cycle 1 call for proposals. I will present our early results. I will also discuss prospects for JWST to follow-up known candidates and discover new galaxies at even higher redshifts (z > 11). The discovery efficiency gains from lensing will be even more pronounced at z > 11 if luminosity function faint end slopes are steeper than alpha ~ -2, as suggested by current models and observational extrapolations.

AGN in the Swift/BAT and INTEGRAL Hard X-ray Surveys

NASA Technical Reports Server (NTRS)

Beckmann, Volker; Tueller, Jack; Baumgartner, Wayne; Markwardt, Craig; Mushotzky, Richard; Skinner, Gerry

2008-01-01

Two hard X-ray surveys are in progress at this time. They provide a unique new window on compact objects and black holes. I will discuss how these two surveys complement each other and the potential for improved coordination that could yield significant near term results in both sensitivity and time coverage. I will pay particular attention to the discovery of faint sources including new results from the 36 month survey from Swift/Burst Alert Telescope (BAT).

A Search for Early Optical Emission at Gamma-Ray Burst Locations by the Solar Mass Ejection Imager (SMEI)

NASA Technical Reports Server (NTRS)

Band, David L.; Buffington, Andrew; Jackson, Bernard V.; Hick, P. Paul; Smith, Aaron C.

2005-01-01

The Solar Mass Ejection Imager (SMEI) views nearly every point on the sky once every 102 minutes and can detect point sources as faint as R approx. 10th magnitude. Therefore, SMEI can detect or provide upper limits for the optical afterglow from gamma-ray bursts in the tens of minutes after the burst when different shocked regions may emit optically. Here we provide upper limits for 58 bursts between 2003 February and 2005 April.

Extent of warm haloes around medium-redshift galaxies

NASA Technical Reports Server (NTRS)

Burbidge, E. M.; Barlow, T. A.; Cohen, R. D.; Junkkarinen, V. T.; Womble, D. S.

1989-01-01

The properties of low-to-medium ionization gaseous haloes around galaxies are briefly reviewed. New observations concerning such haloes are presented. For the galaxy-QSO pair in the field of the radio source 3C303, the higher-redshift QSO has been found to show Mg II absorption at the lower redshift of the faint nearby galaxy. Secondly, new data are presented on one of the galaxies in the environment of the well-known BL Lac object AO 0235 + 164.

VizieR Online Data Catalog: Sample of faint X-ray pulsators (Israel+, 2016)

NASA Astrophysics Data System (ADS)

Israel, G. L.; Esposito, P.; Rodriguez Castillo, G. A.; Sidoli, L.

2018-04-01

As of 2015 December 31, we extracted about 430000 time series from sources with more than 10 counts (after background subtraction); ~190000 of them have more than 50 counts and their PSDs were searched for significant peaks. At the time of writing, the total number of searched Fourier frequencies was about 4.3x109. After a detailed screening, we obtained a final sample of 41 (42) new X-ray pulsators (signals), which are listed in Table 1. (1 data file).

The B3-VLA CSS sample. VIII. New optical identifications from the Sloan Digital Sky Survey The ultraviolet-optical spectral energy distribution of the young radio sources

NASA Astrophysics Data System (ADS)

Fanti, C.; Fanti, R.; Zanichelli, A.; Dallacasa, D.; Stanghellini, C.

2011-04-01

Context. Compact steep-spectrum radio sources and giga-hertz peaked spectrum radio sources (CSS/GPS) are generally considered to be mostly young radio sources. In recent years we studied at many wavelengths a sample of these objects selected from the B3-VLA catalog: the B3-VLA CSS sample. Only ≈60% of the sources were optically identified. Aims: We aim to increase the number of optical identifications and study the properties of the host galaxies of young radio sources. Methods: We cross-correlated the CSS B3-VLA sample with the Sloan Digital Sky Survey (SDSS), DR7, and complemented the SDSS photometry with available GALEX (DR 4/5 and 6) and near-IR data from UKIRT and 2MASS. Results: We obtained new identifications and photometric redshifts for eight faint galaxies and for one quasar and two quasar candidates. Overall we have 27 galaxies with SDSS photometry in five bands, for which we derived the ultraviolet-optical spectral energy distribution (UV-O-SED). We extended our investigation to additional CSS/GPS selected from the literature. Most of the galaxies show an excess of ultra-violet (UV) radiation compared with the UV-O-SED of local radio-quiet ellipticals. We found a strong dependence of the UV excess on redshift and analyzed it assuming that it is generated either from the nucleus (hidden quasar) or from a young stellar population (YSP). We also compare the UV-O-SEDs of our CSS/GPS sources with those of a selection of large size (LSO) powerful radio sources from the literature. Conclusions: If the major process of the UV excess is caused by a YSP, our conclusion is that it is the result of the merger process that also triggered the onset of the radio source with some time delay. We do not see evidence for a major contribution from a YSP triggered by the radio sources itself. Appendices A-G are only available in electronic form at http://www.aanda.org

Valbenazine

MedlinePlus

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The near-infrared counterpart of a variable galactic plane radio source

NASA Technical Reports Server (NTRS)

Margon, Bruce; Phillips, Andrew C.; Ciardullo, Robin; Jacoby, George H.

1992-01-01

A near-infrared counterpart to the highly variable, unresolved galactic plane radio source GT 0116 + 622 is identified. This source is of particular interest, as it has been previously suggested to be the counterpart of the gamma-ray source Cas gamma-l. The present NIR and red images detect a faint, spatially extended (3 arcsec FWHM), very red object coincident with the radio position. There is complex spatial structure which may be due in part to an unrelated superposed foreground object. Observations on multiple nights show no evidence for flux variability, despite the high amplitude variability on a time-scale of days reported for the radio source. The data are consistent with an interpretation of GT 0116 + 622 as an unusually variable, obscured active galaxy at a distance of several hundred megaparsecs, although more exotic, and in particular galactic, interpretations cannot yet be ruled out. If the object is extragalactic, the previously suggested identification with the gamma-ray source would seem unlikely.

The REX survey as a Tool to Test the Beaming Model for BL Lacs

NASA Astrophysics Data System (ADS)

Caccianiga, A.; della Ceca, R.; Gioia, I. M.; Maccacaro, T.; Wolter, A.

We present the preliminary properties of the BL Lacs discovered in the REX survey (Caccianiga et al. 1998). In particular, we discuss a few sources with optical spectral properties ``intermediate'' between those of BL Lacs and those of elliptical galaxies. These objects could harbour weak (in the optical band) sources of non-thermal continuum in their nuclei and, if confirmed, they could represent the faint tail of the BL Lac population. The existence of such ``weak'' BL Lacs is matter of discussion in recent literature (e.g. Marcha et al. 1996) and could lead to a revision of the defining criteria of a BL Lac and, consequently, of their cosmological and statistical properties.

CHARACTERIZING FAINT GALAXIES IN THE REIONIZATION EPOCH: LBT CONFIRMS TWO L < 0.2 L* SOURCES AT z = 6.4 BEHIND THE CLASH/FRONTIER FIELDS CLUSTER MACS0717.5+3745

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

Vanzella, E.; Cusano, F.; Fontana, A.

2014-03-01

We report the LBT/MODS1 spectroscopic confirmation of two images of faint Lyα emitters at z = 6.4 behind the Frontier Fields galaxy cluster MACSJ0717.5+3745. A wide range of lens models suggests that the two images are highly magnified, with a strong lower limit of μ > 5. These are the faintest z > 6 candidates spectroscopically confirmed to date. These may also be multiple images of the same z = 6.4 source as supported by their similar intrinsic properties, but the lens models are inconclusive regarding this interpretation. To be cautious, we derive the physical properties of each image individually.more » Thanks to the high magnification, the observed near-infrared (restframe ultraviolet) part of the spectral energy distributions and Lyα lines are well detected with S/N(m {sub 1500}) ≳ 10 and S/N(Lyα) ≅ 10-15. Adopting μ > 5, the absolute magnitudes, M {sub 1500}, and Lyα fluxes are fainter than –18.7 and 2.8 × 10{sup –18} erg s{sup –1} cm{sup –2}, respectively. We find a very steep ultraviolet spectral slope β = –3.0 ± 0.5 (F {sub λ} = λ{sup β}), implying that these are very young, dust-free, and low metallicity objects, made of standard stellar populations or even extremely metal poor stars (age ≲ 30 Myr, E(B – V) = 0 and metallicity 0.0-0.2 Z/Z {sub ☉}). The objects are compact (<1 kpc{sup 2}) and with a stellar mass M {sub *} < 10{sup 8} M {sub ☉}. The very steep β, the presence of the Lyα line, and the intrinsic FWHM (<300 km s{sup –1}) of these newborn objects do not exclude a possible leakage of ionizing radiation. We discuss the possibility that such faint galaxies may resemble those responsible for cosmic reionization.« less

A Central Source in the Supernova Remnant Kes 79

NASA Astrophysics Data System (ADS)

Seward, F.; Slane, P.; Smith, R.; Sun, M.

2002-04-01

Kes 79 (G33.6+0.1) was observed 31 July 2001 for 30 ks with the Chandra ACIS-I instrument. This remnant, in the constellation Aquila, lies in the galactic plane at a distance of ~10 kpc. The 11^' angular diameter implies an age of a few thousand years. The morphology shows faint outer and bright inner shells. The Chandra image reveals, for the first time, a point-like source at the center of the remnant. This source has a black body spectrum with kT = 0.5 keV. No regular pulsations were found at periods greater than 6.4 s (the ACIS integration time is 3.2 s). No surrounding synchrotron emission wass detected. The X-ray luminosity is 7 × 10^33 erg/s, about 1% the luminosity of the entire remnant. The source may be similar to the one at the center of Cas A.

Chemical Abundance Measurements of Ultra-Faint Dwarf Galaxies Discovered by the Dark Energy Survey

NASA Astrophysics Data System (ADS)

Nagasawa, Daniel; Marshall, Jennifer L.; Simon, Joshua D.; Hansen, Terese; Li, Ting; Bernstein, Rebecca; Balbinot, Eduardo; Drlica-Wagner, Alex; Pace, Andrew; Strigari, Louis; Pellegrino, Craig; DePoy, Darren L.; Suntzeff, Nicholas; Bechtol, Keith; Dark Energy Suvey

2018-01-01

We present chemical abundance analysis results derived from high-resolution spectroscopy of ultra-faint dwarfs discovered by the Dark Energy Survey. Ultra-faint dwarf galaxies preserve a fossil record of the chemical abundance patterns imprinted by the first stars in the Universe. High-resolution spectroscopic observations of member stars in several recently discovered Milky Way satellites reveal a range of abundance patterns among ultra-faint dwarfs suggesting that star formation processes in the early Universe were quite diverse. The chemical content provides a glimpse not only of the varied nucleosynthetic processes and chemical history of the dwarfs themselves, but also the environment in which they were formed. We present the chemical abundance analysis of these objects and discuss possible explanations for the observed abundance patterns.

Beacons in the dark: using the most distant galaxies to probe cosmic reionization

NASA Astrophysics Data System (ADS)

De Barros, Stephane

2017-08-01

One of the major unresolved problems in modern cosmology is when and how the universe was ionized. The consensus scenario is that ultra-faint, low-mass galaxies contributed most to the UV background at high-redshift and that reionization was an inhomogeneous process, with ionized bubbles created first around galaxy overdensities. The very surprising discovery of Ly-alpha emission lines around a large fraction of the most luminous galaxies at z=7.4-8.7, when we expect the universe to be highly neutral, could thus be explained by the fact that they lie in large HII bubbles which were ionized thanks to yet undetected fainter neighbors. Theoretical models indeed predict a boost of up to 6x larger galaxy counts around the brightest sources compared to the general field, when probing down to luminosities as faint as 0.1L_UV of the central source. Here we propose a direct test of these models by searching for fainter neighbors around three bright z>7.4 galaxies emitting Ly-alpha, including two sources that lie only 9 Mpc from each other and could share the same ionized bubble, as well as the most distant confirmed Ly-alpha emitter EGSY-8p7 at z=8.68. Given the expected overdensities, we have the opportunity to detect 20 (and up to 50) new z 7-9 galaxies with only a modest investment of HST time. These observations are thus maximally efficient at providing a large number of precious high-redshift targets for early JWST spectroscopy to directly study the galaxies that are in the process of ionizing the universe. Our imaging will further enhance the legacy of the CANDELS/EGS field, and we will make the reduced data available to the community immediately for JWST follow-up.

The Orion Nebula Cluster as a Paradigm of Star Formation

NASA Astrophysics Data System (ADS)

Robberto, Massimo

2014-10-01

We propose a 52-orbit Treasury Program to investigate two fundamental questions of star formation: a) the low-mass tail of the IMF, down to a few Jupiter masses; b) the dynamical evolution of clusters, as revealed by stellar proper motions. We target the Orion Nebula Cluster (ONC) using WFC3 and ACS in coordinated parallel mode to perform a synoptic survey in the 1.345micron H2O feature and Ic broad-band. Our main objectives are: 1) to discover and classify ~500 brown dwarfs and planetary-mass objects in the field, extending the IMF down to lowest masses formed by gravitational collapse. Using the latest generation of high contrast image processing we will also search for faint companions, reaching down to sub-arcsecond separations and 1E-4 flux ratios. 2) to derive high precision (~0.2km/s) relative proper motions of low-mass stars and substellar objects (about 1000 sources total), leveraging on first epoch data obtained by our previous HST Treasury Program about 10 years ago. These data will unveil the cluster dynamics: velocity dispersion vs. mass, substructures, and the fraction of escaping sources. Only HST can access the IR H2O absorption feature sensitive to the effective temperature of substellar objects, while providing the exceptionally stable PSF needed for the detection of faint companions, and the identical ACS platform for our second epoch proper-motion survey. This program will provide the definitive HST legacy dataset on the ONC. Our High-Level Science Products will be mined by the community, both statistically to constrain competing theories of star formation, and to study in depth the multitude of exotic sources harboured by the cluster.

HUBBLE SPACE TELESCOPE OBSERVATIONS OF DUSTY FILAMENTS IN HERCULES A: EVIDENCE FOR ENTRAINMENT

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

O'Dea, C. P.; Kharb, P.; Baum, S. A.

2013-07-01

We present U-, V-, and I-band images of the host galaxy of Hercules A (3C 348) obtained with HST/WFC3/UVIS. We find a network of dusty filaments which are more complex and extended than seen in earlier Hubble Space Telescope (HST) observations. The filaments are associated with a faint blue continuum light (possibly from young stars) and faint H{alpha} emission. It seems likely that the cold gas and dust has been stripped from a companion galaxy now seen as a secondary nucleus. There are dusty filaments aligned with the base of the jets on both eastern and western sides of themore » galaxy. The morphology of the filaments is different on the two sides-the western filaments are fairly straight, while the eastern filaments are mainly in two loop-like structures. We suggest that despite the difference in morphologies, both sets of filaments have been entrained in a slow-moving boundary layer outside the relativistic flow. As suggested by Fabian et al., magnetic fields in the filaments may stabilize them against disruption. We consider a speculative scenario to explain the relation between the radio source and the shock and cavities in the hot intracluster medium seen in the Chandra data. We suggest that the radio source originally ({approx}60 Myr ago) propagated along a position angle of {approx}35 Degree-Sign where it created the shock and cavities. The radio source axis changed to its current orientation ({approx}100 Degree-Sign ) possibly due to a supermassive black hole merger and began its current epoch of activity about 20 Myr ago.« less

Observing the Sun with NuSTAR

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-07-01

The Nuclear Spectroscopic Telescope Array (NuSTAR) is a space telescope primarily designed to detect high-energy X-rays from faint, distant astrophysical sources. Recently, however, its occasionally been pointing much closer to home, with the goal of solving a few longstanding mysteries about the Sun.Intensity maps from an observation of a quiet-Sun region near the north solar pole and an active region just below the solar limb. The quiet-Sun data will be searched for small flares that could be heating the solar corona, and the high-altitude emission above the limb may provide clues about particle acceleration. [Adapted from Grefenstette et al. 2016]An Unexpected TargetThough we have a small fleet of space telescopes designed to observe the Sun, theres an important gap: until recently, there was no focusing telescope making solar observations in the hard X-ray band (above ~3 keV). Conveniently, there is a tool capable of doing this: NuSTAR.Though NuSTARs primary mission is to observe faint astrophysical X-ray sources, a team of scientists has recently conducted a series of observations in which NuSTAR was temporarily repurposed and turned to focus on the Sun instead.These observations pose an interesting challenge precisely because of NuSTARs extreme sensitivity: pointing at such a nearby, bright source can quickly swamp the detectors. But though the instrument cant be used to observe the bright flares and outbursts from the Sun, its the perfect tool for examining the parts of the Sun weve been unable to explore in hard X-rays before now such as faint flares, or the quiet, inactive solar surface.In a recently published study led by Brian Grefenstette (California Institute of Technology), the team describes the purpose and initial results of NuSTARs first observations of the Sun.Solar MysteriesWhat is NuSTAR hoping to accomplish with its solar observations? There are two main questions that hard X-ray observations may help to answer.How are particles accelerated in solar flares?The process of electron acceleration during solar flares is not well understood. When a flare-producing active region is occulted by the solar limb, NuSTAR will able to directly observe the flare loop above the solar surface which is where that acceleration is thought to happen.How is the solar corona heated?The solar corona is a toasty 13 million Kelvin significantly warmer than the ~6000 K solar photosphere. So how is the corona heated? One proposed explanation is that the Suns surface constantly emits tiny nanoflares in active regions, or even in the quiet Sun that are so faint that we havent detected them. But with its high sensitivity, NuSTAR may be able to!The first NuSTAR full-disk mosaic of the Sun. The checkerboard pattern is an artifact of the detectors being hit by particles from active regions outside of the field of view a problem which will be reduced as the Sun enters the upcoming quieter part of the solar cycle. [Adapted from Grefenstette et al. 2016]First ObservationsIn NuSTARs first four observations of the Sun, the team unexpectedly observed a major flare (which unsurprisingly swamped the detectors), watched the emission above an active region that was hidden by the solar limb, stared at a section of quiet Sun near the north solar pole, and composed a full-disk mosaic of the solar surface from 16 12 x 12 tiles.All of these initial observations are currently being carefully analyzed and will be presented in detail in future publications. In the meantime, NuSTAR has demonstrated its effectiveness in detecting faint emission in solar hard X-rays, proving that it will be a powerful tool for heliophysics as well as for astrophysics. We look forward to seeing the future results from this campaign!CitationBrian W. Grefenstette et al 2016 ApJ 826 20. doi:10.3847/0004-637X/826/1/20

The very soft X-ray emission of X-ray-faint early-type galaxies

NASA Technical Reports Server (NTRS)

Pellegrini, S.; Fabbiano, G.

1994-01-01

A recent reanaylsis of Einstein data, and new ROSAT observations, have revealed the presence of at least two components in the X-ray spectra of X-ray faint early-type galaxies: a relatively hard component (kT greater than 1.5 keV), and a very soft component (kT approximately 0.2-0.3 keV). In this paper we address the problem of the nature of the very soft component and whether it can be due to a hot interstellar medium (ISM), or is most likely originated by the collective emission of very soft stellar sources. To this purpose, hydrodynamical evolutionary sequences for the secular behavior of gas flows in ellipticals have been performed, varying the Type Ia supernovae rate of explosion, and the dark matter amount and distribution. The results are compared with the observational X-ray data: the average Einstein spectrum for six X-ray faint early-type galaxies (among which are NGC 4365 and NGC 4697), and the spectrum obtained by the ROSAT pointed observation of NGC 4365. The very soft component could be entirely explained with a hot ISM only in galaxies such as NGC 4697, i.e., when the depth of the potential well-on which the average ISM temperature strongly depends-is quite shallow; in NGC 4365 a diffuse hot ISM would have a temperature larger than that of the very soft component, because of the deeper potential well. So, in NGC 4365 the softest contribution to the X-ray emission comes certainly from stellar sources. As stellar soft X-ray emitters, we consider late-type stellar coronae, supersoft sources such as those discovered by ROSAT in the Magellanic Clouds and M31, and RS CVn systems. All these candidates can be substantial contributors to the very soft emission, though none of them, taken separately, plausibly accounts entirely for its properties. We finally present a model for the X-ray emission of NGC 4365, to reproduce in detail the results of the ROSAT pointed observation, including the Position Sensitive Proportional Counter (PSPC) spectrum and radial surface brightness distribution. The present data may suggest that the X-ray surface brightness is more extended than the optical profile. In this case, a straightforward explanation in terms of stellar sources could not be satisfactory. The available data can be better explained with three different contributions: a very soft component of stellar origin, a hard component from X-ray binaries, and an approximately 0.6 keV hot ISM. The latter can explain the extended X-ray surface brightness profile, if the galaxy has a dark-to-luminous mass ratio of 9, with the dark matter very broadly distributed, and a SN Ia explosive rate of approximately 0.6 the Tammann rate.

46 CFR 160.041-4 - Contents.

Code of Federal Regulations, 2013 CFR

2013-10-01

... inhalants 10 do 1 Iodine applicators (1/2 ml swab type) 10 do 1 Aspirin, phenacetin and caffeine compound... Ammonia inhalants Break one and inhale for faintness, fainting, or collapse. Aspirin, phenacetin, caffeine...

46 CFR 160.041-4 - Contents.

Code of Federal Regulations, 2014 CFR

2014-10-01

... inhalants 10 do 1 Iodine applicators (1/2 ml swab type) 10 do 1 Aspirin, phenacetin and caffeine compound... Ammonia inhalants Break one and inhale for faintness, fainting, or collapse. Aspirin, phenacetin, caffeine...

The Properties of Faint Field Galaxies

NASA Astrophysics Data System (ADS)

Driver, Simon. P.

1994-12-01

One of the current drawbacks of Charge Coupled Devices (CCDs) is their restrictive fields of view. The Hitchhiker CCD camera overcomes this limitation by operating in parallel with existing instrumentation and is able to cover a large area as well as large volumes. Hitchhiker is mounted on the 4.2m William Herschel Telescope and has been operating for two years. The first use of the Hitchhiker data set has been to study the general properties of faint galaxies. The observed trend of how the differential numbers of galaxies vary with magnitude agrees extremely well with those of other groups and covers, for the first time, all four major optical bandpasses. This multi-band capability has also allowed the study of how the colors of galaxies change with magnitude and how the correlation of galaxies on the sky varies between the optical bandpasses. A dwarf dominated model has been developed to explain these observations and challenges our knowledge of the space-density of dwarf galaxies. The model demonstrates that a simple upward turn in the luminosity distribution of galaxies, similar to that observed in clusters, would remain undetected by the field surveys yet can explain many of the observations without recourse to non-passive galaxy evolution. The conclusion is that the field luminosity distribution is not constrained at faint absolute magnitudes. A combination of a high density of dwarf galaxies and mild evolution could explain all the observations. Continuing work with HST and the Medium Deep Survey Team now reveals the morphological mix of galaxies down to mI ~ 24.0. The results confirm that ellipticals and early-type spirals are well fitted by standard no-evolution models whilst the late-type spirals can only be fitted by strong evolution and/or a significant turn-up in the local field LF.

A spectroscopic search for faint secondaries in cataclysmic variables

NASA Astrophysics Data System (ADS)

Vande Putte, D.; Smith, Robert Connon; Hawkins, N. A.; Martin, J. S.

2003-06-01

The secondary in cataclysmic variables (CVs) is usually detected by cross-correlation of the CV spectrum with that of a K or M dwarf template, to produce a radial velocity curve. Although this method has demonstrated its power, it has its limits in the case of noisy spectra, such as are found when the secondary is faint. A method of coadding spectra, called skew mapping, has been proposed in the past. Gradually, examples of its application are being published; none the less, so far no journal article has described the technique in detail. To answer this need, this paper explores in detail the capabilities of skew mapping when determining the amplitude of the radial velocity for faint secondaries. It demonstrates the power of the method over techniques that are more conventional, when the signal-to-noise ratio is poor. The paper suggests an approach to assessing the quality of results. This leads in the case of the investigated objects to a first tier of results, where we find K2= 127 +/- 23 km s-1 for SY Cnc, K2= 144 +/- 18 km s-1 for RW Sex and K2= 262 +/- 14 km s-1 for UX UMa. These we believe to be the first direct determinations of K2 for these objects. Furthermore, we also obtain K2= 263 +/- 30 km s-1 for RW Tri, close to a skew mapping result obtained elsewhere. In the first three cases, we use these results to derive the mass of the white dwarf companion. A second tier of results includes UU Aqr, EX Hya and LX Ser, for which we propose more tentative values of K2. Clear failures of the method are also discussed (EF Eri, VV Pup and SW Sex).

Sensitive radio survey of obscured quasar candidates

NASA Astrophysics Data System (ADS)

Alexandroff, Rachael M.; Zakamska, Nadia L.; van Velzen, Sjoert; Greene, Jenny E.; Strauss, Michael A.

2016-12-01

We study the radio properties of moderately obscured quasars in samples at both low (z ˜ 0.5) and high (z ˜ 2.5) redshift to understand the role of radio activity in accretion, using the Karl G. Jansky Very Large Array (VLA) at 6.0 GHz and 1.4 GHz. Our z ˜ 2.5 sample consists of optically selected obscured quasar candidates, all of which are radio-quiet, with typical radio luminosities of νLν[1.4 GHz] ≲ 1040 erg s-1. Only a single source is individually detected in our deep (rms˜10 μJy) exposures. This population would not be identified by radio-based selection methods used for distinguishing dusty star-forming galaxies and obscured active nuclei. In our pilot A-array study of z ˜ 0.5 radio-quiet quasars, we spatially resolve four of five objects on scales ˜5 kpc and find they have steep spectral indices with an average value of α = -0.75. Therefore, radio emission in these sources could be due to jet-driven or radiatively driven bubbles interacting with interstellar material on the scale of the host galaxy. Finally, we also study the additional population of ˜200 faint ( ˜ 40 μJy-40 mJy) field radio sources observed over ˜120 arcmin2 of our data. 60 per cent of these detections (excluding our original targets) are matched in the Sloan Digital Sky Survey (SDSS) and/or Wide-Field Infrared Survey Explorer (WISE) and are, in roughly equal shares, active galactic nuclei (AGN) at a broad range of redshifts, passive galaxies with no other signs of nuclear activity and infrared-bright but optically faint sources. Spectroscopically or photometrically confirmed star-forming galaxies constitute only a small minority of the matches. Such sensitive radio surveys allow us to address important questions of AGN evolution and evaluate the AGN contribution to the radio-quiet sky.

Fainting (Syncope)

MedlinePlus

... Attack Heart Valve Problems Join our e-newsletter! Aging & Health A to Z Fainting (Syncope) Basic Facts & ... November 2016 Posted: March 2012 © 2018 Health in Aging. All rights reserved. Feedback • Site Map • Privacy Policy • ...

Faint Ring, Bright Arc

NASA Image and Video Library

2010-01-12

In this image taken by NASA Cassini spacecraft, the bright arc in Saturn faint G ring contains a little something special. Although it cant be seen here, the tiny moonlet Aegaeon orbits within the bright arc.

Improving the Ability of Image Sensors to Detect Faint Stars and Moving Objects Using Image Deconvolution Techniques

PubMed Central

Fors, Octavi; Núñez, Jorge; Otazu, Xavier; Prades, Albert; Cardinal, Robert D.

2010-01-01

In this paper we show how the techniques of image deconvolution can increase the ability of image sensors as, for example, CCD imagers, to detect faint stars or faint orbital objects (small satellites and space debris). In the case of faint stars, we show that this benefit is equivalent to double the quantum efficiency of the used image sensor or to increase the effective telescope aperture by more than 30% without decreasing the astrometric precision or introducing artificial bias. In the case of orbital objects, the deconvolution technique can double the signal-to-noise ratio of the image, which helps to discover and control dangerous objects as space debris or lost satellites. The benefits obtained using CCD detectors can be extrapolated to any kind of image sensors. PMID:22294896

Improving the ability of image sensors to detect faint stars and moving objects using image deconvolution techniques.

PubMed

Fors, Octavi; Núñez, Jorge; Otazu, Xavier; Prades, Albert; Cardinal, Robert D

2010-01-01

In this paper we show how the techniques of image deconvolution can increase the ability of image sensors as, for example, CCD imagers, to detect faint stars or faint orbital objects (small satellites and space debris). In the case of faint stars, we show that this benefit is equivalent to double the quantum efficiency of the used image sensor or to increase the effective telescope aperture by more than 30% without decreasing the astrometric precision or introducing artificial bias. In the case of orbital objects, the deconvolution technique can double the signal-to-noise ratio of the image, which helps to discover and control dangerous objects as space debris or lost satellites. The benefits obtained using CCD detectors can be extrapolated to any kind of image sensors.

Space Telescope and Optical Reverberation Mapping Project. VI. Reverberating Disk Models for NGS 5548

NASA Technical Reports Server (NTRS)

Starkey, D.; Gehrels, Cornelis; Horne, Keith; Fausnaugh, M. M.; Peterson, B. M.; Bentz, M. C.; Kochanek, C. S.; Denney, K. D.; Edelson, R.; Goad, M. R.;

The Chandra Deep Field-North Survey and the cosmic X-ray background.

PubMed

Brandt, W Nielsen; Alexander, David M; Bauer, Franz E; Hornschemeier, Ann E

2002-09-15

Chandra has performed a 1.4 Ms survey centred on the Hubble Deep Field-North (HDF-N), probing the X-ray Universe 55-550 times deeper than was possible with pre-Chandra missions. We describe the detected point and extended X-ray sources and discuss their overall multi-wavelength (optical, infrared, submillimetre and radio) properties. Special attention is paid to the HDF-N X-ray sources, luminous infrared starburst galaxies, optically faint X-ray sources and high-to-extreme redshift active galactic nuclei. We also describe how stacking analyses have been used to probe the average X-ray-emission properties of normal and starburst galaxies at cosmologically interesting distances. Finally, we discuss plans to extend the survey and argue that a 5-10 Ms Chandra survey would lay key groundwork for future missions such as XEUS and Generation-X.

The great galactic centre mystery

NASA Technical Reports Server (NTRS)

Riegler, G. R.

1982-01-01

Gamma-ray observations of the center of the Galaxy show a varying positron-electron annihilation radiation emission, while at radio wavelengths a non-thermal compact source surrounded by ionized gas moving at high velocities can be seen. Line emission maps for atomic and ionized hydrogen and molecular gas suggest gas expulsion and a massive collapsed object. IR observations show that ionized gas in the central few parsecs of the Galactic center is concentrated in at least 14 small clouds. Charge-coupled device images show a pair of faint, very red sources within a few arc seconds of IRS 16 and the compact non-thermal radio source. The positron-electron annihilation line emission implies an annihilation rate of 10 to the 43rd per sec, compared with an observed luminosity at IR wavelengths of 10 to the 40 erg per sec. Some models are briefly discussed.

LSDCat: Detection and cataloguing of emission-line sources in integral-field spectroscopy datacubes

NASA Astrophysics Data System (ADS)

Herenz, Edmund Christian; Wisotzki, Lutz

2017-06-01

We present a robust, efficient, and user-friendly algorithm for detecting faint emission-line sources in large integral-field spectroscopic datacubes together with the public release of the software package Line Source Detection and Cataloguing (LSDCat). LSDCat uses a three-dimensional matched filter approach, combined with thresholding in signal-to-noise, to build a catalogue of individual line detections. In a second pass, the detected lines are grouped into distinct objects, and positions, spatial extents, and fluxes of the detected lines are determined. LSDCat requires only a small number of input parameters, and we provide guidelines for choosing appropriate values. The software is coded in Python and capable of processing very large datacubes in a short time. We verify the implementation with a source insertion and recovery experiment utilising a real datacube taken with the MUSE instrument at the ESO Very Large Telescope. The LSDCat software is available for download at http://muse-vlt.eu/science/tools and via the Astrophysics Source Code Library at http://ascl.net/1612.002

Origin of Outer Solar System

NASA Technical Reports Server (NTRS)

Holman, Matthew J.; Boyce, J. (Technical Monitor)

2003-01-01

We feel that at the present moment the available theoretical models of the Kuiper belt are still in advance of the data, and thus our main task has been to conduct observational work guided by theoretical motivations. Our efforts over the past year can be divided into four categories: A) Wide-field Searches for Kuiper Belt Objects; B) Pencil-beam Searches for Kuiper Belt Objects; C) Wide-field Searches for Moons of the Outer Planets; D) Pencil-beam Searches for Faint Uranian and Neptunian Moons; E) Recovery Observations. As of April 2002, we have conducted several searches for Kuiper belt objects using large-format mosaic CCD camera on 4-meter class telescopes. In May 1999, we used the Kitt Peak 4-meter with the NOAO Mosaic camera we attempted a search for KBOs at a range of ecliptic latitudes. In addition to our wide-field searches, we have conducted three 'pencil-beam' searches in the past year. In a pencil-beam search we take repeated integrations of the same field throughout a night. After preprocessing the resulting images we shift and recombine them along a range of rates and directions consistent with the motion of KBOs. Stationary objects then smear out, while objects moving at near the shift rate appear as point sources. In addition to our searches for Kuiper belt objects, we are completing the inventory of the outer solar system by search for faint satellites of the outer planets. In August 2001 we conducted pencil beam searches for faint Uranian and Neptunian satellites at CFHT and CTIO. These searches resulted in the discover of two Neptunian and four Uranian satellite candidates. The discovery of Kuiper belt objects and outer planet satellites is of little use if the discoveries are not followed by systematic, repeated astrometric observations that permit reliable estimates of their orbits.

[Fainting in Greco-Roman medicine, especially in the traumatology and surgery fields].

PubMed

Salazar, C F

2001-01-01

Occurrences of fainting are very common in medical as well as non-medical literature; in order to restrict the field to a manageable size, this article focuses mainly on surgery and traumatology. An examination of the various passages suggests that there was considerable ambiguity associated with the concept of fainting. On the one hand it was seen as a common occurrence, to be expected in the context of wounds or surgery, but on the other it was also regarded as a life-threatening force in its own right.

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.

THE SUBARU HIGH-z QUASAR SURVEY: DISCOVERY OF FAINT z ∼ 6 QUASARS

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

Kashikawa, Nobunari; Furusawa, Hisanori; Niino, Yuu

2015-01-01

We present the discovery of one or two extremely faint z ∼ 6 quasars in 6.5 deg{sup 2} utilizing a unique capability of the wide-field imaging of the Subaru/Suprime-Cam. The quasar selection was made in (i'-z{sub B} ) and (z{sub B} -z{sub R} ) colors, where z{sub B} and z{sub R} are bandpasses with central wavelengths of 8842 Å and 9841 Å, respectively. The color selection can effectively isolate quasars at z ∼ 6 from M/L/T dwarfs without the J-band photometry down to z{sub R} < 24.0, which is 3.5 mag deeper than the Sloan Digital Sky Survey (SDSS). Wemore » have selected 17 promising quasar candidates. The follow-up spectroscopy for seven targets identified one apparent quasar at z = 6.156 with M {sub 1450} = –23.10. We also identified one possible quasar at z = 6.041 with a faint continuum of M {sub 1450} = –22.58 and a narrow Lyα emission with HWHM =427 km s{sup –1}, which cannot be distinguished from Lyman α emitters. We derive the quasar luminosity function at z ∼ 6 by combining our faint quasar sample with the bright quasar samples by SDSS and CFHQS. Including our data points invokes a higher number density in the faintest bin of the quasar luminosity function than the previous estimate employed. This suggests a steeper faint-end slope than lower z, though it is yet uncertain based on a small number of spectroscopically identified faint quasars, and several quasar candidates still remain to be diagnosed. The steepening of the quasar luminosity function at the faint end does increase the expected emission rate of the ionizing photon; however, it only changes by a factor of approximately two to six. This was found to still be insufficient for the required photon budget of reionization at z ∼ 6.« less

X-ray study of a sample of FR0 radio galaxies: unveiling the nature of the central engine

NASA Astrophysics Data System (ADS)

Torresi, E.; Grandi, P.; Capetti, A.; Baldi, R. D.; Giovannini, G.

2018-06-01

Fanaroff-Riley type 0 radio galaxies (FR0s) are compact radio sources that represent the bulk of the radio-loud active galactic nuclei (AGN) population, but they are still poorly understood. Pilot studies on these sources have been already performed at radio and optical wavelengths: here we present the first X-ray study of a sample of 19 FR0 radio galaxies selected from the Sloan Digital Sky Survey/NRAO VLA Sky Survey/Faint Images of the Radio Sky at Twenty-cm sample of Best & Heckman, with redshift ≤0.15, radio size ≤10 kpc, and optically classified as low-excitation galaxies. The X-ray spectra are modelled with a power-law component absorbed by Galactic column density with, in some cases, a contribution from thermal extended gas. The X-ray photons are likely produced by the jet as attested by the observed correlation between X-ray (2-10 keV) and radio (5 GHz) luminosities, similar to Fanaroff-Riley type I radio galaxies (FRIs). The estimated Eddington-scaled luminosities indicate a low accretion rate. Overall, we find that the X-ray properties of FR0s are indistinguishable from those of FRIs, thus adding another similarity between AGN associated with compact and extended radio sources. A comparison between FR0s and low-luminosity BL Lacs rules out important beaming effects in the X-ray emission of the compact radio galaxies. FR0s have different X-ray properties with respect to young radio sources (e.g. gigahertz-peaked spectrum/compact steep spectrum sources), generally characterized by higher X-ray luminosities and more complex spectra. In conclusion, the paucity of extended radio emission in FR0s is probably related to the intrinsic properties of their jets that prevent the formation of extended structures, and/or to intermittent activity of their engines.

Serendipitous Discovery of RR Lyrae Stars in the Leo V Ultra-faint Galaxy

NASA Astrophysics Data System (ADS)

Medina, Gustavo E.; Muñoz, Ricardo R.; Vivas, A. Katherina; Förster, Francisco; Carlin, Jeffrey L.; Martinez, Jorge; Galbany, Lluis; González-Gaitán, Santiago; Hamuy, Mario; de Jaeger, Thomas; Maureira, Juan Carlos; San Martín, Jaime

2017-08-01

During the analysis of RR Lyrae stars (RRLs) discovered in the High Cadence Transient Survey (HiTS) taken with the Dark Energy Camera at the 4 m telescope at Cerro Tololo Inter-American Observatory, we found a group of three very distant, fundamental mode pulsator RR Lyrae (type ab). The location of these stars agrees with them belonging to the Leo V ultra-faint satellite galaxy, for which no variable stars have been reported to date. The heliocentric distance derived for Leo V based on these stars is 173 ± 5 kpc. The pulsational properties (amplitudes and periods) of these stars locate them within the locus of the Oosterhoff II group, similar to most other ultra-faint galaxies with known RRLs. This serendipitous discovery shows that distant RRLs may be used to search for unknown faint stellar systems in the outskirts of the Milky Way.

X-ray Binaries and the Galaxy Structure in Hard X-rays

NASA Astrophysics Data System (ADS)

Lutovinov, Alexander

The Galaxy structure in the hard X-ray energy band (¿20 keV) was studied using data of the INTEGRAL observatory. A deep and nearly uniform coverage of the galactic plane allowed to increase significantly the sensitivity of the survey and discover several dozens new galac-tic sources. The follow-up observations with XMM-Newton and CHANDRA observatories in X-rays and ground-based telescopes in optical and infrared wavebands gave us a possibility to determine optical counterparts and distances for number of new and already known faint sources. That, in turn, allowed us to build the spatial distribution of different classes of galactic X-ray binaries and obtain preliminary results of the structure of the further part of the Galaxy.

SOFIA/FORCAST Resolves 30 - 40 μm Extended Emission in Nearby AGN

NASA Astrophysics Data System (ADS)

Fuller, Lindsay; Lopez-Rodriguez, Enrique; Packham, Christopher C.; Ichikawa, Kohei; Togi, Aditya

2018-06-01

We present arcsecond-scale observations in the 30 - 40 μm range of seven nearby Seyfert galaxies observed from the Stratospheric Observatory For Infrared Astronomy (SOFIA) using the 31.5 and 37.1 μm filters of the Faint Object infraRed CAmera for the SOFIA Telescope (FORCAST). We find extended diffuse emission in the 37.1 μm images in our sample, and isolate this from unresolved torus emission. Using Spitzer/IRS spectra, we determine the dominant mid-infrared (MIR) emission source and attribute it to dust in the narrow line region (NLR) or star formation. We compare the optical NLR and radio jet axes to the extended 37.1 μm emission and find coincident axes for three sources.

WiseView: Visualizing motion and variability of faint WISE sources

NASA Astrophysics Data System (ADS)

Caselden, Dan; Westin, Paul, III; Meisner, Aaron; Kuchner, Marc; Colin, Guillaume

2018-06-01

WiseView renders image blinks of Wide-field Infrared Survey Explorer (WISE) coadds spanning a multi-year time baseline in a browser. The software allows for easy visual identification of motion and variability for sources far beyond the single-frame detection limit, a key threshold not surmounted by many studies. WiseView transparently gathers small image cutouts drawn from many terabytes of unWISE coadds, facilitating access to this large and unique dataset. Users need only input the coordinates of interest and can interactively tune parameters including the image stretch, colormap and blink rate. WiseView was developed in the context of the Backyard Worlds: Planet 9 citizen science project, and has enabled hundreds of brown dwarf candidate discoveries by citizen scientists and professional astronomers.

Observational challenges in Lyα intensity mapping

NASA Astrophysics Data System (ADS)

Comaschi, P.; Yue, B.; Ferrara, A.

2016-12-01

Intensity mapping (IM) is sensitive to the cumulative line emission of galaxies. As such, it represents a promising technique for statistical studies of galaxies fainter than the limiting magnitude of traditional galaxy surveys. The strong hydrogen Lyα line is the primary target for such an experiment, as its intensity is linked to star formation activity and the physical state of the interstellar and intergalactic medium. However, to extract the meaningful information, one has to solve the confusion problems caused by interloping lines from foreground galaxies. We discuss here the challenges for a Lyα IM experiment targeting z > 4 sources. We find that the Lyα power spectrum can be, in principle, easily (marginally) obtained with a 40 cm space telescope in a few days of observing time up to z ≲ 8 (z ˜ 10) assuming that the interloping lines (e.g. Hα, [O II], [O III] lines) can be efficiently removed. We show that interlopers can be removed by using an ancillary photometric galaxy survey with limiting AB mag ˜26 in the near-infrared bands (Y, J, H, or K). This would enable detection of the Lyα signal from 5 < z < 9 faint sources. However, if a [C II] IM experiment is feasible, by cross-correlating the Lyα with the [C II] signal, the required depth of the galaxy survey can be decreased to AB mag ˜24. This would bring the detection at the reach of future facilities working in close synergy.

Improving interferometers by quantum light: toward testing quantum gravity on an optical bench

NASA Astrophysics Data System (ADS)

Ruo-Berchera, Ivano; Degiovanni, Ivo P.; Olivares, Stefano; Traina, Paolo; Samantaray, Nigam; Genovese, M.

2016-09-01

We analyze in detail a system of two interferometers aimed at the detection of extremely faint phase fluctuations. The idea behind is that a correlated phase-signal like the one predicted by some phenomenological theory of Quantum Gravity (QG) could emerge by correlating the output ports of the interferometers, even when in the single interferometer it confounds with the background. We demonstrated that injecting quantum light in the free ports of the interferometers can reduce the photon noise of the system beyond the shot-noise, enhancing the resolution in the phase-correlation estimation. Our results confirm the benefit of using squeezed beams together with strong coherent beams in interferometry, even in this correlated case. On the other hand, our results concerning the possible use of photon number entanglement in twin beam state pave the way to interesting and probably unexplored areas of application of bipartite entanglement and, in particular, the possibility of reaching surprising uncertainty reduction exploiting new interferometric configurations, as in the case of the system described here.

Extremely faint, diffuse satellite systems in the M31 halo: exceptional star clusters or tiny dwarf galaxies?

NASA Astrophysics Data System (ADS)

Mackey, Dougal

2013-10-01

Recent years have seen the discovery of a variety of low surface brightness, diffuse stellar systems in the Local Group. Of particular prominence are the ultra-faint dwarf satellites of the Milky Way and the extended globular clusters seen in M31, M33, and NGC 6822. As part of the major Pan-Andromeda Archaeological Survey {PAndAS} we have discovered several very faint and diffuse stellar satellites in the M31 halo. In Cycle 19 we obtained ACS/WFC imaging for one of these, PAndAS-48, which has revealed it to be a puzzling and unusual object. On the size-luminosity plane it falls between the extended clusters and ultra-faint dwarfs; however, its characteristics do not allow us to unambiguously class it as either type of system. If PAndAS-48 is an extended cluster then it is the most elliptical, isolated, metal-poor, and lowest-luminosity example yet uncovered. Conversely, while its properties are generally consistent with those observed for the faint dwarf satellites of the Milky Way, it would be a factor 2-3 smaller in spatial extent than its Galactic counterparts at comparable luminosity. Here we propose deep resolved imaging of the remaining five similar objects in our sample, with the aim of probing this hitherto poorly-explored region of parameter space in greater detail. If we are able to confirm any of these objects as faint dwarfs, they will provide the first insight into the behaviour of this class of object in a galaxy other than the Milky Way.

