PAndAS' CUBS: Discovery of Two New Dwarf Galaxies in the Surroundings of the Andromeda and Triangulum Galaxies

NASA Astrophysics Data System (ADS)

Martin, Nicolas F.; McConnachie, Alan W.; Irwin, Mike; Widrow, Lawrence M.; Ferguson, Annette M. N.; Ibata, Rodrigo A.; Dubinski, John; Babul, Arif; Chapman, Scott; Fardal, Mark; Lewis, Geraint F.; Navarro, Julio; Rich, R. Michael

2009-11-01

We present the discovery of two new dwarf galaxies, Andromeda XXI and Andromeda XXII, located in the surroundings of the Andromeda and Triangulum galaxies (M31 and M33). These discoveries stem from the first year data of the Pan-Andromeda Archaeological Survey, a photometric survey of the M31/M33 group conducted with the Megaprime/MegaCam Wide-Field Camera mounted on the Canada-France-Hawaii Telescope. Both satellites appear as spatial overdensities of stars which, when plotted in a color-magnitude diagram, follow metal-poor, [Fe/H] = -1.8, red giant branches at the distance of M31/M33. Andromeda XXI is a moderately bright dwarf galaxy (MV = -9.9 ± 0.6), albeit with low surface brightness, emphasizing again that many relatively luminous M31 satellites still remain to be discovered. It is also a large satellite, with a half-light radius close to 1 kpc, making it the fourth largest Local Group dwarf spheroidal galaxy after the recently discovered Andromeda XIX, Andromeda II, and Sagittarius around the Milky Way, and supports the trend that M31 satellites are larger than their Milky Way counterparts. Andromeda XXII is much fainter (MV = -6.5 ± 0.8) and lies a lot closer in projection to M33 than it does to M31 (42 versus 224 kpc), suggesting that it could be the first Triangulum satellite to be discovered. Although this is a very exciting possibility in the context of a past interaction of M33 with M31 and the fate of its satellite system, a confirmation will have to await a good distance estimate to confirm its physical proximity to M33. Along with the dwarf galaxies found in previous surveys of the M31 surroundings, these two new satellites bring the number of dwarf spheroidal galaxies in this region to 20. Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institute National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

Chemistry of the Triangulum-Andromeda Overdensity as Seen by APOGEE

NASA Astrophysics Data System (ADS)

Rochford Hayes, Christian; Majewski, Steven R.; Hasselquist, Sten; Beaton, Rachael; Cunha, Katia M. L.; Smith, Verne V.; Price-Whelan, Adrian M.; APOGEE Team

2018-06-01

The nature of the Triangulum-Andromeda (TriAnd) system has been debated since the discovery of this distant, low-latitude Milky Way (MW) overdensity more than a decade ago. Explanations for its origin are either as a halo substructure from the disruption of a dwarf galaxy or a distant extension of the Galactic disk. We test these hypotheses using chemical abundances of a dozen TriAnd members from the Sloan Digital Sky Survey’s 14th Data Release of Apache Point Observatory Galactic Evolution Experiment (APOGEE) data to compare to APOGEE abundances of stars with similar metallicity from both the Sagittarius (Sgr) dSph, and the outer MW disk. We find that TriAnd stars are chemically distinct from Sgr across a variety of elements, (C+N), Mg, K, Ca, Mn, and Ni, with a separation in [X/Fe] of about 0.1 to 0.4 dex depending on the element. Instead, the TriAnd stars, with a median metallicity of about -0.8, exhibit chemical abundance ratios similar to those of the lowest metallicity ([Fe/H] ~ -0.7) stars in the outer Galactic disk, and are consistent with expectations of extrapolated chemical gradients in the outer disk of the MW. These results suggest that TriAnd is associated with the MW disk, and, therefore, that the disk extends to this overdensity - i.e., past a Galactocentric radius of 24 kpc - albeit vertically perturbed about 7 kpc below the nominal disk midplane in this region of the Galaxy.

Andromeda and its Satellites: A Kinematic Perspective

NASA Astrophysics Data System (ADS)

Collins, M. L. M.; Rich, R. M.; Chapman, S. C.

2012-08-01

Using spectroscopic data taken with Keck II DEIMOS by the Z-PAndAS team in the Andromeda-Triangulum region, I present a comparison of the disc and satellite systems of Andromeda with those of our own Galaxy. I discuss the observed discrepancies between the masses and scale radii of Andromeda dwarf spheroidal galaxies of a given luminosity with those of the Milky Way. I also present an analysis of the newly discovered M31 thick disc, which is measured to be hotter, more extended and thicker than that seen in the Milky Way.

Disk-like Chemistry of the Triangulum-Andromeda Overdensity as Seen by APOGEE

NASA Astrophysics Data System (ADS)

Hayes, Christian R.; Majewski, Steven R.; Hasselquist, Sten; Beaton, Rachael L.; Cunha, Katia; Smith, Verne V.; Price-Whelan, Adrian M.; Anguiano, Borja; Beers, Timothy C.; Carrera, Ricardo; Fernández-Trincado, J. G.; Frinchaboy, Peter M.; García-Hernández, D. A.; Lane, Richard R.; Nidever, David L.; Nitschelm, Christian; Roman-Lopes, Alexandre; Zamora, Olga

2018-05-01

The nature of the Triangulum-Andromeda (TriAnd) system has been debated since the discovery of this distant, low-latitude Milky Way (MW) overdensity more than a decade ago. Explanations for its origin are either as a halo substructure from the disruption of a dwarf galaxy, or a distant extension of the Galactic disk. We test these hypotheses using the chemical abundances of a dozen TriAnd members from the Sloan Digital Sky Survey-IV’s (SDSS-IV’s) 14th Data Release (DR14) of Apache Point Observatory Galactic Evolution Experiment (APOGEE) data to compare to APOGEE abundances of stars with similar metallicity from both the Sagittarius (Sgr) dSph and the outer MW disk. We find that TriAnd stars are chemically distinct from Sgr across a variety of elements, (C+N), Mg, K, Ca, Mn, and Ni, with a separation in [X/Fe] of about 0.1 to 0.4 dex depending on the element. Instead, the TriAnd stars, with a median metallicity of about ‑0.8, exhibit chemical abundance ratios similar to those of the lowest metallicity ([Fe/H] ∼ ‑0.7) stars in the outer Galactic disk, and are consistent with expectations of extrapolated chemical gradients in the outer disk of the MW. These results suggest that TriAnd is associated with the MW disk, and, therefore, that the disk extends to this overdensity—i.e., past a Galactocentric radius of 24 kpc—albeit vertically perturbed about 7 kpc below the nominal disk midplane in this region of the Galaxy.

M33: A Close Neighbor Reveals its True Size and Splendor

NASA Technical Reports Server (NTRS)

2009-01-01

One of our closest galactic neighbors shows its awesome beauty in this new image from NASA's Spitzer Space Telescope. M33, also known as the Triangulum Galaxy, is a member of what's known as our Local Group of galaxies. Along with our own Milky Way, this group travels together in the universe, as they are gravitationally bound. In fact, M33 is one of the few galaxies that is moving toward the Milky Way despite the fact that space itself is expanding, causing most galaxies in the universe to grow farther and farther apart.

When viewed with Spitzer's infrared eyes, this elegant spiral galaxy sparkles with color and detail. Stars appear as glistening blue gems (many of which are actually foreground stars in our own galaxy), while dust in the spiral disk of the galaxy glows pink and red. But not only is this new image beautiful, it also shows M33 to be surprising large bigger than its visible-light appearance would suggest. With its ability to detect cold, dark dust, Spitzer can see emission from cooler material well beyond the visible range of M33's disk. Exactly how this cold material moved outward from the galaxy is still a mystery, but winds from giant stars or supernovas may be responsible.

M33 is located about 2.9 million light-years away in the constellation Triangulum. This composite image was taken by Spitzer's infrared array camera. The color blue indicates infrared light of 3.6 microns, green shows 4.5-micron light, and red 8.0 microns.

Deep Subaru Hyper Suprime-Cam Observations of Milky Way Satellites Columba I and Triangulum II

NASA Astrophysics Data System (ADS)

Carlin, Jeffrey L.; Sand, David J.; Muñoz, Ricardo R.; Spekkens, Kristine; Willman, Beth; Crnojević, Denija; Forbes, Duncan A.; Hargis, Jonathan; Kirby, Evan; Peter, Annika H. G.; Romanowsky, Aaron J.; Strader, Jay

2017-12-01

We present deep, wide-field Subaru Hyper Suprime-Cam photometry of two recently discovered satellites of the Milky Way (MW): Columba I (Col I) and Triangulum II (Tri II). The color-magnitude diagrams of both objects point to exclusively old and metal-poor stellar populations. We re-derive structural parameters and luminosities of these satellites, and find {M}{{V},{Col}{{I}}}=-4.2+/- 0.2 for Col I and {M}{{V},{Tri}{II}}=-1.2+/- 0.4 for Tri II, with corresponding half-light radii of {r}{{h},{Col}{{I}}}=117+/- 17 pc and {r}{{h},{Tri}{II}}=21+/- 4 pc. The properties of both systems are consistent with observed scaling relations for MW dwarf galaxies. Based on archival data, we derive upper limits on the neutral gas content of these dwarfs, and find that they lack H I, as do the majority of observed satellites within the MW virial radius. Neither satellite shows evidence of tidal stripping in the form of extensions or distortions in matched-filter stellar density maps or surface-density profiles. However, the smaller Tri II system is relatively metal-rich for its luminosity (compared to other MW satellites), possibly because it has been tidally stripped. Through a suite of orbit simulations, we show that Tri II is approaching pericenter of its eccentric orbit, a stage at which tidal debris is unlikely to be seen. In addition, we find that Tri II may be on its first infall into the MW, which helps explain its unique properties among MW dwarfs. Further evidence that Tri II is likely an ultra-faint dwarf comes from its stellar mass function, which is similar to those of other MW dwarfs. Based in part on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

M33: A Close Neighbor Reveals its True Size and Splendor (3-color composite)

NASA Technical Reports Server (NTRS)

2009-01-01

One of our closest galactic neighbors shows its awesome beauty in this new image from NASA's Spitzer Space Telescope. M33, also known as the Triangulum Galaxy, is a member of what's known as our Local Group of galaxies. Along with our own Milky Way, this group travels together in the universe, as they are gravitationally bound. In fact, M33 is one of the few galaxies that is moving toward the Milky Way despite the fact that space itself is expanding, causing most galaxies in the universe to grow farther and farther apart.

When viewed with Spitzer's infrared eyes, this elegant spiral galaxy sparkles with color and detail. Stars appear as glistening blue gems (several of which are actually foreground stars in our own galaxy), while dust rich in organic molecules glows green. The diffuse orange-red glowing areas indicate star-forming regions, while small red flecks outside the spiral disk of M33 are most likely distant background galaxies. But not only is this new image beautiful, it also shows M33 to be surprising large bigger than its visible-light appearance would suggest. With its ability to detect cold, dark dust, Spitzer can see emission from cooler material well beyond the visible range of M33's disk. Exactly how this cold material moved outward from the galaxy is still a mystery, but winds from giant stars or supernovas may be responsible.

M33 is located about 2.9 million light-years away in the constellation Triangulum. This is a three-color composite image showing infrared observations from two of Spitzer instruments. Blue represents combined 3.6- and 4.5-micron light and green shows light of 8 microns, both captured by Spitzer's infrared array camera. Red is 24-micron light detected by Spitzer's multiband imaging photometer.

Exploring halo substructure with giant stars. XIV. The nature of the Triangulum-Andromeda stellar features

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

Sheffield, Allyson A.; Johnston, Kathryn V.; Majewski, Steven R.

As large-scale stellar surveys have become available over the past decade, the ability to detect and characterize substructures in the Galaxy has increased dramatically. These surveys have revealed the Triangulum-Andromeda (TriAnd) region to be rich with substructures in the distance range 20-30 kpc, and the relation of these features to each other, if any, remains unclear. An exploration using Two Micron All Sky Survey (2MASS) photometry reveals not only the faint sequence in M giants detected by Rocha-Pinto et al. spanning the range 100° < l < 160° and –50° < b < –15°, but, in addition, a second, brightermore » and more densely populated sequence. These sequences are likely associated with the distinct main sequences (MSs) discovered (and labeled TriAnd1 and TriAnd2) by Martin et al. in an optical survey in the direction of M31, where TriAnd2 is the optical counterpart of the fainter red giant branch (RGB)/asymptotic giant branch sequence of Rocha-Pinto et al. Here, the age, distance, and metallicity ranges for TriAnd1 and TriAnd2 are estimated by simultaneously fitting isochrones to the 2MASS RGB tracks and the optical MS/MS turn-off features. The two populations are clearly distinct in age and distance: the brighter sequence (TriAnd1) is younger (6-10 Gyr) and closer (distance of ∼15-21 kpc), whereas the fainter sequence (TriAnd2) is older (10-12 Gyr) and at an estimated distance of ∼24-32 kpc. A comparison with simulations demonstrates that the differences and similarities between TriAnd1 and TriAnd2 can simultaneously be explained if they represent debris originating from the disruption of the same dwarf galaxy, but torn off during two distinct pericentric passages.« less

FU Orionis Outbursts in the Triangulum Galaxy (M33)

NASA Astrophysics Data System (ADS)

Zawadzki, Nicole; Moe, Maxwell

2018-01-01

FU Orionis systems (FUors) are young T-Tauri stars that brighten upwards of 6 magnitudes due to an instability in their disk. It is unclear whether all T-Tauri stars experience this period of disk instability to create FUor outbursts, or if a binary companion is required to trigger these instabilities. To date, there have been around 20 known FUors detected in the Milky Way. To better understand the occurrence rate of these instabilities more observations are needed. By using observations of M33 from the Canada-France-Hawaii telescope, SDSS, and an ongoing survey at the Bok 90” telescope, a 15+ year baseline can be established to identify FUor outbursts in M33. By measuring the occurrence rate of FUors in M33 from these observations, the question of whether a binary companion is required can be answered.

Partner choice and fidelity stabilize coevolution in a Cretaceous-age defensive symbiosis

PubMed Central

Kaltenpoth, Martin; Roeser-Mueller, Kerstin; Koehler, Sabrina; Peterson, Ashley; Nechitaylo, Taras Y.; Stubblefield, J. William; Herzner, Gudrun; Seger, Jon; Strohm, Erhard

2014-01-01

Many insects rely on symbiotic microbes for survival, growth, or reproduction. Over evolutionary timescales, the association with intracellular symbionts is stabilized by partner fidelity through strictly vertical symbiont transmission, resulting in congruent host and symbiont phylogenies. However, little is known about how symbioses with extracellular symbionts, representing the majority of insect-associated microorganisms, evolve and remain stable despite opportunities for horizontal exchange and de novo acquisition of symbionts from the environment. Here we demonstrate that host control over symbiont transmission (partner choice) reinforces partner fidelity between solitary wasps and antibiotic-producing bacteria and thereby stabilizes this Cretaceous-age defensive mutualism. Phylogenetic analyses show that three genera of beewolf wasps (Philanthus, Trachypus, and Philanthinus) cultivate a distinct clade of Streptomyces bacteria for protection against pathogenic fungi. The symbionts were acquired from a soil-dwelling ancestor at least 68 million years ago, and vertical transmission via the brood cell and the cocoon surface resulted in host–symbiont codiversification. However, the external mode of transmission also provides opportunities for horizontal transfer, and beewolf species have indeed exchanged symbiont strains, possibly through predation or nest reuse. Experimental infection with nonnative bacteria reveals that—despite successful colonization of the antennal gland reservoirs—transmission to the cocoon is selectively blocked. Thus, partner choice can play an important role even in predominantly vertically transmitted symbioses by stabilizing the cooperative association over evolutionary timescales. PMID:24733936

Pulsating red giants and supergiants as probes of galaxy formation and evolution

NASA Astrophysics Data System (ADS)

Theodorus van Loon, Jacco; Javadi, Atefeh; Khosroshahi, Habib; Rezaei, Sara; Golshan, Roya; Saberi, Maryam

2015-08-01

We have developed new techniques to use pulsating red giant and supergiants stars to reconstruct the star formation history of galaxies over cosmological time, as well as using them to map the dust production across their host galaxies. We describe the large programme on the Local Group spiral galaxy Triangulum (M33), which we have monitored at near-infrared wavelengths for several years using the United Kingdom InfraRed Telescope in Hawai'i. We outline the methodology and present the results for the central square kiloparsec (Javadi et al. 2011a,b, 2013) and - fresh from the press - the disc of M33 (Javadi et al. 2015, and in preparation). We also describe the results from our application of this new technique to other nearby galaxies: the Magellanic Clouds (published in Rezaei et al. 2014), the dwarf galaxies NGC 147 and 185 (Golshan et al. in preparation), and Centaurus A.

The LAMOST survey of background quasars in the vicinity of the Andromeda and Triangulum galaxies. II. Results from the commissioning observations and the pilot surveys

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

Huo, Zhi-Ying; Bai, Zhong-Rui; Chen, Jian-Jun

We present new quasars discovered in the vicinity of the Andromeda and Triangulum galaxies with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, also named the Guoshoujing Telescope, during the 2010 and 2011 observational seasons. Quasar candidates are selected based on the available Sloan Digital Sky Survey, Kitt Peak National Observatory 4 m telescope, Xuyi Schmidt Telescope Photometric Survey optical, and Wide-field Infrared Survey Explorer near-infrared photometric data. We present 509 new quasars discovered in a stripe of ∼135 deg{sup 2} from M31 to M33 along the Giant Stellar Stream in the 2011 pilot survey data sets, and also 17more » new quasars discovered in an area of ∼100 deg{sup 2} that covers the central region and the southeastern halo of M31 in the 2010 commissioning data sets. These 526 new quasars have i magnitudes ranging from 15.5 to 20.0, redshifts from 0.1 to 3.2. They represent a significant increase of the number of identified quasars in the vicinity of M31 and M33. There are now 26, 62, and 139 known quasars in this region of the sky with i magnitudes brighter than 17.0, 17.5, and 18.0, respectively, of which 5, 20, and 75 are newly discovered. These bright quasars provide an invaluable collection with which to probe the kinematics and chemistry of the interstellar/intergalactic medium in the Local Group of galaxies. A total of 93 quasars are now known with locations within 2.°5 of M31, of which 73 are newly discovered. Tens of quasars are now known to be located behind the Giant Stellar Stream, and hundreds are behind the extended halo and its associated substructures of M31. The much enlarged sample of known quasars in the vicinity of M31 and M33 can potentially be utilized to construct a perfect astrometric reference frame to measure the minute proper motions (PMs) of M31 and M33, along with the PMs of substructures associated with the Local Group of galaxies. Those PMs are some of the most fundamental properties of the Local Group.« less

Monitoring pulsating giant stars in M33: star formation history and chemical enrichment

NASA Astrophysics Data System (ADS)

Javadi, A.; van Loon, J. Th

2017-06-01

We have conducted a near-infrared monitoring campaign at the UK InfraRed Telescope (UKIRT), of the Local Group spiral galaxy M33 (Triangulum). A new method has been developed by us to use pulsating giant stars to reconstruct the star formation history of galaxies over cosmological time as well as using them to map the dust production across their host galaxies. In first Instance the central square kiloparsec of M33 was monitored and long period variable stars (LPVs) were identified. We give evidence of two epochs of a star formation rate enhanced by a factor of a few. These stars are also important dust factories, we measure their dust production rates from a combination of our data with Spitzer Space Telescope mid-IR photometry. Then the monitoring survey was expanded to cover a much larger part of M33 including spiral arms. Here we present our methodology and describe results for the central square kiloparsec of M33 [1-4] and disc of M33 [5-8].

Temporal X-ray astronomy with a pinhole camera. [cygnus and scorpius constellation

NASA Technical Reports Server (NTRS)

Holt, S. S.

1975-01-01

Preliminary results from the Ariel-5 all-sky X-ray monitor are presented, along with sufficient experiment details to define the experiment sensitivity. Periodic modulation of the X-ray emission was investigated from three sources with which specific periods were associated, with the results that the 4.8 hour variation from Cyg X-3 was confirmed, a long-term average 5.6 day variation from Cyg X-1 was discovered, and no detectable 0.787 day modulation of Sco X-1 was observed. Consistency of the long-term Sco X-1 emission with a shot-noise model is discussed, wherein the source behavior is shown to be interpretable as approximately 100 flares per day, each with a duration of several hours. A sudden increase in the Cyg X-1 intensity by almost a factor of three on 22 April 1975 is reported, after 5 months of relative source constancy. The light curve of a bright nova-like transient source in Triangulum is presented, and compared with previously observed transient sources. Preliminary evidence for the existence of X-ray bursts with duration less than 1 hour is offered.