The Origin of Ultra-Faint Galaxies

NASA Astrophysics Data System (ADS)

Sand, David

2017-08-01

We request 24 orbits of HST/ACS to obtain imaging in F606W and F814W of apparent tidal features in two ultra-faint dwarf galaxies: Hercules and Leo V. This will enable us to test whether the stars in ultra- faint galaxies-as a population-have been affected by Galactic tides. Most of the new dwarfs show signs of tidal interaction in ground-based photometry, several have measured ellipticities greater than 0.5, and kinematics of a subset show velocity gradients. These ubiquitous hints for tidal effects among distant dwarfs is particularly surprising and suggestive. If most ultra-faint dwarfs are disturbed by tides, then recent tests of galaxy formation in the near field have unstable foundations.HST resolution provides an opportunity to assess whether tidal features (accompanied by tentative kinematic gradients) seen in ground-based observations of Hercules and Leo V are genuine or are instead clumps of compact background galaxies masquerading as stellar debris. In Hercules, a further test is possible: searching for a distance gradient along the stretched body of the galaxy. Parallel pointings will sample similar dwarf-centric radii away from the tidal features, assuring an unambiguous result. Whether we confirm or rule out the presence of stellar loss in these objects, the consequences are important-the origin of the ultra-faint dwarfs tells us the lower limit to both galaxy formation and the number of dark matter subhalos inhabiting the Milky Way.This program is only possible with HST: its exquisite resolution can separate compact galaxies from main sequence dwarf stars at faint magnitudes, which even the best multi-band ground-based schemes struggle with.

Soft X-ray emission from the Lupus Loop and Sn 1006 supernova remnants

NASA Technical Reports Server (NTRS)

Winkler, P. F., Jr.; Hearn, D. R.; Richardson, J. A.; Behnken, J. M.

1979-01-01

X-ray maps of the Lupus region have been obtained in a raster scan observation from SAS 3. These show the Lupus Loop to be a faint extended source of soft X-rays with a temperature about 2.5 million K. The most prominent feature of the region is the A.D. 1006 supernova remnant, which is unexpectedly bright at 0.2-1.0 keV. One speculative interpretation of the low-energy flux from SN 1006 is as blackbody radiation from a hot neutron star.

The White Dwarf Mass and the Accretion Rate of Recurrent Novae: An X-ray Perspective

NASA Technical Reports Server (NTRS)

Mukai, Koji; Sokoloski, Jennifer L.; Nelson, Thomas; Luna, Gerardo J. M.

2011-01-01

We present recent results of quiescent X-ray observations of recurrent novae (RNe) and related objects. Several RNe are luminous hard X-ray sources in quiescence, consistent with accretion onto a near Chandrasekhar mass white dwarf. Detection of similar hard X-ray emissions in old novae and other cataclysmic variables may lead to identification of additional RN candidates. On the other hand, other RNe are found to be comparatively hard X-ray faint. We present several scenarios that may explain this dichotomy, which should be explored further.

Dark matter and weak signals of quantum spacetime

NASA Astrophysics Data System (ADS)

Doplicher, Sergio; Fredenhagen, Klaus; Morsella, Gerardo; Pinamonti, Nicola

2017-03-01

In physically motivated models of quantum spacetime, a U (1 ) gauge theory turns into a U (∞ ) gauge theory; hence, free classical electrodynamics is no longer free and neutral fields may have electromagnetic interactions. We discuss the last point for scalar fields, as a way to possibly describe dark matter; we have in mind the gravitational collapse of binary systems or future applications to self-gravitating Bose-Einstein condensates as possible sources of evidence of quantum gravitational phenomena. The effects considered so far, however, seem too faint to be detectable at present.

Identifications and Photometric Redshifts of the 2 Ms Chandra Deep Field-South Sources

NASA Astrophysics Data System (ADS)

Luo, B.; Brandt, W. N.; Xue, Y. Q.; Brusa, M.; Alexander, D. M.; Bauer, F. E.; Comastri, A.; Koekemoer, A.; Lehmer, B. D.; Mainieri, V.; Rafferty, D. A.; Schneider, D. P.; Silverman, J. D.; Vignali, C.

2010-04-01

We present reliable multiwavelength identifications and high-quality photometric redshifts for the 462 X-ray sources in the ≈2 Ms Chandra Deep Field-South (CDF-S) survey. Source identifications are carried out using deep optical-to-radio multiwavelength catalogs, and are then combined to create lists of primary and secondary counterparts for the X-ray sources. We identified reliable counterparts for 442 (95.7%) of the X-ray sources, with an expected false-match probability of ≈ 6.2%; we also selected four additional likely counterparts. The majority of the other 16 X-ray sources appear to be off-nuclear sources, sources associated with galaxy groups and clusters, high-redshift active galactic nuclei (AGNs), or spurious X-ray sources. A likelihood-ratio method is used for source matching, which effectively reduces the false-match probability at faint magnitudes compared to a simple error-circle matching method. We construct a master photometric catalog for the identified X-ray sources including up to 42 bands of UV-to-infrared data, and then calculate their photometric redshifts (photo-z's). High accuracy in the derived photo-z's is accomplished owing to (1) the up-to-date photometric data covering the full spectral energy distributions (SEDs) of the X-ray sources, (2) more accurate photometric data as a result of source deblending for ≈10% of the sources in the infrared bands and a few percent in the optical and near-infrared bands, (3) a set of 265 galaxy, AGN, and galaxy/AGN hybrid templates carefully constructed to best represent all possible SEDs, (4) the Zurich Extragalactic Bayesian Redshift Analyzer used to derive the photo-z's, which corrects the SED templates to best represent the SEDs of real sources at different redshifts and thus improves the photo-z quality. The reliability of the photo-z's is evaluated using the subsample of 220 sources with secure spectroscopic redshifts. We achieve an accuracy of |Δz|/(1 + z) ≈ 1% and an outlier [with |Δz|/(1 + z)>0.15] fraction of ≈1.4% for sources with spectroscopic redshifts. We performed blind tests to derive a more realistic estimate of the photo-z quality for sources without spectroscopic redshifts. We expect there are ≈9% outliers for the relatively brighter sources (R <~ 26), and the outlier fraction will increase to ≈15%-25% for the fainter sources (R >~ 26). The typical photo-z accuracy is ≈6%-7%. The outlier fraction and photo-z accuracy do not appear to have a redshift dependence (for z ≈ 0-4). These photo-z's appear to be the best obtained so far for faint X-ray sources, and they have been significantly (gsim50%) improved compared to previous estimates of the photo-z's for the X-ray sources in the ≈2 Ms Chandra Deep Field-North and ≈1 Ms CDF-S.

Optical Counterparts to Gravitational Waves

NASA Astrophysics Data System (ADS)

Beroiz, Martin

The novel field of Gravitational Wave Astronomy has opened a new window to the universe. Never before had we received gravitational waves from the distant celestial bodies carried away by space-time perturbations, until the detection of GW150914 on September 14, 2015. But these signals, however faint, carry very little information about their positions on the sky. The sky localization can have uncertainties that span up to a few hundreds square degrees, which makes locating the sources very difficult. Traditional Astronomy can complement this limitation of gravitational wave detection where optical astronomy is stronger: localization. However, this poses other technological challenges of a different kind. In the era of multi-messenger Astronomy, a low latency response time after detection is crucial in order to have any hope of detecting the optically faint electromagnetic counterparts of the event. The mission of the Transient Optical Robotic Observatory of the South (TOROS), in the context of multi-messenger and time-domain astronomy, is to create a facility ready to respond to gravitational wave detections for prompt follow-up observations searching for optical counterparts. This dissertation discusses the implementation of a software pipeline for the TOROS project and the results obtained during the O1 campaign of Advanced LIGO.

History of Hubble Space Telescope (HST)

NASA Image and Video Library

1994-01-01

A comparison image of the M100 Galactic Nucleus, taken by the Hubble Space Telescope (HST) Wide Field Planetary Camera-1 (WF/PC1) and Wide Field Planetary Camera-2 (WF/PC2). The HST was placed in a low-Earth orbit by the Space Shuttle Discovery, STS-31 mission, in April 1990. Two months after its deployment in space, scientists detected a 2-micron spherical aberration in the primary mirror of the HST that affected the telescope's ability to focus faint light sources into a precise point. This imperfection was very slight, one-fiftieth of the width of a human hair. During four spacewalks, the STS-61 crew replaced the solar panel with its flexing problems; the WF/PC1 with the WF/PC2, with built-in corrective optics; and the High-Speed Photometer with the Corrective Optics Space Telescope Axial Replacement (COSTAR), to correct the aberration for the remaining instruments. The purpose of the HST, the most complex and sensitive optical telescope ever made, is to study the cosmos from a low-Earth orbit for 15 years or more. The HST provides fine detail imaging, produces ultraviolet images and spectra, and detects very faint objects.

History of Hubble Space Telescope (HST)

NASA Image and Video Library

1990-04-25

In this photograph, the Hubble Space Telescope (HST) was being deployed on April 25, 1990. The photograph was taken by the IMAX Cargo Bay Camera (ICBC) mounted in a container on the port side of the Space Shuttle orbiter Discovery (STS-31 mission). The purpose of the HST, the most complex and sensitive optical telescope ever made, is to study the cosmos from a low-Earth orbit for 15 years or more. The HST provides fine detail imaging, produces ultraviolet images and spectra, and detects very faint objects. Two months after its deployment in space, scientists detected a 2-micron spherical aberration in the primary mirror of the HST that affected the telescope's ability to focus faint light sources into a precise point. This imperfection was very slight, one-fiftieth of the width of a human hair. A scheduled Space Service servicing mission (STS-61) in 1993 permitted scientists to correct the problem. During four spacewalks, new instruments were installed into the HST that had optical corrections. The Marshall Space Flight Center had responsibility for design, development, and construction of the HST. The Perkin-Elmer Corporation, in Danbury, Cornecticut, developed the optical system and guidance sensors. Photo Credit: NASA/Smithsonian Institution/Lockheed Corporation.

Isolated and companion young brown dwarfs in the taurus and chamaeleon molecular clouds

PubMed

Tamura; Itoh; Oasa; Nakajima

1998-11-06

Infrared imaging observations have detected a dozen faint young stellar objects (YSOs) in the Taurus and Chamaeleon molecular clouds whose near-infrared colors are similar to those of classical T Tauri stars (TTS). They are around four magnitudes fainter than low-luminosity YSOs in Taurus detected in earlier surveys and as much as eight magnitudes fainter than typical TTS. The extreme faintness of the objects and their lower luminosity relative to previously identified brown dwarfs in the Pleiades indicate that these faint YSOs are very young brown dwarfs on the order of 1 million years old.

EoR Foregrounds: the Faint Extragalactic Radio Sky

NASA Astrophysics Data System (ADS)

Prandoni, Isabella

2018-05-01

A wealth of new data from upgraded and new radio interferometers are rapidly improving and transforming our understanding of the faint extra-galactic radio sky. Indeed the mounting statistics at sub-mJy and μJy flux levels is finally allowing us to get stringent observational constraints on the faint radio population and on the modeling of its various components. In this paper I will provide a brief overview of the latest results in areas that are potentially important for an accurate treatment of extra-galactic foregrounds in experiments designed to probe the Epoch of Reionization.

Chemical enrichment in Ultra-Faint Dwarf galaxies

NASA Astrophysics Data System (ADS)

Romano, Donatella

2016-08-01

Our view of the Milky Way's satellite population has radically changed after the discovery, ten years ago, of the first Ultra-Faint Dwarf galaxies (UFDs). These extremely faint, dark-matter dominated, scarcely evolved stellar systems are found in ever-increasing number in our cosmic neighbourhood and constitute a gold-mine for studies of early star formation conditions and early chemical enrichment pathways. Here we show what can be learned from the measurements of chemical abundances in UFD stars read through the lens of chemical evolution studies, point out the limitations of the classic approach, and discuss the way to go to improve the models.

A Study of the Effects of Faint Dust Comae on the Spectra of Asteroids

NASA Astrophysics Data System (ADS)

Rondón, E.; Carvano, J.; Lorenz-Martins, S.

2017-09-01

The presence of dust comae on asteroids and centaurs is a phenomenon that became accepted in the last decades and which challenges the traditional definitions of asteroids and comets. A possible way of improving the chances of discovery of Active Asteroids is to use large multi-colour surveys or catalogs, like SDSS Moving Object Catalog. In this work we analyze the effects of faint dust comae on asteroid spectra and then use it to investigate the effects that a faint dust comae would have over the spectrum, magnitude, and radial profile of asteroids.

Confirmation of Faint Dwarf Galaxies in the M81 Group

NASA Astrophysics Data System (ADS)

Chiboucas, Kristin; Jacobs, Bradley A.; Tully, R. Brent; Karachentsev, Igor D.

2013-11-01

We have followed up on the results of a 65 deg2 CFHT/MegaCam imaging survey of the nearby M81 Group searching for faint and ultra-faint dwarf galaxies. The original survey turned up 22 faint candidate dwarf members. Based on two-color HST ACS/WFC and WFPC2 photometry, we now confirm 14 of these as dwarf galaxy members of the group. Distances and stellar population characteristics are discussed for each. To a completeness limit of M_{r^{\\prime }} = -10, we find a galaxy luminosity function slope of -1.27 ± 0.04 for the M81 Group. In this region, there are now 36 M81 Group members known, including 4 blue compact dwarfs; 8 other late types including the interacting giants M81, NGC 3077, and M82; 19 early type dwarfs; and at least 5 potential tidal dwarf galaxies. We find that the dSph galaxies in M81 appear to lie in a flattened distribution, similar to that found for the Milky Way and M31. One of the newly discovered dSph galaxies has properties similar to the ultra-faint dwarfs being found in the Local Group with a size Re ~ 100 pc and total magnitude estimates M_{r^{\\prime }} = -6.8 and MI ~ -9.1.

CONSTRAINTS ON MACHO DARK MATTER FROM COMPACT STELLAR SYSTEMS IN ULTRA-FAINT DWARF GALAXIES

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

Brandt, Timothy D.

2016-06-20

I show that a recently discovered star cluster near the center of the ultra-faint dwarf galaxy Eridanus II provides strong constraints on massive compact halo objects (MACHOs) of ≳5 M {sub ⊙} as the main component of dark matter. MACHO dark matter will dynamically heat the cluster, driving it to larger sizes and higher velocity dispersions until it dissolves into its host galaxy. The stars in compact ultra-faint dwarf galaxies themselves will be subject to the same dynamical heating; the survival of at least 10 such galaxies places independent limits on MACHO dark matter of masses ≳10 M {sub ⊙}.more » Both Eri II’s cluster and the compact ultra-faint dwarfs are characterized by stellar masses of just a few thousand M {sub ⊙} and half-light radii of 13 pc (for the cluster) and ∼30 pc (for the ultra-faint dwarfs). These systems close the ∼20–100 M {sub ⊙} window of allowed MACHO dark matter and combine with existing constraints from microlensing, wide binaries, and disk kinematics to rule out dark matter composed entirely of MACHOs from ∼10{sup −7} M {sub ⊙} up to arbitrarily high masses.« less

Possible Very Distant or Optically Dark Cluster of Galaxies

NASA Technical Reports Server (NTRS)

Vikhlinin, Alexey; Mushotzky, Richard (Technical Monitor)

2003-01-01

The goal of this proposal was an XMM followup observation of the extended X-ray source detected in our ROSAT PSPC cluster survey. Approximately 95% of extended X-ray sources found in the ROSAT data were optically identified as clusters of galaxies. However, we failed to find any optical counterparts for C10952-0148. Two possibilities remained prior to the XMM observation: (1) This is was a very distant or optically dark cluster of galaxies, too faint in the optical, in which case XMM would easily detect extended X-ray emission and (2) this was a group of point-like sources, blurred to a single extended source in the ROSAT data, but easily resolvable by XMM due to a better energy resolution. The XMM data have settled the case --- C10952-0148 is a group of 7 relatively bright point sources located within 1 square arcmin. All but one source have no optical counterparts down to I=22. Potentially, this can be an interesting group of quasars at a high redshift. We are planning further optical and infrared followup of this system.

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

Diffuse Galactic antimatter from faint thermonuclear supernovae in old stellar populations

NASA Astrophysics Data System (ADS)

Crocker, Roland M.; Ruiter, Ashley J.; Seitenzahl, Ivo R.; Panther, Fiona H.; Sim, Stuart; Baumgardt, Holger; Möller, Anais; Nataf, David M.; Ferrario, Lilia; Eldridge, J. J.; White, Martin; Tucker, Brad E.; Aharonian, Felix

2017-06-01

Our Galaxy hosts the annihilation of a few 1043 low-energy positrons every second. Radioactive isotopes capable of supplying such positrons are synthesized in stars, stellar remnants and supernovae. For decades, however, there has been no positive identification of a main stellar positron source, leading to suggestions that many positrons originate from exotic sources like the Galaxy's central supermassive black hole or dark matter annihilation. Here we show that a single type of transient source, deriving from stellar populations of age 3-6 Gyr and yielding ∼0.03 M ⊙ of the positron emitter 44Ti, can simultaneously explain the strength and morphology of the Galactic positron annihilation signal and the Solar System abundance of the 44Ti decay product 44Ca. This transient is likely the merger of two low-mass white dwarfs, observed in external galaxies as the sub-luminous, thermonuclear supernova known as SN 1991bg-like.

Noise Sources in Photometry and Radial Velocities

NASA Astrophysics Data System (ADS)

Oshagh, Mahmoudreza

The quest for Earth-like, extrasolar planets (exoplanets), especially those located inside the habitable zone of their host stars, requires techniques sensitive enough to detect the faint signals produced by those planets. The radial velocity (RV) and photometric transit methods are the most widely used and also the most efficient methods for detecting and characterizing exoplanets. However, presence of astrophysical "noise" makes it difficult to detect and accurately characterize exoplanets. It is important to note that the amplitude of such astrophysical noise is larger than both the signal of Earth-like exoplanets and state-of-the-art instrumentation limit precision, making this a pressing topic that needs to be addressed. In this chapter, I present a general review of the main sources of noise in photometric and RV observations, namely, stellar oscillations, granulation, and magnetic activity. Moreover, for each noise source I discuss the techniques and observational strategies which allow us to mitigate their impact.

The XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST)

NASA Technical Reports Server (NTRS)

Guedel, M.; Briggs, K. R.; Arzner, K.; Audard, M.; Bouvier, J.; Feigelson, E. D.; Franciosini, E.; Glauser, A.; Grosso, N.; Micela, G.;

Spectral Variability of the UXOR Star RR Tau Over 2.5 Magnitudes in V

NASA Astrophysics Data System (ADS)

Rodgers, B.; Wooden, D. H.; Grinin, V. P.; Shakhovskoy, D.

2000-12-01

We present moderate resolution optical spectra of the highly variable Herbig Ae star RR Tau over 12 epochs spanning 2.5 magnitudes in V. The data cover most of the optical spectrum from the CaII K line in the blue to the CaII infrared triplet in the far red. Using contemporaneous photometric measurements from two sources, we have reliable estimates of the visual magnitude of the system at each spectral epoch. We find some spectral activity to be closely correlated with photometric variability, while other features are remarkably stable. Significant variability is common in the cores of Hα and Hβ , but is not well correlated with photometric variability. On the other hand, the wings (Δ v>400km/s) of the Balmer lines are quite stable, showing no change in spectral type when compared to Kurucz line profiles. This, along with the constant equivalent width seen in several weak metal lines, suggest that the physical conditions of the underlying continuum source are not changing significantly, despite a factor of ten change in brightness. In contrast, strong low-ionization permitted lines, such as FeII, CaII and NaI, are seen in deep absorption when the star is bright (V <= 12), but disappear during photometric minima to reveal weak emission lines. These absorption lines are not being filled in by the emission but rather are physically disappearing from the system. This could occur, for example, if an obscuring screen moved between the continuum source and the absorbing gas. The [OI]6300 line, a common wind diagnostic, is seen in emission at all epochs, with flux which is roughly constant except increasing slightly when the system is faint. We discuss these data in the context of different scenarios for the photometric variability and find them to be more consistent with the obscuration hypothesis, than changing accretion luminosity. This work is part of the dissertation research of B. Rodgers, which has been funded in large part by a NASA Graduate Student Research Program (GSRP) grant, for which D.H. Wooden is Rodgers' advisor. We gratefully acknowledge the use of the database of the Amateur Astronomers Variable Star Organization (AAVSO).

1. Dyea Dock looking south. Note faint evenly spaced circular ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

1. Dyea Dock looking south. Note faint evenly spaced circular dark pieces of grass up through the middle of the picture indicating posts making up the pier. Photograph made from park service cherry picker. - Dyea Dock & Association (Ruins), Skagway, Skagway, AK

ARE THE FAINT STRUCTURES AHEAD OF SOLAR CORONAL MASS EJECTIONS REAL SIGNATURES OF DRIVEN SHOCKS?

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

Lee, Jae-Ok; Moon, Y.-J.; Lee, Kangjin

2014-11-20

Recently, several studies have assumed that the faint structures ahead of coronal mass ejections (CMEs) are caused by CME-driven shocks. In this study, we have conducted a statistical investigation to determine whether or not the appearance of such faint structures depends on CME speeds. For this purpose, we use 127 Solar and Heliospheric Observatory/Large Angle Spectroscopic COronagraph (LASCO) front-side halo (partial and full) CMEs near the limb from 1997 to 2011. We classify these CMEs into two groups by visual inspection of CMEs in the LASCO-C2 field of view: Group 1 has the faint structure ahead of a CME andmore » Group 2 does not have such a structure. We find the following results. (1) Eighty-seven CMEs belong to Group 1 and 40 CMEs belong to Group 2. (2) Group 1 events have much higher speeds (average = 1230 km s{sup –1} and median = 1199 km s{sup –1}) than Group 2 events (average = 598 km s{sup –1} and median = 518 km s{sup –1}). (3) The fraction of CMEs with faint structures strongly depends on CME speeds (V): 0.93 (50/54) for fast CMEs with V ≥ 1000 km s{sup –1}, 0.65 (34/52) for intermediate CMEs with 500 km s{sup –1} ≤ V < 1000 km s{sup –1}, and 0.14 (3/21) for slow CMEs with V < 500 km s{sup –1}. We also find that the fraction of CMEs with deca-hecto metric type II radio bursts is consistent with the above tendency. Our results indicate that the observed faint structures ahead of fast CMEs are most likely an enhanced density manifestation of CME-driven shocks.« less

Deep imaging of high redshift QSO fields below the Lyman limit. II - Number counts and colors of field galaxies

NASA Technical Reports Server (NTRS)

Steidel, Charles C.; Hamilton, Donald

1993-01-01

We present an analysis of the number counts and colors of faint galaxies to about 26.5 mag in the fields of two high Galactic latitude, very-high-redshift QSOs. We concentrate on the general properties of the field galaxies at faint magnitudes. In particular, we readdress the faint galaxy number counts and colors as a function of apparent magnitude and we reexamine the possible contribution of very-high-redshift galaxies to the faint samples. We find that the number counts to R = 26 are well fitted by the relation log N(m) = 0.31R + C. The G-band counts for the same galaxies are consistent with the same slope fainter than G about 23.5, but exhibit a much steeper slope at brighter magnitudes. At R = 25.5, the differential number counts have reached about 1.2 x 10 exp 5/sq deg; the same surface density of galaxies is reached at G = 26.5. We confirm the existence of a gradual 'blueing' trend of the field galaxies toward fainter apparent magnitude; however, the blueing trend appears to extend only as faint as G about 24, fainter than which both the (G-R) and (U sub n-G) colors appear to level off. The mean colors of faint galaxies are considerably redder than flat spectrum. There are essentially no objects to R = 26 which have spectral energy distributions which are bluer than flat spectrum. The potential contribution of very-high-redshift galaxies may have been underestimated in previous analyses; the current data are consistent with the same population of relatively luminous galaxies at z about 3 as exist at z about 0.7.

An X-ray investigation of the unusual supernova remnant CTB 80

NASA Technical Reports Server (NTRS)

Wang, Z. R.; Seward, F. D.

1984-01-01

The X-ray properties of SNR CTB 80 (G68.8 + 2.8) are discussed based on both low- and high-resolution images from the Einstein satellite. The X-ray maps show a point source coinciding with the region of maximum radio emission. Diffuse X-ray emission is evident mainly along the radio lobe extending about 8 arcmin east of the point source and aligned with the projected magnetic field lines. The observed X-ray luminosity is 3.2 x 10 to the 34th ergs/s with 1.0 x 10 to the 3th ergs/s from the point source (assuming a distance of 3 kpc). There is also faint, diffuse, X-ray emission south of the point source, where radio emission is absent. The unusual radio and X-ray morphologies are interpreted as a result of relativistic jets energized by the central object, and the possible association of CTB 80 with SN 1408 as recorded by Chinese observers is discussed.

Multiple-component Decomposition from Millimeter Single-channel Data

NASA Astrophysics Data System (ADS)

Rodríguez-Montoya, Iván; Sánchez-Argüelles, David; Aretxaga, Itziar; Bertone, Emanuele; Chávez-Dagostino, Miguel; Hughes, David H.; Montaña, Alfredo; Wilson, Grant W.; Zeballos, Milagros

2018-03-01

We present an implementation of a blind source separation algorithm to remove foregrounds off millimeter surveys made by single-channel instruments. In order to make possible such a decomposition over single-wavelength data, we generate levels of artificial redundancy, then perform a blind decomposition, calibrate the resulting maps, and lastly measure physical information. We simulate the reduction pipeline using mock data: atmospheric fluctuations, extended astrophysical foregrounds, and point-like sources, but we apply the same methodology to the Aztronomical Thermal Emission Camera/ASTE survey of the Great Observatories Origins Deep Survey–South (GOODS-S). In both applications, our technique robustly decomposes redundant maps into their underlying components, reducing flux bias, improving signal-to-noise ratio, and minimizing information loss. In particular, GOODS-S is decomposed into four independent physical components: one of them is the already-known map of point sources, two are atmospheric and systematic foregrounds, and the fourth component is an extended emission that can be interpreted as the confusion background of faint sources.

GLAST Science Across Wavelengths

NASA Astrophysics Data System (ADS)

Blandford, R. D.

2006-12-01

The GLAST satellites is almost guaranteed to revolutionize GeV gamma ray astronomy because of the great discoveries that are being made at hard X-ray energy by the Suzaku and Swift satellites and in the TeV range using the H.E.S.S. and Magic telescopes. Unidentified EGRET sources are likely to be identified and new and fainter sources will be found. Known classes of sources blazars, pulsars, gamma ray bursts, supernova remnants, binary X-ray sources and so on will be monitored in much greater detail. Finally, there is the need to limit or even detect dark matter through its annihilation signature. The science that will emerge from GLAST will be determined in large measure by the effort that is put into multiwavelength observing. This will require significant commitments of observing time for monitoring pulsar arrival times, measuring faint galaxy spectra, detecting GeV gamma rays gamma ray bursts and so on. In this talk I will attempt to summarize current thinking on the GLAST multi-wavelength observing program and propose some new approaches.

New Constraints on the Faint End of the UV Luminosity Function at z ~ 7-8 Using the Gravitational Lensing of the Hubble Frontier Fields Cluster A2744

NASA Astrophysics Data System (ADS)

Atek, Hakim; Richard, Johan; Kneib, Jean-Paul; Jauzac, Mathilde; Schaerer, Daniel; Clement, Benjamin; Limousin, Marceau; Jullo, Eric; Natarajan, Priyamvada; Egami, Eiichi; Ebeling, Harald

2015-02-01

Exploiting the power of gravitational lensing, the Hubble Frontier Fields (HFF) program aims at observing six massive galaxy clusters to explore the distant universe far beyond the limits of blank field surveys. Using the complete Hubble Space Telescope observations of the first HFF cluster A2744, we report the detection of 50 galaxy candidates at z ~ 7 and eight candidates at z ~ 8 in a total survey area of 0.96 arcmin2 in the source plane. Three of these galaxies are multiply imaged by the lensing cluster. Using an updated model of the mass distribution in the cluster we were able to calculate the magnification factor and the effective survey volume for each galaxy in order to compute the ultraviolet galaxy luminosity function (LF) at both redshifts 7 and 8. Our new measurements reliably extend the z ~ 7 UV LF down to an absolute magnitude of M UV ~ -15.5. We find a characteristic magnitude of M\\star UV = -20.90+0.90-0.73 mag and a faint-end slope α =-2.01+0.20-0.28, close to previous determinations in blank fields. We show here for the first time that this slope remains steep down to very faint luminosities of 0.01 L sstarf. Although prone to large uncertainties, our results at z ~ 8 also seem to confirm a steep faint-end slope below 0.1 L sstarf. The HFF program is therefore providing an extremely efficient way to study the faintest galaxy populations at z > 7 that would otherwise be inaccessible with current instrumentation. The full sample of six galaxy clusters will provide even better constraints on the buildup of galaxies at early epochs and their contribution to cosmic reionization. Based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs 13495, 11386, 13389, and 11689. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. The Hubble Frontier Fields data were obtained from the Mikulski Archive for Space Telescopes (MAST).

AO 0235+164 and Surrounding Field: Surprising HST Results

NASA Technical Reports Server (NTRS)

Burbidge, E. M.; Beaver, E. A.; Cohen, Ross D.; Junkkarinen, V. T.; Lyons, R. W.

1996-01-01

Results obtained with the Hubble Space Telescope on the highly variable radio, x-ray, and gamma-ray emitting QSO (or BL Lac object) AO 0235 + 164 are presented and analyzed. WFPC2 images were obtained in 1994 June, when AO 0235 + 164 was bright (m approx. 17), and the results are described in Sec. 3. After subtraction of the PSF of the QSO, hereafter called AO following the nomenclature of Yanny et al. (1989), the companion object named A, 2 sec south of AO, is discovered not to be an elliptical galaxy as hypothesized earlier, but to be an AGN object, with a central UV-bright point-source nucleus and faint surrounding nebulosity extending to AO. The second companion object 1.3 sec east of AO discovered by Yanny et al. (1989) and named object Al, appears more like a normal spiral galaxy. We have measured the positions, luminosities, and colors of some 30 faint objects in the field around AO 0235 + 16; most are extended and may be star-forming galaxies in a loose group or cluster. Our most surprising result of the HST observations comes from FOS spectra obtained in 1995 July, discussed in Sec. 4. Because of a positioning error of the telescope and AO's faintness at that time (m approx. 20), object A was observed instead of the intended target AO. Serendipitously, we discovered A to have broad deep BALQSO-type absorptions of C IV, Si IV, N V shortward of broad emissions. A is thus ejecting high velocity, highly ionized gas into the surrounding IGM. We discuss in Sec. 5 the relationship of the objects in the central 10 sec X 1O sec region around AO, where redshifts z(sub e) = 0.94, z(sub a) = 0.524, 0.851 in AO, (sub e) = 0.524 and Z(sub BAL)=0.511 in A, are found. We hypothesize that some of the 30 faint objects in the 77 sec. x 77 sec. field may be part of a large star-forming region at z approx. 0.5, as suggested for a few objects by Yanny et al. (1989). The proximity of two highly active extragalactic objects, AO 0235+164 and its AGN companion A, is remarkable and one of the authors (EMB) suggests it may require consideration of a non-cosmological component of redshift in AO 0235+164.

The superiority of L3-CCDs in the high-flux and wide dynamic range regimes

NASA Astrophysics Data System (ADS)

Butler, Raymond F.; Sheehan, Brendan J.

2008-02-01

Low Light Level CCD (L3-CCD) cameras have received much attention for high cadence astronomical imaging applications. Efforts to date have concentrated on exploiting them for two scenarios: post-exposure image sharpening and ``lucky imaging'', and rapid variability in astrophysically interesting sources. We demonstrate their marked superiority in a third distinct scenario: observing in the high-flux and wide dynamic range regimes. We realized that the unique features of L3-CCDs would make them ideal for maximizing signal-to-noise in observations of bright objects (whether variable or not), and for high dynamic range scenarios such as faint targets embedded in a crowded field of bright objects. Conventional CCDs have drawbacks in such regimes, due to a poor duty cycle-the combination of short exposure times (for time-series sampling or to avoid saturation) and extended readout times (for minimizing readout noise). For different telescope sizes, we use detailed models to show that a range of conventional imaging systems are photometrically out-performed across a wide range of object brightness, once the operational parameters of the L3-CCD are carefully set. The cross-over fluxes, above which the L3-CCD is operationally superior, are surprisingly faint-even for modest telescope apertures. We also show that the use of L3-CCDs is the optimum strategy for minimizing atmospheric scintillation noise in photometric observations employing a given telescope aperture. This is particularly significant, since scintillation can be the largest source of error in timeseries photometry. These results should prompt a new direction in developing imaging instrumentation solutions for observatories.

Single photon source with individualized single photon certifications

NASA Astrophysics Data System (ADS)

Migdall, Alan L.; Branning, David A.; Castelletto, Stefania; Ware, M.

2002-12-01

As currently implemented, single-photon sources cannot be made to produce single photons with high probability, while simultaneously suppressing the probability of yielding two or more photons. Because of this, single photon sources cannot really produce single photons on demand. We describe a multiplexed system that allows the probabilities of producing one and more photons to be adjusted independently, enabling a much better approximation of a source of single photons on demand. The scheme uses a heralded photon source based on parametric downconversion, but by effectively breaking the trigger detector area into multiple regions, we are able to extract more information about a heralded photon than is possible with a conventional arrangement. This scheme allows photons to be produced along with a quantitative 'certification' that they are single photons. Some of the single-photon certifications can be significantly better than what is possible with conventional downconversion sources, as well as being better than faint laser sources. With such a source of more tightly certified single photons, it should be possible to improve the maximum secure bit rate possible over a quantum cryptographic link. We present an analysis of the relative merits of this method over the conventional arrangement.

A Suzaku X-ray Observation of One Orbit of the Supergiant Fast X-ray Transient IGR J16479-4514

NASA Technical Reports Server (NTRS)

Sidoli, L.; Esposito, P.; Sguera, V.; Bodaghee, A.; Tomsick, J. A.; Pottschmidt, K.; Rodriguez, J.; Ramano, P.; Wilms, J.

2013-01-01

We report on a 250 ks long X-ray observation of the supergiant fast X-ray transient (SFXT) IGR J16479-4514 performed with Suzaku in 2012 February. During this observation, about 80% of the short orbital period (P(sub orb) approximates 3.32 days) was covered as continuously as possible for the first time. The source light curve displays variability of more than two orders of magnitude, starting with a very low emission state (10(exp -13) erg / sq cm/s; 1-10 keV) lasting the first 46 ks, consistent with being due to the X-ray eclipse by the supergiant companion. The transition to the uneclipsed X-ray emission is energy dependent. Outside the eclipse, the source spends most of the time at a level of 6-7X10)(exp-12) erg/sq. cm/s) punctuated by two structured faint flares with a duration of about 10 and 15 ks, respectively, reaching a peak flux of 3-4X10(exp -11) erg/sq. cm./S, separated by about 0.2 in orbital phase. Remarkably, the first faint flare occurs at a similar orbital phase of the bright flares previously observed in the system. This indicates the presence of a phase-locked large scale structure in the supergiant wind, driving a higher accretion rate onto the compact object. The average X-ray spectrum is hard and highly absorbed, with a column density, NH, of 10*exp 23)/sq cm, clearly in excess of the interstellar absorption. There is no evidence for variability of the absorbing column density, except that during the eclipse, where a less absorbed X-ray spectrum is observed. A narrow Fe K-alpha emission line at 6.4 keV is viewed along the whole orbit, with an intensity which correlates with the continuum emission above 7 keV. The scattered component visible during the X-ray eclipse allowed us to directly probe the wind density at the orbital separation, resulting in rho(sub w)=7X10(exp -14) g/cubic cm. Assuming a spherical geometry for the supergiant wind, the derived wind density translates into a ratio M(sub w)/v(sub infinity) = 7X10(exp -17) Solar M/km which, assuming terminal velocities in a large range 500-3000 km/s, implies an accretion luminosity two orders of magnitude higher than that observed. As a consequence, a mechanism should be at work reducing the mass accretion rate. Different possibilities are discussed.

View of southeast side, faint "141" sign, Cranes P76 and ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

View of southeast side, faint "141" sign, Cranes P-76 and P-71 are behind, view facing northwest - U.S. Naval Base, Pearl Harbor, Dry Dock No. 1, Latrine, Sixth Street, adjacent to Dry Dock No. 1, Pearl City, Honolulu County, HI

The faint galaxy contribution to the diffuse extragalactic background light

NASA Technical Reports Server (NTRS)

Cole, Shaun; Treyer, Marie-Agnes; Silk, Joseph

1992-01-01

Models of the faint galaxy contribution to the diffuse extragalactic background light are presented, which are consistent with current data on faint galaxy number counts and redshifts. The autocorrelation function of surface brightness fluctuations in the extragalactic diffuse light is predicted, and the way in which these predictions depend on the cosmological model and assumptions of biasing is determined. It is confirmed that the recent deep infrared number counts are most compatible with a high density universe (Omega-0 is approximately equal to 1) and that the steep blue counts then require an extra population of rapidly evolving blue galaxies. The faintest presently detectable galaxies produce an interesting contribution to the extragalactic diffuse light, and still fainter galaxies may also produce a significant contribution. These faint galaxies still only produce a small fraction of the total optical diffuse background light, but on scales of a few arcminutes to a few degrees, they produce a substantial fraction of the fluctuations in the diffuse light.

Theoretical colours and isochrones for some Hubble Space Telescope colour systems. II

NASA Technical Reports Server (NTRS)

Paltoglou, G.; Bell, R. A.

1991-01-01

A grid of synthetic surface brightness magnitudes for 14 bandpasses of the Hubble Space Telescope Faint Object Camera is presented, as well as a grid of UBV, uvby, and Faint Object Camera surface brightness magnitudes derived from the Gunn-Stryker spectrophotometric atlas. The synthetic colors are used to examine the transformations between the ground-based Johnson UBV and Stromgren uvby systems and the Faint Object Camera UBV and uvby. Two new four-color systems, similar to the Stromgren system, are proposed for the determination of abundance, temperature, and surface gravity. The synthetic colors are also used to calculate color-magnitude isochrones from the list of theoretical tracks provided by VandenBerg and Bell (1990). It is shown that by using the appropriate filters it is possible to minimize the dependence of this color difference on metallicity. The effects of interstellar reddening on various Faint Object Camera colors are analyzed as well as the observational requirements for obtaining data of a given signal-to-noise for each of the 14 bandpasses.

Tunable All Reflective Spatial Heterodyne Spectroscopy, A Technique For High Resolving Power Observation OI Defused Emission Line Sources

NASA Astrophysics Data System (ADS)

Hosseini, Seyedeh Sona

The solar system presents a challenge to spectroscopic observers, because it is an astrophysically low energy environment populated with often angularly extended targets (e.g, interplanetary medium, comets, planetary upper atmospheres, and planet and satellite near space environments). Spectroscopy is a proven tool for determining compositional and other properties of remote objects. Narrow band imaging and low resolving spectroscopic measurements provide information about composition, photochemical evolution, energy distribution and density. The extension to high resolving power provides further access to temperature, velocity, isotopic ratios, separation of blended sources, and opacity effects. The drawback of high-resolution spectroscopy comes from the instrumental limitations of lower throughput, the necessity of small entrance apertures, sensitivity, field of view, and large physical instrumental size. These limitations quickly become definitive for faint and/or extended targets and for spacecraft encounters. An emerging technique with promise for the study of faint, extended sources at high resolving power is the all-reflective form of the Spatial Heterodyne Spectrometer (SHS). SHS instruments are compact and naturally possess both high etendue and high resolving power. To achieve similar spectral grasp, grating spectrometers require big telescopes. SHS is a common-path beam Fourier transform interferometer that produces Fizeau fringe pattern for all other wavelengths except the tuned wavelength. Compared to similar Fourier transform Spectrometers (FTS), SHS has considerably relaxed optical tolerances that make it easier to use in the visible and UV spectral ranges. The large etendue of SHS instruments makes them ideal for observations of extended, low surface brightness, isolated emission line sources, while their intrinsically high spectral resolution enables the study of the dynamical and spectral characteristics described above. SHS also combines very high (R >105) spectral resolution and large etendue in a small package that is compatible with space mission requirements that have not been met with any other SHS technologies to date. One limitation of current SHS designs is the lack of a broadband capability. To address this gap we are developing a form of the reflective SHS that is tunable over a wide range of wavelength (TSHS). In this work, we describe the primary TSHS concept in a mathematical approach, describe the variations under development, and discuss their scientific potential for the exploration of faint extended targets. An in-development laboratory prototype of a second generation TSHS in which we address several technical limitations noted in earlier studies is shown. This document contains three chapters. Chapter 1, is an overview of the scientific need for a new instrument that we are introducing here and it is an summery of previous papers. Chapter 2 contains new work developing the mathematical frame work for the all reflective SHS. The results presented in this chapter have not been reported in any related literature before and will be presented in an upcoming conference paper. Chapter 3 contains a laboratory report for construction of a tunable all reflective SHS.

Lynx mission concept study

NASA Astrophysics Data System (ADS)

Vikhlinin, Alexey

2018-01-01

Lynx is an observatory-class mission, featuring high throughput, exquisite angular resolution over a substantial field of view, and high spectral resolution for point and extended X-ray sources. The design requirements provide a tremendous leap in capabilities relative to missions such as Chandra and Athena. Lynx will observe the dawn of supermassive black holes through detection of very faint X-ray sources in the early universe and will reveal the "invisible drivers" of galaxy and structure formation through observations of hot, diffuse baryons in and around the galaxies. Lynx will enable breakthroughs across all of astrophysics, ranging from detailed understanding of stellar activity including effects on habitability of associated planets to population statistics of neutron stars and black holes in the Local Group galaxies, to earliest groups and clusters of galaxies, and to cosmology

A study of the discrepant QSO X-ray luminosity function from the HEAO-2 data archive

NASA Technical Reports Server (NTRS)

Margon, B.

1984-01-01

An in-progress investigation aimed at characterizing the X-ray luminosity of very faint QSOs is described. More than 100 faint, previously uncataloged QSOs which lie in areas imaged in X rays at very high sensitivity were discovered.

New Window on the Universe.

ERIC Educational Resources Information Center

Reynolds, Ronald F.

1984-01-01

Describes the basic components of a space telescope that will be launched during a 1986 space shuttle mission. These components include a wide field/planetary camera, faint object spectroscope, high-resolution spectrograph, high-speed photometer, faint object camera, and fine guidance sensors. Data to be collected from these instruments are…

A VLA SURVEY FOR FAINT COMPACT RADIO SOURCES IN THE ORION NEBULA CLUSTER

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

Sheehan, Patrick D.; Eisner, Josh A.; Mann, Rita K.

We present Karl G. Jansky Very Large Array 1.3, 3.6, and 6 cm continuum maps of compact radio sources in the Orion Nebular Cluster (ONC). We mosaicked 34 arcmin{sup 2} at 1.3 cm, 70 arcmin{sup 2} at 3.6 cm and 109 arcmin{sup 2} at 6 cm, containing 778 near-infrared detected young stellar objects and 190 Hubble Space Telescope -identified proplyds (with significant overlap between those characterizations). We detected radio emission from 175 compact radio sources in the ONC, including 26 sources that were detected for the first time at these wavelengths. For each detected source, we fitted a simple free–freemore » and dust emission model to characterize the radio emission. We extrapolate the free–free emission spectrum model for each source to ALMA bands to illustrate how these measurements could be used to correctly measure protoplanetary disk dust masses from submillimeter flux measurements. Finally, we compare the fluxes measured in this survey with previously measured fluxes for our targets, as well as four separate epochs of 1.3 cm data, to search for and quantify the variability of our sources.« less

Interferometric constraints on quantum geometrical shear noise correlations

DOE PAGES

Chou, Aaron; Glass, Henry; Richard Gustafson, H.; ...

2017-07-20

Final measurements and analysis are reported from the first-generation Holometer, the first instrument capable of measuring correlated variations in space-time position at strain noise power spectral densities smaller than a Planck time. The apparatus consists of two co-located, but independent and isolated, 40 m power-recycled Michelson interferometers, whose outputs are cross-correlated to 25 MHz. The data are sensitive to correlations of differential position across the apparatus over a broad band of frequencies up to and exceeding the inverse light crossing time, 7.6 MHz. By measuring with Planck precision the correlation of position variations at spacelike separations, the Holometer searches formore » faint, irreducible correlated position noise backgrounds predicted by some models of quantum space-time geometry. The first-generation optical layout is sensitive to quantum geometrical noise correlations with shear symmetry---those that can be interpreted as a fundamental noncommutativity of space-time position in orthogonal directions. General experimental constraints are placed on parameters of a set of models of spatial shear noise correlations, with a sensitivity that exceeds the Planck-scale holographic information bound on position states by a large factor. This result significantly extends the upper limits placed on models of directional noncommutativity by currently operating gravitational wave observatories.« less

Interferometric constraints on quantum geometrical shear noise correlations

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

Chou, Aaron; Glass, Henry; Richard Gustafson, H.

Final measurements and analysis are reported from the first-generation Holometer, the first instrument capable of measuring correlated variations in space-time position at strain noise power spectral densities smaller than a Planck time. The apparatus consists of two co-located, but independent and isolated, 40 m power-recycled Michelson interferometers, whose outputs are cross-correlated to 25 MHz. The data are sensitive to correlations of differential position across the apparatus over a broad band of frequencies up to and exceeding the inverse light crossing time, 7.6 MHz. By measuring with Planck precision the correlation of position variations at spacelike separations, the Holometer searches formore » faint, irreducible correlated position noise backgrounds predicted by some models of quantum space-time geometry. The first-generation optical layout is sensitive to quantum geometrical noise correlations with shear symmetry---those that can be interpreted as a fundamental noncommutativity of space-time position in orthogonal directions. General experimental constraints are placed on parameters of a set of models of spatial shear noise correlations, with a sensitivity that exceeds the Planck-scale holographic information bound on position states by a large factor. This result significantly extends the upper limits placed on models of directional noncommutativity by currently operating gravitational wave observatories.« less

Solar wind physics

NASA Technical Reports Server (NTRS)

1972-01-01

A double-chambered gas proportional counter was constructed to detect and identify solar wind ions after acceleration by a high voltage power supply. It was determined that the best method of detecting deuterium in the solar wind is to use a tritium target as proposed for IMP H and J. The feasibility of detecting H(+) and He(+) ions of interstellar origin is considered. A program is described to carry out ground-based astronomical observations of faint, diffuse optical emission lines from interstellar gas. Hydrogen and oxygen emission lines from galactic sources were detected and the galactic and geocoronal H alpha and beta lines were clearly resolved.

Near Infrared Imaging of the Hubble Deep Field with Keck Telescope

NASA Technical Reports Server (NTRS)

Hogg, David W.; Neugebauer, G.; Armus, Lee; Matthews, K.; Pahre, Michael A.; Soifer, B. T.; Weinberger, A. J.

1997-01-01

Two deep K-band (2.2 micrometer) images, with point-source detection limits of K=25.2 mag (one sigma), taken with the Keck Telescope in subfields of the Hubble Deep Field, are presented and analyzed. A sample of objects to K=24 mag is constructed and V(sub 606)- I(sub 814) and I(sub 814)-K colors are measured. By stacking visually selected objects, mean I(sub 814)-K colors can be measured to very faint levels, the mean I(sub 814)-K color is constant with apparent magnitude down to V(sub 606)=28 mag.

New Detections of Radio Minihalos in Cool Cores of Galaxy Clusters

NASA Technical Reports Server (NTRS)

Giacintucci, Simona; Markevitch, Maxim; Venturi, Tiziana; Clarke, Tracy E.; Cassano, Rossella; Mazzotta, Pasquale

2013-01-01

Cool cores of some galaxy clusters exhibit faint radio minihalos. Their origin is unclear, and their study has been limited by their small number. We undertook a systematic search for minihalos in a large sample of X-ray luminous clusters with high-quality radio data. In this article, we report four new minihalos (A 478, ZwCl 3146,RXJ 1532.9+3021, and A 2204) and five candidates found in the reanalyzed archival Very Large Array observations.The radio luminosities of our minihalos and candidates are in the range of 102325 W Hz1 at 1.4 GHz, which is consistent with these types of radio sources. Their sizes (40160 kpc in radius) are somewhat smaller than those of previously known minihalos. We combine our new detections with previously known minihalos, obtaining a total sample of 21 objects, and briefly compare the cluster radio properties to the average X-ray temperature and the total masses estimated from Planck.We find that nearly all clusters hosting minihalos are hot and massive. Beyond that, there is no clear correlation between the minihalo radio power and cluster temperature or mass (in contrast with the giant radio halos found in cluster mergers, whose radio luminosity correlates with the cluster mass). Chandra X-ray images indicate gas sloshing in the cool cores of most of our clusters, with minihalos contained within the sloshing regions in many of them. This supports the hypothesis that radio-emitting electrons are reaccelerated by sloshing. Advection of relativistic electrons by the sloshing gas may also play a role in the formation of the less extended minihalos.

The Role of Galaxies and AGN in Reionising the IGM - slowromancapi@: Keck Spectroscopy of 5 < z < 7 Galaxies in the QSO Field J1148+5251

NASA Astrophysics Data System (ADS)

Kakiichi, Koki; Ellis, Richard S.; Laporte, Nicolas; Zitrin, Adi; Eilers, Anna-Christina; Ryan-Weber, Emma; Meyer, Romain A.; Robertson, Brant; Stark, Daniel P.; Bosman, Sarah E. I.

2018-05-01

We introduce a new method for determining the influence of galaxies and active galactic nuclei (AGN) on the intergalactic medium (IGM) at high redshift and illustrate its potential via a first application to the field of the z = 6.42 QSO J1148+5251. Correlating spatial positions Lyman break galaxies (LBGs) with the Lyman alpha forest seen in the spectrum of a background QSO, we provide a statistical measure of the typical escape fraction of Lyman continuum photons. Using Keck DEIMOS spectroscopy to locate 7 colour-selected LBGs in the range 5.3 ≲ z ≲ 6.4 we examine the spatial correlation between this sample and Lyα/Lyβ transmission fluctuations in a Keck ESI spectrum of the QSO. Interpreting the statistical H I proximity effect as arising from faint galaxies clustered around the LBGs, we translate the observed mean Lyα transmitted flux into a constraint on the mean escape fraction ⟨fesc⟩ ≥ 0.08 at z ≃ 6. We also report individual transverse H I proximity effect for a z = 6.177 luminous LBG via a Lyβ transmission spike and two broad Lyα transmission spikes around the z = 5.701 AGN. We discuss the origin of such associations which suggest that while faint galaxies are primarily driving reionisation, luminous galaxies and AGN may provide important contributions to the UV background or thermal fluctuations of the IGM at z ≃ 6. Although a limited sample, our results demonstrate the potential of making progress using this method in resolving one of the most challenging aspects of the contribution of galaxies and AGN to cosmic reionisation.

Diffuse light and building history of the galaxy cluster Abell 2667

NASA Astrophysics Data System (ADS)

Covone, G.; Adami, C.; Durret, F.; Kneib, J.-P.; Lima Neto, G. B.; Slezak, E.

2006-12-01

Aims.We searched for diffuse intracluster light in the galaxy cluster Abell 2667 (z=0.233) from HST images in three broad band-filters. Methods: .We applied an iterative multi-scale wavelet analysis and reconstruction technique to these images, which allows to subtract stars and galaxies from the original images. Results: .We detect a zone of diffuse emission southwest of the cluster center (DS1) and a second faint object (ComDif) within DS1. Another diffuse source (DS2) may be detected at lower confidence level northeast of the center. These sources of diffuse light contribute to 10-15% of the total visible light in the cluster. Whether they are independent entities or part of the very elliptical external envelope of the central galaxy remains unclear. Deep VLT VIMOS integral field spectroscopy reveals a faint continuum at the positions of DS1 and ComDif but do not allow a redshift to be computed, so we conclude if these sources are part of the central galaxy or not. A hierarchical substructure detection method reveals the presence of several galaxy pairs and groups defining a similar direction to the one drawn by the DS1 - central galaxy - DS2 axis. The analysis of archive XMM-Newton and Chandra observations shows X-ray emission elongated in the same direction. The X-ray temperature map shows the presence of a cool core, a broad cool zone stretching from north to south, and hotter regions towards the northeast, southwest, and northwest. This might suggest shock fronts along these directions produced by infalling material, even if uncertainties remain quite large on the temperature determination far from the center. Conclusions: .These various data are consistent with a picture in which diffuse sources are concentrations of tidal debris and harassed matter expelled from infalling galaxies by tidal stripping and undergoing an accretion process onto the central cluster galaxy; as such, they are expected to be found along the main infall directions. Note, however, that the limited signal to noise of the various data and the apparent lack of large numbers of well-defined independent tidal tails, besides the one named ComDif, preclude definitive conclusions on this scenario.

Extreme Faint Flux Imaging with an EMCCD

NASA Astrophysics Data System (ADS)

Daigle, Olivier; Carignan, Claude; Gach, Jean-Luc; Guillaume, Christian; Lessard, Simon; Fortin, Charles-Anthony; Blais-Ouellette, Sébastien

2009-08-01

An EMCCD camera, designed from the ground up for extreme faint flux imaging, is presented. CCCP, the CCD Controller for Counting Photons, has been integrated with a CCD97 EMCCD from e2v technologies into a scientific camera at the Laboratoire d’Astrophysique Expérimentale (LAE), Université de Montréal. This new camera achieves subelectron readout noise and very low clock-induced charge (CIC) levels, which are mandatory for extreme faint flux imaging. It has been characterized in laboratory and used on the Observatoire du Mont Mégantic 1.6 m telescope. The performance of the camera is discussed and experimental data with the first scientific data are presented.

The faint-end of galaxy luminosity functions at the Epoch of Reionization

NASA Astrophysics Data System (ADS)

Yue, B.; Castellano, M.; Ferrara, A.; Fontana, A.; Merlin, E.; Amorín, R.; Grazian, A.; Mármol-Queralto, E.; Michałowski, M. J.; Mortlock, A.; Paris, D.; Parsa, S.; Pilo, S.; Santini, P.; Di Criscienzo, M.

2018-05-01

During the Epoch of Reionization (EoR), feedback effects reduce the efficiency of star formation process in small halos or even fully quench it. The galaxy luminosity function (LF) may then turn over at the faint-end. We analyze the number counts of z > 5 galaxies observed in the fields of four Frontier Fields (FFs) clusters and obtain constraints on the LF faint-end: for the turn-over magnitude at z ~ 6, MUVT >~-13.3 for the circular velocity threshold of quenching star formation process, vc* <~ 47 km s-1. We have not yet found significant evidence of the presence of feedback effects suppressing the star formation in small galaxies.

Second ROSAT all-sky survey (2RXS) source catalogue

NASA Astrophysics Data System (ADS)

Boller, Th.; Freyberg, M. J.; Trümper, J.; Haberl, F.; Voges, W.; Nandra, K.

2016-04-01

Aims: We present the second ROSAT all-sky survey source catalogue, hereafter referred to as the 2RXS catalogue. This is the second publicly released ROSAT catalogue of point-like sources obtained from the ROSAT all-sky survey (RASS) observations performed with the position-sensitive proportional counter (PSPC) between June 1990 and August 1991, and is an extended and revised version of the bright and faint source catalogues. Methods: We used the latest version of the RASS processing to produce overlapping X-ray images of 6.4° × 6.4° sky regions. To create a source catalogue, a likelihood-based detection algorithm was applied to these, which accounts for the variable point-spread function (PSF) across the PSPC field of view. Improvements in the background determination compared to 1RXS were also implemented. X-ray control images showing the source and background extraction regions were generated, which were visually inspected. Simulations were performed to assess the spurious source content of the 2RXS catalogue. X-ray spectra and light curves were extracted for the 2RXS sources, with spectral and variability parameters derived from these products. Results: We obtained about 135 000 X-ray detections in the 0.1-2.4 keV energy band down to a likelihood threshold of 6.5, as adopted in the 1RXS faint source catalogue. Our simulations show that the expected spurious content of the catalogue is a strong function of detection likelihood, and the full catalogue is expected to contain about 30% spurious detections. A more conservative likelihood threshold of 9, on the other hand, yields about 71 000 detections with a 5% spurious fraction. We recommend thresholds appropriate to the scientific application. X-ray images and overlaid X-ray contour lines provide an additional user product to evaluate the detections visually, and we performed our own visual inspections to flag uncertain detections. Intra-day variability in the X-ray light curves was quantified based on the normalised excess variance and a maximum amplitude variability analysis. X-ray spectral fits were performed using three basic models, a power law, a thermal plasma emission model, and black-body emission. Thirty-two large extended regions with diffuse emission and embedded point sources were identified and excluded from the present analysis. Conclusions: The 2RXS catalogue provides the deepest and cleanest X-ray all-sky survey catalogue in advance of eROSITA. The catalogue is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/588/A103

A deep x-ray survey of the Pleiades cluster and the B6-A3 main sequence stars in Orion

NASA Technical Reports Server (NTRS)

Caillault, Jean-Pierre

1993-01-01

We have obtained deep ROSAT images of three regions within the Pleiades open cluster. We have detected 317 X-ray sources in these ROSAT PSPC images, 171 of which we associate with certain probable members of the Pleiades cluster. We detect nearly all Pleiades members with spectral types later than G0 and within 25 arcminutes of our three field centers where our sensitivity is highest. This has allowed us to derive for the first time the luminosity function for the G, K, and M dwarfs of an open cluster without the need to use statistical techniques to account for the presence of upper limits in the data sample. Because of our high X-ray detection frequency down to the faint limit of the optical catalog, we suspect that some of our unidentified X-ray sources are previously unknown, very low-mass members of the Pleiades. A large fraction of the Pleiades members detected with ROSAT have published rotational velocities. Plots of L(sub x)/L(sub bol) versus spectroscopic rotational velocity show tightly correlated 'saturation' type relations for stars with (B - V)(sub O) greater than 0.60. For each of several color ranges, X-ray luminosities rise rapidly with increasing rotation rate until v sin i approximately equals 15 km/s, and then remain essentially flat for rotation rates up to at least v sin i approximately equal to 100 km/s. The dispersion in rotation among low-mass stars in the Pleiades is by far the dominant contributor to the dispersion in L(subx) at a given mass. Only about 35 percent of the B.A. and early F stars in the Pleiades are detected as X-ray sources in our survey. There is no correlation between X-ray flux and rotation for these stars. The X-ray luminosity function for the early-type Pleiades stars appears to be bimodal, with only a few exceptions. We either detect these stars at fluxes in the range found for low-mass stars or we derive X-ray limits below the level found for most Pleiades dwarfs. The X-ray spectra for the early-type Pleiades stars detected by ROSAT are indistinguishable from the spectra of the low-mass Pleiades members. We believe that the simple explanation for this behavior is that the early-type Pleiades stars are not themselves intrinsic X-ray sources and that the X-ray sources and that the X-ray emission actually arises from low-mass companions to these stars.

The mean ultraviolet spectrum of a representative sample of faint z ˜ 3 Lyman alpha emitters

NASA Astrophysics Data System (ADS)

Nakajima, Kimihiko; Fletcher, Thomas; Ellis, Richard S.; Robertson, Brant E.; Iwata, Ikuru

2018-06-01

We discuss the rest-frame ultraviolet (UV) emission line spectra of a large (˜100) sample of low luminosity redshift z ˜ 3.1 Lyman alpha emitters (LAEs) drawn from a Subaru imaging survey in the SSA22 survey field. Our earlier work based on smaller samples indicated that such sources have high [O III]/[O II] line ratios possibly arising from a hard ionizing spectrum that may be typical of similar sources in the reionization era. With optical spectra secured from VLT/VIMOS, we re-examine the nature of the ionizing radiation in a larger sample using the strength of the high ionization diagnostic emission lines of CIII]λ1909, CIVλ1549, HEIIλ1640, and O III]λλ1661, 1666 Å in various stacked subsets. Our analysis confirms earlier suggestions of a correlation between the strength of Ly α and CIII] emission and we find similar trends with broad-band UV luminosity and rest-frame UV colour. Using various diagnostic line ratios and our stellar photoionization models, we determine both the gas phase metallicity and hardness of the ionization spectrum characterized by ξion - the number of Lyman continuum photons per UV luminosity. We confirm our earlier suggestion that ξion is significantly larger for LAEs than for continuum-selected Lyman break galaxies, particularly for those LAEs with the faintest UV luminosities. We briefly discuss the implications for cosmic reionization if the metal-poor intensely star-forming systems studied here are representative examples of those at much higher redshift.

Coronagraphic Imaging with HST and STIS

NASA Technical Reports Server (NTRS)

Grady, C. A.; Proffitt, C.; Malumuth, E.; Woodgate, B. E.; Gull, T. R.; Bowers, C. W.; Heap, S. R.; Kimble, R. A.; Lindler, D.; Plait, P.

2002-01-01

Revealing faint circumstellar nebulosity and faint stellar or substellar companions to bright stars typically requires use of techniques for rejecting the direct, scattered, and diffracted light of the star. One such technique is Lyot coronagraphy. We summarize the performance of the white-light coronagraphic capability of the Space Telescope Imaging spectrograph, on board the Hubble Space Telescope.

An Ultra-faint Galaxy Candidate Discovered in Early Data from the Magellanic Satellites Survey

NASA Astrophysics Data System (ADS)

Drlica-Wagner, A.; Bechtol, K.; Allam, S.; Tucker, D. L.; Gruendl, R. A.; Johnson, M. D.; Walker, A. R.; James, D. J.; Nidever, D. L.; Olsen, K. A. G.; Wechsler, R. H.; Cioni, M. R. L.; Conn, B. C.; Kuehn, K.; Li, T. S.; Mao, Y.-Y.; Martin, N. F.; Neilsen, E.; Noel, N. E. D.; Pieres, A.; Simon, J. D.; Stringfellow, G. S.; van der Marel, R. P.; Yanny, B.

2016-12-01

We report a new ultra-faint stellar system found in Dark Energy Camera data from the first observing run of the Magellanic Satellites Survey (MagLiteS). MagLiteS J0644-5953 (Pictor II or Pic II) is a low surface brightness (μ ={28.5}-1+1 {mag} {arcsec}{}-2 within its half-light radius) resolved overdensity of old and metal-poor stars located at a heliocentric distance of {45}-4+5 {kpc}. The physical size ({r}1/2={46}-11+15 {pc} ) and low luminosity ({M}V=-{3.2}-0.5+0.4 {mag} ) of this satellite are consistent with the locus of spectroscopically confirmed ultra-faint galaxies. MagLiteS J0644-5953 (Pic II) is located {11.3}-0.9+3.1 {kpc} from the Large Magellanic Cloud (LMC), and comparisons with simulation results in the literature suggest that this satellite was likely accreted with the LMC. The close proximity of MagLiteS J0644-5953 (Pic II) to the LMC also makes it the most likely ultra-faint galaxy candidate to still be gravitationally bound to the LMC.

Calibration of HST wide field camera for quantitative analysis of faint galaxy images

NASA Technical Reports Server (NTRS)

Ratnatunga, Kavan U.; Griffiths, Richard E.; Casertano, Stefano; Neuschaefer, Lyman W.; Wyckoff, Eric W.

1994-01-01

We present the methods adopted to optimize the calibration of images obtained with the Hubble Space Telescope (HST) Wide Field Camera (WFC) (1991-1993). Our main goal is to improve quantitative measurement of faint images, with special emphasis on the faint (I approximately 20-24 mag) stars and galaxies observed as a part of the Medium-Deep Survey. Several modifications to the standard calibration procedures have been introduced, including improved bias and dark images, and a new supersky flatfield obtained by combining a large number of relatively object-free Medium-Deep Survey exposures of random fields. The supersky flat has a pixel-to-pixel rms error of about 2.0% in F555W and of 2.4% in F785LP; large-scale variations are smaller than 1% rms. Overall, our modifications improve the quality of faint images with respect to the standard calibration by about a factor of five in photometric accuracy and about 0.3 mag in sensitivity, corresponding to about a factor of two in observing time. The relevant calibration images have been made available to the scientific community.

Galaxy luminosity function: evolution at high redshift

NASA Astrophysics Data System (ADS)

Martinet, N.; Durret, F.; Guennou, L.; Adami, C.

2014-12-01

There are some disagreements about the abundance of faint galaxies in high redshift clusters. DAFT/FADA (Dark energy American French Team) is a medium redshift (0.4

On the faint-end of the high-z galaxy luminosity function

NASA Astrophysics Data System (ADS)

Yue, Bin; Ferrara, Andrea; Xu, Yidong

2016-12-01

Recent measurements of the luminosity function (LF) of galaxies in the Epoch of Reionization (EoR, z ≳ 6) indicate a very steep increase of the number density of low-mass galaxies populating the LF faint-end. However, as star formation in low-mass haloes can be easily depressed or even quenched by ionizing radiation, a turnover is expected at some faint UV magnitudes. Using a physically motivated analytical model, we quantify reionization feedback effects on the LF faint-end shape. We find that if reionization feedback is neglected, the power-law Schechter parametrization characterizing the LF faint-end remains valid up to absolute UV magnitude ˜-9. If instead radiative feedback is strong enough that quenches star formation in haloes with circular velocity smaller than 50 km s-1, the LF starts to drop at absolute UV magnitude ˜-15, I.e. slightly below the detection limits of current (unlensed) surveys at z ˜ 5. The LFs may rise again at higher absolute UV magnitude, where, as a result of interplay between reionization process and galaxy formation, most of the galaxy light is from relic stars formed before the EoR. We suggest that the galaxy number counts data, particularly in lensed fields, can put strong constraints on reionization feedback. In models with stronger reionization feedback, stars in galaxies with absolute UV magnitude higher than ˜-13 and smaller than ˜-8 are typically older. Hence, the stellar age-UV magnitude relation can be used as an alternative feedback probe.

DISCOVERY OF A FAINT QUASAR AT z ∼ 6 AND IMPLICATIONS FOR COSMIC REIONIZATION

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

Kim, Yongjung; Im, Myungshin; Jeon, Yiseul

2015-11-10

Recent studies suggest that faint active galactic nuclei may be responsible for the reionization of the universe. Confirmation of this scenario requires spectroscopic identification of faint quasars (M{sub 1450} > −24 mag) at z ≳ 6, but only a very small number of such quasars have been spectroscopically identified so far. Here, we report the discovery of a faint quasar IMS J220417.92+011144.8 at z ∼ 6 in a 12.5 deg{sup 2} region of the SA22 field of the Infrared Medium-deep Survey (IMS). The spectrum of the quasar shows a sharp break at ∼8443 Å, with emission lines redshifted to zmore » = 5.944 ± 0.002 and rest-frame ultraviolet continuum magnitude M{sub 1450} = −23.59 ± 0.10 AB mag. The discovery of IMS J220417.92+011144.8 is consistent with the expected number of quasars at z ∼ 6 estimated from quasar luminosity functions based on previous observations of spectroscopically identified low-luminosity quasars. This suggests that the number of M{sub 1450} ∼ −23 mag quasars at z ∼ 6 may not be high enough to fully account for the reionization of the universe. In addition, our study demonstrates that faint quasars in the early universe can be identified effectively with a moderately wide and deep near-infrared survey such as the IMS.« less

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

Weisz, Daniel R.; Johnson, Benjamin D.; Conroy, Charlie, E-mail: drw@ucsc.edu

We present a new technique to estimate the evolution of the very faint end of the UV luminosity function (LF) out to z ∼ 5. Measured star formation histories (SFHs) from the fossil record of Local Group (LG) galaxies are used to reconstruct the LF down to M {sub UV} ∼–5 at z ∼ 5 and M {sub UV} ∼–1.5 at z < 1. Such faint limits are well beyond the current observational limits and are likely to remain beyond the limits of next-generation facilities. The reconstructed LFs, when combined with direct measurements of the LFs at higher luminosity, aremore » well-fit by a standard Schechter function with no evidence of a break to the faintest limits probed by this technique. The derived faint-end slope, α, steepens from ≈ – 1.2 at z < 1 to ≈ – 1.6 at 4 < z < 5. We test the effects of burstiness in the SFHs and find the recovered LFs to be only modestly affected. Incompleteness corrections for the faintest LG galaxies and the (unlikely) possibility of significant luminosity-dependent destruction of dwarf galaxies between high redshift and the present epoch are important uncertainties. These and other uncertainties can be mitigated with more detailed modeling and future observations. The reconstructed faint end LF from the fossil record can therefore be a powerful and complementary probe of the high-redshift faint galaxies believed to play a key role in the reionization of the universe.« less

The Faint Optical Afterglow and Host Galaxy of GRB 020124: Implications for the Nature of Dark Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Berger, E.; Kulkarni, S. R.; Bloom, J. S.; Price, P. A.; Fox, D. W.; Frail, D. A.; Axelrod, T. S.; Chevalier, R. A.; Colbert, E.; Costa, E.; Djorgovski, S. G.; Frontera, F.; Galama, T. J.; Halpern, J. P.; Harrison, F. A.; Holtzman, J.; Hurley, K.; Kimble, R. A.; McCarthy, P. J.; Piro, L.; Reichart, D.; Ricker, G. R.; Sari, R.; Schmidt, B. P.; Wheeler, J. C.; Vanderppek, R.; Yost, S. A.

2002-12-01

We present ground-based optical observations of GRB 020124 starting 1.6 hr after the burst, as well as subsequent Very Large Array and Hubble Space Telescope (HST) observations. The optical afterglow of GRB 020124 is one of the faintest afterglows detected to date, and it exhibits a relatively rapid decay, Fν~t-1.60+/-0.04, followed by further steepening. In addition, a weak radio source was found coincident with the optical afterglow. The HST observations reveal that a positionally coincident host galaxy must be the faintest host to date, R>~29.5 mag. The afterglow observations can be explained by several models requiring little or no extinction within the host galaxy, AhostV~0-0.9 mag. These observations have significant implications for the interpretation of the so-called dark bursts (bursts for which no optical afterglow is detected), which are usually attributed to dust extinction within the host galaxy. The faintness and relatively rapid decay of the afterglow of GRB 020124, combined with the low inferred extinction, indicate that some dark bursts are intrinsically dim and not dust obscured. Thus, the diversity in the underlying properties of optical afterglows must be observationally determined before substantive inferences can be drawn from the statistics of dark bursts.

Confirmation and characterization of young planetary companions hidden in the HST NICMOS archive

NASA Astrophysics Data System (ADS)

Pueyo, Laurent

2013-10-01

We propose to conduct WFC3 high contrast observations of six faint planetary candidates orbiting young {1 to 100 Myrs} stars identified in archival HST NICMOS coronagraphic data as part of our team's program AR-12652. Such rare objects are of the utmost importance to comparative exo-planetology as their physical properties reflect the initial conditions of still poorly constrained planetary formation mechanisms. Moreover directly imaged systems are precious artifacts in the expanding exo-planetary treasure trove as they are readily available for spectroscopic characterization. Our statistical analysis, which combines population synthesis models and empirical inspections of the entire NICMOS field of view for all sources observed in coronaraphic mode, almost guarantees that one of these six faint candidates is associated with its putative host star. We will conduct our observation in four near infrared filter, F125W, F160W to establish the baseline luminosity of our candidates and in F127M and F139M in order to probe the depth their water absorption features, characteristic of substellar /exo-planetary like atmospheres. Because of the youth of our targets, this program, which only requires a modest 12 HST orbits, will almost certainly identify and image a young or adolescent exo-planet.

History of Hubble Space Telescope (HST)

NASA Image and Video Library

1993-12-01

Astronaut Hoffman held the Hubble Space Telescope (HST) Wide Field/Planetary Camera-1 (WF/PC1) that was replaced by WF/PC2 in the cargo bay of the Space Shuttle orbiter Endeavour during Extravehicular Activity (EVA). The STS-61 mission was the first of the series of the HST servicing missions. Two months after its deployment in space, scientists detected a 2-micron spherical aberration in the primary mirror of the HST that affected the telescope's ability to focus faint light sources into a precise point. This imperfection was very slight, one-fiftieth of the width of a human hair. During four spacewalks, the STS-61 crew replaced the solar panel with its flexing problems; the WF/PC1 with WF/PC2, with built-in corrective optics; and the High-Speed Photometer with the Corrective Optics Space Telescope Axial Replacement (COSTAR) to correct the aberration for the remaining instruments. The purpose of the HST, the most complex and sensitive optical telescope ever made, is to study the cosmos from a low-Earth orbit for 15 years or more. The HST provides fine detail imaging, produces ultraviolet images and spectra, and detects very faint objects. The Marshall Space Flight Center had responsibility for design, development, and construction of the HST. The Perkin-Elmer Corporation, in Danbury, Cornecticut, developed the optical system and guidance sensors.

Archean Earth Atmosphere Fractal Haze Aggregates: Light Scattering Calculations and the Faint Young Sun Paradox

NASA Astrophysics Data System (ADS)

Boness, D. A.; Terrell-Martinez, B.

2010-12-01

As part of an ongoing undergraduate research project of light scattering calculations involving fractal carbonaceous soot aggregates relevant to current anthropogenic and natural sources in Earth's atmosphere, we have read with interest a recent paper [E.T. Wolf and O.B Toon,Science 328, 1266 (2010)] claiming that the Faint Young Sun paradox discussed four decades ago by Carl Sagan and others can be resolved without invoking heavy CO2 concentrations as a greenhouse gas warming the early Earth enough to sustain liquid water and hence allow the origin of life. Wolf and Toon report that a Titan-like Archean Earth haze, with a fractal haze aggregate nature due to nitrogen-methane photochemistry at high altitudes, should block enough UV light to protect the warming greenhouse gas NH3 while allowing enough visible light to reach the surface of the Earth. To test this hypothesis, we have employed a rigorous T-Matrix arbitrary-particle light scattering technique, to avoid the simplifications inherent in Mie-sphere scattering, on haze fractal aggregates at UV and visible wavelenths of incident light. We generate these model aggregates using diffusion-limited cluster aggregation (DLCA) algorithms, which much more closely fit actual haze fractal aggregates than do diffusion-limited aggregation (DLA) algorithms.

Luminosity Function of Faint Globular Clusters in M87

NASA Astrophysics Data System (ADS)

Waters, Christopher Z.; Zepf, Stephen E.; Lauer, Tod R.; Baltz, Edward A.; Silk, Joseph

2006-10-01

We present the luminosity function to very faint magnitudes for the globular clusters in M87, based on a 30 orbit Hubble Space Telescope (HST) WFPC2 imaging program. The very deep images and corresponding improved false source rejection allow us to probe the mass function further beyond the turnover than has been done before. We compare our luminosity function to those that have been observed in the past, and confirm the similarity of the turnover luminosity between M87 and the Milky Way. We also find with high statistical significance that the M87 luminosity function is broader than that of the Milky Way. We discuss how determining the mass function of the cluster system to low masses can constrain theoretical models of the dynamical evolution of globular cluster systems. Our mass function is consistent with the dependence of mass loss on the initial cluster mass given by classical evaporation, and somewhat inconsistent with newer proposals that have a shallower mass dependence. In addition, the rate of mass loss is consistent with standard evaporation models, and not with the much higher rates proposed by some recent studies of very young cluster systems. We also find that the mass-size relation has very little slope, indicating that there is almost no increase in the size of a cluster with increasing mass.

HIGH-RESOLUTION SPECTROSCOPY OF EXTREMELY METAL-POOR STARS IN THE LEAST EVOLVED GALAXIES: BOÖTES II

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

Ji, Alexander P.; Frebel, Anna; Simon, Joshua D.

2016-01-20

We present high-resolution Magellan/MIKE spectra of the four brightest confirmed red giant stars in the ultra-faint dwarf galaxy Boötes II (Boo II). These stars all inhabit the metal-poor tail of the Boo II metallicity distribution function. The chemical abundance pattern of all detectable elements in these stars is consistent with that of the Galactic halo. However, all four stars have undetectable amounts of neutron-capture elements Sr and Ba, with upper limits comparable to the lowest ever detected in the halo or in other dwarf galaxies. One star exhibits significant radial velocity variations over time, suggesting it to be in a binary system. Itsmore » variable velocity has likely increased past determinations of the Boo II velocity dispersion. Our four stars span a limited metallicity range, but their enhanced α-abundances and low neutron-capture abundances are consistent with the interpretation that Boo II has been enriched by very few generations of stars. The chemical abundance pattern in Boo II confirms the emerging trend that the faintest dwarf galaxies have neutron-capture abundances distinct from the halo, suggesting the dominant source of neutron-capture elements in halo stars may be different than in ultra-faint dwarfs.« less

DEEP ULTRAVIOLET LUMINOSITY FUNCTIONS AT THE INFALL REGION OF THE COMA CLUSTER

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

Hammer, D. M.; Hornschemeier, A. E.; Jenkins, L.

2012-02-01

We have used deep GALEX observations at the infall region of the Coma cluster to measure the faintest ultraviolet (UV) luminosity functions (LFs) presented for a rich galaxy cluster thus far. The Coma UV LFs are measured to M{sub UV} = -10.5 in the GALEX FUV and NUV bands, or 3.5 mag fainter than previous studies, and reach the dwarf early-type galaxy population in Coma for the first time. The Schechter faint-end slopes ({alpha} Almost-Equal-To -1.39 in both GALEX bands) are shallower than reported in previous Coma UV LF studies owing to a flatter LF at faint magnitudes. A Gaussian-plus-Schechtermore » model provides a slightly better parameterization of the UV LFs resulting in a faint-end slope of {alpha} Almost-Equal-To -1.15 in both GALEX bands. The two-component model gives faint-end slopes shallower than {alpha} = -1 (a turnover) for the LFs constructed separately for passive and star-forming galaxies. The UV LFs for star-forming galaxies show a turnover at M{sub UV} Almost-Equal-To -14 owing to a deficit of dwarf star-forming galaxies in Coma with stellar masses below M{sub *} = 10{sup 8} M{sub Sun }. A similar turnover is identified in recent UV LFs measured for the Virgo cluster suggesting this may be a common feature of local galaxy clusters, whereas the field UV LFs continue to rise at faint magnitudes. We did not identify an excess of passive galaxies as would be expected if the missing dwarf star-forming galaxies were quenched inside the cluster. In fact, the LFs for both dwarf passive and star-forming galaxies show the same turnover at faint magnitudes. We discuss the possible origin of the missing dwarf star-forming galaxies in Coma and their expected properties based on comparisons to local field galaxies.« less

Deep UV Luminosity Functions at the Infall Region of the Coma Cluster

NASA Technical Reports Server (NTRS)

Hammer, D. M.; Hornschemeier, A. E.; Salim, S.; Smith, R.; Jenkins, L.; Mobasher, B.; Miller, N.; Ferguson, H.

2011-01-01

We have used deep GALEX observations at the infall region of the Coma cluster to measure the faintest UV luminosity functions (LFs) presented for a rich galaxy cluster thus far. The Coma UV LFs are measured to M(sub uv) = -10.5 in the GALEX FUV and NUV bands, or 3.5 mag fainter than previous studies, and reach the dwarf early-type galaxy population in Coma for the first time. The Schechter faint-end slopes (alpha approximately equal to -1.39 in both GALEX bands) are shallower than reported in previous Coma UV LF studies owing to a flatter LF at faint magnitudes. A Gaussian-plus-Schechter model provides a slightly better parametrization of the UV LFs resulting in a faint-end slope of alpha approximately equal to -1.15 in both GALEX bands. The two-component model gives faint-end slopes shallower than alpha = -1 (a turnover) for the LFs constructed separately for passive and star forming galaxies. The UV LFs for star forming galaxies show a turnover at M(sub UV) approximately equal to -14 owing to a deficit of dwarf star forming galaxies in Coma with stellar masses below M(sub *) = 10(sup 8) solar mass. A similar turnover is identified in recent UV LFs measured for the Virgo cluster suggesting this may be a common feature of local galaxy clusters, whereas the field UV LFs continue to rise at faint magnitudes. We did not identify an excess of passive galaxies as would be expected if the missing dwarf star forming galaxies were quenched inside the cluster. In fact, the LFs for both dwarf passive and star forming galaxies show the same turnover at faint magnitudes. We discuss the possible origin of the missing dwarf star forming galaxies in Coma and their expected properties based on comparisons to local field galaxies.

A Multi-Frequency Study of the Milky Way-Like Spiral Galaxy NGC 6744

NASA Astrophysics Data System (ADS)

Yew, Miranda; Filipović, Miroslav D.; Roper, Quentin; Collier, Jordan D.; Crawford, Evan J.; Jarrett, Thomas H.; Tothill, Nicholas F. H.; O'Brien, Andrew N.; Pavlović, Marko Z.; Pannuti, Thomas G.; Galvin, Timothy J.; Kapińska, Anna D.; Cluver, Michelle E.; Banfield, Julie K.; Schlegel, Eric M.; Maxted, Nigel; Grieve, Kevin R.

2018-03-01

We present a multi-frequency study of the intermediate spiral SAB(r)bc type galaxy NGC 6744, using available data from the Chandra X-Ray telescope, radio continuum data from the Australia Telescope Compact Array and Murchison Widefield Array, and Wide-field Infrared Survey Explorer infrared observations. We identify 117 X-ray sources and 280 radio sources. Of these, we find nine sources in common between the X-ray and radio catalogues, one of which is a faint central black hole with a bolometric radio luminosity similar to the Milky Way's central black hole. We classify 5 objects as supernova remnant (SNR) candidates, 2 objects as likely SNRs, 17 as H ii regions, 1 source as an AGN; the remaining 255 radio sources are categorised as background objects and one X-ray source is classified as a foreground star. We find the star-formation rate (SFR) of NGC 6744 to be in the range 2.8-4.7 M⊙ yr - 1 signifying the galaxy is still actively forming stars. The specific SFR of NGC 6744 is greater than that of late-type spirals such as the Milky Way, but considerably less that that of a typical starburst galaxy.

Star formation rate and extinction in faint z ∼ 4 Lyman break galaxies

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

To, Chun-Hao; Wang, Wei-Hao; Owen, Frazer N.

We present a statistical detection of 1.5 GHz radio continuum emission from a sample of faint z ∼ 4 Lyman break galaxies (LBGs). To constrain their extinction and intrinsic star formation rate (SFR), we combine the latest ultradeep Very Large Array 1.5 GHz radio image and the Hubble Space Telescope Advanced Camera for Surveys (ACS) optical images in the GOODS-N. We select a large sample of 1771 z ∼ 4 LBGs from the ACS catalog using B {sub F435W}-dropout color criteria. Our LBG samples have I {sub F775W} ∼ 25-28 (AB), ∼0-3 mag fainter than M{sub UV}{sup ⋆} at zmore » ∼ 4. In our stacked radio images, we find the LBGs to be point-like under our 2'' angular resolution. We measure their mean 1.5 GHz flux by stacking the measurements on the individual objects. We achieve a statistical detection of S {sub 1.5} {sub GHz} = 0.210 ± 0.075 μJy at ∼3σ for the first time on such a faint LBG population at z ∼ 4. The measurement takes into account the effects of source size and blending of multiple objects. The detection is visually confirmed by stacking the radio images of the LBGs, and the uncertainty is quantified with Monte Carlo simulations on the radio image. The stacked radio flux corresponds to an obscured SFR of 16.0 ± 5.7 M {sub ☉} yr{sup –1}, and implies a rest-frame UV extinction correction factor of 3.8. This extinction correction is in excellent agreement with that derived from the observed UV continuum spectral slope, using the local calibration of Meurer et al. This result supports the use of the local calibration on high-redshift LBGs to derive the extinction correction and SFR, and also disfavors a steep reddening curve such as that of the Small Magellanic Cloud.« less

Io Eclipse Montage

NASA Technical Reports Server (NTRS)

2007-01-01

New Horizons took this montage of images of Jupiter's volcanic moon Io, glowing in the dark of Jupiter's shadow, as the Pluto-bound spacecraft sped through the Jupiter system on Feb. 27, 2007.

(A): In this picture from the Long-Range Reconnaissance Imager (LORRI), dark blotches and straight lines are artifacts. The brightest spots (including the volcanoes Pele [P] and East Girru [EG]) are incandescent lava from active volcanoes. The more diffuse glows, and the many faint spots, are from gas in the plumes and atmosphere, glowing due to bombardment by plasma in Jupiter's magnetosphere, in a display similar to the Earth's aurorae. (B): The same image with a latitude/longitude grid, showing that the cluster of faint spots is centered near longitude 0 degrees, the point on Io that faces Jupiter. The image also shows the locations of the plumes seen in sunlit images (indicated by red diamonds), which glow with auroral emission in eclipse. (C): Simulated sunlit view of Io with the same geometry, based on sunlit LORRI images. (D): A combination of the sunlit image (in cyan) and the eclipse image (in red), showing that all point-like glows in the eclipse image arise from dark volcanoes in the eclipse image. (E): This infrared image, at a wavelength of 2.3 microns, obtained by New Horizons Linear Etalon Spectral Imaging Array (LEISA) an hour after the LORRI image, showing thermal emission from active volcanoes. Elongation of the hot spots is an artifact. (F): Combined visible albedo (cyan) and LEISA thermal emission (red) image, showing the sources of the volcanic emission. That most of the faint point-like glows near longitude zero, seen in visible light in images A, B, and D, do not appear in the infrared view of volcanic heat radiation, is one reason scientists believe that these glows are due to auroral emission, not heat radiation.

This image appears in the Oct. 12, 2007, issue of Science magazine, in a paper by John Spencer, et al.

Precise γ-ray timing and radio observations of 17 FERMI γ-ray pulsars

DOE PAGES

Ray, Paul S.; Kerr, M.; Parent, D.; ...

2011-04-29

Here, we present precise phase-connected pulse timing solutions for 16 γ-ray-selected pulsars recently discovered using the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope plus one very faint radio pulsar (PSR J1124–5916) that is more effectively timed with the LAT. We describe the analysis techniques including a maximum likelihood method for determining pulse times of arrival from unbinned photon data. A major result of this work is improved position determinations, which are crucial for multiwavelength follow-up. For most of the pulsars, we overlay the timing localizations on X-ray images from Swift and describe the status of X-ray counterpartmore » associations. We report glitches measured in PSRs J0007+7303, J1124–5916, and J1813–1246. We analyze a new 20 ks Chandra ACIS observation of PSR J0633+0632 that reveals an arcminute-scale X-ray nebula extending to the south of the pulsar. We were also able to precisely localize the X-ray point source counterpart to the pulsar and find a spectrum that can be described by an absorbed blackbody or neutron star atmosphere with a hard power-law component. Another Chandra ACIS image of PSR J1732–3131 reveals a faint X-ray point source at a location consistent with the timing position of the pulsar. Finally, we present a compilation of new and archival searches for radio pulsations from each of the γ-ray-selected pulsars as well as a new Parkes radio observation of PSR J1124–5916 to establish the γ-ray to radio phase offset.« less

Impact Delivery of Reduced Greenhouse Gases on Early MARS

NASA Technical Reports Server (NTRS)

Haberle, R. M.; Zahnle, K.

2017-01-01

While there is abundant evidence for flowing liquid water on the ancient Martian surface, a widely accepted greenhouse mechanism for explaining this in the presence of a faint young sun has yet to emerge. Gases such as NH3, CO2 alone, SO2, clouds, and CH4, have sustainability issues or limited greenhouse power. Recently, Ramirez et al. proposed that CO2-H2 atmospheres, through collision induced absorptions (CIA), could solve the problem if large amounts are present (1.3-4 bars of CO2, 50-20% H2). However, they had to estimate the strength of the H2- CO2 interaction from the measured strength of the H2- N2 interaction. Recent ab initio calculations show that the strength of CO2-H2 CIA is greater than Ramirez et al. assumed. Wordsworth et al. also calculated the absorption coefficients for CO2-CH4 CIA and show that on early Mars a 0.5 bar CO2 atmosphere with percent levels of H2 or CH4 can raise mean annual temperatures by tens of degrees Kelvin. Freezing temperatures can be reached in atmospheres containing 1-2 bars of CO2 and 2-10% H2 and CH4. The new work demonstrates that less CO2 and reduced gases are needed than Ramirez et al. originally proposed, which improves prospects for their hypothesis. If thick weakly reducing atmospheres are the solution to the faint young sun paradox, then plausible mechanisms must be found to generate and sustain the required concentrations of H2 and CH4. Possible sources of reducing gases include volcanic outgassing, serpentinization, and impact delivery; sinks include photolysis, oxidation, and hydrogen escape. The viability of the reduced greenhouse hypothesis depends, therefore, on the strength of these sources and sinks.