Hubble Sees a Slashing Smudge Across the Sky

NASA Image and Video Library

2017-12-08

The galaxy cutting dramatically across the frame of this NASA/ESA Hubble Space Telescope image is a slightly warped dwarf galaxy known as UGC1281. Seen here from an edge-on perspective, this galaxy lies roughly 18 million light-years away in the constellation of Triangulum (The Triangle). The bright companion to the lower left of UGC 1281 is the small galaxy PGC 6700, officially known as 2MASX J01493473+3234464. Other prominent stars belonging to our own galaxy, the Milky Way, and more distant galaxies can be seen scattered throughout the sky. The side-on view we have of UGC 1281 makes it a perfect candidate for studies into how gas is distributed within galactic halos — the roughly spherical regions of diffuse gas extending outwards from a galaxy’s center. Astronomers have studied this galaxy to see how its gas vertically extends out from its central plane, and found it to be a quite typical dwarf galaxy. However, it does have a slightly warped shape to its outer edges, and is forming stars at a particularly low rate. European Space Agency Credit: ESA/NASA, Acknowledgement Luca Limatola

Constraint on the velocity dependent dark matter annihilation cross section from gamma-ray and kinematic observations of ultrafaint dwarf galaxies

NASA Astrophysics Data System (ADS)

Zhao, Yi; Bi, Xiao-Jun; Yin, Peng-Fei; Zhang, Xinmin

2018-03-01

Searching for γ rays from dwarf spheroidal galaxies (dSphs) is a promising approach to detect dark matter (DM) due to the high DM densities and low baryon components in dSphs. The Fermi-LAT observations from dSphs have set stringent constraints on the velocity independent annihilation cross section. However, the constraints from dSphs may change in velocity dependent annihilation scenarios because of the different velocity dispersions in galaxies. In this work, we study how to set constraints on the velocity dependent annihilation cross section from the combined Fermi-LAT observations of dSphs with the kinematic data. In order to calculate the γ ray flux from the dSph, the correlation between the DM density profile and velocity dispersion at each position should be taken into account. We study such correlation and the relevant uncertainty from kinematic observations by performing a Jeans analysis. Using the observational results of three ultrafaint dSphs with large J-factors, including Willman 1, Reticulum II, and Triangulum II, we set constraints on the p-wave annihilation cross section in the Galaxy as an example.

TriAnd and its siblings: satellites of satellites in the Milky Way halo

NASA Astrophysics Data System (ADS)

Deason, A. J.; Belokurov, V.; Hamren, K. M.; Koposov, S. E.; Gilbert, K. M.; Beaton, R. L.; Dorman, C. E.; Guhathakurta, P.; Majewski, S. R.; Cunningham, E. C.

2014-11-01

We explore the Triangulum-Andromeda (TriAnd) overdensity in the SPLASH (Spectroscopic and Photometric Landscape of Andromeda's Stellar Halo) and SEGUE (the Sloan Extension for Galactic Understanding and Exploration) spectroscopic surveys. Milky Way main-sequence turn-off stars in the SPLASH survey reveal that the TriAnd overdensity and the recently discovered Pan-Andromeda Archaeological Survey (PAndAS) stream share a common heliocentric distance (D ˜ 20 kpc), position on the sky, and line-of-sight velocity (VGSR ˜ 50 km s-1). Similarly, A-type, giant, and main-sequence turn-off stars selected from the SEGUE survey in the vicinity of the Segue 2 satellite show that TriAnd is prevalent in these fields, with a velocity and distance similar to Segue 2. The coincidence of the PAndAS stream and Segue 2 satellite in positional and velocity space to TriAnd suggests that these substructures are all associated, and may be a fossil record of group-infall on to the Milky Way halo. In this scenario, the Segue 2 satellite and PAndAS stream are `satellites of satellites', and the large, metal-rich TriAnd overdensity is the remains of the group central.

Molecular Identification of Cryptosporidium Species from Pet Snakes in Thailand.

PubMed

Yimming, Benjarat; Pattanatanang, Khampee; Sanyathitiseree, Pornchai; Inpankaew, Tawin; Kamyingkird, Ketsarin; Pinyopanuwat, Nongnuch; Chimnoi, Wissanuwat; Phasuk, Jumnongjit

2016-08-01

Cryptosporidium is an important pathogen causing gastrointestinal disease in snakes and is distributed worldwide. The main objectives of this study were to detect and identify Cryptosporidium species in captive snakes from exotic pet shops and snake farms in Thailand. In total, 165 fecal samples were examined from 8 snake species, boa constrictor (Boa constrictor constrictor), corn snake (Elaphe guttata), ball python (Python regius), milk snake (Lampropeltis triangulum), king snake (Lampropeltis getula), rock python (Python sebae), rainbow boa (Epicrates cenchria), and carpet python (Morelia spilota). Cryptosporidium oocysts were examined using the dimethyl sulfoxide (DMSO)-modified acid-fast staining and a molecular method based on nested-PCR, PCR-RFLP analysis, and sequencing amplification of the SSU rRNA gene. DMSO-modified acid-fast staining revealed the presence of Cryptosporidium oocysts in 12 out of 165 (7.3%) samples, whereas PCR produced positive results in 40 (24.2%) samples. Molecular characterization indicated the presence of Cryptosporidium parvum (mouse genotype) as the most common species in 24 samples (60%) from 5 species of snake followed by Cryptosporidium serpentis in 9 samples (22.5%) from 2 species of snake and Cryptosporidium muris in 3 samples (7.5%) from P. regius.

Molecular Identification of Cryptosporidium Species from Pet Snakes in Thailand

PubMed Central

Yimming, Benjarat; Pattanatanang, Khampee; Sanyathitiseree, Pornchai; Inpankaew, Tawin; Kamyingkird, Ketsarin; Pinyopanuwat, Nongnuch; Chimnoi, Wissanuwat; Phasuk, Jumnongjit

2016-01-01

Cryptosporidium is an important pathogen causing gastrointestinal disease in snakes and is distributed worldwide. The main objectives of this study were to detect and identify Cryptosporidium species in captive snakes from exotic pet shops and snake farms in Thailand. In total, 165 fecal samples were examined from 8 snake species, boa constrictor (Boa constrictor constrictor), corn snake (Elaphe guttata), ball python (Python regius), milk snake (Lampropeltis triangulum), king snake (Lampropeltis getula), rock python (Python sebae), rainbow boa (Epicrates cenchria), and carpet python (Morelia spilota). Cryptosporidium oocysts were examined using the dimethyl sulfoxide (DMSO)-modified acid-fast staining and a molecular method based on nested-PCR, PCR-RFLP analysis, and sequencing amplification of the SSU rRNA gene. DMSO-modified acid-fast staining revealed the presence of Cryptosporidium oocysts in 12 out of 165 (7.3%) samples, whereas PCR produced positive results in 40 (24.2%) samples. Molecular characterization indicated the presence of Cryptosporidium parvum (mouse genotype) as the most common species in 24 samples (60%) from 5 species of snake followed by Cryptosporidium serpentis in 9 samples (22.5%) from 2 species of snake and Cryptosporidium muris in 3 samples (7.5%) from P. regius. PMID:27658593

The remnants of galaxy formation from a panoramic survey of the region around M31.

PubMed

McConnachie, Alan W; Irwin, Michael J; Ibata, Rodrigo A; Dubinski, John; Widrow, Lawrence M; Martin, Nicolas F; Côté, Patrick; Dotter, Aaron L; Navarro, Julio F; Ferguson, Annette M N; Puzia, Thomas H; Lewis, Geraint F; Babul, Arif; Barmby, Pauline; Bienaymé, Olivier; Chapman, Scott C; Cockcroft, Robert; Collins, Michelle L M; Fardal, Mark A; Harris, William E; Huxor, Avon; Mackey, A Dougal; Peñarrubia, Jorge; Rich, R Michael; Richer, Harvey B; Siebert, Arnaud; Tanvir, Nial; Valls-Gabaud, David; Venn, Kimberly A

2009-09-03

In hierarchical cosmological models, galaxies grow in mass through the continual accretion of smaller ones. The tidal disruption of these systems is expected to result in loosely bound stars surrounding the galaxy, at distances that reach 10-100 times the radius of the central disk. The number, luminosity and morphology of the relics of this process provide significant clues to galaxy formation history, but obtaining a comprehensive survey of these components is difficult because of their intrinsic faintness and vast extent. Here we report a panoramic survey of the Andromeda galaxy (M31). We detect stars and coherent structures that are almost certainly remnants of dwarf galaxies destroyed by the tidal field of M31. An improved census of their surviving counterparts implies that three-quarters of M31's satellites brighter than M(v) = -6 await discovery. The brightest companion, Triangulum (M33), is surrounded by a stellar structure that provides persuasive evidence for a recent encounter with M31. This panorama of galaxy structure directly confirms the basic tenets of the hierarchical galaxy formation model and reveals the shared history of M31 and M33 in the unceasing build-up of galaxies.

Star-Hopping

NASA Astrophysics Data System (ADS)

Garfinkle, Robert A.

1997-07-01

Introduction; Preface; Acknowledgements; 1. How to use this book and what you are going to see; 2. How the sky works, determining your field of view, observing tips and how to navigate in the night sky; 3. January - Taurus and Orion: the bull and hunter; 4. February - Canis Minor, Canis Major, and Puppis: dog days in February and Jason's Argo; 5. March - Cancer, Leo, and Corvus: a crab, the king of the beasts, and a crow; 6. April - Ursa Major: a dipper round tripper; 7. May - Coma Berenices and Virgo: the sparkling hair of Berenice and the wheat maiden and her bushel of galaxies; 8. June - Libra and Lupus: the balance scales and the wolf; 9. July - Scorpius, Sagittarius, and Scutum: the scorpion, archer, and shield of John Sobieski; 10. August - Draco: following the trail of the dragon; 11. September - Cygnus, Lyra, Vulpecula, and Sagitta: the swan, lyre, fox, and arrow; 12. October - Andromeda and Perseus: the chained lady and her rescuer; 13. November - Cepheus and Cassiopeia: the king and queen of Joppa; 14. December - Pisces, Triangulum, and Aries: of fishes, a triangle, and a ram; 15. Messier Marathon, a sundown to sunup hop across the skies; Appendix A: Classification tables; Appendix B: The constellations; Appendix C: The Greek alphabet; Appendix D: Decimalization of the day; Glossary; Bibliography; Index.

Exploring Halo Substructure with Giant Stars. XV. Discovery of a Connection between the Monoceros Ring and the Triangulum–Andromeda Overdensity?