The ISO-IRAS Faint Galaxy Survey

NASA Technical Reports Server (NTRS)

Smith, Harding E.

1999-01-01

As part of the ISO-IRAS Faint Galaxy Survey ISO Satellite observations of over 600 IRAS sources have been obtained with the ISOCAM instrument. Because our survey strategy involved relatively short integrations, great care was required in developing analysis software including cosmic-ray and transient removal and calibration. These observations have now been through final pipeline processing at IPAC and ground-based follow-up is ongoing. The observations are for sources from two samples: a " Filler' sample selected to be at z greater than 0.1 and a fainter sample which selected for the highest redshift galaxies in the IRAS survey, with redshifts 0.2 less than z less than 1.0. I now have obtained ground-based follow-up spectrophotometry at Lick and Palomar observatories for 100 LFIRGs with 0.1 less than z less than 0.7. Our observations have confirmed that these systems are comparable to nearby LFIRGs such as Arp 220, with L (sub -)(fir) greater than 10(exp 11) L(sub -) sun and typically HII/Liner optical excitation. About 10% of the galaxies show true AGN (Sy2) excitation. Based on our work on a nearby complete sample of LFIRGS, we believe that the majority of these systems are luminous Starbursts, thus this project is tracing the luminous end of the galaxy star-forming luminosity function - the (infrared) star-formation history of the Universe to z approx. 1, a topic of some considerable recent interest. A by-product of these ISOCAM observations is approximately 1 square degree of deep 2 microns pointings outside the IRAS error boxes, allowing us an independent estimate of the mid-infrared log N - log S relation. Ground-based observations of this sample are continuing.

Improving the Multi-Wavelength Capability of Chandra Large Programs

NASA Astrophysics Data System (ADS)

Pacucci, Fabio

2017-09-01

In order to fully exploit the joint Chandra/JWST/HST ventures to detect faint sources, we urgently need an advanced matching algorithm between optical/NIR and X-ray catalogs/images. This will be of paramount importance in bridging the gap between upcoming optical/NIR facilities (JWST) and later X-ray ones (Athena, Lynx). We propose to develop an advanced and automated tool to improve the identification of Chandra X-ray counterparts detected in deep optical/NIR fields based on T-PHOT, a software widely used in the community. The developed code will include more than 20 years in advancements of X-ray data analysis and will be released to the public. Finally, we will release an updated catalog of X-ray sources in the CANDELS regions: a leap forward in our endeavor of charting the Universe.

The Science and Design of the AGIS Observatory

NASA Astrophysics Data System (ADS)

Schroedter, Martin

2010-02-01

The AGIS observatory is a next-generation array of imaging atmospheric Cherenkov telescopes (IACTs) for gamma-ray astronomy between 100 GeV and 100 TeV. The AGIS observatory is the next logical step in high energy gamma-ray astronomy, offering improved angular resolution and sensitivity compared to FERMI, and overlapping the high energy end of FERMI's sensitivity band. The baseline AGIS observatory will employ an array of 36 Schwarzschild-Couder IACTs in combination with a highly pixelated (0.05^o diameter) camera. The instrument is designed to provide millicrab sensitivity over a wide (8^o diameter) field of view, allowing both deep studies of faint point sources as well as efficient mapping of the Galactic plane and extended sources. I will describe science drivers behind the AGIS observatory and the design and status of the project. )

The Science and Design of the AGIS Observatory

NASA Astrophysics Data System (ADS)

Falcone, Abraham; Aliu, E.; Arlen, T.; Benbow, W.; Buckley, J.; Bugaev, S.; Byrum, K.; Ciupik, L.; Coppi, P.; Digel, S.; Drake, G.; Finley, J.; Fortson, L.; Franco, J.; Funk, S.; Guarino, V.; Gyuk, G.; Hanna, D.; Hiriart, D.; Humensky, B.; Holder, J.; Kaaret, P.; Karlsson, N.; Kieda, D.; Konopelko, A.; Krawczynski, H.; Krennrich, F.; LeBohec, S.; Maier, G.; Mukherjee, R.; Ong, R.; Otte, N.; Pareschi, G.; Pohl, M.; Quinn, J.; Ramsey, B.; Romani, R.; Rovero, A. C.; Schroedter, M.; Sinnis, C.; Slane, P.; Smith, A.; Swordy, S.; Tajima, H.; Vassiliev, V.; Wagner, R.; Wakely, S. P.; Weekes, T. C.; Weinstein, A.; Williams, D.

2010-01-01

The AGIS observatory is a next-generation array of imaging atmospheric Cherenkov telescopes (IACTs) for gamma-ray astronomy between 100GeV and 100 TeV. The AGIS observatory is the next logical step in high energy gamma-ray astronomy, offering improved angular resolution and sensitivity compared to FERMI, and overlapping the high energy end of FERMI's sensitivity band. The baseline AGIS observatory will employ an array of 36 Schwarzschild-Couder IACTs in combination with a highly pixelated (0.05 degree/pixel) camera. The instrument is designed to provide millicrab sensitivity over a wide (8 degree diameter) field of view, allowing both deep studies of faint point sources as well as efficient mapping of the Galactic plane and extended sources. This presentation will include a description of science drivers behind the AGIS observatory and the design and status of the project.

Investigating Galactic Structure with COBE/DIRBE and Simulation

NASA Technical Reports Server (NTRS)

Cohen, Martin

1999-01-01

In this work I applied the current version of the SKY model of the point source sky to the interpretation of the diffuse all-sky emission observed by COBE/DIRBE (Cosmic Background Explorer Satellite/Diffuse Infrared Background Experiment). The goal was to refine the SKY model using the all-sky DIRBE maps of the Galaxy, in order that a search could be made for an isotropic cosmic background."Faint Source Model" [FSM] was constructed to remove Galactic fore ground stars from the ZSMA products. The FSM mimics SKY version 1 but it was inadequate to seek cosmic background emission because of the sizeable residual emission in the ZSMA products after this starlight subtraction. At this point I can only support that such models are currently inadequate to reveal a cosmic background. Even SKY5 yields the same disappointing result.

Enormous disc of cool gas surrounding the nearby powerful radio galaxy NGC612 (PKS0131-36)

NASA Astrophysics Data System (ADS)

Emonts, B. H. C.; Morganti, R.; Oosterloo, T. A.; Holt, J.; Tadhunter, C. N.; van der Hulst, J. M.; Ojha, R.; Sadler, E. M.

2008-06-01

We present the detection of an enormous disc of cool neutral hydrogen (HI) gas surrounding the S0 galaxy NGC612, which hosts one of the nearest powerful radio sources (PKS0131-36). Using the Australia Telescope Compact Array, we detect MHI = 1.8 × 109Msolar of HI emission-line gas that is distributed in a 140-kpc wide disc-like structure along the optical disc and dust lane of NGC612. The bulk of the gas in the disc appears to be settled in regular rotation with a total velocity range of 850kms-1, although asymmetries in this disc indicate that perturbations are being exerted on part of the gas, possibly by a number of nearby companions. The HI disc in NGC612 suggests that the total mass enclosed by the system is Menc ~ 2.9 × 1012 sin-2 iMsolar, implying that this early-type galaxy contains a massive dark matter halo. We also discuss an earlier study by Holt et al. that revealed the presence of a prominent young stellar population at various locations throughout the disc of NGC612, indicating that this is a rare example of an extended radio source that is hosted by a galaxy with a large-scale star-forming disc. In addition, we map a faint HI bridge along a distance of 400kpc in between NGC612 and the gas-rich (MHI = 8.9 × 109Msolar) barred galaxy NGC619, indicating that likely an interaction between both systems occurred. From the unusual amounts of HI gas and young stars in this early-type galaxy, in combination with the detection of a faint optical shell and the system's high infrared luminosity, we argue that either ongoing or past galaxy interactions or a major merger event are a likely mechanism for the triggering of the radio source in NGC612. This paper is part of an ongoing study to map the large-scale neutral hydrogen properties of nearby radio galaxies and it presents the first example of large-scale HI detected around a powerful Fanaroff-Riley type II (FR-II) radio galaxy. The HI properties of the FR-II radio galaxy NGC612 are very similar to those found for low-power compact radio sources, but different from those of extended Fanaroff-Riley type I (FR-I) sources.

PSR J1907+0602: A radio-faint gamma-ray pulsar powering a bright TeV pulsar wind nebula

DOE PAGES

Abdo, A. A.

2010-02-06

Here, we present multiwavelength studies of the 106.6 ms γ-ray pulsar PSR J1907+06 near the TeV source MGRO J1908+06. Timing observations with Fermi result in a precise position determination for the pulsar of R.A. = 19 h07 m54more » $$s\\atop{.}$$7(2), decl. = +06°02'16(2)'' placing the pulsar firmly within the TeV source extent, suggesting the TeV source is the pulsar wind nebula of PSR J1907+0602. Pulsed γ-ray emission is clearly visible at energies from 100 MeV to above 10 GeV. The phase-averaged power-law index in the energy range E > 0.1 GeV is Γ = 1.76 ± 0.05 with an exponential cutoff energy E c = 3.6 ± 0.5 GeV. We present the energy-dependent γ-ray pulsed light curve as well as limits on off-pulse emission associated with the TeV source. We also report the detection of very faint (flux density of sime 3.4 μJy) radio pulsations with the Arecibo telescope at 1.5 GHz having a dispersion measure DM = 82.1 ± 1.1 cm –3 pc. This indicates a distance of 3.2 ± 0.6 kpc and a pseudo-luminosity of L 1400 sime 0.035 mJy kpc 2. Furthermore, a Chandra ACIS observation revealed an absorbed, possibly extended, compact (lesssim4'') X-ray source with significant nonthermal emission at R.A. = 19 h07 m54$$s\\atop{.}$$76, decl. = +06°02'14farcs6 with a flux of 2.3 +0.6 –1.4 × 10 –14 erg cm –2 s –1. From archival ASCA observations, we place upper limits on any arcminute scale 2-10 keV X-ray emission of ~1 × 10 –13 erg cm –2 s –1. The implied distance to the pulsar is compatible with that of the supernova remnant G40.5 – 0.5, located on the far side of the TeV nebula from PSR J1907+0602, and the S74 molecular cloud on the nearer side which we discuss as potential birth sites.« less

PSR J1907+0602: A RADIO-FAINT GAMMA-RAY PULSAR POWERING A BRIGHT TeV PULSAR WIND NEBULA

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

Abdo, A. A.; Ackermann, M.; Ajello, M.

2010-03-01

We present multiwavelength studies of the 106.6 ms gamma-ray pulsar PSR J1907+06 near the TeV source MGRO J1908+06. Timing observations with Fermi result in a precise position determination for the pulsar of R.A. = 19{sup h}07{sup m}54.{sup s}7(2), decl. = +06{sup 0}02'16(2)'' placing the pulsar firmly within the TeV source extent, suggesting the TeV source is the pulsar wind nebula of PSR J1907+0602. Pulsed gamma-ray emission is clearly visible at energies from 100 MeV to above 10 GeV. The phase-averaged power-law index in the energy range E > 0.1 GeV is GAMMA = 1.76 +- 0.05 with an exponential cutoffmore » energy E{sub c} = 3.6 +- 0.5 GeV. We present the energy-dependent gamma-ray pulsed light curve as well as limits on off-pulse emission associated with the TeV source. We also report the detection of very faint (flux density of {approx_equal} 3.4 {mu}Jy) radio pulsations with the Arecibo telescope at 1.5 GHz having a dispersion measure DM = 82.1 +- 1.1 cm{sup -3} pc. This indicates a distance of 3.2 +- 0.6 kpc and a pseudo-luminosity of L{sub 1400} {approx_equal} = 0.035 mJy kpc{sup 2}. A Chandra ACIS observation revealed an absorbed, possibly extended, compact ({approx}<4'') X-ray source with significant nonthermal emission at R.A. = 19{sup h}07{sup m}54.{sup s}76, decl. = +06{sup 0}02'14.''6 with a flux of 2.3{sup +0.6}{sub -1.4} x 10{sup -14} erg cm{sup -2} s{sup -1}. From archival ASCA observations, we place upper limits on any arcminute scale 2-10 keV X-ray emission of {approx}1 x 10{sup -13} erg cm{sup -2} s{sup -1}. The implied distance to the pulsar is compatible with that of the supernova remnant G40.5 - 0.5, located on the far side of the TeV nebula from PSR J1907+0602, and the S74 molecular cloud on the nearer side which we discuss as potential birth sites.« less

The Bologna complete sample of nearby radio sources. II. Phase referenced observations of faint nuclear sources

NASA Astrophysics Data System (ADS)

Liuzzo, E.; Giovannini, G.; Giroletti, M.; Taylor, G. B.

2009-10-01

Aims: To study statistical properties of different classes of sources, it is necessary to observe a sample that is free of selection effects. To do this, we initiated a project to observe a complete sample of radio galaxies selected from the B2 Catalogue of Radio Sources and the Third Cambridge Revised Catalogue (3CR), with no selection constraint on the nuclear properties. We named this sample “the Bologna Complete Sample” (BCS). Methods: We present new VLBI observations at 5 and 1.6 GHz for 33 sources drawn from a sample not biased toward orientation. By combining these data with those in the literature, information on the parsec-scale morphology is available for a total of 76 of 94 radio sources with a range in radio power and kiloparsec-scale morphologies. Results: The fraction of two-sided sources at milliarcsecond resolution is high (30%), compared to the fraction found in VLBI surveys selected at centimeter wavelengths, as expected from the predictions of unified models. The parsec-scale jets are generally found to be straight and to line up with the kiloparsec-scale jets. A few peculiar sources are discussed in detail. Tables 1-4 are only available in electronic form at http://www.aanda.org

Deep CCD Photometry of the Rich Galaxy Cluster Abel 1656 Characteristics of the Dwarf Elliptical Galaxy Population in the Cluster Core

NASA Astrophysics Data System (ADS)

Secker, Jeffrey Alan

1995-01-01

We have developed a statistically rigorous and automated method to implement the detection, photometry and classification of faint objects on digital images. We use these methods to analyze deep R- and B-band CCD images of the central ~ 700 arcmin ^2 of the Coma cluster core, and an associated control field. We have detected and measured total R magnitudes and (B-R) colors for a sample of 3741 objects on the galaxy cluster fields, and 1164 objects on a remote control field, complete to a limiting magnitude of R = 22.5 mag. The typical uncertainties are +/- 0.06 and +/-0.12 mag in total magnitude and color respectively. The dwarf elliptical (dE) galaxies are confined to a well-defined sequence in the color range given by 0.7<= (B-R)<= 1.9 mag: within this interval there are 2535 dE candidates on our fields in the cluster core, and 694 objects on the control field. With an image scale of 0.53 arcsec/pixel and seeing near 1.2 arcsec, a large fraction of the dE galaxy candidates are resolved. We find a significant metallicity gradient in the radial distribution of the dwarf elliptical galaxies, which goes as Z~ R^{-0.32 } outwards from the cluster center at NGC 4874. As well, there is a strong color-luminosity correlation, in the sense that more luminous dE galaxies are redder in the mean. These effects give rise to a radial variation in the cluster luminosity function. The spatial distribution of the faint dE galaxies is well fit by a standard King model with a central surface density of Sigma _0 = 1.44 dEs arcmin^{ -2}, a core radius R_{ rm c} = 18.7 arcmin (~eq 0.44 Mpc), and a tidal radius of 1.44 deg ( ~eq 2.05 Mpc). This core is significantly larger than R_{rm c} = 12.3 arcmin (~eq 0.29 Mpc) found for the bright cluster galaxies. The composite luminosity function for Coma galaxies is modeled as the sum of a log -normal distribution for the giant galaxies and a Schechter function for the dwarf elliptical galaxies, with a faint -end slope of alpha = -1.41, consistent with known faint-end slopes for the Virgo and Fornax clusters. The early-type dwarf-to-giant ratio for the Coma cluster core is consistent with that of the Virgo cluster, and thus with the rich Coma cluster being formed as the merger of multiple less-rich galaxy clusters.

Stability of sonic boom metrics regarding signature distortions from atmospheric turbulence.

PubMed

Doebler, William J; Sparrow, Victor W

2017-06-01

The degree of insensitivity to atmospheric turbulence was evaluated for five metrics (A-, B-, E-weighted sound exposure level, Stevens Mark VII Perceived Level, and NASA's Indoor Sonic Boom Annoyance Predictor) that correlate to human annoyance from sonic booms. Eight N-wave shaped sonic booms from NASA's FaINT experiment and five simulated "low-boom" sonic booms were turbulized by Locey's ten atmospheric filter functions. The B-weighted sound exposure level value changed the least due to the turbulence filters for twelve of thirteen booms. This makes it the most turbulence stable metric which may be useful for quiet supersonic aircraft certification.

Rats Can Acquire Conditional Fear of Faint Light Leaking through the Acrylic Resin Used to Mount Fiber Optic Cannulas

ERIC Educational Resources Information Center

Eckmier, Adam; de Marcillac, Willy Daney; Maître, Agnès; Jay, Thérèse M.; Sanders, Matthew J.; Godsil, Bill P.

2016-01-01

Rodents are exquisitely sensitive to light and optogenetic behavioral experiments routinely introduce light-delivery materials into experimental situations, which raises the possibility that light could leak and influence behavioral performance. We examined whether rats respond to a faint diffusion of light, termed caplight, which emanated through…

Galaxy evolution and large-scale structure in the far-infrared. I - IRAS pointed observations

NASA Astrophysics Data System (ADS)

Lonsdale, Carol J.; Hacking, Perry B.

1989-04-01

Redshifts for 66 galaxies were obtained from a sample of 93 60-micron sources detected serendipitously in 22 IRAS deep pointed observations, covering a total area of 18.4 sq deg. The flux density limit of this survey is 150 mJy, 4 times fainter than the IRAS Point Source Catalog (PSC). The luminosity function is similar in shape with those previously published for samples selected from the PSC, with a median redshift of 0.048 for the fainter sample, but shifted to higher space densities. There is evidence that some of the excess number counts in the deeper sample can be explained in terms of a large-scale density enhancement beyond the Pavo-Indus supercluster. In addition, the faintest counts in the new sample confirm the result of Hacking et al. (1989) that faint IRAS 60-micron source counts lie significantly in excess of an extrapolation of the PSC counts assuming no luminosity or density evolution.

Proposed US Contributions to LOFT

NASA Technical Reports Server (NTRS)

Wilson-Hodge, Colleen

2013-01-01

Proposed US Enhancements include:Tantalum X -ray collimator, Additional ground station, Large Observatory for X-Ray Timing (LOFT) instrument team participation, US science support center & data archive, and Science enabled by US hardware. High-Z material with excellent stopping power. Fabricated using a combination of laser micromachining and chemical etching. Known technology capable of producing high-aspect ratio holes and large open fractions. Reduces LOFT LAD background by a factor of 3. Telemetry formats for LOFT based upon RXTE/EDS experience. Ground system software and strategies for WFM based upon RXTE/ASM automated pipeline software. MSFC engineering trade studies supporting the Ta collimator. Burst alert triggers based upon Fermi/GBM and HETE-2. Science Enhancements Enabled by US Hardware include: Tantalum collimator: Reduces background by factor of 3. Improves sensitivity to faint sources such as AGN. Eliminates contamination by bright/variable sources. outside the LAD field of view. US Ground Station: Enables continuous telemetry of all events from the WFM. Allows LAD to observe very bright >500 mCrab sources with full event resolution.

Galaxy evolution and large-scale structure in the far-infrared. I. IRAS pointed observations

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

Lonsdale, C.J.; Hacking, P.B.

1989-04-01

Redshifts for 66 galaxies were obtained from a sample of 93 60-micron sources detected serendipitously in 22 IRAS deep pointed observations, covering a total area of 18.4 sq deg. The flux density limit of this survey is 150 mJy, 4 times fainter than the IRAS Point Source Catalog (PSC). The luminosity function is similar in shape with those previously published for samples selected from the PSC, with a median redshift of 0.048 for the fainter sample, but shifted to higher space densities. There is evidence that some of the excess number counts in the deeper sample can be explained inmore » terms of a large-scale density enhancement beyond the Pavo-Indus supercluster. In addition, the faintest counts in the new sample confirm the result of Hacking et al. (1989) that faint IRAS 60-micron source counts lie significantly in excess of an extrapolation of the PSC counts assuming no luminosity or density evolution. 81 refs.« less

Galaxy evolution and large-scale structure in the far-infrared. I - IRAS pointed observations

NASA Technical Reports Server (NTRS)

Lonsdale, Carol J.; Hacking, Perry B.

1989-01-01

Redshifts for 66 galaxies were obtained from a sample of 93 60-micron sources detected serendipitously in 22 IRAS deep pointed observations, covering a total area of 18.4 sq deg. The flux density limit of this survey is 150 mJy, 4 times fainter than the IRAS Point Source Catalog (PSC). The luminosity function is similar in shape with those previously published for samples selected from the PSC, with a median redshift of 0.048 for the fainter sample, but shifted to higher space densities. There is evidence that some of the excess number counts in the deeper sample can be explained in terms of a large-scale density enhancement beyond the Pavo-Indus supercluster. In addition, the faintest counts in the new sample confirm the result of Hacking et al. (1989) that faint IRAS 60-micron source counts lie significantly in excess of an extrapolation of the PSC counts assuming no luminosity or density evolution.

Development of latent fingerprints on thermal paper by the controlled application of heat.

PubMed

Bond, John W

2013-05-01

Apparatus to produce a spatially and temporally uniform heat source is described and this is used to visualize latent fingerprints deposited onto thermal paper by raising the temperature of the paper. Results show an improvement over previous research when fingerprint deposits are aged or the developed fingerprints faint; visualization being enhanced by the use of a blue LED light source of 465 nm peak wavelength. An investigation of the components in fingerprint sweat likely to affect the solubility and hence color change of the dye present in the thermal paper has shown that polar protic solvents able to donate a proton are favored and a polar amino acid found commonly in eccrine fingerprint sweat (lysine) has been shown able to produce the desired color change. Aged fingerprint deposits on thermal paper from a variety of sources up to 4 years old have been visualized with this technique. © 2013 American Academy of Forensic Sciences.

SXDF-UDS-CANDELS-ALMA 1.5 arcmin2 deep survey

NASA Astrophysics Data System (ADS)

Kohno, Kotaro; Tamura, Yoichi; Yamaguchi, Yuki; Umehata, Hideki; Rujopakarn, Wiphu; Lee, Minju; Motohara, Kentaro; Makiya, Ryu; Izumi, Takuma; Ivison, Rob; Ikarashi, Soh; Tadaki, Ken-ichi; Kodama, Tadayuki; Hatsukade, Bunyo; Yabe, Kiyoto; Hayashi, Masao; Iono, Daisuke; Matsuda, Yuichi; Nakanishi, Kouichiro; Kawabe, Ryohei; Wilson, Grant; Yun, Min S.; Hughes, David; Caputi, Karina; Dunlop, James

2015-08-01

We have conducted 1.1 mm ALMA observations of a contiguous 105″ × 50″ or 1.5 arcmin2 window (achieved by 19 point mosaic) in the SXDF-UDS-CANDELS. We achieved a 5σ sensitivity of 0.28 mJy, giving a flat sensus of dusty star-forming galaxies with LIR ~6 × 1011 L⊙ (if Tdust = 40 K) or SFR ~100 M⊙ yr-1 up to z~10 thanks to the negative K-correction at this wavelength. We detect 5 brightest sources (S/N>6) and 18 low-significant sources (5 > S/N > 4; they may contain spurious detections, though) in the field. We find that these discrete sources are responsible for a faint filamentary emission seen in low-resolution (~30″) heavily confused AzTEC 1.1mm and SPIRE 0.5mm images. One of the 5 brightest ALMA sources is very dark in deep WFC3 and HAWK-I NIR images as well as VLA 1.4 GHz images, demonstrating that deep ALMA imaging can unveil new obscured star-forming galaxy population.

M31 in the Chandra Era: A High Definition Movie of a Nearby Galaxy

NASA Astrophysics Data System (ADS)

Kong, Albert; di Stefano, Rosanne

2009-09-01

M31 has been a prime targets for all X-ray missions since the first detection in 1974. With its superb spatial resolution, Chandra is unique in resolving dense source regions and detecting faint sources. Since the launch of Chandra, M31 has been regularly observed. It is perhaps the only nearby galaxy which is observed by an X-ray telescope regularly throughout operation. With 10 years of observations, the center of M31 has been observed with Chandra for nearly 1 Msec. The X-ray skies of M31 not only consist of many transients and variables, globular cluster X-ray sources in M31 are also different from our Milky Way. They are in general more luminous and one of them may even host an intermediate-mass black hole. Supersoft and quasi-soft X-ray sources in M31 are the best kept secret to unlock the nature of the progenitor of Type Ia supernova. In this talk, I will review some of the important Chandra discoveries in M31 in the past 10 years.

Isolating relativistic effects in large-scale structure

NASA Astrophysics Data System (ADS)

Bonvin, Camille

2014-12-01

We present a fully relativistic calculation of the observed galaxy number counts in the linear regime. We show that besides the density fluctuations and redshift-space distortions, various relativistic effects contribute to observations at large scales. These effects all have the same physical origin: they result from the fact that our coordinate system, namely the galaxy redshift and the incoming photons’ direction, is distorted by inhomogeneities in our Universe. We then discuss the impact of the relativistic effects on the angular power spectrum and on the two-point correlation function in configuration space. We show that the latter is very well adapted to isolate the relativistic effects since it naturally makes use of the symmetries of the different contributions. In particular, we discuss how the Doppler effect and the gravitational redshift distortions can be isolated by looking for a dipole in the cross-correlation function between a bright and a faint population of galaxies.

The relation between tilt table and acceleration-tolerance and their dependence on stature and physical fitness

NASA Technical Reports Server (NTRS)

Klein, K. E.; Backhausen, F.; Bruner, H.; Eichhorn, J.; Jovy, D.; Schotte, J.; Vogt, L.; Wegman, H. M.

1980-01-01

A group of 12 highly trained athletes and a group of 12untrained students were subjected to passive changes of position on a tilt table and positive accelerations in a centrifuge. During a 20 min tilt, including two additional respiratory maneuvers, the number of faints and average cardiovascular responses did not differ significantly between the groups. During linear increase of acceleration, the average blackout level was almost identical in both groups. Statistically significant coefficients of product-moment correlation for various relations were obtained. The coefficient of multiple determination computed for the dependence of acceleration tolerance on heart-eye distance and systolic blood pressure at rest allows the explanation of almost 50% of the variation of acceleration tolerance. The maximum oxygen uptake showed the expected significant correlation to the heart rate at rest, but not the acceleration tolerance, or to the cardiovascular responses to tilting.

Fingerprints of the first black holes? Crosscorrelationg the Near-Infrared and X-ray background in COSMOS

NASA Astrophysics Data System (ADS)

Hasinger, Guenther

Unresolved cosmic backgrounds carry information about the populations of stars and black holes not accessible by any other current observational technique. Studies using both Spitzer and AKARI have revealed large-scale fluctuations in the Cosmic Infrared Background (CIB) after subtracting resolved sources to faint levels. The signal, which is stronger than all foreground contributions, has been attributed to the earliest light in the universe. Other teams, by using Spitzer and CIBER, suggested that this signal could originate from stars tidally stripped from their parent galaxies at low redshift as a result of mergers. Only sensitive multi-wavelength observations can distinguish between these radically different interpretations. Recently our team discovered an intriguing cross-correlation signal between the unresolved CIB and X-ray background (CXB) suggesting significant black hole populations among the CIB sources (C13). The analysis used data from Spitzer and Chandra in an overlapping 8'x45' region of the All-Wavelength Extended Groth strip International Survey (AEGIS), probing the clustering of the underlying sources to angular scales 20', but the experiment is limited by the size and the elongated configuration of the field. Here we propose to use the much more extended multiwavelength observations in the COSMOS field to obtain new constraints on this important debate. Spitzer has recently completed the Spitzer Large Area Survey with Hyper-Suprime-Cam (SPLASH), which observed the full 2 square degree COSMOS field to about half the depth of the AEGIS field, but a 20 times larger sky area. SPLASH, focusing on the COSMOS field with excellent multi-wavelength coverage from space and ground-based observatories, is ideally suited to study the CIB to better precision and at larger scales than available so far. We propose to cross-correlate the Spitzer unresolved CIB to the unresolved CXB observed by Chandra and XMM-Newton. Chandra has covered the full 2 deg2 COSMOS field with a total exposure of 5.6 Ms. XMM-Newton has covered the whole 2 deg2 COSMOS field with an exposure time of about 1.5 Ms . The technique for our cross-correlation analysis has been described in detail by C13. All the known instrumental and non-cosmic backgrounds are removed from the data and all discrete sources are excised using the same mask for both datasets. Then the exposure-corrected images are cross-correlated with each other. Compared to the AEGIS cross-correlation signal we expect a significantly better signal to noise ratio, which together with the larger area, will allow us to reach much larger angular scales, where different models can be constrained. The better photon statistics will also allow to separate the signal into at least four independent X-ray energy bands, thus yielding coarse spectral information allowing to discriminate between different models for the X-ray emitting sources. If the X-ray sources are High-Mass X-ray binaries with stellar-mass black holes descendent from massive Pop III stars at z>7, we would expect the X-ray emission to be only moderately absorbed. If on the other hand, the X-ray emission originates from direct collapse black holes with masses in the range 10^5-6 solar masses, we expect a significant Compton-thick absorption component, similar to the resolved X-ray background produced at lower redshifts. Finally, the new data on the CIB-CXB crosscorrelation will also strongly constrain the intrahalo light scenario proposed as an alternative interpretation. At any rate, these measurements allow diagnostics into the faintest discrete source populations right after they emerged from the dark ages or buried within halos. Until the next generation of telescopes, JWST, WFIRST, and EUCLID, the ground based 30m telescopes and later the ESA X-ray observatory Athena, this is one of the few avenues to constrain the formation and early evolution of stars and black holes in the Universe.

Exploring the Universe with the Hubble Space Telescope

NASA Technical Reports Server (NTRS)

1990-01-01

A general overview is given of the operations, engineering challenges, and components of the Hubble Space Telescope. Deployment, checkout and servicing in space are discussed. The optical telescope assembly, focal plane scientific instruments, wide field/planetary camera, faint object spectrograph, faint object camera, Goddard high resolution spectrograph, high speed photometer, fine guidance sensors, second generation technology, and support systems and services are reviewed.

VizieR Online Data Catalog: CANDID code for interferometric observations (Gallenne+, 2015)

NASA Astrophysics Data System (ADS)

Gallenne, A.; Merand, A.; Kervella, P.; Monnier, J. D.; Schaefer, G. H.; Baron, F.; Breitfelder, J.; Le Bouquin, J. B.; Roettenbacher, R. M.; Gieren, W.; Pietrzynski, G.; McAlister, H.; Ten Brummelaar, T.; Sturmann, J.; Sturmann, L.; Turner, N.; Ridgway, S.; Kraus, S.

2015-07-01

This is a suite of Python2.7 tools to find faint companion around star in interferometric data in the OIFITS format. This tool allows to systematically search for faint companions in OIFITS data, and if not found, estimates the detection limit. All files are also available at https://github.com/amerand/CANDID . (3 data files).

An ultra-faint galaxy candidate discovered in early data from the Magellanic Satellites Survey

DOE PAGES

Drlica-Wagner, A.; Bechtol, Keith; Allam, S.; ...

2016-11-30

Here, we report a new ultra-faint stellar system found in Dark Energy Camera data from the first observing run of the Magellanic Satellites Survey (MagLiteS). MagLiteS J0644–5953 (Pictor II or Pic II) is a low surface brightness (more » $$\\mu ={28.5}_{-1}^{+1}\\,\\mathrm{mag}\\,\\,\\mathrm{arcsec}{}^{-2}$$ within its half-light radius) resolved overdensity of old and metal-poor stars located at a heliocentric distance of $${45}_{-4}^{+5}\\,\\mathrm{kpc}$$. The physical size ($${r}_{1/2}={46}_{-11}^{+15}\\,\\mathrm{pc}\\,$$) and low luminosity ($${M}_{V}=-{3.2}_{-0.5}^{+0.4}\\,\\mathrm{mag}\\,$$) of this satellite are consistent with the locus of spectroscopically confirmed ultra-faint galaxies. MagLiteS J0644–5953 (Pic II) is located $${11.3}_{-0.9}^{+3.1}\\,\\mathrm{kpc}\\,$$ from the Large Magellanic Cloud (LMC), and comparisons with simulation results in the literature suggest that this satellite was likely accreted with the LMC. The close proximity of MagLiteS J0644–5953 (Pic II) to the LMC also makes it the most likely ultra-faint galaxy candidate to still be gravitationally bound to the LMC.« less

A low-energy core-collapse supernova without a hydrogen envelope.

PubMed

Valenti, S; Pastorello, A; Cappellaro, E; Benetti, S; Mazzali, P A; Manteca, J; Taubenberger, S; Elias-Rosa, N; Ferrando, R; Harutyunyan, A; Hentunen, V P; Nissinen, M; Pian, E; Turatto, M; Zampieri, L; Smartt, S J

2009-06-04

The final fate of massive stars depends on many factors. Theory suggests that some with initial masses greater than 25 to 30 solar masses end up as Wolf-Rayet stars, which are deficient in hydrogen in their outer layers because of mass loss through strong stellar winds. The most massive of these stars have cores which may form a black hole and theory predicts that the resulting explosion of some of them produces ejecta of low kinetic energy, a faint optical luminosity and a small mass fraction of radioactive nickel. An alternative origin for low-energy supernovae is the collapse of the oxygen-neon core of a star of 7-9 solar masses. No weak, hydrogen-deficient, core-collapse supernovae have hitherto been seen. Here we report that SN 2008ha is a faint hydrogen-poor supernova. We propose that other similar events have been observed but have been misclassified as peculiar thermonuclear supernovae (sometimes labelled SN 2002cx-like events). This discovery could link these faint supernovae to some long-duration gamma-ray bursts, because extremely faint, hydrogen-stripped core-collapse supernovae have been proposed to produce such long gamma-ray bursts, the afterglows of which do not show evidence of associated supernovae.

An ultra-faint galaxy candidate discovered in early data from the Magellanic Satellites Survey

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

Drlica-Wagner, A.; Bechtol, Keith; Allam, S.

Here, we report a new ultra-faint stellar system found in Dark Energy Camera data from the first observing run of the Magellanic Satellites Survey (MagLiteS). MagLiteS J0644–5953 (Pictor II or Pic II) is a low surface brightness (more » $$\\mu ={28.5}_{-1}^{+1}\\,\\mathrm{mag}\\,\\,\\mathrm{arcsec}{}^{-2}$$ within its half-light radius) resolved overdensity of old and metal-poor stars located at a heliocentric distance of $${45}_{-4}^{+5}\\,\\mathrm{kpc}$$. The physical size ($${r}_{1/2}={46}_{-11}^{+15}\\,\\mathrm{pc}\\,$$) and low luminosity ($${M}_{V}=-{3.2}_{-0.5}^{+0.4}\\,\\mathrm{mag}\\,$$) of this satellite are consistent with the locus of spectroscopically confirmed ultra-faint galaxies. MagLiteS J0644–5953 (Pic II) is located $${11.3}_{-0.9}^{+3.1}\\,\\mathrm{kpc}\\,$$ from the Large Magellanic Cloud (LMC), and comparisons with simulation results in the literature suggest that this satellite was likely accreted with the LMC. The close proximity of MagLiteS J0644–5953 (Pic II) to the LMC also makes it the most likely ultra-faint galaxy candidate to still be gravitationally bound to the LMC.« less

ARC-1989-A89-7015

NASA Image and Video Library

1989-08-21

Range : 4.8 million km. ( 3 million miles ) P-34648 This Voyager 2, sixty-one second exposure, shot through clear filters, of Neptunes rings. The Voyager cameras were programmed to make a systematic search of the entire ring system for new material. The previously ring arc is visible as a long bright streak at the bottom of the image. Extening beyond the bright arc is a much fainter component which follows the arc in its orbit. this faint material was also visible leading the ring arc and, in total, covers at least half of the orbit before it becomes too faint to identify. Also visible in this image, is a continuous ring of faint material previously identified as a possible ring arc by Voyager. this continuous ring is located just outside the orbit of the moon 1989N3, which was also discovered by Voyager. This moon is visible as a streak in the lower left. the smear of 1989N3 is due to its own orbital motion during the exposure. Extreme computer processing of this image was made to enhance the extremely faint features of Neptunes moon system. the dark area surrounding the moon as well as the bright corners are due to this special processing.

The Faint End of the Lyman Alpha Luminosity Function at 2 < z < 3.8

NASA Astrophysics Data System (ADS)

Devarakonda, Yaswant; Livermore, Rachael; Indahl, Briana; Wold, Isak; Davis, Dustin; Finkelstein, Steven

2018-01-01

Most current models predict that our universe is mostly composed of small, dim galaxies. Due to these galaxies being so faint, it is very difficult to study these types of galaxies outside of our local universe. This is particularly an issue for studying how these small galaxies evolved over their lifetimes. With the benefit of gravitational lensing, however, we are able to observe galaxies that are farther and fainter than ever before possible. In this particular study, we focus on Lyman-Alpha emitting galaxies between the redshifts of 2-3.8, so that we may study these galaxies during the epoch of peak star formation in the universe. We use the McDonald Observatory 2.7, Harlan Smith telescope with the VIRUS-P IFU spectrograph to observe several Hubble Frontier Field lensing clusters to spectroscopically discover faint galaxies over this redshift range. In addition to providing insight into the faint-end slope of the Lyman alpha luminosity function, the spectroscopic redshifts will allow us to better constrain the mass models of the foreground clusters, such as Abell 370, so that we may better understand lensing effects for this and future studies.

The second ROSAT All-Sky Survey source catalogue: the deepest X-ray All-Sky Survey before eROSITA

NASA Astrophysics Data System (ADS)

Boller, T.; Freyberg, M.; Truemper, J.

2014-07-01

We present the second ROSAT all-sky survey source catalogue (RASS2, (Boller, Freyberg, Truemper 2014, submitted)). The RASS2 is an extension of the ROSAT Bright Source Catalogue (BSC) and the ROSAT Faint Source Catalogue (FSC). The total number of sources in the second RASS catalogue is 124489. The extensions include (i) the supply of new user data products, i.e., X-ray images, X-ray spectra, and X-ray light curves, (ii) a visual screening of each individual detection, (iii) an improved detection algorithm compared to the SASS II processing. This results into an as most as reliable and as most as complete catalogue of point sources detected during the ROSAT Survey observations. We discuss for the first time the intra-day timing and spectral properties of the second RASS catalogue. We find new highly variable sources and we discuss their timing properties. Power law fits have been applied which allows to determine X-ray fluxes, X-ray absorbing columns, and X-ray photon indices. We give access to the second RASS catalogue and the associated data products via a web-interface to allow the community to perform further scientific exploration. The RASS2 catalogue provides the deepest X-ray All-Sky Survey before eROSITA data will become available.

On-Orbit Sky Background Measurements with the FOS

NASA Technical Reports Server (NTRS)

Lyons, R. W.; Baity, W. A.; Beaver, E. A.; Cohen, R. D.; Junkkarinen, V. T.; Linsky, J. B.; Bohlin, R. C.

1993-01-01

Observations of the sky background obtained with the Faint Object Spectrograph during 1991-1992 are discussed. Sky light can be an important contributor to the observed count rate in several of the instrument configurations especially when large apertures are used. In general, the sky background is consistent with the pre-launch expectations and showed the expected effects of zodiacal light and diffuse galactic light. In addition to these sources, there is, particularly during the daytime, a highly variable airglow component which includes a number of emission lines. The sky background will have an impact on the reduction and possibly the interpretation of some spectra.

On the feasibility of detecting extrasolar planets by reflected starlight using the Hubble Space Telescope

NASA Technical Reports Server (NTRS)

Brown, Robert A.; Burrows, Christopher J.

1990-01-01

The best metrology data extant are presently used to estimate the center and wing point-spread function of the HST, in order to ascertain the implications of an observational criterion according to which a faint source's discovery can occur only when the signal recorded near its image's location is sufficiently larger than would be expected in its absence. After defining the maximum star-planet flux ratio, a figure of merit Q, defined as the contrast ratio between a 'best case' planet and the scattered starlight background, is introduced and shown in the HST's case to be unfavorable for extrasolar planet detection.

Multi-axial interferometry: demonstration of deep nulling

NASA Astrophysics Data System (ADS)

Buisset, Christophe; Rejeaunier, Xavier; Rabbia, Yves; Ruilier, Cyril; Barillot, Marc; Lierstuen, Lars; Perdigués Armengol, Josep Maria

2017-11-01

The ESA-Darwin mission is devoted to direct detection and spectroscopic characterization of earthlike exoplanets. Starlight rejection is achieved by nulling interferometry from space so as to make detectable the faintly emitting planet in the neighborhood. In that context, Alcatel Alenia Space has developed a nulling breadboard for ESA in order to demonstrate in laboratory conditions the rejection of an on-axis source. This device, the Multi Aperture Imaging Interferometer (MAII) demonstrated high rejection capability at a relevant level for exoplanets, in singlepolarized and mono-chromatic conditions. In this paper we report on the new multi-axial configuration of MAII and we summarize our late nulling results.

Fast optical source for quantum key distribution based on semiconductor optical amplifiers.

PubMed

Jofre, M; Gardelein, A; Anzolin, G; Amaya, W; Capmany, J; Ursin, R; Peñate, L; Lopez, D; San Juan, J L; Carrasco, J A; Garcia, F; Torcal-Milla, F J; Sanchez-Brea, L M; Bernabeu, E; Perdigues, J M; Jennewein, T; Torres, J P; Mitchell, M W; Pruneri, V

2011-02-28

A novel integrated optical source capable of emitting faint pulses with different polarization states and with different intensity levels at 100 MHz has been developed. The source relies on a single laser diode followed by four semiconductor optical amplifiers and thin film polarizers, connected through a fiber network. The use of a single laser ensures high level of indistinguishability in time and spectrum of the pulses for the four different polarizations and three different levels of intensity. The applicability of the source is demonstrated in the lab through a free space quantum key distribution experiment which makes use of the decoy state BB84 protocol. We achieved a lower bound secure key rate of the order of 3.64 Mbps and a quantum bit error ratio as low as 1.14×10⁻² while the lower bound secure key rate became 187 bps for an equivalent attenuation of 35 dB. To our knowledge, this is the fastest polarization encoded QKD system which has been reported so far. The performance, reduced size, low power consumption and the fact that the components used can be space qualified make the source particularly suitable for secure satellite communication.

Starburst galaxies

NASA Technical Reports Server (NTRS)

Weedman, Daniel W.

1987-01-01

The infrared properties of star-forming galaxies, primarily as determined by the Infrared Astronomy Satellite (IRAS), are compared to X-ray, optical, and radio properties. Luminosity functions are reviewed and combined with those derived from optically discovered samples using 487 Markarian galaxies with redshifts and published IRAS 60 micron fluxes, and 1074 such galaxies in the Center for Astrophysics redshift survey. It is found that the majority of infrared galaxies which could be detected are low luminosity sources already known from the optical samples, but non-infrared surveys have found only a very small fraction of the highest luminosity sources. Distributions of infrared to optical fluxes and available spectra indicate that the majority of IRAS-selected galaxies are starburst galaxies. Having a census of starburst galaxies and associated dust allow severl important global calculations. The source counts are predicted as a function of flux limits for both infrared and radio fluxes. These galaxies are found to be important radio sources at faint flux limits. Taking the integrated flux to z = 3 indicates that such galaxies are a significant component of the diffuse X-ray background, and could be the the dominant component depending on the nature of the X-ray spectra and source evolution.

Simultaneous Observatinos of H2O and SiO Masers Toward Known Extragalactic Water Maser Sources

NASA Astrophysics Data System (ADS)

Cho, Se-Hyung; Yoon, Dong-Hwan; Kim, Jaeheon; Byun, Do-Young; Wagner, Jan

2015-12-01

We observe ten known 22 GHz H_{2}O maser galaxies during February 19-22, 2011 using the 21 m Tamna telescope of the Korean VLBI Network and a new wide-band digital spectrometer. Simultaneously we searched for 43 GHz SiO v = 1, 2, J = 1-0 maser emission. We detect H_{2}O maser emission towards five sources (M 33, NGC 1052, NGC 1068, NGC 4258, M 82), with non-detections towards the remaining sources (UGC 3193, UGC 3789, Antennae H_{2}O-West, M 51, NGC 6323) likely due to sensitivity. Our 22 GHz spectra are consistent with earlier findings. Our simultaneous 43 GHz SiO maser search produced non-detections, yielding - for the first time - upper limits on the 43 GHz SiO maser emission in these sources at a 3 σ sensitivity level of 0.018 K-0.033 K (0.24 Jy-0.44 Jy) in a 1.75 km s^{-1} velocity resolution. Our findings suggest that any 43 GHz SiO masers in these sources (some having starburst-associated H_{2}O kilomasers) must be faint compared to the 22 GHz H_{2}O maser emission.