DOE PAGES

Li, Ting S.; Sheffield, Allyson A.; Johnston, Kathryn V.; ...

2017-07-24

Thanks to modern sky surveys, over twenty stellar streams and overdensity structures have been discovered in the halo of the Milky Way. Here, in this paper, we present an analysis of spectroscopic observations of individual stars from one such structure, "A13", first identified as an overdensity using the M giant catalog from the Two Micron All-Sky Survey. Our spectroscopic observations show that stars identified with A13 have a velocity dispersion ofmore » $$\\lesssim$$ 40 $$\\mathrm{km~s^{-1}}$$, implying that it is a genuine coherent structure rather than a chance super-position of random halo stars. From its position on the sky, distance ($$\\sim$$15 kpc heliocentric), and kinematical properties, A13 is likely to be an extension of another low Galactic latitude substructure -- the Galactic Anticenter Stellar Structure (also known as the Monoceros Ring) -- towards smaller Galactic longitude and farther distance. Furthermore, the kinematics of A13 also connect it with another structure in the southern Galactic hemisphere -- the Triangulum-Andromeda overdensity. Finally, we discuss these three connected structures within the context of a previously proposed scenario that one or all of these features originate from the disk of the Milky Way.« less

Exploring Halo Substructure with Giant Stars. XV. Discovery of a Connection between the Monoceros Ring and the Triangulum–Andromeda Overdensity?

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

Li, Ting S.; Sheffield, Allyson A.; Johnston, Kathryn V.

Thanks to modern sky surveys, over twenty stellar streams and overdensity structures have been discovered in the halo of the Milky Way. Here, in this paper, we present an analysis of spectroscopic observations of individual stars from one such structure, "A13", first identified as an overdensity using the M giant catalog from the Two Micron All-Sky Survey. Our spectroscopic observations show that stars identified with A13 have a velocity dispersion ofmore » $$\\lesssim$$ 40 $$\\mathrm{km~s^{-1}}$$, implying that it is a genuine coherent structure rather than a chance super-position of random halo stars. From its position on the sky, distance ($$\\sim$$15 kpc heliocentric), and kinematical properties, A13 is likely to be an extension of another low Galactic latitude substructure -- the Galactic Anticenter Stellar Structure (also known as the Monoceros Ring) -- towards smaller Galactic longitude and farther distance. Furthermore, the kinematics of A13 also connect it with another structure in the southern Galactic hemisphere -- the Triangulum-Andromeda overdensity. Finally, we discuss these three connected structures within the context of a previously proposed scenario that one or all of these features originate from the disk of the Milky Way.« less

Dactylogyrid monogeneans parasitising Cyphocharax voga (Hensel) (Teleostei: Curimatidae) from the Pampas region, Argentina: new and previously described species.

PubMed

Rossin, María Alejandra; Timi, Juan Tomás

2016-09-01

Most studies on dactylogyrid monogeneans in Argentina have been carried out during 1980s and 1990s. Many of these species have been later synonymised and other remain under a confusing taxonomic status, particularly those parasitising Cyphocharax voga (Hensel) (Teleostei: Curimatidae). In order to clarify the identity of dactylogyrids, new material was collected from fishes in Lake Chascomús, Buenos Aires Province, Argentina. A total of four species was found in the gills of C. voga. Two known species, Curvianchoratus singularis (Suriano, 1980) Suriano, 1986 and Palombitrema triangulum (Suriano, 1981) Suriano, 1997, are redescribed and their generic and specific status discussed, and two new species are described. Urocleidoides surianoae n. sp. can be distinguished from its congeners by having an anterior medial projection in the ventral bar and a laminar ligament connecting the base of the male copulatory organ and accessory piece. Annulotrematoides bonaerensis n. sp. differs from its congeners principally by having a ventral bar with an anterior medial projection. The diversity of dactylogyrids harboured by C. voga indicates the need of further studies in the Pampas region, which will provide interesting and valuable sources of evidence for future zoogeographical and evolutionary research on dactylogyrids in the Neotropics.

Explaining formation of Astronomical Jets using Dynamic Universe Model

NASA Astrophysics Data System (ADS)

Naga Parameswara Gupta, Satyavarapu

2016-07-01

Astronomical jets are observed from the centres of many Galaxies including our own Milkyway. The formation of such jet is explained using SITA simulations of Dynamic Universe Model. For this purpose the path traced by a test neutron is calculated and depicted using a set up of one densemass of the mass equivalent to mass of Galaxy center, 90 stars with similar masses of stars near Galaxy center, mass equivalents of 23 Globular Cluster groups, 16 Milkyway parts, Andromeda and Triangulum Galaxies at appropriate distances. Five different kinds of theoretical simulations gave positive results The path travelled by this test neutron was found to be an astronomical jet emerging from Galaxy center. This is another result from Dynamic Universe Model. It solves new problems like a. Variable Mass Rocket Trajectory Problem b. Explaining Very long baseline interferometry (VLBI) observations c. Astronomical jets observed from Milkyway Center d. Prediction of Blue shifted Galaxies e. Explaining Pioneer Anomaly f. Prediction of New Horizons satellite trajectory etc. Dynamic Universe Model never reduces to General relativity on any condition. It uses a different type of mathematics based on Newtonian physics. This mathematics used here is simple and straightforward. As there are no differential equations present in Dynamic Universe Model, the set of equations give single solution in x y z Cartesian coordinates for every point mass for every time step

Response of a reptile guild to forest harvesting.

PubMed

Todd, Brian D; Andrews, Kimberly M

2008-06-01

Despite the growing concern over reptile population declines, the effects of modern industrial silviculture on reptiles have been understudied, particularly for diminutive and often overlooked species such as small-bodied snakes. We created 4 replicated forest-management landscapes to determine the response of small snakes to forest harvesting in the Coastal Plain of the southeastern United States. We divided the replicated landscapes into 4 treatments that represented a range of disturbed habitats: clearcut with coarse woody debris removed; clearcut with coarse woody debris retained; thinned pine stand; and control (unharvested second-growth planted pines). Canopy cover and ground litter were significantly reduced in clearcuts, intermediate in thinned forests, and highest in unharvested controls. Bare soil, maximum air temperatures, and understory vegetation all increased with increasing habitat disturbance. Concomitantly, we observed significantly reduced relative abundance of all 6 study species (scarletsnake[Cemophora coccinea], ring-neck snake[Diadophis punctatus], scarlet kingsnake[Lampropeltis triangulum], red-bellied snake[Storeria occipitomaculata], southeastern crowned snake[Tantilla coronata], and smooth earthsnake[Virginia valeriae]) in clearcuts compared with unharvested or thinned pine stands. In contrast, the greatest relative snake abundance occurred in thinned forest stands. Our results demonstrate that at least one form of forest harvesting is compatible with maintaining snake populations. Our results also highlight the importance of open-canopy structure and ground litter to small snakes in southeastern forests and the negative consequences of forest clearcutting for small snakes.

A VLA Search for Radio Signals from M31 and M33

NASA Astrophysics Data System (ADS)

Gray, Robert H.; Mooley, Kunal

2017-03-01

Observing nearby galaxies would facilitate the search for artificial radio signals by sampling several billions of stars simultaneously, but few efforts have been made to exploit this opportunity. An added attraction is that the Milky Way is the second largest member of the Local Group, so our galaxy might be a probable target for hypothetical broadcasters in nearby galaxies. We present the first relatively high spectral resolution (<1 kHz) 21 cm band search for intelligent radio signals of complete galaxies in the Local Group with the Jansky VLA, observing the galaxies M31 (Andromeda) and M33 (Triangulum)—the first and third largest members of the group, respectively—sampling more stars than any prior search of this kind. We used 122 Hz channels over a 1 MHz spectral window in the target galaxy velocity frame of reference, and 15 Hz channels over a 125 kHz window in our local standard of rest. No narrowband signals were detected above a signal-to-noise ratio of 7, suggesting the absence of continuous narrowband flux greater than approximately 0.24 and 1.33 Jy in the respective spectral windows illuminating our part of the Milky Way during our observations in 2014 December and 2015 January. This is also the first study in which the upgraded VLA has been used for SETI.

The stellar populations of M 33

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

Van den bergh, S.

1991-07-01

A review is given of present ideas on the evolution and stellar content of the Triangulum nebula = M 33 = NGC 598. The disk of M 33 is embedded in a halo of globular clusters, metal-poor red giants, and RR Lyrae stars. Its nuclear bulge component is weak, suggesting that the halos of galaxies are not extensions of their bulges to large radii. The ages of M 33 clusters do not appear to exhibit a hiatus in their star-forming history like that which is observed in the Large Magellanic Cloud (LMC). Young and intermediate-age clusters with luminosities rivaling themore » populous clusters in the LMC are rare in M 33. The integrated light of the semistellar nucleus of M 33, which contains the strongest X-ray source in the Local Group, is dominated by a young metal-rich population. At optical wavelengths the disk scale length of M 33 is 9.6 arcmin, which is similar to the 9.9 arcmin scale length of OB associations. The ratio of the nova rate in M 33 to that in M 31 is approximately equal to the ratio of their luminosities. This suggests that the nova rate in a galaxy is not determined entirely by the integrated luminosity of old bulge stars. The gas-depletion time scale in the central region of M 33 is found to be about 1.7 {times} 10 to the 9th yr, which is significantly shorter than a Hubble time. 141 refs.« less

The UK Infrared Telescope M33 monitoring project - IV. Variable red giant stars across the galactic disc

NASA Astrophysics Data System (ADS)

Javadi, Atefeh; Saberi, Maryam; van Loon, Jacco Th.; Khosroshahi, Habib; Golabatooni, Najmeh; Mirtorabi, Mohammad Taghi

2015-03-01

We have conducted a near-infrared monitoring campaign at the UK InfraRed Telescope, of the Local Group spiral galaxy M33 (Triangulum). The main aim was to identify stars in the very final stage of their evolution, and for which the luminosity is more directly related to the birth mass than the more numerous less-evolved giant stars that continue to increase in luminosity. In this fourth paper of the series, we present a search for variable red giant stars in an almost square degree region comprising most of the galaxy's disc, carried out with the WFCAM (Wide Field CAMera) instrument in the K band. These data, taken during the period 2005-2007, were complemented by J- and H-band images. Photometry was obtained for 403 734 stars in this region; of these, 4643 stars were found to be variable, most of which are asymptotic giant branch (AGB) stars. The variable stars are concentrated towards the centre of M33, more so than low-mass, less-evolved red giants. Our data were matched to optical catalogues of variable stars and carbon stars and to mid-infrared photometry from the Spitzer Space Telescope. Most dusty AGB stars had not been previously identified in optical variability surveys, and our survey is also more complete for these types of stars than the Spitzer survey. The photometric catalogue is made publicly available at the Centre de Données astronomiques de Strasbourg.