The Brightest of Reionizing Galaxies Survey: Constraints on the Bright End of the z ~ 8 Luminosity Function

NASA Astrophysics Data System (ADS)

Bradley, L. D.; Trenti, M.; Oesch, P. A.; Stiavelli, M.; Treu, T.; Bouwens, R. J.; Shull, J. M.; Holwerda, B. W.; Pirzkal, N.

2012-12-01

We report the discovery of 33 Lyman-break galaxy candidates at z ~ 8 detected in Hubble Space Telescope Wide Field Camera 3 (WFC3) imaging as part of the Brightest of Reionizing Galaxies (BoRG) pure-parallel survey. The ongoing BoRG survey currently has the largest area (274 arcmin2) with Y 098 (or Y 105), J 125, and H 160 band coverage needed to search for z ~ 8 galaxies, about three times the current CANDELS area, and slightly larger than what will be the final CANDELS wide component with Y 105 data (required to select z ~ 8 sources). Our sample of 33 relatively bright Y 098-dropout galaxies have J 125-band magnitudes between 25.5 and 27.4 mag. This is the largest sample of bright (J 125 <~ 27.4) z ~ 8 galaxy candidates presented to date. Combining our data set with the Hubble Ultra-Deep Field data set, we constrain the rest-frame ultraviolet galaxy luminosity function at z ~ 8 over the widest dynamic range currently available. The combined data sets are well fitted by a Schechter function, i.e., \\phi (L) = \\phi _{*} (L/L_{*})^{\\alpha }\\ e^{-(L/L_{*})}, without evidence for an excess of sources at the bright end. At 68% confidence, for h = 0.7 we derive phi* = (4.3+3.5 -2.1) × 10-4 Mpc-3, M * = -20.26+0.29 -0.34, and a very steep faint-end slope α = -1.98+0.23 -0.22. While the best-fit parameters still have a strong degeneracy, especially between phi* and M *, our improved coverage at the bright end has reduced the uncertainty of the faint-end power-law slope at z ~ 8 compared to the best previous determination at ±0.4. With a future expansion of the BoRG survey, combined with planned ultradeep WFC3/IR observations, it will be possible to further reduce this uncertainty and clearly demonstrate the steepening of the faint-end slope compared to measurements at lower redshift, thereby confirming the key role played by small galaxies in the reionization of the universe. Based 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 under NASA contract NAS5-26555. These observations are associated with programs 11519, 11520, 11524, 11528, 11530, 11533, 11534, 11541, 11700, 11702, 12024, 12025, and 12572.

Applications of independent component analysis in SAR images

NASA Astrophysics Data System (ADS)

Huang, Shiqi; Cai, Xinhua; Hui, Weihua; Xu, Ping

2009-07-01

The detection of faint, small and hidden targets in synthetic aperture radar (SAR) image is still an issue for automatic target recognition (ATR) system. How to effectively separate these targets from the complex background is the aim of this paper. Independent component analysis (ICA) theory can enhance SAR image targets and improve signal clutter ratio (SCR), which benefits to detect and recognize faint targets. Therefore, this paper proposes a new SAR image target detection algorithm based on ICA. In experimental process, the fast ICA (FICA) algorithm is utilized. Finally, some real SAR image data is used to test the method. The experimental results verify that the algorithm is feasible, and it can improve the SCR of SAR image and increase the detection rate for the faint small targets.

Finding new sub-stellar co-moving companion candidates - the case of CT Cha

NASA Astrophysics Data System (ADS)

Schmidt, Tobias; Neuhäuser, Ralph

2008-05-01

We have searched for close and faint companions around T Tauri stars in the Chamaeleon star forming region. Two epochs of direct imaging data were taken with the VLT Adaptive Optics instrument NaCo in February 2006 and March 2007 in Ks band for the classical T Tauri star CT Cha together with a Hipparcos binary for astrometric calibration. Moreover a J band image was taken in March 2007 to get color information. We found CT Cha to have a very faint companion (Ks0=14.6 mag) of 2.67” separation corresponding to 440AU. We show that CT Cha A and the faint object form a common proper motion pair and that the companion is not a non-moving background object (with 4σ significance).

Deep 1.1mm-wavelength imaging of the GOODS-S field by AzTEC/ASTE - I. Source catalogue and number counts

NASA Astrophysics Data System (ADS)

Scott, K. S.; Yun, M. S.; Wilson, G. W.; Austermann, J. E.; Aguilar, E.; Aretxaga, I.; Ezawa, H.; Ferrusca, D.; Hatsukade, B.; Hughes, D. H.; Iono, D.; Giavalisco, M.; Kawabe, R.; Kohno, K.; Mauskopf, P. D.; Oshima, T.; Perera, T. A.; Rand, J.; Tamura, Y.; Tosaki, T.; Velazquez, M.; Williams, C. C.; Zeballos, M.

2010-07-01

We present the first results from a confusion-limited map of the Great Observatories Origins Deep Survey-South (GOODS-S) taken with the AzTEC camera on the Atacama Submillimeter Telescope Experiment. We imaged a field to a 1σ depth of 0.48-0.73 mJybeam-1, making this one of the deepest blank-field surveys at mm-wavelengths ever achieved. Although by traditional standards our GOODS-S map is extremely confused due to a sea of faint underlying sources, we demonstrate through simulations that our source identification and number counts analyses are robust, and the techniques discussed in this paper are relevant for other deeply confused surveys. We find a total of 41 dusty starburst galaxies with signal-to-noise ratios S/N >= 3. 5 within this uniformly covered region, where only two are expected to be false detections, and an additional seven robust source candidates located in the noisier (1σ ~ 1 mJybeam-1) outer region of the map. We derive the 1.1 mm number counts from this field using two different methods: a fluctuation or ``P(d)'' analysis and a semi-Bayesian technique and find that both methods give consistent results. Our data are well fit by a Schechter function model with . Given the depth of this survey, we put the first tight constraints on the 1.1 mm number counts at S1.1mm = 0.5 mJy, and we find evidence that the faint end of the number counts at from various SCUBA surveys towards lensing clusters are biased high. In contrast to the 870μm survey of this field with the LABOCA camera, we find no apparent underdensity of sources compared to previous surveys at 1.1mm the estimates of the number counts of SMGs at flux densities >1mJy determined here are consistent with those measured from the AzTEC/SHADES survey. Additionally, we find a significant number of SMGs not identified in the LABOCA catalogue. We find that in contrast to observations at λ <= 500μm, MIPS 24μm sources do not resolve the total energy density in the cosmic infrared background at 1.1 mm, demonstrating that a population of z >~ 3 dust-obscured galaxies that are unaccounted for at these shorter wavelengths potentially contribute to a large fraction (~2/3) of the infrared background at 1.1 mm.

The evolution of the cluster optical galaxy luminosity function between z = 0.4 and 0.9 in the DAFT/FADA survey

NASA Astrophysics Data System (ADS)

Martinet, Nicolas; Durret, Florence; Guennou, Loïc; Adami, Christophe; Biviano, Andrea; Ulmer, Melville P.; Clowe, Douglas; Halliday, Claire; Ilbert, Olivier; Márquez, Isabel; Schirmer, Mischa

2015-03-01

Context. There is some disagreement about the abundance of faint galaxies in high-redshift clusters, with contradictory results in the literature arising from studies of the optical galaxy luminosity function (GLF) for small cluster samples. Aims: We compute GLFs for one of the largest medium-to-high-redshift (0.4 ≤ z < 0.9) cluster samples to date in order to probe the abundance of faint galaxies in clusters. We also study how the GLF depends on cluster redshift, mass, and substructure and compare the GLFs of clusters with those of the field. We separately investigate the GLFs of blue and red-sequence (RS) galaxies to understand the evolution of different cluster populations. Methods: We calculated the GLFs for 31 clusters taken from the DAFT/FADA survey in the B,V,R, and I rest-frame bands. We used photometric redshifts computed from BVRIZJ images to constrain galaxy cluster membership. We carried out a detailed estimate of the completeness of our data. We distinguished the red-sequence and blue galaxies using a V - I versus I colour-magnitude diagram. We studied the evolution of these two populations with redshift. We fitted Schechter functions to our stacked GLFs to determine average cluster characteristics. Results: We find that the shapes of our GLFs are similar for the B,V,R, and I bands with a drop at the red GLF faint ends that is more pronounced at high redshift: αred ~ -0.5 at 0.40 ≤ z < 0.65 and αred > 0.1 at 0.65 ≤ z < 0.90. The blue GLFs have a steeper faint end (αblue ~ -1.6) than the red GLFs, which appears to be independent of redshift. For the full cluster sample, blue and red GLFs meet at MV = -20, MR = -20.5, and MI = -20.3. A study of how galaxy types evolve with redshift shows that late-type galaxies appear to become early types between z ~ 0.9 and today. Finally, the faint ends of the red GLFs of more massive clusters appear to be richer than less massive clusters, which is more typical of the lower redshift behaviour. Conclusions: Our results indicate that these clusters form at redshifts higher than z = 0.9 from galaxy structures that already have an established red sequence. Late-type galaxies then appear to evolve into early types, enriching the red sequence between this redshift and today. This effect is consistent with the evolution of the faint-end slope of the red sequence and the galaxy type evolution that we find. Finally, faint galaxies accreted from the field environment at all redshifts might have replaced the blue late-type galaxies that converted into early types, explaining the lack of evolution in the faint-end slopes of the blue GLFs. Appendix is available in electronic form at http://www.aanda.org

The Faint End of the Quasar Luminosity Function at z ~ 4

NASA Astrophysics Data System (ADS)

Glikman, Eilat; Bogosavljević, Milan; Djorgovski, S. G.; Stern, Daniel; Dey, Arjun; Jannuzi, Buell T.; Mahabal, Ashish

2010-02-01

The evolution of the quasar luminosity function (QLF) is one of the basic cosmological measures providing insight into structure formation and mass assembly in the universe. We have conducted a spectroscopic survey to find faint quasars (-26.0 < M 1450 < -22.0) at redshifts z = 3.8-5.2 in order to measure the faint end of the QLF at these early times. Using available optical imaging data from portions of the NOAO Deep Wide-Field Survey and the Deep Lens Survey, we have color-selected quasar candidates in a total area of 3.76 deg2. Thirty candidates have R <= 23 mag. We conducted spectroscopic follow-up for 28 of our candidates and found 23 QSOs, 21 of which are reported here for the first time, in the 3.74 < z < 5.06 redshift range. We estimate our survey completeness through detailed Monte Carlo simulations and derive the first measurement of the density of quasars in this magnitude and redshift interval. We find that the binned luminosity function (LF) is somewhat affected by the K-correction used to compute the rest-frame absolute magnitude at 1450 Å. Considering only our R <= 23 sample, the best-fit single power law (Φ vprop L β) gives a faint-end slope β = -1.6 ± 0.2. If we consider our larger, but highly incomplete sample going 1 mag fainter, we measure a steeper faint-end slope -2 < β < -2.5. In all cases, we consistently find faint-end slopes that are steeper than expected based on measurements at z ~ 3. We combine our sample with bright quasars from the Sloan Digital Sky Survey to derive parameters for a double-power-law LF. Our best fit finds a bright-end slope, α = -2.4 ± 0.2, and faint-end slope, β = -2.3 ± 0.2, without a well-constrained break luminosity. This is effectively a single power law, with β = -2.7 ± 0.1. We use these results to place limits on the amount of ultraviolet radiation produced by quasars and find that quasars are able to ionize the intergalactic medium at these redshifts. 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.

Faint Debris Detection by Particle Based Track-Before-Detect Method

NASA Astrophysics Data System (ADS)

Uetsuhara, M.; Ikoma, N.

2014-09-01

This study proposes a particle method to detect faint debris, which is hardly seen in single frame, from an image sequence based on the concept of track-before-detect (TBD). The most widely used detection method is detect-before-track (DBT), which firstly detects signals of targets from single frame by distinguishing difference of intensity between foreground and background then associate the signals for each target between frames. DBT is capable of tracking bright targets but limited. DBT is necessary to consider presence of false signals and is difficult to recover from false association. On the other hand, TBD methods try to track targets without explicitly detecting the signals followed by evaluation of goodness of each track and obtaining detection results. TBD has an advantage over DBT in detecting weak signals around background level in single frame. However, conventional TBD methods for debris detection apply brute-force search over candidate tracks then manually select true one from the candidates. To reduce those significant drawbacks of brute-force search and not-fully automated process, this study proposes a faint debris detection algorithm by a particle based TBD method consisting of sequential update of target state and heuristic search of initial state. The state consists of position, velocity direction and magnitude, and size of debris over the image at a single frame. The sequential update process is implemented by a particle filter (PF). PF is an optimal filtering technique that requires initial distribution of target state as a prior knowledge. An evolutional algorithm (EA) is utilized to search the initial distribution. The EA iteratively applies propagation and likelihood evaluation of particles for the same image sequences and resulting set of particles is used as an initial distribution of PF. This paper describes the algorithm of the proposed faint debris detection method. The algorithm demonstrates performance on image sequences acquired during observation campaigns dedicated to GEO breakup fragments, which would contain a sufficient number of faint debris images. The results indicate the proposed method is capable of tracking faint debris with moderate computational costs at operational level.

Gravitational Lensing and Microlensing in Clusters: Clusters as Dark Matter Telescopes

NASA Astrophysics Data System (ADS)

Safonova, Margarita

2018-04-01

Gravitational lensing is brightening of background objects due to deflection of light by foreground sources. Rich clusters of galaxies are very effective lenses because they are centrally concentrated. Such natural Gravitational Telescopes provide us with strongly magnified galaxies at high redshifts otherwise too faint to be detected or analyzed. With a lensing boost, we can study galaxies shining at the end of the “Dark Ages”. We propose to exploit the opportunity provided by the large field of view and depth, to search for sources magnified by foreground clusters in the vicinity of the cluster critical curves, where enhancements can be of several tens in brightness. Another aspect is microlensing (ML), where we would like to continue our survey of a number of Galactic globular clusters over time-scales of weeks to years to search for ML events from planets to hypothesized central intermediate-mass black holes (IMBH).

Rocket and laboratory studies in astronomy

NASA Technical Reports Server (NTRS)

Feldman, P. D.

1993-01-01

This report covers the period from September 1, 1992 to August 31, 1993. During the reporting period we launched the Faint Object Telescope to measure absolute fluxes of two hot dwarf stars in the spectral range below 1200 A. Although all systems worked normally, a higher than anticipated pressure in the detector led to ion-feedback that masked the useable data from the source. We have identified the source of the problem and are preparing for a reflight in the Fall of 1993. Our laboratory program for the evaluation of the ultraviolet performance of charge-coupled-detector (CCD) arrays continued with the aim of including a UV-sensitive CCD in a payload to be flown in 1994, and we have begun the assembly of this payload. Work has continued on the analysis of data from previous rocket experiments and from the UVX experiment which flew on STS-61C in January 1986.

Detection of Double White Dwarf Binaries with Gaia, LSST and eLISA

NASA Astrophysics Data System (ADS)

Korol, V.; Rossi, E. M.; Groot, P. J.

2017-03-01

According to simulations around 108 double degenerate white dwarf binaries are expected to be present in the Milky Way. Due to their intrinsic faintness, the detection of these systems is a challenge, and the total number of detected sources so far amounts only to a few tens. This will change in the next two decades with the advent of Gaia, the LSST and eLISA. We present an estimation of how many compact DWDs with orbital periods less than a few hours we will be able to detect 1) through electromagnetic radiation with Gaia and LSST and 2) through gravitational wave radiation with eLISA. We find that the sample of simultaneous electromagnetic and gravitational waves detections is expected to be substantial, and will provide us a powerful tool for probing the white dwarf astrophysics and the structure of the Milky Way, letting us into the era of multi-messenger astronomy for these sources.

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

Brewer, Brendon J.; Foreman-Mackey, Daniel; Hogg, David W., E-mail: bj.brewer@auckland.ac.nz

We present and implement a probabilistic (Bayesian) method for producing catalogs from images of stellar fields. The method is capable of inferring the number of sources N in the image and can also handle the challenges introduced by noise, overlapping sources, and an unknown point-spread function. The luminosity function of the stars can also be inferred, even when the precise luminosity of each star is uncertain, via the use of a hierarchical Bayesian model. The computational feasibility of the method is demonstrated on two simulated images with different numbers of stars. We find that our method successfully recovers the inputmore » parameter values along with principled uncertainties even when the field is crowded. We also compare our results with those obtained from the SExtractor software. While the two approaches largely agree about the fluxes of the bright stars, the Bayesian approach provides more accurate inferences about the faint stars and the number of stars, particularly in the crowded case.« less

Active wavefront control challenges of the NASA Large Deployable Reflector (LDR)

NASA Technical Reports Server (NTRS)

Meinel, Aden B.; Meinel, Marjorie P.; Manhart, Paul K.; Hochberg, Eric B.

1989-01-01

The 20-m Large Deployable Reflector will have a segmented primary mirror. Achieving diffraction-limited performance at 50 microns requires correction for the errors of tilt and piston of the primary mirror. This correction can be obtained in two ways, the use of an active primary or a correction at a demagnified pupil of the primary. A critical requirement is the means for measurement of the wavefront error and maintaining phasing during the observation of objects that may be too faint for determining the error. Absolute phasing can only be determined using a cooperative source. Maintenance of phasing can be done with an on-board source. A number of options are being explored as discussed below. The many issues concerning the assessment and control of an active segmented mirror will be addressed with an early construction of the Precision Segmented Reflector testbed.

Active wavefront control challenges of the NASA Large Deployable Reflector (LDR)

NASA Astrophysics Data System (ADS)

Meinel, Aden B.; Meinel, Marjorie P.; Manhart, Paul K.; Hochberg, Eric B.

1989-09-01

The 20-m Large Deployable Reflector will have a segmented primary mirror. Achieving diffraction-limited performance at 50 microns requires correction for the errors of tilt and piston of the primary mirror. This correction can be obtained in two ways, the use of an active primary or a correction at a demagnified pupil of the primary. A critical requirement is the means for measurement of the wavefront error and maintaining phasing during the observation of objects that may be too faint for determining the error. Absolute phasing can only be determined using a cooperative source. Maintenance of phasing can be done with an on-board source. A number of options are being explored as discussed below. The many issues concerning the assessment and control of an active segmented mirror will be addressed with an early construction of the Precision Segmented Reflector testbed.

HERUS: A CO ATLAS FROM SPIRE SPECTROSCOPY OF LOCAL ULIRGs

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

Pearson, Chris; Rigopoulou, Dimitra; Hurley, Peter

We present the Herschel SPIRE Fourier Transform Spectroscopy (FTS) atlas for a complete flux-limited sample of local ultraluminous infrared galaxies (ULIRGs) as part of the HERschel Ultra Luminous InfraRed Galaxy Survey (HERUS). The data reduction is described in detail and was optimized for faint FTS sources ,with particular care being taken for the subtraction of the background, which dominates the continuum shape of the spectra. To improve the final spectra, special treatment in the data reduction has been given to any observation suffering from artifacts in the data caused by anomalous instrumental effects. Complete spectra are shown covering 200–671 μmore » m, with photometry in the SPIRE bands at 250, 350, and 500 μ m. The spectra include near complete CO ladders for over half of our sample, as well as fine structure lines from [C i] 370 μ m, [C i] 609 μ m, and [N ii] 205 μ m. We also detect H{sub 2}O lines in several objects. We construct CO spectral line energy distributions (SLEDs) for the sample, and compare their slopes with the far-infrared (FIR) colors and luminosities. We show that the CO SLEDs of ULIRGs can be broadly grouped into three classes based on their excitation. We find that the mid- J (5 <  J  < 8) lines are better correlated with the total FIR luminosity, suggesting that the warm gas component is closely linked to recent star formation. The higher J transitions do not linearly correlate with the FIR luminosity, consistent with them originating in hotter, denser gas that is unconnected to the current star formation. We conclude that in most cases more than one temperature component is required to model the CO SLEDs.« less

Deep CFHT Y-band Imaging of VVDS-F22 Field. II. Quasar Selection and Quasar Luminosity Function

NASA Astrophysics Data System (ADS)

Yang, Jinyi; Wu, Xue-Bing; Liu, Dezi; Fan, Xiaohui; Yang, Qian; Wang, Feige; McGreer, Ian D.; Fan, Zuhui; Yuan, Shuo; Shan, Huanyuan

2018-03-01

We report the results of a faint quasar survey in a one-square-degree field. The aim is to test the Y-K/g-z and J-K/i-Y color selection criteria for quasars at faint magnitudes to obtain a complete sample of quasars based on deep optical and near-infrared color–color selection and to measure the faint end of the quasar luminosity function (QLF) over a wide redshift range. We carried out a quasar survey based on the Y-K/g-z and J-K/i-Y quasar selection criteria, using the deep Y-band data obtained from our CFHT/WIRCam Y-band images in a two-degree field within the F22 field of the VIMOS VLT deep survey, optical co-added data from Sloan Digital Sky Survey Stripe 82 and deep near-infrared data from the UKIDSS Deep Extragalactic Survey in the same field. We discovered 25 new quasars at 0.5< z< 4.5 and i< 22.5 mag within one-square-degree field. The survey significantly increases the number of faint quasars in this field, especially at z∼ 2{--}3. It confirms that our color selections are highly complete in a wide redshift range (z< 4.5), especially over the quasar number density peak at z∼ 2{--}3, even for faint quasars. Combining all previous known quasars and new discoveries, we construct a sample with 109 quasars and measure the binned QLF and parametric QLF. Although the sample is small, our results agree with a pure luminosity evolution at lower redshift and luminosity evolution and density evolution model at redshift z> 2.5.

Eight ultra-faint galaxy candidates discovered in year two of the Dark Energy Survey

DOE PAGES

Drlica-Wagner, A.

2015-11-04

Here, we report the discovery of eight new ultra-faint dwarf galaxy candidates in the second year of optical imaging data from the Dark Energy Survey (DES). Six of these candidates are detected at high confidence, while two lower-confidence candidates are identified in regions of non-uniform survey coverage. The new stellar systems are found by three independent automated search techniques and are identified as overdensities of stars, consistent with the isochrone and luminosity function of an old and metal-poor simple stellar population. The new systems are faint (M V > –4.7more » $$\\mathrm{mag}$$) and span a range of physical sizes (17 $$\\mathrm{pc}$$ < r 1/2 < 181 $$\\mathrm{pc}$$) and heliocentric distances (25 kpc < D ⊙ < 214 kpc). All of the new systems have central surface brightnesses consistent with known ultra-faint dwarf galaxies (μ ≳ 27.5 $$\\mathrm{mag}$$ $$\\mathrm{arcsec}$$ –2). Roughly half of the DES candidates are more distant, less luminous, and/or have lower surface brightnesses than previously known Milky Way satellite galaxies. Most of the candidates are found in the southern part of the DES footprint close to the Magellanic Clouds. We find that the DES data alone exclude (p < 10 –3) a spatially isotropic distribution of Milky Way satellites and that the observed distribution can be well, though not uniquely, described by an association between several of the DES satellites and the Magellanic system. Our model predicts that the full sky may hold ~100 ultra-faint galaxies with physical properties comparable to the DES satellites and that 20%–30% of these would be spatially associated with the Magellanic Clouds.« less

End-tidal pCO2 in blood phobics during viewing of emotion- and disease-related films.

PubMed

Ritz, Thomas; Wilhelm, Frank H; Gerlach, Alexander L; Kullowatz, Antje; Roth, Walton T

2005-01-01

Many patients with blood, injection, and injury (BII) phobia respond to specific stimuli with vasovagal dysregulation and fainting. However, little is known about the role of hyperventilation in the distress of these patients. Hyperventilation, defined by subnormal arterial pCO2 levels, induces anxiety and may promote the development of fainting. We studied end-tidal pCO2 in 12 patients with BII phobia and 14 nonanxious controls during presentation of emotional films. Ten film clips were shown, two in each of 5 categories: pleasant, unpleasant, neutral, BII-related (surgery), and asthma-related (portraying labored breathing). For each subject, two subsets were created, each containing one clip from each category. For one subset, the instruction was simply to view the film, and for the other subset, to view the film while tensing the leg muscles. PCO2, heart rate, blood pressure, and leg electromyogram were recorded continuously during viewing, and self-report of symptoms and emotion was collected after each film. Patients reported the greatest anxiety and disgust during surgery films. PCO2 was relatively stable throughout all categories except surgery films, during which minima were below 30 mm Hg, indicating significant hypocapnia. Cardiovascular variables suggested biphasic patterns in two patients with BII phobia. These patients, together with one additional patient and one control who were close to fainting after or during one surgery film, also showed a marked fall in pCO2) Leg muscle tension raised heart rate and systolic blood pressure for all films, but was not related to near-fainting or endurance in surgery film viewing. Hyperventilation is part of the fear response of patients with BII phobia, but was transitory in experimental fear induction using surgery films. Its role in real-life exposure and fainting deserves further study.

A PECULIAR FAINT SATELLITE IN THE REMOTE OUTER HALO OF M31

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

Mackey, A. D.; Dotter, A.; Huxor, A. P.

2013-06-20

We present Hubble Space Telescope imaging of a newly discovered faint stellar system, PAndAS-48, in the outskirts of the M31 halo. Our photometry reveals this object to be comprised of an ancient and very metal-poor stellar population with age {approx}> 10 Gyr and [Fe/H] {approx}< -2.3. Our inferred distance modulus (m - M){sub 0} = 24.57 {+-} 0.11 confirms that PAndAS-48 is most likely a remote M31 satellite with a three-dimensional galactocentric radius of 149{sup +19}{sub -8} kpc. We observe an apparent spread in color on the upper red giant branch that is larger than the photometric uncertainties should allow,more » and briefly explore the implications of this. Structurally, PAndAS-48 is diffuse, faint, and moderately flattened, with a half-light radius r{sub h}=26{sup +4}{sub -3} pc, integrated luminosity M{sub V} = -4.8 {+-} 0.5, and ellipticity {epsilon}=0.30{sup +0.08}{sub -0.15}. On the size-luminosity plane it falls between the extended globular clusters seen in several nearby galaxies and the recently discovered faint dwarf satellites of the Milky Way; however, its characteristics do not allow us to unambiguously classify it as either type of system. If PAndAS-48 is a globular cluster then it is among the most elliptical, isolated, and metal-poor of any seen in the Local Group, extended or otherwise. Conversely, while its properties are generally consistent with those observed for the faint Milky Way dwarfs, it would be a factor of {approx}2-3 smaller in spatial extent than any known counterpart of comparable luminosity.« less

Sweating the small stuff: simulating dwarf galaxies, ultra-faint dwarf galaxies, and their own tiny satellites

NASA Astrophysics Data System (ADS)

Wheeler, Coral; Oñorbe, Jose; Bullock, James S.; Boylan-Kolchin, Michael; Elbert, Oliver D.; Garrison-Kimmel, Shea; Hopkins, Philip F.; Kereš, Dušan

2015-10-01

We present Feedback in Realistic Environment (FIRE)/GIZMO hydrodynamic zoom-in simulations of isolated dark matter haloes, two each at the mass of classical dwarf galaxies (Mvir ≃ 1010 M⊙) and ultra-faint galaxies (Mvir ≃ 109 M⊙), and with two feedback implementations. The resulting central galaxies lie on an extrapolated abundance matching relation from M⋆ ≃ 106 to 104 M⊙ without a break. Every host is filled with subhaloes, many of which form stars. Each of our dwarfs with M⋆ ≃ 106 M⊙ has 1-2 well-resolved satellites with M⋆ = 3-200 × 103 M⊙. Even our isolated ultra-faint galaxies have star-forming subhaloes. If this is representative, dwarf galaxies throughout the Universe should commonly host tiny satellite galaxies of their own. We combine our results with the Exploring the Local Volume in Simulations (ELVIS) simulations to show that targeting ˜ 50 kpc regions around nearby isolated dwarfs could increase the chances of discovering ultra-faint galaxies by ˜35 per cent compared to random pointings, and specifically identify the region around the Phoenix dwarf galaxy as a good potential target. The well-resolved ultra-faint galaxies in our simulations (M⋆ ≃ 3-30 × 103 M⊙) form within Mpeak ≃ 0.5-3 × 109 M⊙ haloes. Each has a uniformly ancient stellar population ( > 10 Gyr) owing to reionization-related quenching. More massive systems, in contrast, all have late-time star formation. Our results suggest that Mhalo ≃ 5 × 109 M⊙ is a probable dividing line between haloes hosting reionization `fossils' and those hosting dwarfs that can continue to form stars in isolation after reionization.

X-ray versus infrared selection of distant galaxy clusters: A case study using the XMM-LSS and SpARCS cluster samples

NASA Astrophysics Data System (ADS)

Willis, J. P.; Ramos-Ceja, M. E.; Muzzin, A.; Pacaud, F.; Yee, H. K. C.; Wilson, G.

2018-04-01

We present a comparison of two samples of z > 0.8 galaxy clusters selected using different wavelength-dependent techniques and examine the physical differences between them. We consider 18 clusters from the X-ray selected XMM-LSS distant cluster survey and 92 clusters from the optical-MIR selected SpARCS cluster survey. Both samples are selected from the same approximately 9 square degree sky area and we examine them using common XMM-Newton, Spitzer-SWIRE and CFHT Legacy Survey data. Clusters from each sample are compared employing aperture measures of X-ray and MIR emission. We divide the SpARCS distant cluster sample into three sub-samples: a) X-ray bright, b) X-ray faint, MIR bright, and c) X-ray faint, MIR faint clusters. We determine that X-ray and MIR selected clusters display very similar surface brightness distributions of galaxy MIR light. In addition, the average location and amplitude of the galaxy red sequence as measured from stacked colour histograms is very similar in the X-ray and MIR-selected samples. The sub-sample of X-ray faint, MIR bright clusters displays a distribution of BCG-barycentre position offsets which extends to higher values than all other samples. This observation indicates that such clusters may exist in a more disturbed state compared to the majority of the distant cluster population sampled by XMM-LSS and SpARCS. This conclusion is supported by stacked X-ray images for the X-ray faint, MIR bright cluster sub-sample that display weak, centrally-concentrated X-ray emission, consistent with a population of growing clusters accreting from an extended envelope of material.

Eight ultra-faint galaxy candidates discovered in year two of the Dark Energy Survey

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

Drlica-Wagner, A.

Here, we report the discovery of eight new ultra-faint dwarf galaxy candidates in the second year of optical imaging data from the Dark Energy Survey (DES). Six of these candidates are detected at high confidence, while two lower-confidence candidates are identified in regions of non-uniform survey coverage. The new stellar systems are found by three independent automated search techniques and are identified as overdensities of stars, consistent with the isochrone and luminosity function of an old and metal-poor simple stellar population. The new systems are faint (M V > –4.7more » $$\\mathrm{mag}$$) and span a range of physical sizes (17 $$\\mathrm{pc}$$ < r 1/2 < 181 $$\\mathrm{pc}$$) and heliocentric distances (25 kpc < D ⊙ < 214 kpc). All of the new systems have central surface brightnesses consistent with known ultra-faint dwarf galaxies (μ ≳ 27.5 $$\\mathrm{mag}$$ $$\\mathrm{arcsec}$$ –2). Roughly half of the DES candidates are more distant, less luminous, and/or have lower surface brightnesses than previously known Milky Way satellite galaxies. Most of the candidates are found in the southern part of the DES footprint close to the Magellanic Clouds. We find that the DES data alone exclude (p < 10 –3) a spatially isotropic distribution of Milky Way satellites and that the observed distribution can be well, though not uniquely, described by an association between several of the DES satellites and the Magellanic system. Our model predicts that the full sky may hold ~100 ultra-faint galaxies with physical properties comparable to the DES satellites and that 20%–30% of these would be spatially associated with the Magellanic Clouds.« less

A deep imaging survey of the Pleiades with ROSAT

NASA Technical Reports Server (NTRS)

Stauffer, J. R.; Caillault, J.-P.; Gagne, M.; Prosser, C. F.; Hartmann, L. W.

1994-01-01

We have obtained deep ROSAT images of three regions within the Pleiades open cluster. We have detected 317 X-ray sources in these ROSAT Position Sensitive Proportional Counter (PSPC) images, 171 of which we associate with certain or probable members of the Pleiades cluster. We detect nearly all Pleiades members with spectral types later than G0 and within 25 arcminutes of our three field centers where our sensitivity is highest. This has allowed us to derive for the first time the luminosity function for the G, K, amd M dwarfs of an open cluster without the need to use statistical techniques to account for the presence of upper limits in the data sample. Because of our high X-ray detection frequency down to the faint limit of the optical catalog, we suspect that some of our unidentified X-ray sources are previously unknown, very low-mass members of Pleiades. A large fraction of the Pleiades members detected with ROSAT have published rotational velocities. Plots of L(sub X)/L(sub Bol) versus spectroscopic rotational velocity show tightly correlated `saturation' type relations for stars with ((B - V)(sub 0)) greater than or equal to 0.60. For each of several color ranges, X-ray luminosities rise rapidly with increasing rotation rate until c sin i approximately equal to 15 km/sec, and then remains essentially flat for rotation rates up to at least v sin i approximately equal to 100 km/sec. The dispersion in rotation among low-mass stars in the Pleiades is by far the dominant contributor to the dispersion in L(sub X) at a given mass. Only about 35% of the B, A, and early F stars in the Pleiades are detected as X-ray sources in our survey. There is no correlation between X-ray flux and rotation for these stars. The X-ray luminosity function for the early-type Pleiades stars appears to be bimodal -- with only a few exceptions, we either detect these stars at fluxes in the range found for low-mass stars or we derive X-ray limits below the level found for most Pleiades dwarfs. The X-ray spectra for the early-type Pleiades stars detected by ROSAT are indistinguishable from the spectra of the low-mass Pleiades members. We believe that the simplest explanation for this behavior is that the early-type Pleiades stars are not themselves intrinsic X-ray sources and that the X-ray emission actually arises from low-mass companions to these stars.

Measures of star formation rates from infrared (Herschel) and UV (GALEX) emissions of galaxies in the HerMES fields

NASA Astrophysics Data System (ADS)

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

2010-11-01

The reliability of infrared (IR) and ultraviolet (UV) emissions to measure star formation rates (SFRs) in galaxies is investigated for a large sample of galaxies observed with the Spectral and Photometric Imaging Receiver (SPIRE) and the Photodetector Array Camera and Spectrometer (PACS) instruments on Herschel as part of the Herschel Multi-Tiered Extragalactic Survey (HerMES) project. We build flux-limited 250-μm samples of sources at redshift z < 1, cross-matched with the Spitzer/MIPS and GALEX catalogues. About 60 per cent of the Herschel sources are detected in UV. The total IR luminosities, LIR, of the sources are estimated using a spectral energy distribution (SED) fitting code that fits to fluxes between 24 and 500 μm. Dust attenuation is discussed on the basis of commonly used diagnostics: the LIR/LUV ratio and the slope, β, of the UV continuum. A mean dust attenuation AUV of mag is measured in the samples. LIR/LUV is found to correlate with LIR. Galaxies with and 0.5 < z < 1 exhibit a mean dust attenuation AUV of about 0.7 mag lower than that found for their local counterparts, although with a large dispersion. Our galaxy samples span a large range of β and LIR/LUV values which, for the most part, are distributed between the ranges defined by the relations found locally for starburst and normal star-forming galaxies. As a consequence the recipe commonly applied to local starbursts is found to overestimate the dust attenuation correction in our galaxy sample by a factor of ~2-3. The SFRs deduced from LIR are found to account for about 90 per cent of the total SFR; this percentage drops to 71 per cent for galaxies with (or ). For these faint objects, one needs to combine UV and IR emissions to obtain an accurate measure of the SFR.

1.4 GHz on the Fundamental Plane of black hole activity

NASA Astrophysics Data System (ADS)

Saikia, Payaswini; Körding, Elmar; Dibi, Salome

2018-06-01

The Fundamental Plane (FP) of black hole activity is an empirical relationship between the O III/X-ray luminosity depicting the accretion power, the radio luminosity as a probe of the instantaneous jet power and the mass of the black hole. For the first time, we use the 1.4 GHz FIRST radio luminosities on the optical FP, to investigate whether or not Faint Images of the Radio Sky at Twenty-Centimetres (FIRST) fluxes can trace nuclear activity. We use an SDSS-FIRST cross-correlated sample of 10 149 active galaxies and analyse their positioning on the optical FP. We focus on various reasons that can cause the discrepancy between the observed FIRST radio fluxes and the theoretically expected core radio fluxes, and show that FIRST fluxes are heavily contaminated by non-nuclear, extended components and other environmental factors. We show that the subsample of `compact sources', which should have negligible lobe contribution, statistically follow the FP when corrected for relativistic beaming, while all the other sources lie above the plane. The sample of low-ionization nuclear emission-line regions (LINERs), which should have negligible lobe and beaming contribution, also follow the FP. A combined fit of the low-luminosity AGN and the X-ray binaries, with the LINERs, results in the relation log LR = 0.77 log L_{O III} + 0.69 log M. Assuming that the original FP relation is correct, we conclude that 1.4 GHz FIRST fluxes do not trace the pure `core' jet and instantaneous nuclear activity in the AGN, and one needs to be careful while using it on the FP of black hole activity.

Dissociable Electroencephalograph Correlates of Visual Awareness and Feature-Based Attention

PubMed Central

Chen, Yifan; Wang, Xiaochun; Yu, Yanglan; Liu, Ying

2017-01-01

Background: The relationship between awareness and attention is complex and controversial. A growing body of literature has shown that the neural bases of consciousness and endogenous attention (voluntary attention) are independent. The important role of exogenous attention (reflexive attention) on conscious experience has been noted in several studies. However, exogenous attention can also modulate subliminal processing, suggesting independence between the two processes. The question of whether visual awareness and exogenous attention rely on independent mechanisms under certain circumstances remains unanswered. Methods: In the current study, electroencephalograph recordings were conducted using 64 channels from 16 subjects while subjects attempted to detect faint speed changes of colored rotating dots. Awareness and attention were manipulated throughout trials in order to test whether exogenous attention and visual awareness rely on independent mechanisms. Results: Neural activity related to consciousness was recorded in the following cue-locked time-windows (event related potential, cluster- based permutation test): 0–50, 150–200, and 750–800 ms. With a more liberal threshold, the inferior occipital lobe was found to be the source of awareness-related activity in the 0–50 ms range. In the later 150–200 ms range, activity in the fusiform and post-central gyrus was related to awareness. Awareness-related activation in the later 750–800 ms range was more widely distributed. This awareness-related activation pattern was quite different from that of attention. Attention-related neural activity was emphasized in the 750–800 ms time window and the main source of attention-related activity was localized to the right angular gyrus. These results suggest that exogenous attention and visual consciousness correspond to different and relatively independent neural mechanisms and are distinct processes under certain conditions. PMID:29180950

First Results from Faint Infrared Grism Survey (Figs): First Simultaneous Detection of Ly Alpha Emission and Lyman Break From a Galaxy at Z =7.51

NASA Technical Reports Server (NTRS)

Tilvi, V.; Pirzkal, N.; Malhotra, S.; Finkelstein, S. L.; Rhoads, J. E.; Windhorst, R.; Grogin, N. A.; Koekemoer, A.; Zakamska, N. L.; Ryan, R.;

A Magnified View of the Epoch of Reionization with the Hubble Frontier Fields

NASA Astrophysics Data System (ADS)

Livermore, Rachael C.; Finkelstein, Steven L.; Lotz, Jennifer M.

2017-06-01

The Hubble Frontier Fields program has obtained deep optical and near-infrared Hubble Space Telescope imaging of six galaxy clusters and associated parallel fields. The depth of the imaging (m_AB ~ 29) means we can identify faint galaxies at z >6, and those in the cluster fields also benefit from magnification due to strong gravitational lensing. Using wavelet decomposition to subtract the foreground cluster galaxies, we can reach intrinsic absolute magnitudes of M_UV ~ -12.5 at z ~ 6. Here, we present the UV luminosity functions at 6

The UV Luminosity Function at 6 < z < 10 from the Hubble Frontier Fields

NASA Astrophysics Data System (ADS)

Livermore, Rachael C.; Finkelstein, Steven L.; Lotz, Jennifer M.

2017-01-01

The Hubble Frontier Fields program has obtained deep optical and near-infrared Hubble Space Telescope imaging of six galaxy clusters and associated parallel fields. The depth of the imaging (m_AB ~ 29) means we can identify faint galaxies at z > 6, and those in the cluster fields also benefit from magnification due to strong gravitational lensing that allows us to reach intrinsic absolute magnitudes of M_UV ~ -12.5 at z ~ 6. Here, we present the UV luminosity functions at 6 < z < 10 from the complete Hubble Frontier Fields data, revealing a steep faint-end slope that extends to the limits of the data. The lack of any apparent turnover in the luminosity functions means that faint galaxies in the early Universe may have provided sufficient ionizing radiation to sustain reionization.

A radio spectral index map and catalogue at 147-1400 MHz covering 80 per cent of the sky

NASA Astrophysics Data System (ADS)

de Gasperin, F.; Intema, H. T.; Frail, D. A.

2018-03-01

The radio spectral index is a powerful probe for classifying cosmic radio sources and understanding the origin of the radio emission. Combining data at 147 MHz and 1.4 GHz from the TIFR GMRT Sky Survey (TGSS) and the NRAO VLA Sky Survey (NVSS), we produced a large-area radio spectral index map of ˜80 per cent of the sky (Dec. > - 40 deg), as well as a radio spectral index catalogue containing 1396 515 sources, of which 503 647 are not upper or lower limits. Almost every TGSS source has a detected counterpart, while this is true only for 36 per cent of NVSS sources. We released both the map and the catalogue to the astronomical community. The catalogue is analysed to discover systematic behaviours in the cosmic radio population. We find a differential spectral behaviour between faint and bright sources as well as between compact and extended sources. These trends are explained in terms of radio galaxy evolution. We also confirm earlier reports of an excess of steep-spectrum sources along the galactic plane. This corresponds to 86 compact and steep-spectrum source in excess compared to expectations. The properties of this excess are consistent with normal non-recycled pulsars, which may have been missed by pulsation searches due to larger than average scattering along the line of sight.

CDM analysis

NASA Technical Reports Server (NTRS)

Larson, Robert E.; Mcentire, Paul L.; Oreilly, John G.

1993-01-01

The C Data Manager (CDM) is an advanced tool for creating an object-oriented database and for processing queries related to objects stored in that database. The CDM source code was purchased and will be modified over the course of the Arachnid project. In this report, the modified CDM is referred to as MCDM. Using MCDM, a detailed series of experiments was designed and conducted on a Sun Sparcstation. The primary results and analysis of the CDM experiment are provided in this report. The experiments involved creating the Long-form Faint Source Catalog (LFSC) database and then analyzing it with respect to following: (1) the relationships between the volume of data and the time required to create a database; (2) the storage requirements of the database files; and (3) the properties of query algorithms. The effort focused on defining, implementing, and analyzing seven experimental scenarios: (1) find all sources by right ascension--RA; (2) find all sources by declination--DEC; (3) find all sources in the right ascension interval--RA1, RA2; (4) find all sources in the declination interval--DEC1, DEC2; (5) find all sources in the rectangle defined by--RA1, RA2, DEC1, DEC2; (6) find all sources that meet certain compound conditions; and (7) analyze a variety of query algorithms. Throughout this document, the numerical results obtained from these scenarios are reported; conclusions are presented at the end of the document.

Faint Photoelectric Photometric Standard Star Sequences

DTIC Science & Technology

1988-07-15

data awaiting additional study which will result in published research papers . The following list is a compilation of the publications which have...Astrophysical Journal, 323, 271, 1987. papers in preparation.... 1. "The Open Cluster van den Bergh Hagen-Harris No. 99", by A. U. Landolt, C. L...REPORT For a Grant for Basic Scientific Research (AFOSR Grant No. 82-0192) from The Air Force Office of Scientific Research entitled FAINT

Does faint galaxy clustering contradict gravitational instability?

NASA Technical Reports Server (NTRS)

Melott, Adrian L.

1992-01-01

It has been argued, based on the weakness of clustering of faint galaxies, that these objects cannot be the precursors of present galaxies in a simple Einstein-de Sitter model universe with clustering driven by gravitational instability. It is shown that the assumptions made about the growth of clustering were too restrictive. In such a universe, the growth of clustering can easily be fast enough to match the data.