Traversing the triangulum: the intersection of tobacco, legalised marijuana and electronic vaporisers in Denver, Colorado

PubMed Central

McDonald, Emily Anne; Popova, Lucy; Ling, Pamela M

2016-01-01

Objective To explore the intersection of tobacco, legalised marijuana and electronic vaporiser use among young adults in the ‘natural laboratory’ of Colorado, the first state with legalised retail marijuana. Methods We conducted semistructured interviews with 32 young adults (18–26 years old) in Denver, Colorado, in 2015 to understand the beliefs and practices related to the use of tobacco, marijuana and vaporisers. Results We found ambiguity about whether the phrase ‘to smoke’ refers to the use of tobacco or marijuana products. Smoking marijuana blunts (emptied cigarillo or tobacco wrap filled with marijuana) was common, but few interpreted this as tobacco use. Marijuana vaporisers were used to circumvent public consumption laws (eg, while at work or when driving). Young adults considered secondhand tobacco smoke dangerous, but perceived secondhand marijuana smoke as benign. Discussion Using tobacco products as a delivery method for marijuana (eg, blunts) might be increasing and normalising tobacco use among young adults. Surveillance should explicitly ask about use of tobacco products for marijuana. Marijuana vaporisers, often indistinguishable from nicotine vaporisers, may be used to circumvent public consumption laws; communities concerned about use of marijuana in public spaces should include vaporisers (for nicotine or marijuana) in smoke-free regulations. Tobacco, marijuana and electronic vaporisers should be studied together, rather than separately. This approach is essential in informing research and policy as more US states and countries worldwide move to legalise marijuana. PMID:27697954

A Disk Origin for the Monoceros Ring and A13 Stellar Overdensities

NASA Astrophysics Data System (ADS)

Sheffield, Allyson A.; Price-Whelan, Adrian M.; Tzanidakis, Anastasios; Johnston, Kathryn V.; Laporte, Chervin F. P.; Sesar, Branimir

2018-02-01

The Monoceros Ring (also known as the Galactic Anticenter Stellar Structure) and A13 are stellar overdensities at estimated heliocentric distances of d ∼ 11 kpc and 15 kpc observed at low Galactic latitudes toward the anticenter of our Galaxy. While these overdensities were initially thought to be remnants of a tidally disrupted satellite galaxy, an alternate scenario is that they are composed of stars from the Milky Way (MW) disk kicked out to their current location due to interactions between a satellite galaxy and the disk. To test this scenario, we study the stellar populations of the Monoceros Ring and A13 by measuring the number of RR Lyrae and M giant stars associated with these overdensities. We obtain low-resolution spectroscopy for RR Lyrae stars in the two structures and measure radial velocities to compare with previously measured velocities for M giant stars in the regions of the Monoceros Ring and A13, to assess the fraction of RR Lyrae to M giant stars (f RR:MG) in A13 and Mon/GASS. We perform velocity modeling on 153 RR Lyrae stars (116 in the Monoceros Ring and 37 in A13) and find that both structures have very low f RR:MG. The results support a scenario in which stars in A13 and Mon/GASS formed in the MW disk. We discuss a possible association between Mon/GASS, A13, and the Triangulum-Andromeda overdensity based on their similar velocity distributions and f RR:MG.

The UK Infrared Telescope M33 monitoring project - I. Variable red giant stars in the central square kiloparsec

NASA Astrophysics Data System (ADS)

Javadi, Atefeh; van Loon, Jacco Th.; Mirtorabi, Mohammad Taghi

2011-02-01

We have conducted a near-infrared monitoring campaign at the UK Infrared Telescope (UKIRT), of the Local Group spiral galaxy M33 (Triangulum). The main aim was to identify stars in the very final stage of their evolution, and for which the luminosity is more directly related to the birth mass than the more numerous less-evolved giant stars that continue to increase in luminosity. The most extensive data set was obtained in the K band with the UIST instrument for the central 4 × 4 arcmin2 (1 kpc2) - this contains the nuclear star cluster and inner disc. These data, taken during the period 2003-2007, were complemented by J- and H-band images. Photometry was obtained for 18 398 stars in this region; of these, 812 stars were found to be variable, most of which are asymptotic giant branch (AGB) stars. Our data were matched to optical catalogues of variable stars and carbon stars and to mid-infrared photometry from the Spitzer Space Telescope. In this first of a series of papers, we present the methodology of the variability survey and the photometric catalogue - which is made publicly available at the Centre de Données astronomiques de Strasbourg - and discuss the properties of the variable stars. The most dusty AGB stars had not been previously identified in optical variability surveys, and our survey is also more complete for these types of stars than the Spitzer survey.

Pet snakes illegally marketed in Brazil: Climatic viability and establishment risk.

PubMed

Fonseca, Érica; Solé, Mirco; Rödder, Dennis; de Marco, Paulo

2017-01-01

Invasive species are one among many threats to biodiversity. Brazil has been spared, generically, of several destructive invasive species. Reports of invasive snakes' populations are nonexistent, but the illegal pet trade might change this scenario. Despite the Brazilian laws forbid to import most animals, illegal trade is frequently observed and propagules are found in the wild. The high species richness within Brazilian biomes and accelerated fragmentation of natural reserves are a critical factors facilitating successful invasion. An efficient way to ease damages caused by invasive species is identifying potential invaders and consequent prevention of introductions. For the identification of potential invaders many factors need to be considered, including estimates of climate matching between areas (native vs. invaded). Ecological niche modelling has been widely used to predict potential areas for invasion and is an important tool for conservation biology. This study evaluates the potential geographical distribution and establishment risk of Lampropeltis getula (Linnaeus, 1766), Lampropeltis triangulum (Lacépède, 1789), Pantherophis guttatus (Linnaeus, 1766), Python bivittatus Kuhl, 1820 and Python regius (Shaw, 1802) through the Maximum Entropy modelling approach to estimate the potential distribution of the species within Brazil and qualitative evaluation of specific biological attributes. Our results suggest that the North and Midwest regions harbor major suitable areas. Furthermore, P. bivittatus and P. guttatus were suggested to have the highest invasive potential among the analyzed species. Potentially suitable areas for these species were predicted within areas which are highly relevant for Brazilian biodiversity, including several conservation units. Therefore, these areas require special attention and preventive measures should be adopted.

Pet snakes illegally marketed in Brazil: Climatic viability and establishment risk

PubMed Central

Rödder, Dennis; de Marco, Paulo

2017-01-01

Invasive species are one among many threats to biodiversity. Brazil has been spared, generically, of several destructive invasive species. Reports of invasive snakes’ populations are nonexistent, but the illegal pet trade might change this scenario. Despite the Brazilian laws forbid to import most animals, illegal trade is frequently observed and propagules are found in the wild. The high species richness within Brazilian biomes and accelerated fragmentation of natural reserves are a critical factors facilitating successful invasion. An efficient way to ease damages caused by invasive species is identifying potential invaders and consequent prevention of introductions. For the identification of potential invaders many factors need to be considered, including estimates of climate matching between areas (native vs. invaded). Ecological niche modelling has been widely used to predict potential areas for invasion and is an important tool for conservation biology. This study evaluates the potential geographical distribution and establishment risk of Lampropeltis getula (Linnaeus, 1766), Lampropeltis triangulum (Lacépède, 1789), Pantherophis guttatus (Linnaeus, 1766), Python bivittatus Kuhl, 1820 and Python regius (Shaw, 1802) through the Maximum Entropy modelling approach to estimate the potential distribution of the species within Brazil and qualitative evaluation of specific biological attributes. Our results suggest that the North and Midwest regions harbor major suitable areas. Furthermore, P. bivittatus and P. guttatus were suggested to have the highest invasive potential among the analyzed species. Potentially suitable areas for these species were predicted within areas which are highly relevant for Brazilian biodiversity, including several conservation units. Therefore, these areas require special attention and preventive measures should be adopted. PMID:28817630

The influence of Sagittarius and the Large Magellanic Cloud on the stellar disc of the Milky Way Galaxy

NASA Astrophysics Data System (ADS)

Laporte, Chervin F. P.; Johnston, Kathryn V.; Gómez, Facundo A.; Garavito-Camargo, Nicolas; Besla, Gurtina

2018-06-01

We present N-body simulations of a Sagittarius-like dwarf spheroidal galaxy (Sgr) that follow its orbit about the Milky Way (MW) since its first crossing of the Galaxy's virial radius to the present day. As Sgr orbits around the MW, it excites vertical oscillations, corrugating and flaring the Galactic stellar disc. These responses can be understood by a two-phase picture in which the interaction is first dominated by torques from the wake excited by Sgr in the MW dark halo before transitioning to tides from Sgr's direct impact on the disc at late times. We show for the first time that a massive Sgr model simultaneously reproduces the locations and motions of arc-like over densities, such as the Monoceros Ring and the Triangulum Andromeda stellar clouds, that have been observed at the extremities of the disc, while also satisfying the solar neighbourhood constraints on the vertical structure and streaming motions of the disc. In additional simulations, we include the Large Magellanic Cloud (LMC) self consistently with Sgr. The LMC introduces coupling through constructive and destructive interference, but no new corrugations. In our models, the excitation of the current structure of the outer disk can be traced to interactions as far back as 6-7 Gyr ago (corresponding to z ≤ 1). Given the apparently quiescent accretion history of the MW over this timescale, this places Sgr as the main culprit behind the vertical oscillations of the disc and the last major accretion event for the Galaxy with the capacity to modulate its chemodynamical structure.

The star-formation law at GMC scales in M33, the Triangulum Galaxy

NASA Astrophysics Data System (ADS)

Williams, Thomas G.; Gear, Walter K.; Smith, Matthew W. L.

2018-06-01

We present a high spatial resolution study, on scales of ˜100pc, of the relationship between star-formation rate (SFR) and gas content within Local Group galaxy M33. Combining deep SCUBA-2 observations with archival GALEX, SDSS, WISE, Spitzer and submillimetre Herschel data, we are able to model the entire SED from UV to sub-mm wavelengths. We calculate the SFR on a pixel-by-pixel basis using the total infrared luminosity, and find a total SFR of 0.17 ± 0.06 {M}_⊙/yr, somewhat lower than our other two measures of SFR - combined FUV and 24μ SFR (0.25^{+0.10}_{-0.07} {M}_⊙/yr) and SED-fitting tool MAGPHYS (0.33^{+0.05}_{-0.06} {M}_⊙/yr). We trace the total gas using a combination of the 21cm HI line for atomic hydrogen, and CO(J=2-1) data for molecular hydrogen. We have also traced the total gas using dust masses. We study the star-formation law in terms of molecular gas, total gas, and gas from dust. We perform an analysis of the star-formation law on a variety of pixel scales, from 25" to 500" (100pc to 2kpc). At kpc scales, we find that a linear Schmidt-type power law index is suitable for molecular gas, but the index appears to be much higher with total gas, and gas from dust. Whilst we find a strong scale dependence on the Schmidt index, the gas depletion timescale is invariant with pixel scale.

A Novel Pattern of Yolk Processing in Developing Snake Eggs (Colubridae: Lampropeltini) and its Functional and Evolutionary Implications.

PubMed

Powers, Kathryn G; Blackburn, Daniel G

2017-07-01

Early amniotic vertebrates evolved large-yolked eggs that permitted production of well-developed, terrestrial hatchlings. This reproductive pattern required new mechanisms for cellularizing the yolk and mobilizing it for embryonic use. In birds, cells that line the yolk sac cavity phagocytose and digest the yolk material, a pattern that is commonly assumed to be universal among oviparous amniotes. However, recent evidence challenges the assumption that all squamate reptiles conform to the avian developmental pattern. In this paper, scanning electron microscopy and histology were used to study mechanisms of yolk processing in two colubrid snakes, the kingsnake Lampropeltis getula and the milksnake L. triangulum. Endodermal cells from the yolk sac splanchnopleure proliferate massively as they invade the yolk sac cavity, forming elaborate chains of interlinked cells. These cells grow in size as they phagocytose yolk material. Subsequently, vitelline capillaries invade the masses of yolk-laden cells and become coated with the endodermal cells, forming an elaborate meshwork of cell-coated strands. The close association of cells, yolk, and blood vessels allows yolk material to be cellularized, digested, and transported for embryonic use. The overall pattern is like that of the corn snake Pantherophis guttatus, but contrasts markedly with that of birds. Given recent evidence that this developmental pattern may also occur in certain lizards, we postulate that it is ancestral for squamates. Studies of lizards, crocodilians, and turtles are needed to clarify the evolutionary history of this pattern and its implications for the evolution of the amniotic (terrestrial) vertebrate egg. © 2017 Wiley Periodicals, Inc.

Structures in the Great Attractor region

NASA Astrophysics Data System (ADS)

Radburn-Smith, D. J.; Lucey, J. R.; Woudt, P. A.; Kraan-Korteweg, R. C.; Watson, F. G.

2006-07-01

To further our understanding of the Great Attractor (GA), we have undertaken a redshift survey using the 2-degree Field (2dF) instrument on the Anglo-Australian Telescope (AAT). Clusters and filaments in the GA region were targeted with 25 separate pointings resulting in approximately 2600 new redshifts. Targets included poorly studied X-ray clusters from the Clusters in the Zone of Avoidance (CIZA) Catalogue as well as the Cen-Crux and PKS 1343-601 clusters, both of which lie close to the classic GA centre. For nine clusters in the region, we report velocity distributions as well as virial and projected mass estimates. The virial mass of CIZA J1324.7-5736, now identified as a separate structure from the Cen-Crux cluster, is found to be ˜3 × 1014-M⊙, in good agreement with the X-ray inferred mass. In the PKS 1343-601 field, five redshifts are measured of which four are new. An analysis of redshifts from this survey, in combination with those from the literature, reveals the dominant structure in the GA region to be a large filament, which appears to extend from Abell S0639 (l= 281°, b=+11°) to (l˜ 5°, b˜-50°), encompassing the Cen-Crux, CIZA J1324.7-5736, Norma and Pavo II clusters. Behind the Norma cluster at cz˜ 15-000-km-s-1, the masses of four rich clusters are calculated. These clusters (Triangulum Australis, Ara, CIZA J1514.6-4558 and CIZA J1410.4-4246) may contribute to a continued large-scale flow beyond the GA. The results of these observations will be incorporated into a subsequent analysis of the GA flow.

Evaluating galactic habitability using high-resolution cosmological simulations of galaxy formation

NASA Astrophysics Data System (ADS)

Forgan, Duncan; Dayal, Pratika; Cockell, Charles; Libeskind, Noam

2017-01-01

We present the first model that couples high-resolution simulations of the formation of local group galaxies with calculations of the galactic habitable zone (GHZ), a region of space which has sufficient metallicity to form terrestrial planets without being subject to hazardous radiation. These simulations allow us to make substantial progress in mapping out the asymmetric three-dimensional GHZ and its time evolution for the Milky Way (MW) and Triangulum (M33) galaxies, as opposed to works that generally assume an azimuthally symmetric GHZ. Applying typical habitability metrics to MW and M33, we find that while a large number of habitable planets exist as close as a few kiloparsecs from the galactic centre, the probability of individual planetary systems being habitable rises as one approaches the edge of the stellar disc. Tidal streams and satellite galaxies also appear to be fertile grounds for habitable planet formation. In short, we find that both galaxies arrive at similar GHZs by different evolutionary paths, as measured by the first and third quartiles of surviving biospheres. For the MW, this interquartile range begins as a narrow band at large radii, expanding to encompass much of the Galaxy at intermediate times before settling at a range of 2-13 kpc. In the case of M33, the opposite behaviour occurs - the initial and final interquartile ranges are quite similar, showing gradual evolution. This suggests that Galaxy assembly history strongly influences the time evolution of the GHZ, which will affect the relative time lag between biospheres in different galactic locations. We end by noting the caveats involved in such studies and demonstrate that high-resolution cosmological simulations will play a vital role in understanding habitability on galactic scales, provided that these simulations accurately resolve chemical evolution.

RINGS AND RADIAL WAVES IN THE DISK OF THE MILKY WAY

DOE PAGES

Xu, Yan; Newberg, Heidi Jo; Carlin, Jeffrey L.; ...

2015-03-11

Here, we show that in the anticenter region, between Galactic longitudes of 110° < l < 229°, there is an oscillating asymmetry in the main-sequence star counts on either side of the Galactic plane using data from the Sloan Digital Sky Survey. This asymmetry oscillates from more stars in the north at distances of about 2 kpc from the Sun to more stars in the south at 4–6 kpc from the Sun to more stars in the north at distances of 8–10 kpc from the Sun. We also see evidence that there are more stars in the south at distancesmore » of 12–16 kpc from the Sun. The three more distant asymmetries form roughly concentric rings around the Galactic center, opening in the direction of the Milky Way's spiral arms. The northern ring, 9 kpc from the Sun, is easily identified with the previously discovered Monoceros Ring. Parts of the southern ring at 14 kpc from the Sun (which we call the TriAnd Ring) have previously been identified as related to the Monoceros Ring, and others have been called the Triangulum Andromeda Overdensity. The two nearer oscillations are approximated by a toy model in which the disk plane is offset by the order of 100 pc up and then down at different radii. We also show that the disk is not azimuthally symmetric around the Galactic anticenter and that there could be a correspondence between our observed oscillations and the spiral structure of the Galaxy. Lastly, our observations suggest that the TriAnd and Monoceros Rings (which extend to at least 25 kpc from the Galactic center) are primarily the result of disk oscillations.« less

A deep narrowband survey for planetary nebulae at the outskirts of M 33

NASA Astrophysics Data System (ADS)

Galera-Rosillo, R.; Corradi, R. L. M.; Mampaso, A.

2018-04-01

Context. Planetary nebulae (PNe) are excellent tracers of stellar populations with low surface brightness, and therefore provide a powerful method to detect and explore the rich system of substructures discovered around the main spiral galaxies of the local group. Aim. We searched the outskirts of the local group spiral galaxy M 33 (the Triangulum) for PNe to gain new insights into the extended stellar substructure on the northern side of the disc and to study the existence of a faint classical halo. Methods: The search is based on wide field imaging covering a 4.5 square degree area out to a maximum projected distance of about 40 kpc from the centre of the galaxy. The PN candidates are detected by the combination of images obtained in narrowband filters selecting the [OIII]λ5007 Å and Hα + [NII] nebular lines and in the continuum g' and r' broadband filters. Results: Inside the bright optical disc of M 33, eight new PN candidates were identified, three of which were spectroscopically confirmed. No PN candidates were found outside the limits of the disc. Fourteen additional sources showing [OIII] excess were also discovered. Conclusions: The absence of bright PN candidates in the area outside the galaxy disc covered by this survey sets an upper limit to the luminosity of the underlying population of 1.6 × 107 L⊙, suggesting the lack of a massive classical halo, which is in agreement with the results obtained using the red giant branch population. Based on observations made with the Isaac Newton Telescope and service observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group of Telescopes in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

Hubble Spots a Barred Lynx Spiral

NASA Image and Video Library

2017-12-08

Discovered by British astronomer William Herschel over 200 years ago, NGC 2500 lies about 30 million light-years away in the northern constellation of Lynx. As this NASA/ESA Hubble Space Telescope image shows, NGC 2500 is a particular kind of spiral galaxy known as a barred spiral, its wispy arms swirling out from a bright, elongated core. Barred spirals are actually more common than was once thought. Around two-thirds of all spiral galaxies — including the Milky Way — exhibit these straight bars cutting through their centers. These cosmic structures act as glowing nurseries for newborn stars, and funnel material towards the active core of a galaxy. NGC 2500 is still actively forming new stars, although this process appears to be occurring very unevenly. The upper half of the galaxy — where the spiral arms are slightly better defined — hosts many more star-forming regions than the lower half, as indicated by the bright, dotted islands of light. There is another similarity between NGC 2500 and our home galaxy. Together with Andromeda, Triangulum and many smaller natural satellites, the Milky Way is part of the Local Group of galaxies, a gathering of over 50 galaxies all loosely held together by gravity. NGC 2500 forms a similar group with some of its nearby neighbors, including NGC 2541, NGC 2552, NGC 2537 and the bright, Andromeda-like spiral NGC 2481 (known collectively as the NGC 2841 group). Image Credit: ESA/Hubble/NASA NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