Horologium II: A Second Ultra-faint Milky Way Satellite in the Horologium Constellation

NASA Astrophysics Data System (ADS)

Kim, Dongwon; Jerjen, Helmut

2015-08-01

We report the discovery of a new ultra-faint Milky Way satellite candidate, Horologium II (Hor II), detected in the Dark Energy Survey Y1A1 public data. Hor II features a half-light radius of {r}{{h}}=47+/- 10 pc and a total luminosity of {M}V=-{2.6}-0.3+0.2 that place it in the realm of ultra-faint dwarf galaxies on the size-luminosity plane. The stellar population of the new satellite is consistent with an old (˜13.5 Gyr) and metal-poor ([Fe/H] ˜ -2.1) isochrone at a distance modulus of (m-M)=19.46+/- 0.20, or a heliocentric distance of 78 ± 8 kpc, in the color-magnitude diagram. Hor II has a distance similar to the Sculptor dwarf spheroidal galaxy (˜82 kpc) and the recently reported ultra-faint satellites Eridanus III (87 ± 8 kpc) and Horologium I (79 ± 8 kpc). All four satellites are well aligned on the sky, which suggests a possible common origin. As Sculptor is moving on a retrograde orbit within the Vast Polar Structure when compared to the other classical MW satellite galaxies including the Magellanic Clouds, this hypothesis can be tested once proper motion measurements become available.

Serendipitous discovery of a faint dwarf galaxy near a Local Volume dwarf

NASA Astrophysics Data System (ADS)

Makarova, L. N.; Makarov, D. I.; Antipova, A. V.; Karachentsev, I. D.; Tully, R. B.

2018-03-01

A faint dwarf irregular galaxy has been discovered in the HST/ACS field of LV J1157+5638. The galaxy is resolved into individual stars, including the brightest magnitude of the red giant branch. The dwarf is very likely a physical satellite of LV J1157+5638. The distance modulus of LV J1157+5638 using the tip of the red giant branch (TRGB) distance indicator is 29.82 ± 0.09 mag (D = 9.22 ± 0.38 Mpc). The TRGB distance modulus of LV J1157+5638 sat is 29.76 ± 0.11 mag (D = 8.95 ± 0.42 Mpc). The distances to the two galaxies are consistent within the uncertainties. The projected separation between them is only 3.9 kpc. LV J1157+5638 has a total absolute V magnitude of -13.26 ± 0.10 and linear Holmberg diameter of 1.36 kpc, whereas its faint satellite LV J1157+5638 sat has MV = -9.38 ± 0.13 mag and Holmberg diameter of 0.37 kpc. Such a faint dwarf was discovered for the first time beyond the nearest 4 Mpc from us. The presence of main-sequence stars in both galaxies unambiguously indicates the classification of the objects as dwarf irregulars with recent or ongoing star formation events in both galaxies.

The Faint End of the z = 5 Quasar Luminosity Function from the CFHTLS

NASA Astrophysics Data System (ADS)

McGreer, Ian D.; Fan, Xiaohui; Jiang, Linhua; Cai, Zheng

2018-03-01

We present results from a spectroscopic survey of z ∼ 5 quasars in the CFHT Legacy Survey. Using both optical color selection and a likelihood method, we select 97 candidates over an area of 105 deg2 to a limit of i AB < 23.2, and 7 candidates in the range 23.2 < i AB < 23.7 over an area of 18.5 deg2. Spectroscopic observations for 43 candidates were obtained with Gemini, MMT, and Large Binocular Telescope, of which 37 are z > 4 quasars. This sample extends measurements of the quasar luminosity function ∼1.5 mag fainter than our previous work in Sloan Digital Sky Survey Stripe 82. The resulting luminosity function is in good agreement with our previous results, and suggests that the faint end slope is not steep. We perform a detailed examination of our survey completeness, particularly the impact of the Lyα emission assumed in our quasar spectral models, and find hints that the observed Lyα emission from faint z ∼ 5 quasars is weaker than for z ∼ 3 quasars at a similar luminosity. Our results strongly disfavor a significant contribution of faint quasars to the hydrogen-ionizing background at z = 5.

Local Group ultra-faint dwarf galaxies in the reionization era

NASA Astrophysics Data System (ADS)

Weisz, Daniel R.; Boylan-Kolchin, Michael

2017-07-01

Motivated by the stellar fossil record of Local Group (LG) dwarf galaxies, we show that the star-forming ancestors of the faintest ultra-faint dwarf galaxies (UFDs; MV ˜ -2 or M⋆ ˜ 102 at z = 0) had ultraviolet (UV) luminosities of MUV ˜ -3 to -6 during reionization (z ˜ 6-10). The existence of such faint galaxies has substantial implications for early epochs of galaxy formation and reionization. If the faint-end slopes of the UV luminosity functions (UVLFs) during reionization are steep (α ≲ -2) to MUV ˜ -3, then (I) the ancestors of UFDs produced >50 per cent of UV flux from galaxies; (II) galaxies can maintain reionization with escape fractions that are more than two times lower than currently adopted values; (III) direct Hubble Space Telescope and James Webb Space Telescope observations may detect only ˜10-50 per cent of the UV light from galaxies; and (IV) the cosmic star formation history increases by ≳ 4-6 at z ≳ 6. Significant flux from UFDs, and resultant tensions with LG dwarf galaxy counts, is reduced if the high-redshift UVLF turns over. Independent of the UVLF shape, the existence of a large population of UFDs requires a non-zero luminosity function to MUV ˜ -3 during reionization.

Chandra Detection of a Pulsar Wind Nebula Associated With Supernova Remnant 3C 396

NASA Technical Reports Server (NTRS)

Olbert, C. M.; Keohane, J. W.; Arnaud, K. A.; Dyer, K. K.; Reynolds, S. P.; Safi-Harb, S.

2003-01-01

We present a 100 ks observation of the Galactic supernova remnant 3C396 (G39.2-0.3) with the Chandra X-Ray Observatory that we compare to a 20cm map of the remnant from the Very Large Array. In the Chandra images, a nonthermal nebula containing an embedded pointlike source is apparent near the center of the remnant which we interpret as a synchrotron pulsar wind nebula surrounding a yet undetected pulsar. From the 2-10 keV spectrum for the nebula (N(sub H) = 5.3 plus or minus 0.9 x 10(exp 22) per square centimeter, GAMMA =1.5 plus or minus 0.3) we derive an unabsorbed x-ray flux of S(sub z)=1.62 x 10(exp -12) erg per square centimeter per second, and from this we estimate the spin-down power of the neutron star to be E(sup dot) = 7.2 x 10(exp 36) ergs per second. The central nebula is morphologically complex, showing bent, extended structure. The radio and X-ray shells of the remnant correlate poorly on large scales, particularly on the eastern half of the remnant, which appears very faint in X-ray images. At both radio and X-ray wavelengths the western half of the remnant is substantially brighter than the east.

Tunable Reflective Spatial Heterodyne Spectrometer: A Technique for High Resolving Power, Wide Field Of View Observation Of Diffuse Emission Line Sources

NASA Astrophysics Data System (ADS)

Hosseini, Seyedeh Sona

The purpose of this dissertation is to discuss the need for new technology in broadband high-resolution spectroscopy based on the emerging technique of Spatial Heterodyne Spectroscopy (SHS) and to propose new solutions that should enhance and generalize this technology to other fields. Spectroscopy is a proven tool for determining compositional and other properties of remote objects. Narrow band imaging and low resolving spectroscopic measurements provide information about composition, photochemical evolution, energy distribution and density. The extension to high resolving power provides further access to temperature, velocity, isotopic ratios, separation of blended sources, and opacity effects. In current high resolving power devices, the drawback of high-resolution spectroscopy is bound to the instrumental limitations of lower throughput, the necessity of small entrance apertures, sensitivity, field of view, and large physical instrumental size. These limitations quickly become handicapping for observation of faint and/or extended targets and for spacecraft encounters. A technique with promise for the study of faint and extended sources at high resolving power is the reflective format of the Spatial Heterodyne Spectrometer (SHS). SHS instruments are compact and naturally tailored for both high etendue (defined in section 2.2.5) and high resolving power. In contrast, to achieve similar spectral grasp, grating spectrometers require large telescopes. For reference, SHS is a cyclical interferometer that produces Fizeau fringe pattern for all other wavelengths except the tuned wavelength. The large etendue obtained by SHS instruments makes them ideal for observations of extended, low surface brightness, isolated emission line sources, while their intrinsically high spectral resolution enables one to study the dynamical and physical properties described above. This document contains four chapters. Chapter 1, introduces a class of scientific targets that formerly have not been extensively observed due to absence of technical capabilities in current apparatus. We will introduce the concept of Special Heterodyne Spectrometers and address how it can fill the gap. Chapter 2 reports on the development of a new mathematical frame work for the Reflective SHS. Chapter 3 provides the details of the design and construction of a Tunable Reflective SHS at both UC Davis laboratory and Mt. Hamilton, Lick Observatory, CA. And chapter 4 contains an overview of the prospects of SHS instruments in future.

KECK SPECTROSCOPY OF FAINT 3 < z < 8 LYMAN BREAK GALAXIES: EVIDENCE FOR A DECLINING FRACTION OF EMISSION LINE SOURCES IN THE REDSHIFT RANGE 6 < z < 8

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

Schenker, Matthew A.; Ellis, Richard S.; Robertson, Brant E.

2012-01-10

Using deep Keck spectroscopy of Lyman break galaxies selected from infrared imaging data taken with the Wide Field Camera 3 on board the Hubble Space Telescope, we present new evidence for a reversal in the redshift-dependent fraction of star-forming galaxies with detectable Lyman alpha (Ly{alpha}) emission in the redshift range 6.3 < z < 8.8. Our earlier surveys with the DEIMOS spectrograph demonstrated a significant increase with redshift in the fraction of line emitting galaxies over the interval 4 < z < 6, particularly for intrinsically faint systems which dominate the luminosity density. Using the longer wavelength sensitivities of Lowmore » Resolution Imaging Spectrometer and NIRSPEC, we have targeted 19 Lyman break galaxies selected using recent WFC3/IR data whose photometric redshifts are in the range 6.3 < z < 8.8 and which span a wide range of intrinsic luminosities. Our spectroscopic exposures typically reach a 5{sigma} sensitivity of <50 A for the rest-frame equivalent width (EW) of Ly{alpha} emission. Despite the high fraction of emitters seen only a few hundred million years later, we find only two convincing and one possible line emitter in our more distant sample. Combining with published data on a further seven sources obtained using FORS2 on the ESO Very Large Telescope, and assuming continuity in the trends found at lower redshift, we discuss the significance of this apparent reversal in the redshift-dependent Ly{alpha} fraction in the context of our range in continuum luminosity. Assuming all the targeted sources are at their photometric redshift and our assumptions about the Ly{alpha} EW distribution are correct, we would expect to find so few emitters in less than 1% of the realizations drawn from our lower redshift samples. Our new results provide further support for the suggestion that, at the redshifts now being probed spectroscopically, we are entering the era where the intergalactic medium is partially neutral. With the arrival of more sensitive multi-slit infrared spectrographs, the prospects for improving the statistical validity of this result are promising.« less

The faint end of the red sequence galaxy luminosity function: unveiling surface brightness selection effects with the CLASH clusters

NASA Astrophysics Data System (ADS)

Martinet, Nicolas; Durret, Florence; Adami, Christophe; Rudnick, Gregory

2017-08-01

Characterizing the evolution of the faint end of the cluster red sequence (RS) galaxy luminosity function (GLF) with redshift is a milestone in understanding galaxy evolution. However, the community is still divided in that respect, hesitating between an enrichment of the RS due to efficient quenching of blue galaxies from z 1 to present-day or a scenario in which the RS is built at a higher redshift and does not evolve afterwards. Recently, it has been proposed that surface brightness (SB) selection effects could possibly solve the literature disagreement, accounting for the diminishing RS faint population in ground-based observations. We investigate this hypothesis by comparing the RS GLFs of 16 CLASH clusters computed independently from ground-based Subaru/Suprime-Cam V and Ip or Ic images and space-based HST/ACS F606W and F814W images in the redshift range 0.187 ≤ z ≤ 0.686. We stack individual cluster GLFs in two redshift bins (0.187 ≤ z ≤ 0.399 and 0.400 ≤ z ≤ 0.686) and two mass (6 × 1014M⊙ ≤ M200< 1015M⊙ and 1015M⊙ ≤ M200) bins, and also measure the evolution with the enclosing radius from 0.5 Mpc up to the virial radius for the Subaru large field of view data. Finally, we simulate the low-redshift clusters at higher redshift to investigate SB dimming effects. We find similar RS GLFs for space- and ground-based data, with a difference of 0.2σ in the faint end parameter α when stacking all clusters together and a maximum difference of 0.9σ in the case of the high-redshift stack, demonstrating a weak dependence on the type of observation in the probed range of redshift and mass. When considering the full sample, we estimate α = - 0.76 ± 0.07 and α = - 0.78 ± 0.06 with HST and Subaru, respectively. We note a mild variation of the faint end between the high- and low-redshift subsamples at a 1.7σ and 2.6σ significance. We investigate the effect of SB dimming by simulating our low-redshift galaxies at high redshift. We measure an evolution in the faint end slope of less than 1σ in this case, implying that the observed signature is larger than one would expect from SB dimming alone, and indicating a true evolution in the faint end slope. Finally, we find no variation with mass or radius in the probed range of these two parameters. We therefore conclude that quenching is mildly affecting cluster galaxies at z ≲ 0.7 leading to a small enrichment of the RS until today, and that the different faint end slopes observed in the literature are probably due to specific cluster-to-cluster variation. Based on publicly available HST data acquired with ACS through the CLASH and COSMOS surveys. Also based on Subaru Suprime-Cam archive data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

Panchromatic properties of 99000 galaxies detected by SDSS, and (some by) ROSAT, GALEX, 2MASS, IRAS, GB6, FIRST, NVSS and WENSS surveys

NASA Astrophysics Data System (ADS)

Obrić, M.; Ivezić, Ž.; Best, P. N.; Lupton, R. H.; Tremonti, C.; Brinchmann, J.; Agüeros, M. A.; Knapp, G. R.; Gunn, J. E.; Rockosi, C. M.; Schlegel, D.; Finkbeiner, D.; Gaćeša, M.; Smolčić, V.; Anderson, S. F.; Voges, W.; Jurić, M.; Siverd, R. J.; Steinhardt, W.; Jagoda, A. S.; Blanton, M. R.; Schneider, D. P.

2006-08-01

We discuss the panchromatic properties of 99088 galaxies selected from the Sloan Digital Sky Survey (SDSS) Data Release 1 `main' spectroscopic sample (a flux-limited sample for 1360deg2). These galaxies are positionally matched to sources detected by ROSAT, Galaxy Evolution Explorer (GALEX), two-Micron All-Sky Survey (2MASS), Infrared Astronomical Satellite (IRAS), Green Bank GB6 survey (GB6), Faint Images of the Radio Sky at Twenty-centimetres (FIRST), NRAO VLA Sky Survey (NVSS) and Westerbork Northern Sky Survey (WENSS). The matching fraction varies from <1 per cent for ROSAT and GB6 to ~40 per cent for GALEX and 2MASS. In addition to its size, the advantages of this sample are well-controlled selection effects, faint flux limits and the wealth of measured parameters, including accurate X-ray to radio photometry, angular sizes and optical spectra. We find strong correlations between the detection fraction at other wavelengths and optical properties such as flux, colours and emission-line strengths. For example, ~2/3 of SDSS `main' galaxies classified as active galactic nucleus (AGN) using emission-line strengths are detected by 2MASS, while the corresponding fraction for star-forming galaxies (SFs) is only ~1/10. Similarly, over 90 per cent of galaxies detected by IRAS display strong emission lines in their optical spectra, compared to ~50 per cent for the whole SDSS sample. Using GALEX, SDSS and 2MASS data, we construct the ultraviolet-infrared (UV-IR) broad-band spectral energy distributions for various types of galaxies, and find that they form a nearly one-parameter family. For example, the SDSS u- and r-band data, supplemented with redshift, can be used to `predict' K-band magnitudes measured by 2MASS with an rms scatter of only 0.2mag. When a dust content estimate determined from SDSS spectra with the aid of models is also utilized, this scatter decreases to 0.1mag and can be fully accounted for by measurement uncertainties. We demonstrate that this interstellar dust content, inferred from optical SDSS spectra by Kauffmann et al., is indeed higher for galaxies detected by IRAS and that it can be used to `predict' measured IRAS 60μm flux density within a factor of 2 using only SDSS data. We also show that the position of a galaxy in the emission-line-based Baldwin-Phillips-Terlevich diagram is correlated with the optical light concentration index and u - r colour determined from the SDSS broad-band imaging data, and discuss changes in the morphology of this diagram induced by requiring detections at other wavelengths. Notably, we find that SDSS `main' galaxies detected by GALEX include a non-negligible fraction (10-30 per cent) of AGNs, and hence do not represent a clean sample of starburst galaxies. We study the IR-radio correlation and find evidence that its slope may be different for AGN and SFs and related to the Hα/Hβ line-strength ratio.

MOXE: An X-ray all-sky monitor for Soviet Spectrum-X-Gamma Mission

NASA Technical Reports Server (NTRS)

Priedhorsky, W.; Fenimore, E. E.; Moss, C. E.; Kelley, R. L.; Holt, S. S.

1989-01-01

A Monitoring Monitoring X-Ray Equipment (MOXE) is being developed for the Soviet Spectrum-X-Gamma Mission. MOXE is an X-ray all-sky monitor based on array of pinhole cameras, to be provided via a collaboration between Goddard Space Flight Center and Los Alamos National Laboratory. The objectives are to alert other observers on Spectrum-X-Gamma and other platforms of interesting transient activity, and to synoptically monitor the X-ray sky and study long-term changes in X-ray binaries. MOXE will be sensitive to sources as faint as 2 milliCrab (5 sigma) in 1 day, and cover the 2 to 20 KeV band.

A search for N-type galaxies

NASA Technical Reports Server (NTRS)

Jefferies, J. T.

1971-01-01

A large number of distant clusters of galaxies was examined for the presence of a bright compact galaxy or blue stellar object. Nearly 600 square degrees of sky were searched using glass copies of the National Geographic Society-Palomar Observatory Sky Survey plates, and over 20 fields were selected for observation. The objects were examined for infrared and ultraviolet excesses, using wideband filter photography and spectroscopy. Initial findings include a faint, distant cluster of galaxies near the quasi-stellar radio source 4C 37.43 with a red shift of 0.370. One of these galaxies has an emission line at 6895 A, indicating a possible red shift of 0.377 of the 5007 A line of (0 III).

Extending the ICRF into the Infrared: 2MASS - UCAC Astrometry

NASA Technical Reports Server (NTRS)

Zacharias, Norbert; McCallon, Howard L.; Kopan, Eugene; Cutri, Roc M.

2000-01-01

An external comparison between the infrared 2MASS and the optical UCAC positions was performed, both being on the same system, the ICRS. About 48 million sources in common were identified. Random errors of the 2MASS catalog positions are about 60 to 70 mas per coordinate for the Ks = 4 to 14 range, increasing to about 100 to 150 mas for saturated and very faint stars. Systematic position differences between the 2 catalogs are very small, about 5 to 10 mas as a function of magnitude and color, with somewhat larger errors as a function of right ascension and declination. The extension of the ICRF into the infrared has become a reality.

Around Marshall

NASA Image and Video Library

1993-06-30

This photograph shows STS-61 crewmemmbers training for the Hubble Space Telescope (HST) servicing mission in the Marshall Space Flight Center's (MSFC's) Neutral Buoyancy Simulator (NBS). Two months after its deployment in space, scientists detected a 2-micron spherical aberration in the primary mirror of the HST that affected the telescope's ability to focus faint light sources into a precise point. This imperfection was very slight, one-fiftieth of the width of a human hair. A scheduled Space Service servicing mission (STS-61) in 1993 permitted scientists to correct the problem. The MSFC NBS provided an excellent environment for testing hardware to examine how it would operate in space and for evaluating techniques for space construction and spacecraft servicing.

Mid-Infrared Observations of Possible Intergalactic Star Forming Regions in the Leo Ring

NASA Astrophysics Data System (ADS)

Giroux, Mark; Smith, B.; Struck, C.

2011-05-01

Within the Leo group of galaxies lies a gigantic loop of intergalactic gas known as the Leo Ring. Not clearly associated with any particular galaxy, its origin remains uncertain. It may be a primordial intergalactic cloud alternatively, it may be a collision ring, or have a tidal origin. Combining archival Spitzer images of this structure with published UV and optical data, we investigate the mid-infrared properties of possible knots of star formation in the ring. These sources are very faint in the mid-infrared compared to star forming regions in the tidal features of interacting galaxies. This suggests they are either deficient in dust, or they may not be associated with the ring.

The far-infrared properties of the CfA galaxy sample. I - The catalog

NASA Technical Reports Server (NTRS)

Thuan, T. X.; Sauvage, M.

1992-01-01

IRAS flux densities are presented for all galaxies in the Center for Astrophysics magnitude-limited sample (mB not greater than 14.5) detected in the IRAS Faint Source Survey (FSS), a total of 1544 galaxies. The detection rate in the FSS is slightly larger than in the PSC for the long-wavelength 60- and 100-micron bands, but improves by a factor of about 3 or more for the short wavelength 12- and 25-micron bands. This optically selected sample consists of galaxies which are, on average, much less IR-active than galaxies in IR-selected samples. It possesses accurate and complete redshift, morphological, and magnitude information, along with observations at other wavelengths.

Multiparty Quantum Secret Sharing of Key Using Practical Faint Laser Pulses

NASA Astrophysics Data System (ADS)

Zhang, Zhan-Jun; Man, Zhong-Xiao

2005-07-01

Based on a bidirectional quantum key distribution protocol [Phys. Rev. A 70 (2004) 012311], we propose a (m-1,m-1)-threshold scheme of m (m >= 3)-party quantum secret sharing of key by using practical faint laser pulses. In our scheme, if all the m-1 sharers collaborate, they can obtain the joint secret key from the message sender. Our scheme is more feasible according to the present-day technology.

Variable Stars in the Field of the Hydra II Ultra-Faint Dwarf Galaxy

NASA Astrophysics Data System (ADS)

Vivas, Anna Katherina; Olsen, Knut A.; Blum, Robert D.; Nidever, David L.; Walker, Alistair R.; Martin, Nicolas; Besla, Gurtina; Gallart, Carme; Van Der Marel, Roeland P.; Majewski, Steven R.; Munoz, Ricardo; Kaleida, Catherine C.; Saha, Abhijit; Conn, Blair; Jin, Shoko

2016-06-01

We searched for variable stars in Hydra II, one of the recently discovered ultra-faint dwarf satellites of the Milky Way, using gri time-series obtained with the Dark Energy Camera (DECam) at Cerro Tololo Inter-American Observatory, Chile. We discovered one RR Lyrae star in the galaxy which was used to derive a distance of 154±8 kpc to this system and to re-calculate its absolute magnitude and half-light radius.A comparison with other RR Lyrae stars in ultra-faint systems indicates similar pulsational properties among them, which are different to those found among halo field stars and those in the largest of the Milky Way satellites. We also report the discovery of 31 additional short period variables in the field of view (RR Lyrae, SX Phe, eclipsing binaries, and a likely anomalous cepheid) which are likely not related with Hydra II.

Gravity and Extreme Magnetism SMEX

NASA Technical Reports Server (NTRS)

Swank, Jean; Kallman, Timothy R.; Jahoda, Keith M.

2008-01-01

Gas accreting ont,o black holes and neutron stars form a dynamic system generating X-rays with spectroscopic signatures and varying on time scales determined by the system. The radiation from various parts of these systems is surely polarized and compact sources have been calculated to give rise to net polarization from the unresolved sum of the radiation from the systems. Polarization has been looked to for some time as also bearing the imprint of strong gravity and providing complementary information that could resolve ambiguities between the physical models that can give rise to frequencies, time delays, and spectra. In the cases of both stellar black holes and supermassive black holes the net polarizations predicted for probable disk and corona models are less than 10 needed. This sensitivity can be achieved, even for sources as faint as 1 milliCrab, in the Gravity and Extreme Magnetism SMEX (GEMS) mission that uses foil mirrors and Time Projection Chamber detectors. Similarities have been pointed out between the timing and the spectral characteristics of low mass X-ray binaries and stellar black hole sources. Polarization measurements for these sources could play a role in determining the configuration of the disk and the neutron star.

Monitoring the variability of active galactic nuclei from a space-based platform

NASA Technical Reports Server (NTRS)

Peterson, Bradley M.; Atwood, Bruce; Byard, Paul L.

1994-01-01

Detailed monitoring of AGN's with FRESIP can provide well-sampled light curves for a large number of AGN's. Such data are completely unprecedented in this field, and will provide powerful new constraints on the origin of the UV/optical continuum in AGN's. The FRESIP baseline design will allow 1 percent photometry on sources brighter than V approximately equals 19.6 mag, and we estimate that over 300 sources can be studied. We point out that digitization effects will have a significant negative impact on the faint limit and the number of detectable sources will decrease dramatically if a fixed gain setting (estimated to be nominally 25 e(-) per ADU) is used for all read-outs. We note that the primary limitation to studying AGN's is background (sky and read-out noise) rather than source/background contrast with a focused telescope and by longer integrations. While we believe that it may be possible to achieve the AGN-monitoring science goals with a more compact and much less expensive telescope, the proposed FRESIP satellite affords an excellent opportunity to attain the required data at essentially zero cost as a secondary goal of a more complex mission.

Stellar Clusters in the NGC 6334 Star-Forming Complex

NASA Astrophysics Data System (ADS)

Feigelson, Eric D.; Martin, Amanda L.; McNeill, Collin J.; Broos, Patrick S.; Garmire, Gordon P.

2009-07-01

The full stellar population of NGC 6334, one of the most spectacular regions of massive star formation in the nearby Galaxy, has not been well sampled in past studies. We analyze here a mosaic of two Chandra X-ray Observatory images of the region using sensitive data analysis methods, giving a list of 1607 faint X-ray sources with arcsecond positions and approximate line-of-sight absorption. About 95% of these are expected to be cluster members, most lower mass pre-main-sequence stars. Extrapolating to low X-ray levels, the total stellar population is estimated to be 20,000-30,000 pre-main-sequence stars. The X-ray sources show a complicated spatial pattern with ~10 distinct star clusters. The heavily obscured clusters are mostly associated with previously known far-infrared sources and radio H II regions. The lightly obscured clusters are mostly newly identified in the X-ray images. Dozens of likely OB stars are found, both in clusters and dispersed throughout the region, suggesting that star formation in the complex has proceeded over millions of years. A number of extraordinarily heavily absorbed X-ray sources are associated with the active regions of star formation.

Detecting new γ-ray sources based on multi-frequency data the case of 1WHSPJ031423.9+061956

NASA Astrophysics Data System (ADS)

Arsioli, Bruno; Chang, Yu Ling

2015-12-01

We use the Fermi Science Tools in an attempt to unveil faint γ-ray blazars that may be above the threshold for detectability with Fermi-LAT and are not identified by automated methods. Our search for new sources in the 100MeV-300GeV band is mainly driven by the 1/2WHSP catalogs, which list high synchrotron peaked blazars expected to be emitters of VHE photons. Here we present the γ-ray detection of 1WHSP J031423.9+061956, modelling its high energy spectrum as a power law. We describe an example where multi-frequency selection, performed at much lower energies (from radio to X-ray), helps to pin-point a high energy source. The 1/2WHSP catalogs are built with the aim of providing a list of TeV targets for the VHE arrays of Cherenkov telescopes. Moreover, these catalogs provide useful seeds for identifying new high energy sources within the raw-data from Fermi. With the aid of multi-frequency data, we can explore the very high energy domain in greater details, improving the description of the γ-ray sky.

The Top 10 List of Gravitational Lens Candidates from the HUBBLE SPACE TELESCOPE Medium Deep Survey

NASA Astrophysics Data System (ADS)

Ratnatunga, Kavan U.; Griffiths, Richard E.; Ostrander, Eric J.

1999-05-01

A total of 10 good candidates for gravitational lensing have been discovered in the WFPC2 images from the Hubble Space Telescope (HST) Medium Deep Survey (MDS) and archival primary observations. These candidate lenses are unique HST discoveries, i.e., they are faint systems with subarcsecond separations between the lensing objects and the lensed source images. Most of them are difficult objects for ground-based spectroscopic confirmation or for measurement of the lens and source redshifts. Seven are ``strong lens'' candidates that appear to have multiple images of the source. Three are cases in which the single image of the source galaxy has been significantly distorted into an arc. The first two quadruply lensed candidates were reported by Ratnatunga et al. We report on the subsequent eight candidates and describe them with simple models based on the assumption of singular isothermal potentials. Residuals from the simple models for some of the candidates indicate that a more complex model for the potential will probably be required to explain the full structural detail of the observations once they are confirmed to be lenses. We also discuss the effective survey area that was searched for these candidate lens objects.

The Einstein@Home Gamma-ray Pulsar Survey. II. Source Selection, Spectral Analysis, and Multiwavelength Follow-up

NASA Astrophysics Data System (ADS)

Wu, J.; Clark, C. J.; Pletsch, H. J.; Guillemot, L.; Johnson, T. J.; Torne, P.; Champion, D. J.; Deneva, J.; Ray, P. S.; Salvetti, D.; Kramer, M.; Aulbert, C.; Beer, C.; Bhattacharyya, B.; Bock, O.; Camilo, F.; Cognard, I.; Cuéllar, A.; Eggenstein, H. B.; Fehrmann, H.; Ferrara, E. C.; Kerr, M.; Machenschalk, B.; Ransom, S. M.; Sanpa-Arsa, S.; Wood, K.

2018-02-01

We report on the analysis of 13 gamma-ray pulsars discovered in the Einstein@Home blind search survey using Fermi Large Area Telescope (LAT) Pass 8 data. The 13 new gamma-ray pulsars were discovered by searching 118 unassociated LAT sources from the third LAT source catalog (3FGL), selected using the Gaussian Mixture Model machine-learning algorithm on the basis of their gamma-ray emission properties being suggestive of pulsar magnetospheric emission. The new gamma-ray pulsars have pulse profiles and spectral properties similar to those of previously detected young gamma-ray pulsars. Follow-up radio observations have revealed faint radio pulsations from two of the newly discovered pulsars and enabled us to derive upper limits on the radio emission from the others, demonstrating that they are likely radio-quiet gamma-ray pulsars. We also present results from modeling the gamma-ray pulse profiles and radio profiles, if available, using different geometric emission models of pulsars. The high discovery rate of this survey, despite the increasing difficulty of blind pulsar searches in gamma rays, suggests that new systematic surveys such as presented in this article should be continued when new LAT source catalogs become available.

Center determination for trailed sources in astronomical observation images

NASA Astrophysics Data System (ADS)

Du, Jun Ju; Hu, Shao Ming; Chen, Xu; Guo, Di Fu

2014-11-01

Images with trailed sources can be obtained when observing near-Earth objects, such as small astroids, space debris, major planets and their satellites, no matter the telescopes track on sidereal speed or the speed of target. The low centering accuracy of these trailed sources is one of the most important sources of the astrometric uncertainty, but how to determine the central positions of the trailed sources accurately remains a significant challenge to image processing techniques, especially in the study of faint or fast moving objects. According to the conditions of one-meter telescope at Weihai Observatory of Shandong University, moment and point-spread-function (PSF) fitting were chosen to develop the image processing pipeline for space debris. The principles and the implementations of both two methods are introduced in this paper. And some simulated images containing trailed sources are analyzed with each technique. The results show that two methods are comparable to obtain the accurate central positions of trailed sources when the signal to noise (SNR) is high. But moment tends to fail for the objects with low SNR. Compared with moment, PSF fitting seems to be more robust and versatile. However, PSF fitting is quite time-consuming. Therefore, if there are enough bright stars in the field, or the high astronometric accuracy is not necessary, moment is competent. Otherwise, the combination of moment and PSF fitting is recommended.

STELLAR X-RAY SOURCES IN THE CHANDRA COSMOS SURVEY

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

Wright, N. J.; Drake, J. J.; Civano, F., E-mail: nwright@cfa.harvard.ed

2010-12-10

We present an analysis of the X-ray properties of a sample of solar- and late-type field stars identified in the Chandra Cosmic Evolution Survey (COSMOS), a deep (160 ks) and wide ({approx}0.9 deg{sup 2}) extragalactic survey. The sample of 60 sources was identified using both morphological and photometric star/galaxy separation methods. We determine X-ray count rates, extract spectra and light curves, and perform spectral fits to determine fluxes and plasma temperatures. Complementary optical and near-IR photometry is also presented and combined with spectroscopy for 48 of the sources to determine spectral types and distances for the sample. We find distancesmore » ranging from 30 pc to {approx}12 kpc, including a number of the most distant and highly active stellar X-ray sources ever detected. This stellar sample extends the known coverage of the L{sub X}-distance plane to greater distances and higher luminosities, but we do not detect as many intrinsically faint X-ray sources compared to previous surveys. Overall the sample is typically more luminous than the active Sun, representing the high-luminosity end of the disk and halo X-ray luminosity functions. The halo population appears to include both low-activity spectrally hard sources that may be emitting through thermal bremsstrahlung, as well as a number of highly active sources in close binaries.« less

Evidence of a Non-universal Stellar Initial Mass Function. Insights from HST Optical Imaging of Six Ultra-faint Dwarf Milky Way Satellites

NASA Astrophysics Data System (ADS)

Gennaro, Mario; Tchernyshyov, Kirill; Brown, Thomas M.; Geha, Marla; Avila, Roberto J.; Guhathakurta, Puragra; Kalirai, Jason S.; Kirby, Evan N.; Renzini, Alvio; Simon, Joshua D.; Tumlinson, Jason; Vargas, Luis C.

2018-03-01

Using deep observations obtained with the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope (HST), we demonstrate that the sub-solar stellar initial mass function (IMF) of six ultra-faint dwarf Milky Way satellites (UFDs) is more bottom light than the IMF of the Milky Way disk. Our data have a lower-mass limit of ∼0.45 M ⊙, while the upper limit is ∼0.8 M ⊙, set by the turnoff mass of these old, metal-poor systems. If formulated as a single power law, we obtain a shallower IMF slope than the Salpeter value of ‑2.3, ranging from ‑1.01 for Leo IV to ‑1.87 for Boötes I. The significance of these deviations depends on the galaxy and is typically 95% or more. When modeled as a log-normal, the IMF fit results in a higher peak mass than in the Milky Way disk, but a Milky Way disk value for the characteristic system mass (∼0.22 M ⊙) is excluded at only 68% significance, and only for some UFDs in the sample. We find that the IMF slope correlates well with the galaxy mean metallicity, and to a lesser degree, with the velocity dispersion and the total mass. The strength of the observed correlations is limited by shot noise in the number of observed stars, but future space-based missions like the James Webb Space Telescope (JWST) and the Wide-Field Infrared Survey Telescope ( WFIRST) will enhance both the number of dwarf Milky Way satellites that can be studied in such detail and the observation depth for individual galaxies. Based 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 GO-12549.

Optical Properties of High Area-to-Mass Objects at GEO

NASA Technical Reports Server (NTRS)

Seitzer, Patrick; Schildknecht, Thomas; Musci, Reto; Flohrer, Tim; Barker, Ed; Stansbery, Eugene; Agapov, Vladimir; Rumyantsev, Vasilij; Biryukov, Vadym; Abercromby, Kira;

X-ray Spectra and Pulse Frequency Changes in SAX J2103.5+4545

NASA Technical Reports Server (NTRS)

Baykal, A.; Stark, M. J.; Swank, J. H.; White, Nicholas E. (Technical Monitor)

2002-01-01

The November 1999 outburst of the transient pulsar SAX J2103.5+4545 was monitored with the large area detectors of the Rossi X-Ray Timing Explorer until the pulsar faded after a year. The 358 s pulsar was spun up for 150 days, at which point the flux dropped quickly by a factor of approximately 7, the frequency saturated and, as the flux continued to decline, a weak spin-down began. The pulses remained strong during the decay and the spin-up/flux correlation can be fit to the Ghosh and Lamb derivations for the spin-up caused by accretion from a thin, pressure-dominated disk, for a distance approximately 3.2 kpc and a surface magnetic field approximately 1.2 x 10(exp 13) Gauss. During the bright spin-up part of the outburst, the flux was subject to strong orbital modulation, peaking approximately 3 days after periastron of the eccentric 12.68 day orbit, while during the faint part, there was little orbital modulation. The X-ray spectra were typical of accreting pulsars, describable by a cut-off power-law, with an emission line near the 6.4 keV of Kappa(sub alpha) fluorescence from cool iron. The equivalent width of this emission did not share the orbital modulation, but nearly doubled during the faint phase, despite little change in the column density. The outburst could have been caused by an episode of increased wind from a Be star, such that a small accretion disk is formed during each periastron passage. A change in the wind and disk structure apparently occurred after 5 months such that the accretion rate was no longer modulated or the diffusion time was longer. The distance estimate implies the X-ray luminosity observed was between 1 X 10(exp 36) ergs s(exp -1) and 6 x 10(exp 34) ergs s(exp -1), with a small but definite correlation of the intrinsic power-law spectral index.

Cross Matching as Strategy to Find Radio Stars

NASA Astrophysics Data System (ADS)

Christian, Tiffany; Kimball, Amy

2018-01-01

Using cross-matching between the FIRST (20cm) and GPS1 (optical) catalogs, we identified possible radio star candidates. This is an extension of earlier work by Kimball et al. (2009), who sought to identify radiostar candidates by cross-matching the FIRST (radio)and SDSS (optical) catalogs, but did not include the consideration of stellar proper motions. We used proper motions from GPS1 to match with FIRST radio sources; the region of sky where they overlap contains ~900,000 FIRST sources and several million GPS1 sources. We used WISE near-infrared and PanSTARRS optical information to identify matches that have stellar colors. Our selection constraints identified 6 stars (spectroscopically confirmed) as radio star candidates. They are faint in the radio (<1 mJy) indicating we may be searching at the limits of the radio survey. Other candidates had no spectral confirmation or object type identification in SIMBAD, which would make them ideal for follow up radio observations. However, random analysis indicated that many other possible candidates were random associations, which may also be true for these 6 stars.

Deep Rapid Optical Follow-Up of Gravitational Wave Sources with the Dark Energy Camera

NASA Astrophysics Data System (ADS)

Cowperthwaite, Philip

2018-01-01

The detection of an electromagnetic counterpart associated with a gravitational wave detection by the Advanced LIGO and VIRGO interferometers is one of the great observational challenges of our time. The large localization regions and potentially faint counterparts require the use of wide-field, large aperture telescopes. As a result, the Dark Energy Camera, a 3.3 sq deg CCD imager on the 4-m Blanco telescope at CTIO in Chile is the most powerful instrument for this task in the Southern Hemisphere. I will report on the results from our joint program between the community and members of the dark energy survey to conduct rapid and efficient follow-up of gravitational wave sources. This includes systematic searches for optical counterparts, as well as developing an understanding of contaminating sources on timescales not normally probed by traditional untargeted supernova surveys. I will additionally comment on the immense science gains to be made by a joint detection and discuss future prospects from the standpoint of both next generation wide-field telescopes and next generation gravitational wave detectors.

Improving MWA/HERA Calibration Using Extended Radio Source Models

NASA Astrophysics Data System (ADS)

Cunningham, Devin; Tasker, Nicholas; University of Washington EoR Imaging Team

2018-01-01

The formation of the first stars and galaxies in the universe is among the greatest mysteries in astrophysics. Using special purpose radio interferometers, it is possible to detect the faint 21 cm radio line emitted by neutral hydrogen in order to characterize the Epoch of Reionization (EoR) and the formation of the first stars and galaxies. We create better models of extended radio sources by reducing component number of deconvolved Murchison Widefield Array (MWA) data by up to 90%, while preserving real structure and flux information. This real structure is confirmed by comparisons to observations of the same extended radio sources from the TIFR GMRT Sky Survey (TGSS) and NRAO VLA Sky Survey (NVSS), which detect at a similar frequency range as the MWA. These sophisticated data reduction techniques not only offer improvements to the calibration of the MWA, but also hold applications for the future sky-based calibration of the Hydrogen Epoch of Reionization Array (HERA). This has the potential to reduce noise in the power spectra from these instruments, and consequently provide a deeper view into the window of EoR.

The missing links of neutron star evolution in the eROSITA all-sky X-ray survey

NASA Astrophysics Data System (ADS)

Pires, A. M.

2017-12-01

The observational manifestation of a neutron star is strongly connected with the properties of its magnetic field. During the star’s lifetime, the field strength and its changes dominate the thermo-rotational evolution and the source phenomenology across the electromagnetic spectrum. Signatures of magnetic field evolution are best traced among elusive groups of X-ray emitting isolated neutron stars (INSs), which are mostly quiet in the radio and γ-ray wavelengths. It is thus important to investigate and survey INSs in X-rays in the hope of discovering peculiar sources and the long-sought missing links that will help us to advance our understanding of neutron star evolution. The Extended Röntgen Survey with an Imaging Telescope Array (eROSITA), the primary instrument on the forthcoming Spectrum-RG mission, will scan the X-ray sky with unprecedented sensitivity and resolution. The survey has thus the unique potential to unveil the X-ray faint end of the neutron star population and probe sources that cannot be assessed by standard pulsar surveys.

High-Resolution Infrared Imaging of FSC 10214+4724: Evidence for Gravitational Lensing

NASA Astrophysics Data System (ADS)

Graham, James R.; Liu, Michael C.

1995-08-01

We present near-infrared observations of the ultraluminous high-redshift (z = 2.286) IRAS source FSC 10214+4724 obtained in 0."4 seeing at the W. M. Keck telescope. These observations show that FSC 10214+4724 consists of a highly symmetric circular arc centered on a second weaker source. The arc has an angular extent of about 140 deg and is probably unresolved in the transverse direction. This morphology constitutes compelling prima facie evidence for a gravitationally lensed system. Our images also contain evidence for the faint counterimage predicted by the lens hypothesis. The morphology of FSC 10214+4724 can be explained in terms of a gravitationally lensed background source if the object at the center of curvature of the arc is an L* galaxy at z ~ 0.7. If FSC 10214+4724 is lensed, then there is significant magnification and its luminosity has been overestimated by a large factor. Our results suggest that FSC 10214+4724 is not a uniquely luminous object but ranks among the most powerful quasars and ultraluminous IRAS galaxies.

Sequencing the Earliest Stages of Active Galactic Nuclei Development Using The Youngest Radio Sources

NASA Astrophysics Data System (ADS)

Collier, Jordan; Filipovic, Miroslav; Norris, Ray; Chow, Kate; Huynh, Minh; Banfield, Julie; Tothill, Nick; Sirothia, Sandeep Kumar; Shabala, Stanislav

2014-04-01

This proposal is a continuation of an extensive project (the core of Collier's PhD) to explore the earliest stages of AGN formation, using Gigahertz-Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) sources. Both are widely believed to represent the earliest stages of radio-loud AGN evolution, with GPS sources preceding CSS sources. In this project, we plan to (a) test this hypothesis, (b) place GPS and CSS sources into an evolutionary sequence with a number of other young AGN candidates, and (c) search for evidence of the evolving accretion mode. We will do this using high-resolution radio observations, with a number of other multiwavelength age indicators, of a carefully selected complete faint sample of 80 GPS/CSS sources. Analysis of the C2730 ELAIS-S1 data shows that we have so far met our goals, resolving the jets of 10/49 sources, and measuring accurate spectral indices from 0.843-10 GHz. This particular proposal is to almost triple the sample size by observing an additional 80 GPS/CSS sources in the Chandra Deep Field South (arguably the best-studied field) and allow a turnover frequency - linear size relation to be derived at >10-sigma. Sources found to be unresolved in our final sample will subsequently be observed with VLBI. Comparing those sources resolved with ATCA to the more compact sources resolved with VLBI will give a distribution of source sizes, helping to answer the question of whether all GPS/CSS sources grow to larger sizes.

The Ancient Martian Climate System

NASA Technical Reports Server (NTRS)

Haberle, Robert M.

2014-01-01

Today Mars is a cold, dry, desert planet. The atmosphere is thin and liquid water is not stable. But there is evidence that very early in its history it was warmer and wetter. Since Mariner 9 first detected fluvial features on its ancient terrains researchers have been trying to understand what climatic conditions could have permitted liquid water to flow on the surface. Though the evidence is compelling, the problem is not yet solved. The main issue is coping with the faint young sun. During the period when warmer conditions prevailed 3.5-3.8 Gy the sun's luminosity was approximately 25% less than it is today. How can we explain the presence of liquid water on the surface of Mars under such conditions? A similar problem exists for Earth, which would have frozen over under a faint sun even though the evidence suggests otherwise. Attempts to solve the "Faint Young Sun Paradox" rely on greenhouse warming from an atmosphere with a different mass and composition than we see today. This is true for both Mars and Earth. However, it is not a straightforward solution. Any greenhouse theory must (a) produce the warming and rainfall needed, (b) have a plausible source for the gases required, (c) be sustainable, and (d) explain how the atmosphere evolved to its present state. These are challenging requirements and judging from the literature they have yet to be met. In this talk I will review the large and growing body of work on the early Mars climate system. I will take a holistic approach that involves many disciplines since our goal is to present an integrated view that touches on each of the requirements listed in the preceding paragraph. I will begin with the observational evidence, which comes from the geology, mineralogy, and isotopic data. Each of the data sets presents a consistent picture of a warmer and wetter past with a thicker atmosphere. How much warmer and wetter and how much thicker is a matter of debate, but conditions then were certainly different than what they are today. I will then discuss the origin and evolution of the early atmosphere from accretion and core formation to the end of the late heavy bombardment, including estimates of the volatile inventory, outgassing history, and potential escape mechanisms. This sets the stage for a comprehensive look at the climate system of early Mars and the attempts to solve the faint young sun problem. I will review the basic physics involved and then step through the different ideas highlighting their strengths and weaknesses. I will then conclude with a summary and a discussion of potentially promising avenues of future research

The Rest-frame Optical Spectroscopic Properties of Lyalpha-emitters at Z~2.5: The Physical Origins of Strong Lyalpha Emission

NASA Astrophysics Data System (ADS)

Trainor, Ryan F.; Strom, Allison L.; Steidel, Charles C.; Rudie, Gwen C.

2016-12-01

We present the rest-frame optical spectroscopic properties of 60 faint (R AB ˜ 27; L ˜ 0.1 L *) Lyα-selected galaxies (LAEs) at z ≈ 2.56. These LAEs also have rest-UV spectra of their Lyα emission line morphologies, which trace the effects of interstellar and circumgalactic gas on the escape of Lyα photons. We find that the LAEs have diverse rest-optical spectra, but their average spectroscopic properties are broadly consistent with the extreme low-metallicity end of the populations of continuum-selected galaxies selected at z ≈ 2-3. In particular, the LAEs have extremely high [O III] λ5008/Hβ ratios (log([O III]/Hβ) ˜ 0.8) and low [N II] λ6585/Hα ratios (log([N II]/Hα) < 1.15). Coupled with a detection of the [O III] λ4364 auroral line, these measurements indicate that the star-forming regions in faint LAEs are characterized by high electron temperatures (T e ≈ 1.8 × 104 K), low oxygen abundances (12 + log(O/H) ≈ 8.04, Z neb ≈ 0.22Z ⊙), and high excitations with respect to their more luminous continuum-selected analogs. Several of our faintest LAEs have line ratios consistent with even lower metallicities, including six with 12 + log(O/H) ≈ 6.9-7.4 (Z neb ≈ 0.02-0.05Z ⊙). We interpret these observations in light of new models of stellar evolution (including binary interactions) that have been shown to produce long-lived populations of hot, massive stars at low metallicities. We find that strong, hard ionizing continua are required to reproduce our observed line ratios, suggesting that faint galaxies are efficient producers of ionizing photons and important analogs of reionization-era galaxies. Furthermore, we investigate the physical trends accompanying Lyα emission across the largest current sample of combined Lyα and rest-optical galaxy spectroscopy, including both the 60 KBSS-Lyα LAEs and 368 more luminous galaxies at similar redshifts. We find that the net Lyα emissivity (parameterized by the Lyα equivalent width) is strongly correlated with nebular excitation and ionization properties and weakly correlated with dust attenuation, suggesting that metallicity plays a strong role in determining the observed properties of these galaxies by modulating their stellar spectra, nebular excitation, and dust content. Based on 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 NASA, and was made possible by the generous financial support of the W.M. Keck Foundation.

THE REST-FRAME OPTICAL SPECTROSCOPIC PROPERTIES OF LY α -EMITTERS AT z  ∼ 2.5: THE PHYSICAL ORIGINS OF STRONG LY α EMISSION

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

Trainor, Ryan F.; Strom, Allison L.; Steidel, Charles C.

We present the rest-frame optical spectroscopic properties of 60 faint ( R {sub AB} ∼ 27; L ∼ 0.1 L {sub *}) Ly α -selected galaxies (LAEs) at z  ≈ 2.56. These LAEs also have rest-UV spectra of their Ly α emission line morphologies, which trace the effects of interstellar and circumgalactic gas on the escape of Ly α photons. We find that the LAEs have diverse rest-optical spectra, but their average spectroscopic properties are broadly consistent with the extreme low-metallicity end of the populations of continuum-selected galaxies selected at z  ≈ 2–3. In particular, the LAEs have extremely high [O iii]more » λ 5008/H β ratios (log([O iii]/H β ) ∼ 0.8) and low [N ii] λ 6585/H α ratios (log([N ii]/H α ) < 1.15). Coupled with a detection of the [O iii] λ 4364 auroral line, these measurements indicate that the star-forming regions in faint LAEs are characterized by high electron temperatures (T{sub e} ≈ 1.8 × 10{sup 4} K), low oxygen abundances (12 + log(O/H) ≈ 8.04, Z{sub neb} ≈ 0.22 Z {sub ⊙}), and high excitations with respect to their more luminous continuum-selected analogs. Several of our faintest LAEs have line ratios consistent with even lower metallicities, including six with 12 + log(O/H) ≈ 6.9–7.4 (Z {sub neb} ≈ 0.02–0.05 Z{sub ⊙}). We interpret these observations in light of new models of stellar evolution (including binary interactions) that have been shown to produce long-lived populations of hot, massive stars at low metallicities. We find that strong, hard ionizing continua are required to reproduce our observed line ratios, suggesting that faint galaxies are efficient producers of ionizing photons and important analogs of reionization-era galaxies. Furthermore, we investigate the physical trends accompanying Ly α emission across the largest current sample of combined Ly α and rest-optical galaxy spectroscopy, including both the 60 KBSS-Ly α LAEs and 368 more luminous galaxies at similar redshifts. We find that the net Ly α emissivity (parameterized by the Ly α equivalent width) is strongly correlated with nebular excitation and ionization properties and weakly correlated with dust attenuation, suggesting that metallicity plays a strong role in determining the observed properties of these galaxies by modulating their stellar spectra, nebular excitation, and dust content.« less

Source detection in astronomical images by Bayesian model comparison

NASA Astrophysics Data System (ADS)

Frean, Marcus; Friedlander, Anna; Johnston-Hollitt, Melanie; Hollitt, Christopher

2014-12-01

The next generation of radio telescopes will generate exabytes of data on hundreds of millions of objects, making automated methods for the detection of astronomical objects ("sources") essential. Of particular importance are faint, diffuse objects embedded in noise. There is a pressing need for source finding software that identifies these sources, involves little manual tuning, yet is tractable to calculate. We first give a novel image discretisation method that incorporates uncertainty about how an image should be discretised. We then propose a hierarchical prior for astronomical images, which leads to a Bayes factor indicating how well a given region conforms to a model of source that is exceptionally unconstrained, compared to a model of background. This enables the efficient localisation of regions that are "suspiciously different" from the background distribution, so our method looks not for brightness but for anomalous distributions of intensity, which is much more general. The model of background can be iteratively improved by removing the influence on it of sources as they are discovered. The approach is evaluated by identifying sources in real and simulated data, and performs well on these measures: the Bayes factor is maximized at most real objects, while returning only a moderate number of false positives. In comparison to a catalogue constructed by widely-used source detection software with manual post-processing by an astronomer, our method found a number of dim sources that were missing from the "ground truth" catalogue.

Observation of Kilohertz Quasiperiodic Oscillations from the Atoll Source 4U 1702-429 by RXTE

NASA Technical Reports Server (NTRS)

Markwardt, C. B.; Strohmayer, Tod E.; Swank, Jean H.

1998-01-01

We present results of Rossi X-Ray Timing Explorer (RXTE) observations of the atoll source 4U 1702-429 in the middle of its luminosity range. Kilohertz-range quasiperiodic oscillations (QPOS) were observed first as a narrow (FWHM approximately 7 Hz) peak near 900 Hz, and later as a pair consisting of a narrow peak in the range 625 825 Hz and a faint broad (FWHM 91 Hz) peak. When the two peaks appeared simultaneously the separation was 333 +/- 5 Hz. Six type I thermonuclear bursts were detected, of which five exhibited almost coherent oscillations near 330 Hz, which makes 4U 1702-429 only the second source to show burst oscillations very close to the kilohertz QPO separation frequency. The energy spectrum and color-color diagram indicate that the source executed variations in the range between the "island" and "lower banana" atoll states. In addition to the kilohertz variability, oscillations at approximately 10, approximately 35, and 80 Hz were also detected at various times, superimposed on a red noise continuum. The centroid of the approximately 35 Hz QPO tracks the frequency of the kilohertz oscillation when they were both present. A Lense-Thirring gravitomagnetic precession interpretation appears more plausible in this case, compared to other atoll sources with low frequency QPOs.

Spatially Resolving the Very High Energy Emission from MGRO J2019+37 with VERITAS

NASA Astrophysics Data System (ADS)

Aliu, E.; Aune, T.; Behera, B.; Beilicke, M.; Benbow, W.; Berger, K.; Bird, R.; Bouvier, A.; Buckley, J. H.; Bugaev, V.; Cerruti, M.; Chen, X.; Ciupik, L.; Connolly, M. P.; Cui, W.; Dumm, J.; Dwarkadas, V. V.; Errando, M.; Falcone, A.; Federici, S.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Fortin, P.; Fortson, L.; Furniss, A.; Galante, N.; Gillanders, G. H.; Gotthelf, E. V.; Griffin, S.; Griffiths, S. T.; Grube, J.; Gyuk, G.; Hanna, D.; Holder, J.; Hughes, G.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kargaltsev, O.; Kertzman, M.; Khassen, Y.; Kieda, D.; Krennrich, F.; Lang, M. J.; Madhavan, A. S.; Maier, G.; McArthur, S.; McCann, A.; Millis, J.; Moriarty, P.; Mukherjee, R.; Nieto, D.; O'Faoláin de Bhróithe, A.; Ong, R. A.; Otte, A. N.; Pandel, D.; Park, N.; Pohl, M.; Popkow, A.; Prokoph, H.; Quinn, J.; Ragan, K.; Rajotte, J.; Reyes, L. C.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Roberts, M.; Sembroski, G. H.; Shahinyan, K.; Smith, A. W.; Staszak, D.; Telezhinsky, I.; Tucci, J. V.; Tyler, J.; Vincent, S.; Wakely, S. P.; Weinstein, A.; Welsing, R.; Wilhelm, A.; Williams, D. A.; Zitzer, B.

2014-06-01

We present very high energy (VHE) imaging of MGRO J2019+37 obtained with the VERITAS observatory. The bright extended (~2°) unidentified Milagro source is located toward the rich star formation region Cygnus-X. MGRO J2019+37 is resolved into two VERITAS sources. The faint, point-like source VER J2016+371 overlaps CTB 87, a filled-center remnant (SNR) with no evidence of a supernova remnant shell at the present time. Its spectrum is well fit in the 0.65-10 TeV energy range by a power-law model with photon index 2.3 ± 0.4. VER J2019+378 is a bright extended (~1°) source that likely accounts for the bulk of the Milagro emission and is notably coincident with PSR J2021+3651 and the star formation region Sh 2-104. Its spectrum in the range 1-30 TeV is well fit with a power-law model of photon index 1.75 ± 0.3, among the hardest values measured in the VHE band, comparable to that observed near Vela-X. We explore the unusual spectrum and morphology in the radio and X-ray bands to constrain possible emission mechanisms for this source.

X-Ray Dust Scattering At Small Angles: The Complete Halo Around GX13+1

NASA Technical Reports Server (NTRS)

Smith, Randall K.

2007-01-01

The exquisite angular resolution available with Chandra should allow precision measurements of faint diffuse emission surrounding bright sources, such as the X-ray scattering halos created by interstellar dust. However, the ACIS CCDs suffer from pileup when observing bright sources, and this creates difficulties when trying to extract the scattered halo near the source. The initial study of the X-ray halo around GX13+1 using only the ACIS-I detector done by Smith, Edgar & Shafer (2002) suffered from a lack of sensitivity within 50" of the source, limiting what conclusions could be drawn. To address this problem, observations of GX13+1 were obtained with the Chandra HRC-I and simultaneously with the RXTE PCA. Combined with the existing ACIS-I data, this allowed measurements of the X-ray halo between 2-1000". After considering a range of dust models, each assumed to be smoothly distributed with or without a dense cloud along the line of sight, the results show that there is no evidence in this data for a dense cloud near the source, as suggested by Xiang et al. (2005). In addition, although no model leads to formally acceptable results, the Weingartner & Draine (2001) and all but one of the composite grain models from Zubko, Dwek & Arendt (2004) give particularly poor fits.

CANDELS/GOODS-S, CDFS, and ECDFS: photometric redshifts for normal and X-ray-detected galaxies

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

Hsu, Li-Ting; Salvato, Mara; Nandra, Kirpal

2014-11-20

We present photometric redshifts and associated probability distributions for all detected sources in the Extended Chandra Deep Field South (ECDFS). This work makes use of the most up-to-date data from the Cosmic Assembly Near-IR Deep Legacy Survey (CANDELS) and the Taiwan ECDFS Near-Infrared Survey (TENIS) in addition to other data. We also revisit multi-wavelength counterparts for published X-ray sources from the 4 Ms CDFS and 250 ks ECDFS surveys, finding reliable counterparts for 1207 out of 1259 sources (∼96%). Data used for photometric redshifts include intermediate-band photometry deblended using the TFIT method, which is used for the first time inmore » this work. Photometric redshifts for X-ray source counterparts are based on a new library of active galactic nuclei/galaxy hybrid templates appropriate for the faint X-ray population in the CDFS. Photometric redshift accuracy for normal galaxies is 0.010 and for X-ray sources is 0.014 and outlier fractions are 4% and 5.2%, respectively. The results within the CANDELS coverage area are even better, as demonstrated both by spectroscopic comparison and by galaxy-pair statistics. Intermediate-band photometry, even if shallow, is valuable when combined with deep broadband photometry. For best accuracy, templates must include emission lines.« less

CANDID: Companion Analysis and Non-Detection in Interferometric Data

NASA Astrophysics Data System (ADS)

Gallenne, A.; Mérand, A.; Kervella, P.; Monnier, J. D.; Schaefer, G. H.; Baron, F.; Breitfelder, J.; Le Bouquin, J. B.; Roettenbacher, R. M.; Gieren, W.; Pietrzynski, G.; McAlister, H.; ten Brummelaar, T.; Sturmann, J.; Sturmann, L.; Turner, N.; Ridgway, S.; Kraus, S.

2015-05-01

CANDID finds faint companion around star in interferometric data in the OIFITS format. It allows systematically searching for faint companions in OIFITS data, and if not found, estimates the detection limit. The tool is based on model fitting and Chi2 minimization, with a grid for the starting points of the companion position. It ensures all positions are explored by estimating a-posteriori if the grid is dense enough, and provides an estimate of the optimum grid density.

UBV and H. beta. photometry of faint early-type stars in Crux and Centaurus

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

Muzzio, J.C.; Feinstein, A.; Orsatti, A.M.

1976-08-01

UBV and H..beta.. photoelectric observations of faint early-type stars in a small region in Crux near the open cluster Hogg 15 and another in Centaurus are presented. The data suggest large absorption in Crux and small absorption in Centaurus. The spread in the distance moduli of the observed stars seems to be in agreement with the view that a spiral arm is seen tangentially near l = 305/sup 0/.

The Joint Facial and Invasive Neck Trauma (J-FAINT) Project, Iraq and Afghanistan 2003-2011

DTIC Science & Technology

2013-01-01

Original Research— Facial Plastic and Reconstructive Surgery The Joint Facial and Invasive Neck Trauma (J-FAINT) Project, Iraq and Afghanistan 2003...number and type of facial and penetrat- ing neck trauma injuries sustained in Operation Iraqi Freedom (OIF) and Operation Enduring Freedom (OEF). Study...queried for data from OIF and OEF from January 2003 to May 2011. Information on demographics; type and severity of facial , neck, and associated trauma

Is dental phobia a blood-injection-injury phobia?

PubMed

van Houtem, C M H H; Aartman, I H A; Boomsma, D I; Ligthart, L; Visscher, C M; de Jongh, A

2014-12-01

Dental phobia is part of the Blood-Injection-Injury (B-I-I) phobia subtype of specific phobia within DSM-IV-TR. To investigate the conceptual validity of this classification, the purpose of the present study was to determine the co-occurrence of dental phobia, typical dental (and B-I-I related) fears, vasovagal fainting, and avoidance of dental care. Data were collected by an online survey in Dutch twin families (n = 11,213). Individuals with a positive screen of dental phobia (0.4% of the sample) rated typical B-I-I-related stimuli as relatively little anxiety provoking (e.g. of all 28 fears the stimulus "the sight of blood" was ranked lowest). Presence of dental phobia was significantly associated with a history of dizziness or fainting during dental treatment (OR = 3.4; 95% CI: 1.5-8.1), but of the dental phobic individuals only 13.0% reported a history of dizziness or fainting during dental treatment. Presence of dental phobia (OR = 5.0; 95% CI: 2.8-8.8) was found to be associated with avoidance of dental care, but a history of dizziness or fainting during dental treatment was not (OR = 1.0; 95% CI: 0.8-1.2). The present findings converge to the conclusion that dental phobia should be considered a specific phobia subtype independent of the B-I-I cluster within the DSM classification system. © 2013 Wiley Periodicals, Inc.

On the Nature of Ultra-faint Dwarf Galaxy Candidates. II. The Case of Cetus II

NASA Astrophysics Data System (ADS)

Conn, Blair C.; Jerjen, Helmut; Kim, Dongwon; Schirmer, Mischa

2018-04-01

We obtained deep Gemini GMOS-S g, r photometry of the ultra-faint dwarf galaxy candidate Cetus II with the aim of providing stronger constraints on its size, luminosity, and stellar population. Cetus II is an important object in the size–luminosity plane, as it occupies the transition zone between dwarf galaxies and star clusters. All known objects smaller than Cetus II (r h ∼ 20 pc) are reported to be star clusters, while most larger objects are likely dwarf galaxies. We found a prominent excess of main-sequence stars in the color–magnitude diagram of Cetus II, best described by a single stellar population with an age of 11.2 Gyr, metallicity of [Fe/H] = ‑1.28 dex, an [α/Fe] = 0.0 dex at a heliocentric distance of 26.3 ± 1.2 kpc. As well as being spatially located within the Sagittarius dwarf tidal stream, these properties are well matched to the Sagittarius galaxy’s Population B stars. Interestingly, like our recent findings on the ultra-faint dwarf galaxy candidate Tucana V, the stellar field in the direction of Cetus II shows no evidence of a concentrated overdensity despite tracing the main sequence for over six magnitudes. These results strongly support the picture that Cetus II is not an ultra-faint stellar system in the Milky Way halo, but made up of stars from the Sagittarius tidal stream.

FAINT EXTENDED OH EMISSION FROM THE LOCAL INTERSTELLAR MEDIUM IN THE DIRECTION l Almost-Equal-To 108 Degree-Sign , b Almost-Equal-To 5 Degree-Sign

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

Allen, Ronald J.; Rodriguez, Monica Ivette; Black, John H.

We have mapped faint 1667 OH line emission (T{sub A} Almost-Equal-To 20-40 mK in our Almost-Equal-To 30' beam) along many lines of sight in the Galaxy covering an area of Almost-Equal-To 4 Degree-Sign Multiplication-Sign 4 Degree-Sign in the general direction of l Almost-Equal-To 108 Degree-Sign , b Almost-Equal-To 5 Degree-Sign . The OH emission is widespread, similar in extent to the local H I (r {approx}< 2 kpc) both in space and in velocity. The OH profile amplitudes show a good general correlation with those of H I in spectral channels of Almost-Equal-To 1 km s{sup -1}; this relation ismore » described by T{sub A} (OH) Almost-Equal-To 1.50 Multiplication-Sign 10{sup -4} T{sub B} (H I) for values of T{sub B} (H I) {approx}< 60-70 K. Beyond this the H I line appears to 'saturate', and few values are recorded above Almost-Equal-To 90 K. However, the OH brightness continues to rise, by a further factor Almost-Equal-To 3. The OH velocity profiles show multiple features with widths typically 2-3 km s{sup -1}, but less than 10% of these features are associated with CO(1-0) emission in existing surveys of the area smoothed to comparable resolution.« less

[Symptomatic sinus dysfunction. A new use of electrophysiology].

PubMed

Graux, P; Jacquemart, T; Carlioz, R; Lemaire, N; Dutoit, A; Croccel, L

1993-06-01

The authors undertook a prospective electrophysiological study of 950 patients: 53 subjects considered to be "controls" since they were free of any history of syncope or faintness were identified, as well as 39 symptomatic subjects with a strong suspicion of sinus dysfunction, since no other detectable cause of fainting episodes was found by extracardiac investigation, 24 hour ECG nor electrophysiology. Following the creation of a computerised tool enabling not only the entry of indirect tests, processing, averaging of results, printing and memorization, but also assistance in interpretation, several electrophysiological parameters were used: heart rate and existence of sinus arrhythmia, Strauss tests with adjusted data or not, effective nodal refractory period, Guize, Narula and Mandel tests, and an atropine (0.03 mg/kg) test which was performed only in the symptomatic group. These tests were studied by single-variate and correlative analysis to define their normal ranges, their critical values and their dependence or independence. The performance of each test (i.e. its efficiency, and the specificity and sensitivity of each critical value) was measured. Tests found to be most useful (specificity and efficiency > 90%) were as follows: Mandel test = CSRT > or = 534 ms, Narula test = TECASA > or = 339 ms, heart rate < or = 55/min, type II, IIa and chaotic Strauss curve associated with a pathological Guize test. The combination of these tests in this algorithm resulted in an increase in sensitivity to 84%, at the price of a very moderate fall in specificity to 87%.(ABSTRACT TRUNCATED AT 250 WORDS)

Corneal Densitometry as a Tool to Measure Epithelial Ingrowth After Laser In Situ Keratomileusis.

PubMed

Adran, Daniel; Vaillancourt, Louis; Harissi-Dagher, Mona; Kruh, Jonathan N; Syed, Zeba A; Robinson, Steven; Melki, Samir

2017-04-01

This study evaluates the correlation between corneal densitometry and epithelial ingrowth (EI) after laser in situ keratomileusis (LASIK). Corneal densitometry of 3 patients who developed EI after LASIK was measured with the Oculus Pentacam. Corneal densitometry readings of each patient were obtained preoperatively and postoperatively after ingrowth was discovered. Densitometry was recorded at the central nest of opacity and at the leading edges of EI. For all patients, the most severe stages of EI observed on slit-lamp photographs correlated with the highest densitometry readings, with peak densitometry ranging from 73.3 to 95.1. These values were much higher than preoperative densitometry readings, which ranged from 21.8 to 27.2. In 2 cases, the Pentacam densitometry map revealed progression of EI toward the visual axis that was only faintly detectable or not detectable at all on the corresponding slit-lamp photographs. Corneal densitometry seems to be an objective measure of the severity and progression of EI after LASIK.

Infrared-faint radio sources: a cosmological view. AGN number counts, the cosmic X-ray background and SMBH formation

NASA Astrophysics Data System (ADS)

Zinn, P.-C.; Middelberg, E.; Ibar, E.

2011-07-01

Context. Infrared-faint radio sources (IFRS) are extragalactic emitters clearly detected at radio wavelengths but barely detected or undetected at optical and infrared wavelengths, with 5σ sensitivities as low as 1 μJy. Aims: Spectral energy distribution (hereafter SED) modelling and analyses of their radio properties indicate that IFRS are consistent with a population of (potentially extremely obscured) high-redshift AGN at 3 ≤ z ≤ 6. We demonstrate some astrophysical implications of this population and compare them to predictions from models of galaxy evolution and structure formation. Methods: We compiled a list of IFRS from four deep extragalactic surveys and extrapolated the IFRS number density to a survey-independent value of (30.8 ± 15.0) deg-2. We computed the IFRS contribution to the total number of AGN in the Universe to account for the cosmic X-ray background. By estimating the black hole mass contained in IFRS, we present conclusions for the SMBH mass density in the early universe and compare it to relevant simulations of structure formation after the Big Bang. Results: The number density of AGN derived from the IFRS density was found to be ~310 deg-2, which is equivalent to a SMBH mass density of the order of 103 M⊙ Mpc-3 in the redshift range 3 ≤ z ≤ 6. This produces an X-ray flux of 9 × 10-16 W m-2 deg-2 in the 0.5-2.0 keV band and 3 × 10-15 W m-2 deg-2 in the 2.0-10 keV band, in agreement with the missing unresolved components of the Cosmic X-ray Background. To address SMBH formation after the Big Bang we invoke a scenario involving both halo gas accretion and major mergers.

Massive 70 μm quiet clumps I: evidence of embedded low/intermediate-mass star formation activity

NASA Astrophysics Data System (ADS)

Traficante, A.; Fuller, G. A.; Billot, N.; Duarte-Cabral, A.; Merello, M.; Molinari, S.; Peretto, N.; Schisano, E.

2017-10-01

Massive clumps, prior to the formation of any visible protostars, are the best candidates to search for the elusive massive starless cores. In this work, we investigate the dust and gas properties of massive clumps selected to be 70 μm quiet, therefore good starless candidates. Our sample of 18 clumps has masses 300 ≲ M ≲ 3000 M⊙, radius 0.54 ≤ R ≤ 1.00 pc, surface densities Σ ≥ 0.05 g cm-2 and luminosity/mass ratio L/M ≤ 0.3. We show that half of these 70 μm quiet clumps embed faint 24 μm sources. Comparison with GLIMPSE counterparts shows that five clumps embed young stars of intermediate stellar mass up to ≃5.5 M⊙. We study the clump dynamics with observations of N2H+ (1-0), HNC (1-0) and HCO+ (1-0) made with the IRAM 30 m telescope. Seven clumps have blue-shifted spectra compatible with infall signatures, for which we estimate a mass accretion rate 0.04≲ \\dot{M}≲ 2.0× 10^{-3} M⊙ yr-1, comparable with values found in high-mass protostellar regions, and free-fall time of the order of tff ≃ 3 × 105 yr. The only appreciable difference we find between objects with and without embedded 24 μm sources is that the infall rate appears to increase from 24 μm dark to 24 μm bright objects. We conclude that all 70 μm quiet objects have similar properties on clump scales, independently of the presence of an embedded protostar. Based on our data, we speculate that the majority, if not all of these clumps, may already embed faint, low-mass protostellar cores. If these clumps are to form massive stars, this must occur after the formation of these lower mass stars.

Linking surface morphology, composition and activity on the 67P/Churyumov-Gerasimenko’s nucleus

NASA Astrophysics Data System (ADS)

Fornasier, Sonia; Hoang, Van Hong; Hasselmann, Pedro H.; Barucci, Maria Antonieta; Feller, Clement; Prasanna Deshapriya, Jasinghege Don; Keller, Horst Uwe; OSIRIS Team

2017-10-01

The Rosetta mission orbited around the comet 67P/Churyumov-Gerasimenko for more than 2 years, getting an incredible amount of unique data of the comet nucleus and inner coma. This has enabled us to study its activity continuously from 4 AU inbound to 3.6 AU outbound, including the perihelion passage at 1.25 AU.This work focuses on the identification of the regions sources of faint jets and outbursts, and on the study of their spectrophotometric properties, from observations acquired with the OSIRIS/NAC camera during the July-October 2015 period, i.e. close to perihelion. More than 150 jets of different intensities were identified directly on the nucleus from NAC color sequences acquired in 7-11 filters covering the 250-1000 nm wavelength range, and their spectrophotometric properties studied for the first time. Some spectacular outbursts appear dominated by water ice particles, while fainter jets often show colors redder than the nucleus and appear dominated by dusty particles. Some jets are very faint and were identified on the nucleus thanks to the unprecedented spatial and temporal resolution of the ROSETTA/OSIRIS observations. Some of them have an extremely short lifetime, appearing on the cometary surface during the color sequence observations, reaching their peak in flux and then vanishing in less than a couple of minutes.We will present the results on the location, duration, and colors of active sources on the 67P nucleus from the relatively low resolution (i.e. 6-10 m/pixel) images acquired close to the perihelion passage. Some of this active regions were observed and investigated in higher resolution (up to few dm per pixel) during other phases of the mission. These observations allow us to study the morphological and spectral evolution of the regions found to be active and to further investigate the link between morphology, composition, and activity on cometary nuclei.

X-ray versus infrared selection of distant galaxy clusters: a case study using the XMM-LSS and SpARCS cluster samples

NASA Astrophysics Data System (ADS)

Willis, J. P.; Ramos-Ceja, M. E.; Muzzin, A.; Pacaud, F.; Yee, H. K. C.; Wilson, G.

2018-07-01

We present a comparison of two samples of z> 0.8 galaxy clusters selected using different wavelength-dependent techniques and examine the physical differences between them. We consider 18 clusters from the X-ray-selected XMM Large Scale Structure (LSS) distant cluster survey and 92 clusters from the optical-mid-infrared (MIR)-selected Spitzer Adaptation of the Red Sequence Cluster survey (SpARCS) cluster survey. Both samples are selected from the same approximately 9 sq deg sky area and we examine them using common XMM-Newton, Spitizer Wide-Area Infrared Extra-galactic (SWIRE) survey, and Canada-France-Hawaii Telescope Legacy Survey data. Clusters from each sample are compared employing aperture measures of X-ray and MIR emission. We divide the SpARCS distant cluster sample into three sub-samples: (i) X-ray bright, (ii) X-ray faint, MIR bright, and (iii) X-ray faint, MIR faint clusters. We determine that X-ray- and MIR-selected clusters display very similar surface brightness distributions of galaxy MIR light. In addition, the average location and amplitude of the galaxy red sequence as measured from stacked colour histograms is very similar in the X-ray- and MIR-selected samples. The sub-sample of X-ray faint, MIR bright clusters displays a distribution of brightest cluster galaxy-barycentre position offsets which extends to higher values than all other samples. This observation indicates that such clusters may exist in a more disturbed state compared to the majority of the distant cluster population sampled by XMM-LSS and SpARCS. This conclusion is supported by stacked X-ray images for the X-ray faint, MIR bright cluster sub-sample that display weak, centrally concentrated X-ray emission, consistent with a population of growing clusters accreting from an extended envelope of material.

A Peculiar Faint Satellite in the Remote Outer Halo of M31

NASA Astrophysics Data System (ADS)

Mackey, A. D.; Huxor, A. P.; Martin, N. F.; Ferguson, A. M. N.; Dotter, A.; McConnachie, A. W.; Ibata, R. A.; Irwin, M. J.; Lewis, G. F.; Sakari, C. M.; Tanvir, N. R.; Venn, K. A.

2013-06-01

We present Hubble Space Telescope imaging of a newly discovered faint stellar system, PAndAS-48, in the outskirts of the M31 halo. Our photometry reveals this object to be comprised of an ancient and very metal-poor stellar population with age >~ 10 Gyr and [Fe/H] lsim -2.3. Our inferred distance modulus (m - M)0 = 24.57 ± 0.11 confirms that PAndAS-48 is most likely a remote M31 satellite with a three-dimensional galactocentric radius of 149^{+19}_{-8} kpc. We observe an apparent spread in color on the upper red giant branch that is larger than the photometric uncertainties should allow, and briefly explore the implications of this. Structurally, PAndAS-48 is diffuse, faint, and moderately flattened, with a half-light radius r_h=26^{+4}_{-3} pc, integrated luminosity MV = -4.8 ± 0.5, and ellipticity \\epsilon =0.30^{+0.08}_{-0.15}. On the size-luminosity plane it falls between the extended globular clusters seen in several nearby galaxies and the recently discovered faint dwarf satellites of the Milky Way; however, its characteristics do not allow us to unambiguously classify it as either type of system. If PAndAS-48 is a globular cluster then it is among the most elliptical, isolated, and metal-poor of any seen in the Local Group, extended or otherwise. Conversely, while its properties are generally consistent with those observed for the faint Milky Way dwarfs, it would be a factor of ~2-3 smaller in spatial extent than any known counterpart of comparable luminosity. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute (STScI), 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 GO 12515.

The luminosity function for different morphological types in the CfA Redshift Survey

NASA Technical Reports Server (NTRS)

Marzke, Ronald O.; Geller, Margaret J.; Huchra, John P.; Corwin, Harold G., Jr.

1994-01-01

We derive the luminosity function for different morphological types in the original CfA Redshift Survey (CfA1) and in the first two slices of the CfA Redshift Survey Extension (CfA2). CfA1 is a complete sample containing 2397 galaxies distributed over 2.7 steradians with m(sub z) less than or equal 14.5. The first two complete slices of CfA2 contain 1862 galaxies distributed over 0.42 steradians with m(sub z)=15.5. The shapes of the E-S0 and spiral luminosity functions (LF) are indistinguishable. We do not confirm the steeply decreasing faint end in the E-S0 luminosity function found by Loveday et al. for an independent sample in the southern hemisphere. We demonstrate that incomplete classification in deep redshift surveys can lead to underestimates of the faint end of the elliptical luminosity function and could be partially responsible for the difference between the CfA survey and other local field surveys. The faint end of the LF for the Magellanic spirals and irregulars is very steep. The Sm-Im luminosity function is well fit by a Schechter function with M*=-18.79, alpha=-1.87, and phi*=0.6x10(exp -3) for M(sub z) less than or equal to -13. These galaxies are largely responsible for the excess at the faint end of the general CfA luminosity function. The abundance of intrinsically faint, blue galaxies nearby affects the interpretation of deep number counts. The dwarf population increases the expected counts at B=25 in a no-evolution, q(sub 0)=0.05 model by a factor of two over standard no-evolution estimates. These dwarfs change the expected median redshift in deep redshift surveys by less than 10 percent . Thus the steep Sm-Im LF may contribute to the reconciliation of deep number counts with deep redshift surveys.

Galaxy modelling. II. Multi-wavelength faint counts from a semi-analytic model of galaxy formation

NASA Astrophysics Data System (ADS)

Devriendt, J. E. G.; Guiderdoni, B.

2000-11-01

This paper predicts self-consistent faint galaxy counts from the UV to the submm wavelength range. The stardust spectral energy distributions described in Devriendt et al. \\citeparyear{DGS99} (Paper I) are embedded within the explicit cosmological framework of a simple semi-analytic model of galaxy formation and evolution. We begin with a description of the non-dissipative and dissipative collapses of primordial perturbations, and plug in standard recipes for star formation, stellar evolution and feedback. We also model the absorption of starlight by dust and its re-processing in the IR and submm. We then build a class of models which capture the luminosity budget of the universe through faint galaxy counts and redshift distributions in the whole wavelength range spanned by our spectra. In contrast with a rather stable behaviour in the optical and even in the far-IR, the submm counts are dramatically sensitive to variations in the cosmological parameters and changes in the star formation history. Faint submm counts are more easily accommodated within an open universe with a low value of Omega_0 , or a flat universe with a non-zero cosmological constant. We confirm the suggestion of Guiderdoni et al. \\citeparyear{GHBM98} that matching the current multi-wavelength data requires a population of heavily-extinguished, massive galaxies with large star formation rates ( ~ 500 M_sun yr-1) at intermediate and high redshift (z >= 1.5). Such a population of objects probably is the consequence of an increase of interaction and merging activity at high redshift, but a realistic quantitative description can only be obtained through more detailed modelling of such processes. This study illustrates the implementation of multi-wavelength spectra into a semi-analytic model. In spite of its simplicity, it already provides fair fits of the current data of faint counts, and a physically motivated way of interpolating and extrapolating these data to other wavelengths and fainter flux levels.

The FIRST Survey: Faint Images of the Radio Sky at Twenty Centimeters

NASA Astrophysics Data System (ADS)

Becker, Robert H.; White, Richard L.; Helfand, David J.

1995-09-01

The FIRST survey to produce Faint Images of the Radio Sky at Twenty centimeters is now underway using the NRAO Very Large Array. We describe here the scientific motivation for a large-area sky survey at radio frequencies which has a sensitivity and angular resolution comparable to the Palomar Observatory Sky Survey, and we recount the history that led to the current survey project. The technical design of the survey is covered in detail, including a description and justification of the grid pattern chosen, the rationale behind the integration time and angular resolution selected, and a summary of the other considerations which informed our planning for the project. A comprehensive description of the automated data analysis pipeline we have developed is presented. We also report here the results of the first year of FIRST observations. A total of 144 hr of time in 1993 April and May was used for a variety of tests, as well as to cover an initial strip of the survey extending between 07h 15m and 16h 30m in a 2°.8 wide declination zone passing through the local zenith (28.2 <δ < 31.0). A total of 2153 individual pointings yielded an image database containing 1039 merged images 46'.5 × 34'.5 in extent with 1".8 pixels and a typical rms of 0.13 mJy. A catalog derived from this 300 deg2 region contains 28,000 radio sources. We have performed extensive tests on the images and source list in order to establish the photometric and astrometric accuracy of these data products. We find systematic astrometric errors of < 0".05 individual sources down to the 1 mJy survey flux density threshold have 90% confidence error circles with radii of < 1". CLEAN bias introduces a systematic underestimate of point-source flux densities of ˜0.25 mJy; the bias is more severe for extended sources. Nonetheless, a comparison with a published deep survey field demonstrates that we successfully detect 39/49 sources with integrated flux densities greater than 0.75 mJy, including 19 of 20 sources above 2.0 mJy; the sources not detected are known to be very extended and so have surface brightnesses well below our threshold. With 480 hr of observing time committed for each of the next three B-configuration periods, FIRST will complete nearly one-half of its goal of covering the 10,000 deg2 of the north Galactic cap scheduled for inclusion in the Sloan Digital Sky Survey. All of the FIRST data raw visibilities, self-calibrated UV data sets, individual pointing maps, final merged images, source catalogs, and individual source images are being placed in the public domain as soon as they are verified; all of the 1993 data are now available through the NRAO and/or the STScI archive. We conclude with a brief summary of the scientific significance of FIRST, which represents an improvement by a factor of 50 in both angular resolution and sensitivity over the best available large area radio surveys.

Carbon dioxide UV laser-induced fluorescence in high-pressure flames

NASA Astrophysics Data System (ADS)

Bessler, W. G.; Schulz, C.; Lee, T.; Jeffries, J. B.; Hanson, R. K.

2003-07-01

Laser-induced fluorescence (LIF) of carbon dioxide is investigated with excitation between 215 and 255 nm with spectrally resolved detection in 5-40 bar premixed CH 4/O 2/Ar and CH 4/air flat-flames at fuel/air ratios between 0.8 and 1.9. The LIF signal consists of a broad (200-450 nm) continuum with a faint superimposed structure, and this signal is absent in similar H 2/O 2/Ar flames. There is strong evidence this signal arises from CO 2, as the signal variations with excitation wavelength, equivalence ratio and flame temperature all correlate with CO 2 absorption cross-sections. The signal is linear with pressure and laser fluence within the investigated ranges.

Galactic Starburst NGC 3603 from X-Rays to Radio

NASA Technical Reports Server (NTRS)

Moffat, A. F. J.; Corcoran, M. F.; Stevens, I. R.; Skalkowski, G.; Marchenko, S. V.; Muecke, A.; Ptak, A.; Koribalski, B. S.; Brenneman, L.; Mushotzky, R.;

Innovations in the Analysis of Chandra-ACIS Observations

NASA Astrophysics Data System (ADS)

Broos, Patrick S.; Townsley, Leisa K.; Feigelson, Eric D.; Getman, Konstantin V.; Bauer, Franz E.; Garmire, Gordon P.

2010-05-01

As members of the instrument team for the Advanced CCD Imaging Spectrometer (ACIS) on NASA's Chandra X-ray Observatory and as Chandra General Observers, we have developed a wide variety of data analysis methods that we believe are useful to the Chandra community, and have constructed a significant body of publicly available software (the ACIS Extract package) addressing important ACIS data and science analysis tasks. This paper seeks to describe these data analysis methods for two purposes: to document the data analysis work performed in our own science projects and to help other ACIS observers judge whether these methods may be useful in their own projects (regardless of what tools and procedures they choose to implement those methods). The ACIS data analysis recommendations we offer here address much of the workflow in a typical ACIS project, including data preparation, point source detection via both wavelet decomposition and image reconstruction, masking point sources, identification of diffuse structures, event extraction for both point and diffuse sources, merging extractions from multiple observations, nonparametric broadband photometry, analysis of low-count spectra, and automation of these tasks. Many of the innovations presented here arise from several, often interwoven, complications that are found in many Chandra projects: large numbers of point sources (hundreds to several thousand), faint point sources, misaligned multiple observations of an astronomical field, point source crowding, and scientifically relevant diffuse emission.

Asteroid families - An initial search

NASA Technical Reports Server (NTRS)

Williams, James G.

1992-01-01

A stereo examination was conducted for clusters in three-dimensional proper element space within a sample of both numbered and faint Palomar-Leiden Survey (PLS) asteroids. The clusters were then objectively filtered for small Poisson probability of chance occurrence; 104 were accepted as families with 4- to 12-member populations, and are interpreted as impact-generated. Structure is common in the well-populated families: the better-sampled families are accordingly discussed in terms of their geometry and taxonomy. Some families are very rich in faint PLS members.

High-resolution imaging of the Pluto-Charon system with the Faint Object Camera of the Hubble Space Telescope

NASA Technical Reports Server (NTRS)

Albrecht, R.; Barbieri, C.; Adorf, H.-M.; Corrain, G.; Gemmo, A.; Greenfield, P.; Hainaut, O.; Hook, R. N.; Tholen, D. J.; Blades, J. C.

1994-01-01

Images of the Pluto-Charon system were obtained with the Faint Object Camera (FOC) of the Hubble Space Telescope (HST) after the refurbishment of the telescope. The images are of superb quality, allowing the determination of radii, fluxes, and albedos. Attempts were made to improve the resolution of the already diffraction limited images by image restoration. These yielded indications of surface albedo distributions qualitatively consistent with models derived from observations of Pluto-Charon mutual eclipses.

FIRST OBSERVATIONAL SUPPORT FOR OVERLAPPING REIONIZED BUBBLES GENERATED BY A GALAXY OVERDENSITY

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

Castellano, M.; Pentericci, L.; Fontana, A.

2016-02-10

We present an analysis of deep Hubble Space Telescope (HST) multi-band imaging of the BDF field specifically designed to identify faint companions around two of the few Lyα emitting galaxies spectroscopically confirmed at z ∼ 7. Although separated by only 4.4 proper Mpc these galaxies cannot generate H ii regions large enough to explain the visibility of their Lyα lines, thus requiring a population of fainter ionizing sources in their vicinity. We use deep HST and VLT-Hawk-I data to select z ∼ 7 Lyman break galaxies around the emitters. We select six new robust z ∼ 7 LBGs at Y ∼ 26.5–27.5 whose average spectral energy distribution ismore » consistent with the objects being at the redshift of the close-by Lyα emitters. The resulting number density of z ∼ 7 LBGs in the BDF field is a factor of approximately three to four higher than expected in random pointings of the same size. We compare these findings with cosmological hydrodynamic plus radiative transfer simulations of a universe with a half neutral IGM: we find that indeed Lyα emitter pairs are only found in completely ionized regions characterized by significant LBG overdensities. Our findings match the theoretical prediction that the first ionization fronts are generated within significant galaxy overdensities and support a scenario where faint, “normal” star-forming galaxies are responsible for reionization.« less

THE INFLUENCE OF RED SPIRAL GALAXIES ON THE SHAPE OF THE LOCAL K-BAND LUMINOSITY FUNCTION

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

Bonne, Nicolas J.; Brown, Michael J. I.; Jones, Heath

2015-02-01

We have determined K-band luminosity functions for 13,325 local universe galaxies as a function of morphology and color (for K {sub tot} ≤ 10.75). Our sample is drawn from the Two Micron All Sky Survey Extended Source Catalog, with all sample galaxies having measured morphologies and distances (including 4219 archival redshift-independent distances). The luminosity function for our total sample is in good agreement with previous works, but is relatively smooth at faint magnitudes (due to bulk flow distance corrections). We investigated the differences due to morphological and color selection using 5417 sample galaxies with NASA Sloan Atlas optical colors and find thatmore » red spirals comprise 20%-50% of all spirals with –25 ≤ M{sub K}  < –20. Fainter than M{sub K} = –24, red spirals are as common as early types, explaining the different faint end slopes (α = –0.87 and –1.00 for red and early-types, respectively). While we find red spirals comprise more than 50% of all M{sub K}  < –25 spiral galaxies, they do not dominate the bright end of the overall red galaxy luminosity function, which is dominated by early-type galaxies. The brightest red spirals have ongoing star formation and those without are frequently misclassified as early-types. The faintest ones have an appearance and Sérsic indices consistent with faded disks, rather than true bulge-dominated galaxies.« less

The nature of X-ray selected star candidates

NASA Astrophysics Data System (ADS)

Mickaelian, A. M.; Paronyan, G. M.; Abrahamyan, H. V.; Gigoyan, K. S.; Gyulzadyan, M. V.; Kostandyan, G. R.