NASA Galaxy Mission Celebrates Sixth Anniversary

NASA Image and Video Library

2009-04-28

NASA Galaxy Evolution Explorer Mission celebrates its sixth anniversary studying galaxies beyond our Milky Way through its sensitive ultraviolet telescope, the only such far-ultraviolet detector in space. Pictured here, the galaxy NGC598 known as M33. The mission studies the shape, brightness, size and distance of distant galaxies across 10 billion years of cosmic history, giving scientists a wealth of data to help us better understand the origins of the universe. One such object is pictured here, the galaxy NGC598, more commonly known as M33. This image is a blend of the Galaxy Evolution Explorer's M33 image and another taken by NASA's Spitzer Space Telescope. M33, one of our closest galactic neighbors, is about 2.9 million light-years away in the constellation Triangulum, part of what's known as our Local Group of galaxies. Together, the Galaxy Evolution Explorer and Spitzer can see a broad spectrum of sky. Spitzer, for example, can detect mid-infrared radiation from dust that has absorbed young stars' ultraviolet light. That's something the Galaxy Evolution Explorer cannot see. This combined image shows in amazing detail the beautiful and complicated interlacing of the heated dust and young stars. In some regions of M33, dust gathers where there is very little far-ultraviolet light, suggesting that the young stars are obscured or that stars farther away are heating the dust. In some of the outer regions of the galaxy, just the opposite is true: There are plenty of young stars and very little dust. Far-ultraviolet light from young stars glimmers blue, near-ultraviolet light from intermediate age stars glows green, and dust rich in organic molecules burns red. This image is a 3-band composite including far infrared as red. http://photojournal.jpl.nasa.gov/catalog/PIA11998

NASA Galaxy Mission Celebrates Sixth Anniversary

NASA Image and Video Library

2009-04-28

NASA Galaxy Evolution Explorer Mission celebrates its sixth anniversary studying galaxies beyond our Milky Way through its sensitive ultraviolet telescope, the only such far-ultraviolet detector in space. The mission studies the shape, brightness, size and distance of distant galaxies across 10 billion years of cosmic history, giving scientists a wealth of data to help us better understand the origins of the universe. One such object is pictured here, the galaxy NGC598, more commonly known as M33. This image is a blend of the Galaxy Evolution Explorer's M33 image and another taken by NASA's Spitzer Space Telescope. M33, one of our closest galactic neighbors, is about 2.9 million light-years away in the constellation Triangulum, part of what's known as our Local Group of galaxies. Together, the Galaxy Evolution Explorer and Spitzer can see a broad spectrum of sky. Spitzer, for example, can detect mid-infrared radiation from dust that has absorbed young stars' ultraviolet light. That's something the Galaxy Evolution Explorer cannot see. This combined image shows in amazing detail the beautiful and complicated interlacing of the heated dust and young stars. In some regions of M33, dust gathers where there is very little far-ultraviolet light, suggesting that the young stars are obscured or that stars further away are heating the dust. In some of the outer regions of the galaxy, just the opposite is true: There are plenty of young stars and very little dust. Far-ultraviolet light from young stars glimmers blue, near-ultraviolet light from intermediate age stars glows green, near-infrared light from old stars burns yellow and orange, and dust rich in organic molecules burns red. The small blue flecks outside the spiral disk of M33 are most likely distant background galaxies. This image is a four-band composite that, in addition to the two ultraviolet bands, includes near infrared as yellow/orange and far infrared as red. http://photojournal.jpl.nasa.gov/catalog/PIA11999

Grassland bird productivity in warm season grass fields in southwest Wisconsin

USGS Publications Warehouse

Byers, Carolyn M.; Ribic, Christine; Sample, David W.; Dadisman, John D.; Guttery, Michael

2017-01-01

Surrogate grasslands established through federal set-aside programs, such as U.S. Department of Agriculture's Conservation Reserve Program (CRP), provide important habitat for grassland birds. Warm season grass CRP fields as a group have the potential for providing a continuum of habitat structure for breeding birds, depending on how the fields are managed and their floristic composition. We studied the nesting activity of four obligate grassland bird species, Bobolink (Dolichonyx oryzivorus), Eastern Meadowlark (Sturnella magna), Grasshopper Sparrow (Ammodramus savannarum), and Henslow's Sparrow (A. henslowii), in relation to vegetative composition and fire management in warm season CRP fields in southwest Wisconsin during 2009–2011. Intraspecific variation in apparent nest density was related to the number of years since the field was burned. Apparent Grasshopper Sparrow nest density was highest in the breeding season immediately following spring burns, apparent Henslow's Sparrow nest density was highest 1 y post burn, and apparent Bobolink and Eastern Meadowlark nest densities were higher in post fire years one to three. Grasshopper Sparrow nest density was highest on sites with more diverse vegetation, specifically prairie forbs, and on sites with shorter less dense vegetation. Bobolink, Eastern Meadowlark, and Henslow's Sparrow apparent nest densities were higher on sites with deeper litter; litter was the vegetative component that was most affected by spring burns. Overall nest success was 0.487 for Bobolink (22 d nesting period), 0.478 for Eastern Meadowlark (25 d nesting period), 0.507 for Grasshopper Sparrow (22 d nesting period), and 0.151 for Henslow's Sparrow (21 d nesting period). The major nest predators were grassland-associated species: thirteen-lined ground squirrel (Ictidomys tridecemlineatus), striped skunk (Mephitis mephitis), milk snake (Lampropeltis triangulum), American badger (Taxidea taxus), and western fox snake (Elaphe vulpina). Overall depredation rate was not affected by the number of years since the site had been burned. The diversity of vegetation on warm season CRP fields created by management using fire provides a continuum of structure for obligate grassland birds to use for breeding and habitat for a diversity of nest predators.

The UK Infrared Telescope M 33 monitoring project - V. The star formation history across the galactic disc

NASA Astrophysics Data System (ADS)

Javadi, Atefeh; van Loon, Jacco Th.; Khosroshahi, Habib G.; Tabatabaei, Fatemeh; Hamedani Golshan, Roya; Rashidi, Maryam

2017-01-01

We have conducted a near-infrared monitoring campaign at the UK Infrared Telescope of the Local Group spiral galaxy M 33 (Triangulum). On the basis of their variability, we have identified stars in the very final stage of their evolution, and for which the luminosity is more directly related to the birth mass than the more numerous less-evolved giant stars that continue to increase in luminosity. In this fifth paper of the series, we construct the birth mass function and hence derive the star formation history across the galactic disc of M 33. The star formation rate has varied between ˜0.010 ± 0.001 (˜0.012 ± 0.007) and 0.060±0.005 (0.052±0.009) M⊙ yr-1 kpc-2 statistically (systematically) in the central square kiloparsec of M 33, comparable with the values derived previously with another camera. The total star formation rate in M 33 within a galactocentric radius of 14 kpc has varied between ˜0.110 ± 0.005 (˜0.174 ± 0.060) and ˜0.560 ± 0.028 (˜0.503 ± 0.100) M⊙ yr-1 statistically (systematically). We find evidence of two epochs during which the star formation rate was enhanced by a factor of a few - one that started ˜6 Gyr ago and lasted ˜3 Gyr and produced ≥71 per cent of the total mass in stars, and one ˜250 Myr ago that lasted ˜200 Myr and formed ≤13 per cent of the mass in stars. Radial star formation history profiles suggest that the inner disc of M 33 was formed in an inside-out formation scenario. The outskirts of the disc are dominated by the old population, which may be the result of dynamical effects over many Gyr. We find correspondence to spiral structure for all stars, but enhanced only for stars younger than ˜100 Myr; this suggests that the spiral arms are transient features and not a part of a global density wave potential.

The Haunted Halos of Andromeda and Triangulum: A Panorama of Galaxy Formation in Action

NASA Astrophysics Data System (ADS)

Ibata, R.; Martin, N. F.; Irwin, M.; Chapman, S.; Ferguson, A. M. N.; Lewis, G. F.; McConnachie, A. W.

2007-12-01

We present a deep photometric survey of the Andromeda galaxy, conducted with the wide-field cameras of CFHT and INT, that covers the inner 50 kpc of the galaxy and the southern quadrant out to ~150 kpc and includes an extension to M33 at >200 kpc. This is the first systematic panoramic study of this very outermost region of galaxies. We detect a multitude of large-scale structures of low surface brightness, including several streams, and two new relatively luminous (MV~-9) dwarf galaxies: And XV and And XVI. Significant variations in stellar populations due to intervening stream-like structures are detected in the inner halo, which is particularly important in shedding light on the mixed and sometimes conflicting results reported in previous studies. Underlying the many substructures lies a faint, smooth, and extremely extended halo component, reaching out to 150 kpc, whose stellar populations are predominantly metal-poor. We find that the smooth halo component in M31 has a radially decreasing profile that can be fitted with a Hernquist model of immense scale radius ~55 kpc, almost 4 times larger than theoretical predictions. Alternatively a power law with ΣV~R-1.91+/-0.11 can be fitted to the projected profile, similar to the density profile in the Milky Way. If it is symmetric, the total luminosity of this structure is ~109 Lsolar, again similar to the stellar halo of the Milky Way. This vast, smooth, underlying halo is reminiscent of a classical ``monolithic'' model and completely unexpected from modern galaxy formation models. M33 is also found to have an extended metal-poor halo component, which can be fitted with a Hernquist model also of scale radius ~55 kpc. These extended slowly decreasing halos will provide a challenge and strong constraints for further modeling. Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institute National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

The peculiar asymmetry of NGC 949

NASA Image and Video Library

2015-05-04

This image provides the clearest ever view of galaxy NGC 949, which lies over 30 million light-years away in the constellation of Triangulum. The galaxy has an unusual shape, made more obscure due to its inclination. From our point of view, it is difficult to discern exactly what type of galaxy NGC 949 is, but it is certainly a disc galaxy of some kind, most likely a spiral. NGC 949 was first discovered by Sir William Herschel on 21 September 1786, using an 18.7-inch reflecting telescope. The galaxy was one of about 3000 objects Herschel catalogued as "nebulae" during an intense and systematic deep sky survey, the results of which eventually formed the bulk of the New General Catalogue (NGC). Taken with Hubble’s Advanced Camera for Surveys (ACS), this new image shows extraordinary detail. This detail allows us to see a strange asymmetric alignment in the dark lanes of dust that snake across the galaxy. The top-right half of the galaxy appears considerably more marbled with dust in this image; a curious observation explained by stars tending to favour locations towards the centre of a galaxy, and dust preferring almost invariably to reside along the galactic plane. When a galaxy is inclined as NGC 949 is, some regions — in this case the top-right — are tipped towards us and the light from the stars we see in these regions has had to travel through more dust. This causes the light to appear redder — the result of the same process that gives the sun’s light a red hue at dusk — or else disappear entirely, making the dust appear more prominent on that side of the galaxy. In the part tipped away from us, the light from the stars has had to pass through much less dust to reach us, so it appears brighter, and the dust is much less prominent. Were it possible to view NGC 949 from the opposite side, the apparent alignment of the dust would be reversed. The scientific advantages of this effect were recently displayed in suitably stunning style in the M31 PHAT mosa