2016-12-01

The joint HRC/BHRC catalogue of optical identifications of ROSAT BSC and FSC X-ray sources is based on merging the Hamburg-ROSAT Catalogue (HRC) and Byurakan-Hamburg-ROSAT Catalogue (BHRC). Both have been made by optical identifications of X-ray sources based on low-dispersion spectra of the Hamburg QuasarSurvey (HQS) using the ROSAT Catalogues. HRC/BHRC contains a sample of 8132 (5341+2791) optically identified X-ray sources with count rate (CR) of photons ≥ 0.04 ct/s in the area of the low-dispersion Hamburg Quasar Survey (HQS), |b| ≥ 20° and δ ≥ 0°. Based on low-dispersion spectral classification, there are 4253 AGN, 492 galaxies, 1800 stars and 1587 unknown objects in the sample. 1800 star candidates include 1429 objects listed in SDSS DR12 photometric catalogue and 433 given in SDSS spectroscopic catalogue. Using these spectra, we have carried out classification of these star candidates to reveal new interesting objects, as well as to define the true content of our sample. 34 cataclysmic variables (including 7 new ones), 19 white dwarfs, 19 late-type stars (K-M and C types), 16 early type stars (O-B), 40 hot coronal stars (A-F types), 2 composite spectrum objects, and 17 bright stars have been revealed, as well as 286 objects which turned out to be extragalactic ones; 75 emission-line galaxies (HII/SB and AGN, including QSOs, Seyferts, and LINERs) and 211 absorption line galaxies were revealed (wrong classifications in HRC/BHRC due to their faint images and low-quality spectra). We have retrieved multiwavelength data from recent catalogues and carried out statistical investigations of the multiwavelength properties for the whole sample of stars. All stars have been found in GSC 2.3.2, as well as most of them are in GALEX, USNO-B1.0, 2MASS and WISE catalogues. Relations between the radiation fluxes in different bands from X-ray to radio for different types of sources are studied and analysis of their characteristics is made. X-ray selected stars are an important complement to the stellar populations of our Galaxy in solar neighbourhood and beyond. Keywords: X-ray sources, cross-correlations, white dwarfs, cataclysmic variables, carbon stars

The Evolution of the Faint End of the UV Luminosity Function during the Peak Epoch of Star Formation (1 < z < 3)

NASA Astrophysics Data System (ADS)

Alavi, Anahita; Siana, Brian; Richard, Johan; Rafelski, Marc; Jauzac, Mathilde; Limousin, Marceau; Freeman, William R.; Scarlata, Claudia; Robertson, Brant; Stark, Daniel P.; Teplitz, Harry I.; Desai, Vandana

2016-11-01

We present a robust measurement of the rest-frame UV luminosity function (LF) and its evolution during the peak epoch of cosmic star formation at 1\\lt z\\lt 3. We use our deep near-ultraviolet imaging from WFC3/UVIS on the Hubble Space Telescope and existing Advanced Camera for Surveys (ACS)/WFC and WFC3/IR imaging of three lensing galaxy clusters, Abell 2744 and MACS J0717 from the Hubble Frontier Field survey and Abell 1689. Combining deep UV imaging and high magnification from strong gravitational lensing, we use photometric redshifts to identify 780 ultra-faint galaxies with {M}{UV}\\lt -12.5 AB mag at 1\\lt z\\lt 3. From these samples, we identified five new, faint, multiply imaged systems in A1689. We run a Monte Carlo simulation to estimate the completeness correction and effective volume for each cluster using the latest published lensing models. We compute the rest-frame UV LF and find the best-fit faint-end slopes of α =-1.56+/- 0.04, α =-1.72+/- 0.04, and α =-1.94+/- 0.06 at 1.0\\lt z\\lt 1.6, 1.6\\lt z\\lt 2.2, and 2.2\\lt z\\lt 3.0, respectively. Our results demonstrate that the UV LF becomes steeper from z˜ 1.3 to z˜ 2.6 with no sign of a turnover down to {M}{UV}=-14 AB mag. We further derive the UV LFs using the Lyman break “dropout” selection and confirm the robustness of our conclusions against different selection methodologies. Because the sample sizes are so large and extend to such faint luminosities, the statistical uncertainties are quite small, and systematic uncertainties (due to the assumed size distribution, for example) likely dominate. If we restrict our analysis to galaxies and volumes above \\gt 50 % completeness in order to minimize these systematics, we still find that the faint-end slope is steep and getting steeper with redshift, though with slightly shallower (less negative) values (α =-1.55+/- 0.06, -1.69 ± 0.07, and -1.79 ± 0.08 for z˜ 1.3, 1.9, and 2.6, respectively). Finally, we conclude that the faint star-forming galaxies with UV magnitudes of -18.5\\lt {M}{UV}\\lt -12.5 covered in this study produce the majority (55%-60%) of the unobscured UV luminosity density at 1\\lt z\\lt 3. Some of 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.

Galaxy populations in the Antlia cluster - III. Properties of faint early-type galaxies

NASA Astrophysics Data System (ADS)

Smith Castelli, Analía. V.; Cellone, Sergio A.; Faifer, Favio R.; Bassino, Lilia P.; Richtler, Tom; Romero, Gisela A.; Calderón, Juan Pablo; Caso, Juan Pablo

2012-01-01

We present a new analysis of the early-type galaxy population in the central region of the Antlia cluster, focusing on the faint systems such as dwarf ellipticals (dEs) and dwarf spheroidals (dSphs). The colour-magnitude relation (CMR) and the relation between luminosity and mean effective surface brightness for galaxies in the central region of Antlia have been previously studied in Paper I of the present series. Now we confirm 22 early-type galaxies as Antlia members, using Gemini-GMOS and Magellan-MIKE spectra. Among them, 15 are dEs from the FS90 Antlia Group catalogue, two belong to the rare type of compact ellipticals (cEs) and five are new faint dwarfs that had never been catalogued before. In addition, we present 16 newly identified low-surface-brightness galaxy candidates, almost half of them displaying morphologies consistent with being Antlia's counterparts of Local Group dSphs, which extend the faint luminosity limit of our study down to MB=-10.1(BT= 22.6) mag. With these new data, we built an improved CMR in the Washington photometric system, i.e. integrated T1 magnitudes versus (C-T1) colours, which extends ˜4 mag faintwards the limit of spectroscopically confirmed Antlia members. When only confirmed early-type members are considered, this relation extends over 10 mag in luminosity with no apparent change in slope or increase in colour dispersion towards its faint end. The intrinsic colour scatter of the relation is compared with those reported for other clusters of galaxies; we argue that it is likely that the large scatter of the CMR, usually reported at faint magnitudes, is mostly due to photometric errors along with an improper membership/morphological classification. The distinct behaviour of the luminosity versus mean effective surface brightness relation at the bright and faint ends is analysed, while it is confirmed that dE galaxies on the same relation present a very similar effective radius, regardless of their colour. The projected spatial distribution of the member sample confirms the existence of two groups in Antlia, each one dominated by a giant elliptical galaxy and with one cE located close to each giant. Size and position, with respect to massive galaxies, of the dSph candidates are estimated and compared to Local Group counterparts. Based on observations carried out at the Cerro Tololo Inter-American Observatory (Chile), at Las Campanas Observatory (Chile) and at the European Southern Observatory, Paranal (Chile). Also based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministerio da Ciencia e Tecnologia (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).

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

Minchin, Robert F., E-mail: rminchin@naic.edu

I investigate whether it is possible to reconcile the recent Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) observation that the neutral hydrogen mass function (HIMF) across different galactic densities has the same, non-flat, faint-end slope, with observations of isolated galaxies and many galaxy groups that show their HIMFs to have flat faint-end slopes. I find that a fairly simple model in which the position of the knee in the mass function of each individual group is allowed to vary is able to account for both of these observations. If this model reflects reality, the ALFALFA results point to anmore » interesting “conspiracy” whereby the differing group HIMFs always sum up to form global HIMFs with the same faint-end slope in different environments. More generally, this result implies that global environmental HIMFs do not necessarily reflect the HIMFs in individual groups belonging to that environment and cannot be used to directly measure variations in group-specific HIMFs with environment.« less

What do you gain from deconvolution? - Observing faint galaxies with the Hubble Space Telescope Wide Field Camera

NASA Technical Reports Server (NTRS)

Schade, David J.; Elson, Rebecca A. W.

1993-01-01

We describe experiments with deconvolutions of simulations of deep HST Wide Field Camera images containing faint, compact galaxies to determine under what circumstances there is a quantitative advantage to image deconvolution, and explore whether it is (1) helpful for distinguishing between stars and compact galaxies, or between spiral and elliptical galaxies, and whether it (2) improves the accuracy with which characteristic radii and integrated magnitudes may be determined. The Maximum Entropy and Richardson-Lucy deconvolution algorithms give the same results. For medium and low S/N images, deconvolution does not significantly improve our ability to distinguish between faint stars and compact galaxies, nor between spiral and elliptical galaxies. Measurements from both raw and deconvolved images are biased and must be corrected; it is easier to quantify and remove the biases for cases that have not been deconvolved. We find no benefit from deconvolution for measuring luminosity profiles, but these results are limited to low S/N images of very compact (often undersampled) galaxies.

Calibration of EFOSC2 Broadband Linear Imaging Polarimetry

NASA Astrophysics Data System (ADS)

Wiersema, K.; Higgins, A. B.; Covino, S.; Starling, R. L. C.

2018-03-01

The European Southern Observatory Faint Object Spectrograph and Camera v2 is one of the workhorse instruments on ESO's New Technology Telescope, and is one of the most popular instruments at La Silla observatory. It is mounted at a Nasmyth focus, and therefore exhibits strong, wavelength and pointing-direction-dependent instrumental polarisation. In this document, we describe our efforts to calibrate the broadband imaging polarimetry mode, and provide a calibration for broadband B, V, and R filters to a level that satisfies most use cases (i.e. polarimetric calibration uncertainty 0.1%). We make our calibration codes public. This calibration effort can be used to enhance the yield of future polarimetric programmes with the European Southern Observatory Faint Object Spectrograph and Camera v2, by allowing good calibration with a greatly reduced number of standard star observations. Similarly, our calibration model can be combined with archival calibration observations to post-process data taken in past years, to form the European Southern Observatory Faint Object Spectrograph and Camera v2 legacy archive with substantial scientific potential.

Bridging the gap: New ALMA observations of lensed dusty galaxies in the Frontier Fields

NASA Astrophysics Data System (ADS)

Kearney, Zoe; Pope, Alexandra; Aretxaga, Itziar; Hughes, David; Marchesini, Danilo; Montana, Alfredo; Murphy, Eric Joseph; Wilson, Grant; Yun, Min

2018-01-01

During much of cosmic time, most star formation activity in galaxies is obscured by dust. In order to complete the census of star formation, we must bridge the gap between optical and infrared galaxy populations. With AzTEC on the Large Millimeter Telescope (LMT), we surveyed two of the HST Frontier Fields in order to exploit the gravitational lensing from foreground clusters to study dust-obscured in galaxies below the nominal confusion limit. We detect millimeter galaxies with magnifications ranging from 1.1-8, allowing us to detect dust-obscured star formation rates in galaxies as low as ~10 Msun/year. We present new observations with ALMA in order to localize the millimeter emission of the AzTEC/LMT sources and make unambiguous associations with the optical galaxies in the deep HST images. We investigate the issue of multiplicity within our sample. We discuss the multi-wavelength counterparts of our faint millimeter sources and how they relate to brighter dusty galaxies from previous surveys.

ISO Observations of Starless Bok Globules: Usually No Embedded Stars

NASA Technical Reports Server (NTRS)

Clemens, D.; Byrne, A.; Yun, J.; Kane, B.

1996-01-01

We have used ISOCAM to search the cores of a sample of small Bok globules previously classified to be mostly starless based on analysis of IRAS data. The ISO observations at 6.75microns (LW2 filter) and 14.5microns (LW3 filter) were sufficiently deep to enable detection of any low-mass hydrogen burning star or young stellar object (YSO) embedded in these globules. Of the 20 Bok globules observed by ISOCAM to date, we have reduced the data for 14. Of these, 13 show no evidence for faint red (S(sub v)(LW3) greater than S(sub v)(LW2)) stars missed by IRAS. One (CB68) does show the first mid-infrared detection of the very cool IRAS source toward this cloud, and may be a Class I or 0 YSO. We conclude, based on these new ISO observations, that Bok globules which have no IRAS sources are in general bona fide starless molecular clouds.

Observing Solar Radio Bursts from the Lunar Surface

NASA Technical Reports Server (NTRS)

MacDowall, R. J.; Gopalswamy, N.; Kaiser, M. L.; Lazio, T. J.; Jones, D. L.; Bale, S. D.; Burns, J.; Kasper, J. C.; Weiler, K. W.

2011-01-01

Locating low frequency radio observatories on the lunar surface has a number of advantages, including fixes locations for the antennas and no terrestrial interference on the far side of the moon. Here, we describe the Radio Observatory for Lunar Sortie Science (ROLSS), a concept for a low frequency, radio imaging interferometric array designed to study particle acceleration in the corona and inner heliosphere. ROLSS would be deployed during an early lunar sortie or by a robotic rover as part of an unmanned landing. The prime science mission is to image type II and type III solar radio bursts with the aim of determining the sites at and mechanisms by which the radiating particles are accelerated. Secondary science goals include constraining the density of the lunar ionosphere by searching for a low radio frequency cutoff of the solar radio emissions and constraining the low energy electron population in astrophysical sources. Furthermore, ROLSS serves a pathfinder function for larger lunar radio arrays designed for faint sources.

Photometric Redshifts for the Large-Area Stripe 82X Multiwavelength Survey

NASA Astrophysics Data System (ADS)

Tasnim Ananna, Tonima; Salvato, Mara; Urry, C. Megan; LaMassa, Stephanie M.; STRIPE 82X

2016-06-01

The Stripe 82X survey currently includes 6000 X-ray sources in 31.3 square degrees of XMM-Newton and Chandra X-ray coverage, most of which are AGN. Using a maximum-likelihood approach, we identified optical and infrared counterparts in the SDSS, VHS K-band and WISE W1-band catalogs. 1200 objects which had different best associations in different catalogs were checked by eye. Our most recent paper provided the multiwavelength catalogs for this sample. More than 1000 counterparts have spectroscopic redshifts, either from SDSS spectroscopy or our own follow-up program. Using the extensive multiwavelength data in this field, we provide photometric redshift estimates for most of the remaining sources, which are 80-90% accurate according to the training set. Our sample has a large number of candidates that are very faint in optical and bright in IR. We expect a large fraction of these objects to be the obscured AGN sample we need to complete the census on black hole growth at a range of redshifts.

Astronaut Training in the Neutral Buoyancy Simulator

NASA Technical Reports Server (NTRS)

1993-01-01

This photograph shows an STS-61 astronaut training for the Hubble Space Telescope (HST) servicing mission (STS-61) in the Marshall Space Flight Center's (MSFC's) Neutral Buoyancy Simulator (NBS). Two months after its deployment in space, scientists detected a 2-micron spherical aberration in the primary mirror of the HST that affected the telescope's ability to focus faint light sources into a precise point. This imperfection was very slight, one-fiftieth of the width of a human hair. A scheduled Space Service servicing mission (STS-61) in 1993 permitted scientists to correct the problem. The MSFC NBS provided an excellent environment for testing hardware to examine how it would operate in space and for evaluating techniques for space construction and spacecraft servicing.

History of Hubble Space Telescope (HST)

NASA Image and Video Library

1993-07-09

This photograph shows an STS-61 astronaut training for the Hubble Space Telescope (HST) servicing mission (STS-61) in the Marshall Space Flight Center's (MSFC's) Neutral Buoyancy Simulator (NBS). Two months after its deployment in space, scientists detected a 2-micron spherical aberration in the primary mirror of the HST that affected the telescope's ability to focus faint light sources into a precise point. This imperfection was very slight, one-fiftieth of the width of a human hair. A scheduled Space Service servicing mission (STS-61) in 1993 permitted scientists to correct the problem. The MSFC NBS provided an excellent environment for testing hardware to examine how it would operate in space and for evaluating techniques for space construction and spacecraft servicing.

Point Source All Sky

NASA Image and Video Library

2003-03-27

This panoramic view encompasses the entire sky as seen by Two Micron All-Sky Survey. The measured brightnesses of half a billion stars (points) have been combined into colors representing three distinct wavelengths of infrared light: blue at 1.2 microns, green at 1.6 microns, and red at 2.2 microns. This image is centered on the core of our own Milky Way galaxy, toward the constellation of Sagittarius. The reddish stars seemingly hovering in the middle of the Milky Way's disc -- many of them never observed before -- trace the densest dust clouds in our galaxy. The two faint smudges seen in the lower right quadrant are our neighboring galaxies, the Small and Large Magellanic Clouds. http://photojournal.jpl.nasa.gov/catalog/PIA04250

Restoration of HST images with missing data

NASA Technical Reports Server (NTRS)

Adorf, Hans-Martin

1992-01-01

Missing data are a fairly common problem when restoring Hubble Space Telescope observations of extended sources. On Wide Field and Planetary Camera images cosmic ray hits and CCD hot spots are the prevalent causes of data losses, whereas on Faint Object Camera images data are lossed due to reseaux marks, blemishes, areas of saturation and the omnipresent frame edges. This contribution discusses a technique for 'filling in' missing data by statistical inference using information from the surrounding pixels. The major gain consists in minimizing adverse spill-over effects to the restoration in areas neighboring those where data are missing. When the mask delineating the support of 'missing data' is made dynamic, cosmic ray hits, etc. can be detected on the fly during restoration.

AN ENIGMATIC POINT-LIKE FEATURE WITHIN THE HD 169142 TRANSITIONAL DISK ,

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

Biller, Beth A.; Males, Jared; Morzinski, Katie

2014-09-01

We report the detection of a faint point-like feature possibly related to ongoing planet-formation in the disk of the transition disk star HD 169142. The point-like feature has a Δmag(L) ∼ 6.4, at a separation of ∼0.''11 and position angle ∼0°. Given its lack of an H or K{sub S} counterpart despite its relative brightness, this candidate cannot be explained by purely photospheric emission and must be a disk feature heated by an as yet unknown source. Its extremely red colors make it highly unlikely to be a background object, but future multi-wavelength follow up is necessary for confirmation and characterization ofmore » this feature.« less

The morphology of faint galaxies in Medium Deep Survey images using WFPC2

NASA Technical Reports Server (NTRS)

Griffiths, R. E.; Casertano, S.; Ratnatunga, K. U.; Neuschaefer, L. W.; Ellis, R. S.; Gilmore, G. F.; Glazebrook, K.; Santiago, B.; Huchra, J. P.; Windhorst, R. A.

1994-01-01

First results from Hubble Space Telescope (HST) Medium Deep Survey images taken with Wide Field/Planetary Camera-2 (WFPC2) demonstrate that galaxy classifications can be reliably performed to magnitudes I814 approximately less than 22.0 in the F815W band. Published spectroscopic surveys to this depth indicate a mean redshift of bar-z approximately 0.5. We have classified over 200 galaxies in nine WFPC2 fields according to a basic morphological scheme. The majority of these faint galaxies appear to be similar to regular Hubble-sequence examples observed at low redshift. To the precision of our classification scheme, the relative proportion of spheroidal and disk systems of normal appearance is as expected from nearby samples, indicating that the bulk of the local galaxy population was in place at half the Hubble time. However, the most intriguing result is the relatively high proportion (approximately 40%) of objects which are in some way anomalous, and which may be of relevance in understanding the origin of the familiar excess population of faint galaxies established by others. These diverse objects include apparently interacting pairs whose multiple structure is only revealed with HST's angular resolution, galaxies with superluminous star-forming regions, diffuse low surface brightness galaxies of various forms, and compact galaxies. These anomalous galaxies contribute a substantial fraction of the excess counts at our limiting magnitude, and may provide insights into the 'faint blue galaxy' problem.

DISCOVERY OF A NEW FAINT DWARF GALAXY ASSOCIATED WITH NGC 253

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

Sand, D. J.; Crnojević, D.; Strader, J.

2014-09-20

We report the discovery of a new faint dwarf galaxy, which we dub Scl-MM-Dw1, at a projected distance of ∼65 kpc from the spiral galaxy NGC 253. The discovery results from the Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS), a program with the Magellan/Megacam imager to study faint substructure in resolved stellar light around massive galaxies outside of the Local Group. We measure a tip of the red giant branch distance to Scl-MM-Dw1 of D = 3.9 ± 0.5 Mpc, consistent with that of NGC 253, making their association likely. The new dwarf's stellar population is complex, with an old, metal-poor red giant branch (≳10 Gyr, [Fe/H] ∼ –2), andmore » an asymptotic giant branch with an age of ∼500 Myr. Scl-MM-Dw1 has a half-light radius of r{sub h} = 340 ± 50 pc and an absolute magnitude of M{sub V}  = –10.3 ± 0.6 mag, comparable to the Milky Way's satellites at the same luminosity. Once complete, our imaging survey of NGC 253 and other nearby massive galaxies will provide a census of faint substructure in halos beyond the Local Group, both to put our own environment into context and to confront models of hierarchical structure formation.« less

A catalogue of faint local radio AGN and the properties of their host galaxies

NASA Astrophysics Data System (ADS)

Lofthouse, E. K.; Kaviraj, S.; Smith, D. JB; Hardcastle, M. J.

2018-05-01

We present a catalogue of local (z < 0.1) galaxies that contain faint AGN. We select these objects by identifying galaxies that exhibit a significant excess in their radio luminosities, compared to what is expected from the observed levels of star-formation activity in these systems. This is achieved by comparing the optical (spectroscopic) star formation rate (SFR) to the 1.4 GHz luminosity measured from the FIRST survey. The majority of the AGN identified in this study are fainter than those in previous work, such as in the Best and Heckman (2012) catalogue. We show that these faint AGN make a non-negligible contribution to the radio luminosity function at low luminosities (below 1022.5 W Hz-1), and host ˜13 per cent of the local radio luminosity budget. Their host galaxies are predominantly high stellar-mass systems (with a median stellar mass of 1011M⊙), are found across a range of environments (but typically in denser environments than star-forming galaxies) and have early-type morphologies. This study demonstrates a general technique to identify AGN in galaxy populations where reliable optical SFRs can be extracted using spectro-photometry and where radio data are also available so that a radio excess can be measured. Our results also demonstrate that it is unsafe to infer SFRs from radio emission alone, even if bright AGN have been excluded from a sample, since there is a significant population of faint radio AGN which may contaminate the radio-derived SFRs.

HST/WFC3: Evolution of the UVIS Channel's Charge Transfer Efficiency

NASA Astrophysics Data System (ADS)

Gosmeyer, Catherine; Baggett, Sylvia M.; Anderson, Jay; WFC3 Team

2016-06-01

The Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) contains both an IR and a UVIS channel. After more than six years on orbit, the UVIS channel performance remains stable; however, on-orbit radiation damage has caused the charge transfer efficiency (CTE) of UVIS's two CCDs to degrade. This degradation is seen as vertical charge 'bleeding' from sources during readout and its effect evolves as the CCDs age. The WFC3 team has developed software to perform corrections that push the charge back to the sources, although it cannot recover faint sources that have been bled out entirely. Observers can mitigate this effect in various ways such as by placing sources near the amplifiers, observing bright targets, and by increasing the total background to at least 12 electrons, either by using a broader filter, lengthening exposure time, or post-flashing. We present results from six years of calibration data to re-evaluate the best level of total background for mitigating CTE loss and to re-verify that the pixel-based CTE correction software is performing optimally over various background levels. In addition, we alert observers that CTE-corrected products are now available for retrieval from MAST as part of the CALWF3 v3.3 pipeline upgrade.

Searching for faint AGN in the CDFS: an X-ray (Chandra) vs optical variability (HST) comparison.

NASA Astrophysics Data System (ADS)

Georgantopoulos, I.; Pouliasis, E.; Bonanos, A.; Sokolovsky, K.; Yang, M.; Hatzidimitriou, D.; Bellas, I.; Gavras, P.; Spetsieri, Z.

2017-10-01

X-ray surveys are believed to be the most efficient way to detect AGN. Recently though, optical variability studies are claimed to probe even fainter AGN. We are presenting results from an HST study aimed to identify Active Galactic Nuclei (AGN) through optical variability selection in the CDFS.. This work is part of the 'Hubble Catalogue of Variables'project of ESA that aims to identify variable sources in the Hubble Source Catalogue.' In particular, we used Hubble Space Telescope (HST) z-band images taken over 5 epochs and performed aperture photometry to derive the lightcurves of the sources. Two statistical methods (standard deviation & interquartile range) resulting in a final sample of 175 variable AGN candidates, having removed the artifacts by visual inspection and known stars and supernovae. The fact that the majority of the sources are extended and variable indicates AGN activity. We compare the efficiency of the method by comparing with the 7Ms Chandra detections. Our work shows that the optical variability probes AGN at comparable redshifts but at deeper optical magnitudes. Our candidate AGN (non detected in X-rays) have luminosities of L_x<6×10^{40} erg/sec at z˜0.7 suggesting that these are associated with low luminosity Seyferts and LINERS.

New Measurements of the Cosmic Infrared Background Fluctuations in Deep SpitzerllRAC Survey Data and their Cosmological Implications

NASA Technical Reports Server (NTRS)

Kashlinsky, A.; Arendt, R. G.; Ashby, M. L. N.; Fazio, G. G.; Mather, J.; Moseley, S. H.

2012-01-01

We extend the previous measurements of CIB fluctuations to angular scales of less than or equal to 1 degree new data obtained in the course of the 2,000+ hour Spitzer Extended Deep Survey. Two fields with completed observations of approximately equal to 12 hr/pixel are analyzed for source-subtracted CIB fluctuations at 3.6 and 4.5 micrometers. The fields, EGS and UDS, cover a total area of approximately 0.25 deg and lie at high Galactic and Ecliptic latitudes, thus minimizing cirrus and zodiacal light contributions to the fluctuations. The observations have been conducted at 3 distinct epochs separated by about 6 months. As in our previous studies, the fields were assembled using the self-calibration method which is uniquely suitable for probing faint diffuse backgrounds. The assembled fields were cleaned off the bright sources down to the low shot noise levels corresponding to AB mag approximately equal to 25, Fourier-transformed and their power spectra evaluated. The noise was estimated from the time-differenced data and subtracted from the signal isolating the fluctuations remaining above the noise levels. The power spectra of the source-subtracted fields remain identical (within the observational uncertainties) for the three epochs of observations indicating that zodiacal light contributes negligibly to the fluctuations. By comparing to the measurements for the same regions at 8 micrometers we demonstrate that Galactic cirrus cannot account for the levels of the fluctuations either. The signal appears isotropically distributed on the sky as required by its origin in the CIB fluctuations. This measurement thus extends our earlier results to the important range of sub-degree scales. We find that the CIB fluctuations continue to diverge to more than 10 times those of known galaxy populations on angular scales out to less than or equal to 1 degree. The low shot noise levels remaining in the diffuse maps indicate that the large scale fluctuations arise from spatial clustering of faint sources well within the confusion noise. The spatial spectrum of these fluctuations is in reasonable agreement with simple fitting assuming that they originate in early populations spatially distributed according to the standard cosmological model (ACDM) at epochs coinciding with the first stars era. The alternative to this identification would require a new population never observed before, nor expected on theoretical grounds, but if true this would represent an important discovery in its own right.

Spectroscopic observations of comets

NASA Technical Reports Server (NTRS)

1982-01-01

Development of a spectrograph using a microchannel plate intensifier for observing faint comets is described. The spectrograph is capable of obtaining useful spectra of objects as faint as M(2) = 18. The increased guiding efficiency achieved by the optical coupling of the ISIT vidicon of the 154 cm telescope has resulted in a better signal to noise ratio. The ability to take a direct image of the comet aids in the interpretation of the spatial profile of the emissions. Spectra of comets Schwassmann-Wachmann 1, Bradfield, Encke, Tuttle, and Stephen-Oterma are discussed.

Dwarf galaxies: a lab to investigate the neutron capture elements production

NASA Astrophysics Data System (ADS)

Cescutti, Gabriele

2018-06-01

In this contribution, I focus on the neutron capture elements observed in the spectra of old halo and ultra faint galaxies stars. Adopting a stochastic chemical evolution model and the Galactic halo as a benchmark, I present new constraints on the rate and time scales of r-process events, based on the discovery of the r-process rich stars in the ultra faint galaxy Reticulum 2. I also show that an s-process activated by rotation in massive stars can play an important role in the production of heavy elements.

VizieR Online Data Catalog: Deep Herschel PACS point spread functions (Bocchio+, 2016)

NASA Astrophysics Data System (ADS)

Bocchio, M.; Bianchi, A.; Abergel, S.

2016-06-01

Herschel PACS dedicated PSF observations are scanmaps centred on various objects taken at 70 (blue channel), 100 (green channel) and 160 (red channel) um. The core of the PSF is best characterised observing faint objects (e.g. the asteroid Vesta), while the wings of the PSF can only be seen in observations of bright objects (e.g. Mars). Using a combination of images of bright and faint objects it is therefore possible to have a good characterisation of the PACS PSFs. (2 data files).

Astrometric and Photometric Follow-up of Faint Near Earth Objects

NASA Technical Reports Server (NTRS)

Morgan, T. (Technical Monitor); Spahr, Timothy

2005-01-01

During the period April 2003 - April 2005, roughly 150 different faint NEO's were observed using the 1.2-m telescope at Mt. Hopkins. Among these were a couple of spacecraft/radar targets, including support observations in support of the Deep Impact mission. While not strictly an NEO target, comet P/Tempel 1 was nonetheless observed as an object of very high importance. During this time and independent contractor, Kyle Smalley, was trained in the use of the telescope and provided some basic software support for the project.

The early faint sun paradox: organic shielding of ultraviolet-labile greenhouse gases

NASA Technical Reports Server (NTRS)

Sagan, C.; Chyba, C.

1997-01-01

Atmospheric mixing ratios of approximately 10(-5 +/- 1) for ammonia on the early Earth would have been sufficient, through the resulting greenhouse warming, to counteract the temperature effects of the faint early sun. One argument against such model atmospheres has been the short time scale for ammonia photodissociation by solar ultraviolet light. Here it is shown that ultraviolet absorption by steady-state amounts of high-altitude organic solids produced from methane photolysis may have shielded ammonia sufficiently that ammonia resupply rates were able to maintain surface temperatures above freezing.

Self-Calibration of CMB Polarimeters

NASA Astrophysics Data System (ADS)

Keating, Brian

2013-01-01

Precision measurements of the polarization of the cosmic microwave background (CMB) radiation, especially experiments seeking to detect the odd-parity "B-modes", have far-reaching implications for cosmology. To detect the B-modes generated during inflation the flux response and polarization angle of these experiments must be calibrated to exquisite precision. While suitable flux calibration sources abound, polarization angle calibrators are deficient in many respects. Man-made polarized sources are often not located in the antenna's far-field, have spectral properties that are radically different from the CMB's, are cumbersome to implement and may be inherently unstable over the (long) duration these searches require to detect the faint signature of the inflationary epoch. Astrophysical sources suffer from time, frequency and spatial variability, are not visible from all CMB observatories, and none are understood with sufficient accuracy to calibrate future CMB polarimeters seeking to probe inflationary energy scales of ~1000 TeV. CMB TB and EB modes, expected to identically vanish in the standard cosmological model, can be used to calibrate CMB polarimeters. By enforcing the observed EB and TB power spectra to be consistent with zero, CMB polarimeters can be calibrated to levels not possible with man-made or astrophysical sources. All of this can be accomplished without any loss of observing time using a calibration source which is spectrally identical to the CMB B-modes. The calibration procedure outlined here can be used for any CMB polarimeter.

Chandra Discovers X-ray Source at the Center of Our Galaxy

NASA Astrophysics Data System (ADS)

2000-01-01

Culminating 25 years of searching by astronomers, researchers at Massachusetts Institute of Technology say that a faint X-ray source, newly detected by NASA's Chandra X-ray Observatory, may be the long-sought X-ray emission from a known supermassive black hole at the center of our galaxy. Frederick K. Baganoff and colleagues from Pennsylvania State University, University Park, and the University of California, Los Angeles, will present their findings today in Atlanta at the 195th national meeting of the American Astronomical Society. Baganoff, lead scientist for the Chandra X-ray Observatory's Advanced CCD Imaging Spectrometer (ACIS) team's "Sagittarius A* and the Galactic Center" project and postdoctoral research associate at MIT, said that the precise positional coincidence between the new X-ray source and the radio position of a long-known source called Sagittarius A* "encourages us to believe that the two are the same." Sagittarius A* is a point-like, variable radio source at the center of our galaxy. It looks like a faint quasar and is believed to be powered by gaseous matter falling into a supermassive black hole with 2.6 million times the mass of our Sun. Chandra's remarkable detection of this X-ray source has placed astronomers within a couple of years of a coveted prize: measuring the spectrum of energy produced by Sagittarius A* to determine in detail how the supermassive black hole that powers it works. "The race to be the first to detect X-rays from Sagittarius A* is one of the hottest and longest-running in all of X-ray astronomy," Baganoff said. "Theorists are eager to hear the results of our observation so they can test their ideas." But now that an X-ray source close to Sagittarius A* has been found, it has taken researchers by surprise by being much fainter than expected. "There must be something unusual about the environment around this black hole that affects how it is fed and how the gravitational energy released from the infalling matter is converted into the X-ray light that we see," Baganoff said. "This new result provides fresh insight that will no doubt stir heated debates on these issues "Chandra's sensitivity is 20 times better than achieved with the best previous X-ray telescopes," said Gordon Garmire, the Evan Pugh Professor of Astronomy and Astrophysics at Penn State University and head of the team that conceived and built Chandra's Advanced CCD Imaging Spectrometer (ACIS) X-ray camera, which Chandra's mirrors, make Chandra the perfect tool for studying this faint X-ray source in its crowded field." "The luminosity of the X-ray source we have discovered already is a factor of five satelllite," Baganoff said. "This poses a problem for theorists. The galactic center is a crowded place. If we were to find that most or all of the X-ray emission is not from all up." Astronomers believe that most galaxies harbor massive black holes at their centers. Many of these black holes are thought to produce powerful and brilliant point-like sources of light that astronomers call quasars and active galactic nuclei. Why the center of our galaxy is so dim is a long-standing puzzle. One Source Standing Out in a Crowd Sagittarius A*, which stands out on a radio map as a bright dot, was detected at the dynamical center of the Milky Way galaxy by radio telescopes in 1974. More recently, infrared observations of the movements of stars around Sagittarius A* has convinced most astronomers that there is a supermassive black hole at the center of our galaxy and that it is probably associated with Sagittarius A*. A black hole is an object so compact that light itself cannot escape its gravitational pull. A black hole sucks up material thrown out by normal stars around it. Because there are a million times more stars in a given volume in the galactic center than elsewhere in the galaxy, researchers cannot yet say definitively that Sagittarius A* is the newly detected source of the X-rays. "We need more data to clarify our observations," Baganoff said. If Sagittarius A* is powered by a supermassive black hole, astronomers expected that there would be a lot of matter to suck up in a crowded place like the galactic center. The faintness of the source may indicate a dearth of matter floating toward the black hole or it may indicate that the environment of the black hole is for some reason rejecting most of the infalling material. Chandra's Powerful Vision Optical telescopes such as the Hubble Space Telescope cannot see the center of our galaxy, which is enshrouded in thick clouds of dust and gas in the plane of the galaxy. However, hot gas and charged particles moving at nearly the speed of light produce X-rays that penetrate this shroud. Only a few months after its launch, Chandra accomplished what no other optical or X-ray satellite was able to do: separate the emissions from the surrounding hot gas and nearby compact sources that prevented other satellites from detecting this new X-ray source. Mark Morris of the University of California at Los Angeles, who has studied this region intensely for 20 years, called Chandra's data "a gold mine" for astronomers. "With more observing time on Chandra in the next two or three years, we will be able to build up a spectrum that will allow us to rule out various classes of objects and either emission," Baganoff said. "If we show that the emission is from a supermassive black hole, we will then be set to begin a detailed study of the X-ray emission from the nearest analog of a quasar or active galactic nucleus." Chandra's ACIS detector, the Advanced CCD Imaging Spectrometer, was conceived and developed for NASA by Penn State University and MIT under the leadership of Penn State Professor Gordon Garmire. Related Press Press Room: Sagittarius A* Press Release (06 Jan 03) Press Room: Galactic Center (Survey) Press Release (09 Jan 02) To follow Chandra's progress or download images visit the Chandra sites at http://chandra.harvard.edu/photo/2000/0204/index.html AND http://chandra.nasa.gov NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. TRW Inc., Redondo Beach, Calif., is the prime contractor for the spacecraft. The Smithsonian's Chandra X-ray Center controls science and flight operations from Cambridge, Mass.

An Ultradeep Chandra Catalog of X-Ray Point Sources in the Galactic Center Star Cluster

NASA Astrophysics Data System (ADS)

Zhu, Zhenlin; Li, Zhiyuan; Morris, Mark R.

2018-04-01

We present an updated catalog of X-ray point sources in the inner 500″ (∼20 pc) of the Galactic center (GC), where the nuclear star cluster (NSC) stands, based on a total of ∼4.5 Ms of Chandra observations taken from 1999 September to 2013 April. This ultradeep data set offers unprecedented sensitivity for detecting X-ray sources in the GC, down to an intrinsic 2–10 keV luminosity of 1.0 × 1031 erg s‑1. A total of 3619 sources are detected in the 2–8 keV band, among which ∼3500 are probable GC sources and ∼1300 are new identifications. The GC sources collectively account for ∼20% of the total 2–8 keV flux from the inner 250″ region where detection sensitivity is the greatest. Taking advantage of this unprecedented sample of faint X-ray sources that primarily traces the old stellar populations in the NSC, we revisit global source properties, including long-term variability, cumulative spectra, luminosity function, and spatial distribution. Based on the equivalent width and relative strength of the iron lines, we suggest that in addition to the arguably predominant population of magnetic cataclysmic variables (CVs), nonmagnetic CVs contribute substantially to the detected sources, especially in the lower-luminosity group. On the other hand, the X-ray sources have a radial distribution closely following the stellar mass distribution in the NSC, but much flatter than that of the known X-ray transients, which are presumably low-mass X-ray binaries (LMXBs) caught in outburst. This, together with the very modest long-term variability of the detected sources, strongly suggests that quiescent LMXBs are a minor (less than a few percent) population.

VizieR Online Data Catalog: Multiwavelenght photometry of Sh 2-138 YSOs (Baug+, 2015)

NASA Astrophysics Data System (ADS)

Baug, T.; Ojha, D. K.; Dewangan, L. K.; Ninan, J. P.; Bhatt, B. C.; Ghosh, S. K.; Mallick, K. K.

2016-07-01

Optical BVRI imaging observations of the Sh2-138 region were carried out on 2005 September 8 using the Himalaya Faint Object Spectrograph and Camera (HFOSC) mounted on the 2 m Himalayan Chandra Telescope (HCT). In order to identify strong Hα emission sources in the Sh2-138 region, slitless Hα spectra were obtained using the HFOSC on 2007 November 16. Optical spectroscopic observations of the central brightest source were performed using the HFOSC on 2014 November 18. The newly installed TIFR Near Infrared Spectrometer and Imager Camera (TIRSPEC) on the HCT was used for NIR observations on 2014 November 18 under photometric conditions with an average seeing of 1.4 arcsec. We obtained NIR spectra of the central brightest source on 2014 May 29, using the TIRSPEC, in NIR Y (1.02-1.20um), J (1.21-1.48um), H (1.49-1.78um), and K (2.04-2.35um) bands. We conducted optical narrow-band imaging observations of the region in Hα filter (λ~6563Å, Δλ~100Å) with exposure times of 600s, 250s, and 50s on 2005 September 8 using the HFOSC. (1 data file).

catsHTM: A Tool for Fast Accessing and Cross-matching Large Astronomical Catalogs

NASA Astrophysics Data System (ADS)

Soumagnac, Maayane T.; Ofek, Eran O.

2018-07-01

Fast access to large catalogs is required for some astronomical applications. Here we introduce the catsHTM tool, consisting of several large catalogs reformatted into HDF5-based file format, which can be downloaded and used locally. To allow fast access, the catalogs are partitioned into hierarchical triangular meshes and stored in HDF5 files. Several tools are provided to perform efficient cone searches at resolutions spanning from a few arc-seconds to degrees, within a few milliseconds time. The first released version includes the following catalogs (by alphabetical order): 2MASS, 2MASS extended sources, AKARI, APASS, Cosmos, DECaLS/DR5, FIRST, GAIA/DR1, GAIA/DR2, GALEX/DR6Plus7, HSC/v2, IPHAS/DR2, NED redshifts, NVSS, Pan-STARRS1/DR1, PTF photometric catalog, ROSAT faint source, SDSS sources, SDSS/DR14 spectroscopy, SkyMapper, Spitzer/SAGE, Spitzer/IRAC galactic center, UCAC4, UKIDSS/DR10, VST/ATLAS/DR3, VST/KiDS/DR3, WISE and XMM. We provide Python code that allows to perform cone searches, as well as MATLAB code for performing cone searches, catalog cross-matching, general searches, as well as load and create these catalogs.

Design and expected performance of a novel hybrid detector for very-high-energy gamma-ray astrophysics

NASA Astrophysics Data System (ADS)

Assis, P.; Barres de Almeida, U.; Blanco, A.; Conceição, R.; D'Ettorre Piazzoli, B.; De Angelis, A.; Doro, M.; Fonte, P.; Lopes, L.; Matthiae, G.; Pimenta, M.; Shellard, R.; Tomé, B.

2018-05-01

Current detectors for Very-High-Energy γ-ray astrophysics are either pointing instruments with a small field of view (Cherenkov telescopes), or large field-of-view instruments with relatively large energy thresholds (extensive air shower detectors). In this article, we propose a new hybrid extensive air shower detector sensitive in an energy region starting from about 100 GeV. The detector combines a small water-Cherenkov detector, able to provide a calorimetric measurement of shower particles at ground, with resistive plate chambers which contribute significantly to the accurate shower geometry reconstruction. A full simulation of this detector concept shows that it is able to reach better sensitivity than any previous gamma-ray wide field-of-view experiment in the sub-TeV energy region. It is expected to detect with a 5σ significance a source fainter than the Crab Nebula in one year at 100 GeV and, above 1 TeV a source as faint as 10% of it. As such, this instrument is suited to detect transient phenomena making it a very powerful tool to trigger observations of variable sources and to detect transients coupled to gravitational waves and gamma-ray bursts.

Testing the TPF Interferometry Approach before Launch

NASA Technical Reports Server (NTRS)

Serabyn, Eugene; Mennesson, Bertrand

2006-01-01

One way to directly detect nearby extra-solar planets is via their thermal infrared emission, and with this goal in mind, both NASA and ESA are investigating cryogenic infrared interferometers. Common to both agencies' approaches to faint off-axis source detection near bright stars is the use of a rotating nulling interferometer, such as the Terrestrial Planet Finder interferometer (TPF-I), or Darwin. In this approach, the central star is nulled, while the emission from off-axis sources is transmitted and modulated by the rotation of the off-axis fringes. Because of the high contrasts involved, and the novelty of the measurement technique, it is essential to gain experience with this technique before launch. Here we describe a simple ground-based experiment that can test the essential aspects of the TPF signal measurement and image reconstruction approaches by generating a rotating interferometric baseline within the pupil of a large singleaperture telescope. This approach can mimic potential space-based interferometric configurations, and allow the extraction of signals from off-axis sources using the same algorithms proposed for the space-based missions. This approach should thus allow for testing of the applicability of proposed signal extraction algorithms for the detection of single and multiple near-neighbor companions...