Orbits of massive satellite galaxies - II. Bayesian estimates of the Milky Way and Andromeda masses using high-precision astrometry and cosmological simulations

NASA Astrophysics Data System (ADS)

Patel, Ekta; Besla, Gurtina; Mandel, Kaisey

2017-07-01

In the era of high-precision astrometry, space observatories like the Hubble Space Telescope (HST) and Gaia are providing unprecedented 6D phase-space information of satellite galaxies. Such measurements can shed light on the structure and assembly history of the Local Group, but improved statistical methods are needed to use them efficiently. Here we illustrate such a method using analogues of the Local Group's two most massive satellite galaxies, the Large Magellanic Cloud (LMC) and Triangulum (M33), from the Illustris dark-matter-only cosmological simulation. We use a Bayesian inference scheme combining measurements of positions, velocities and specific orbital angular momenta (j) of the LMC/M33 with importance sampling of their simulated analogues to compute posterior estimates of the Milky Way (MW) and Andromeda's (M31) halo masses. We conclude that the resulting host halo mass is more susceptible to bias when using measurements of the current position and velocity of satellites, especially when satellites are at short-lived phases of their orbits (I.e. at pericentre). Instead, the j value of a satellite is well conserved over time and provides a more reliable constraint on host mass. The inferred virial mass of the MW (M31) using j of the LMC (M33) is {{M}}_{vir, MW} = 1.02^{+0.77}_{-0.55} × 10^{12} M⊙ ({{M}}_{vir, M31} = 1.37^{+1.39}_{-0.75} × 10^{12} M⊙). Choosing simulated analogues whose j values are consistent with the conventional picture of a previous (<3 Gyr ago), close encounter (<100 kpc) of M33 about M31 results in a very low virial mass for M31 (˜1012 M⊙). This supports the new scenario put forth in Patel, Besla & Sohn, wherein M33 is on its first passage about M31 or on a long-period orbit. We conclude that this Bayesian inference scheme, utilizing satellite j, is a promising method to reduce the current factor of 2 spread in the mass range of the MW and M31. This method is easily adaptable to include additional satellites as new 6D phase-space information becomes available from HST, Gaia and the James Webb Space Telescope.

Spot evolution on the red giant star XX Triangulum. A starspot-decay analysis based on time-series Doppler imaging

NASA Astrophysics Data System (ADS)

Künstler, A.; Carroll, T. A.; Strassmeier, K. G.

2015-06-01

Context. Solar spots appear to decay linearly proportional to their size. The decay rate of solar spots is directly related to magnetic diffusivity, which itself is a key quantity for the length of a magnetic-activity cycle. Is a linear spot decay also seen on other stars, and is this in agreement with the large range of solar and stellar activity cycle lengths? Aims: We investigate the evolution of starspots on the rapidly-rotating (Prot≈24 d) K0 giant XX Tri, using consecutive time-series Doppler images. Our aim is to obtain a well-sampled movie of the stellar surface over many years, and thereby detect and quantify a starspot decay law for further comparison with the Sun. Methods: We obtained continuous high-resolution and phase-resolved spectroscopy with the 1.2-m robotic STELLA telescope on Tenerife over six years, and these observations are ongoing. For each observing season, we obtained between 5 to 7 independent Doppler images, one per stellar rotation, making up a total of 36 maps. All images were reconstructed with our line-profile inversion code iMap. A wavelet analysis was implemented for denoising the line profiles. To quantify starspot area decay and growth, we match the observed images with simplified spot models based on a Monte Carlo approach. Results: It is shown that the surface of XX Tri is covered with large high-latitude and even polar spots and with occasional small equatorial spots. Just over the course of six years, we see a systematically changing spot distribution with various timescales and morphology, such as spot fragmentation and spot merging as well as spot decay and formation. An average linear decay of D = -0.022 ± 0.002 SH/day is inferred. We found evidence of an active longitude in phase toward the (unseen) companion star. Furthermore, we detect a weak solar-like differential rotation with a surface shear of α = 0.016 ± 0.003. From the decay rate, we determine a turbulent diffusivity of ηT = (6.3 ± 0.5) × 1014 cm2/s and predict a magnetic activity cycle of ≈26 ± 6 yr. Finally, we present a short movie of the spatially resolved surface of XX Tri. Based on data obtained with the STELLA robotic telescopes in Tenerife, an AIP facility jointly operated with IAC.Appendices and the movie are available in electronic form at http://www.aanda.org

A Hubble Study of the Peculiar Asymmetry of NGC 949

NASA Image and Video Library

2015-05-08

This image provides the clearest ever view of galaxy NGC 949, which lies over 30 million light-years away in the constellation of Triangulum. The galaxy has an unusual shape, made more obscure due to its inclination. From our point of view, it is difficult to discern exactly what type of galaxy NGC 949 is, but it is certainly a disk galaxy of some kind, most likely a spiral. NGC 949 was first discovered by Sir William Herschel on September 21, 1786, using an 18.7-inch reflecting telescope. The galaxy was one of about 3,000 objects Herschel cataloged as "nebulae" during an intense and systematic deep sky survey, the results of which eventually formed the bulk of the New General Catalogue (NGC). Taken with Hubble’s Advanced Camera for Surveys (ACS), this image shows extraordinary detail. This detail allows us to see a strange asymmetric alignment in the dark lanes of dust that snake across the galaxy. The top-right half of the galaxy appears considerably more marbled with dust in this image; a curious observation explained by stars tending to favor locations towards the center of a galaxy, and dust preferring almost invariably to reside along the galactic plane. When a galaxy is inclined as NGC 949 is, some regions — in this case the top-right — are tipped toward us and the light from the stars we see in these regions has had to travel through more dust. This causes the light to appear redder — the result of the same process that gives the sun’s light a red hue at dusk — or else disappear entirely, making the dust appear more prominent on that side of the galaxy. In the part tipped away from us, the light from the stars has had to pass through much less dust to reach us, so it appears brighter, and the dust is much less prominent. Were it possible to view NGC 949 from the opposite side, the apparent alignment of the dust would be reversed. The scientific advantages of this effect were recently displayed in suitably stunning style in the M31 PHAT mosaic, which allowed astronomers to produce a partial three-dimensional dust map of M31 four times clearer than any previously attempted. Credit: ESA/Hubble & NASA NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

MSU Contributes to New Research on Star Formation

NASA Astrophysics Data System (ADS)

2010-01-01

EAST LANSING, Mich. - "Crazy" and "cool" are two of the words Michigan State University astronomer Megan Donahue uses to describe the two distinct "tails" found on a long tail of gas that is believed to be forming stars where few stars have been formed before. Donahue was part of an international team of astronomers that viewed the gas tail with a very long, new observation made by the Chandra X-ray Observatory and detailed it in a paper published this month in the publication Astrophysical Journal. "The double tail is very cool - that is, interesting - and ridiculously hard to explain," said Donahue, a professor in MSU's Department of Physics and Astronomy. "It could be two different sources of gas or something to do with magnetic fields. We just don't know." What is also unusual is the gas tail, which is more than 200,000 light years in length, extends well outside any galaxy. It is within objects such as this that new stars are formed, but usually within the confines of a galaxy. "This system is really crazy because where we're seeing the star formation is well away from any galaxy," Donahue said. "Star formation happens primarily in the disks of galaxies. What we're seeing here is very unexpected." This gas tail was originally spotted by astronomers three years ago using a multitude of telescopes, including NASA's Chandra X-ray Observatory and the SOuthern Astrophysical Research telescope, a Chilean-based observatory in which MSU is one of the partners. The new observations show a second tail, and a fellow galaxy, ESO 137-002, that also has a tail of hot X-ray-emitting gas. How these newly formed stars came to be in this particular place remains a mystery as well. Astronomers theorize this gas tail might have "pulled" star-making material from nearby gases, creating what some have called "orphan stars." "This system continues to surprise us as we get better observations of it," Donahue said. The gas tail is located in the southern hemisphere near a constellation called Triangulum Australe, in a giant cluster of galaxies called Abell 3627. It is associated with a galaxy known as ESO 137-001 which is about 219 million light years from our own Milky Way Galaxy. Star formation is a continuous process throughout the universe, where there are estimated to be billions of galaxies, each of which contains billions of stars. Stars are formed from clouds of dusty, cool, dense molecular gas. Molecular gas clouds prefer to inhabit galaxies, particularly the disks of galaxies like the Milky Way. Our sun, a star located within the Milky Way Galaxy, is an average-size star estimated to be about 4.6 billion years old. Michigan State University has been advancing knowledge and transforming lives through innovative teaching, research and outreach for more than 150 years. MSU is known internationally as a major public university with global reach and extraordinary impact. Its 17 degree-granting colleges attract scholars worldwide who are interested in combining education with practical problem solving. More information, including images and other multimedia, can be found at: http://chandra.harvard.edu and http://chandra.nasa.gov

Making Supermassive Black Holes Spin

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-12-01

Where does the angular momentum come from that causes supermassive black holes (SMBHs) to spin on their axes and launch powerful jets? A new study of nearby SMBHs may help to answer this question.High-mass SMBHs are thought to form when two galaxies collide and the SMBHs at their centers merge. [NASA/Hubble Heritage Team (STScI)]High- vs. Low-Mass MonstersObservational evidence suggests a dichotomy between low-mass SMBHs (those with 106-7 M) and high-mass ones (those with 108-10 M). High-mass SMBHs are thought to form via the merger of two smaller black holes, and the final black hole is likely spun up by the rotational dynamics of the merger. But what spins up low-mass SMBHs, which are thought to build up very gradually via accretion?A team of scientists led by Jing Wang (National Astronomical Observatories, Chinese Academy of Sciences) have attempted to address this puzzle by examining the properties of the galaxies hosting low-mass SMBHs.A Sample of Neighboring SMBHsWang and collaborators began by constructing a sample of radio-selected nearby Seyfert 2 galaxies: those galaxies in which the stellar population and morphology of the host galaxy are visible to us, instead of being overwhelmed by continuum emission from the galaxys active nucleus.An example of a galaxy with a concentrated, classical bulge (M87; top) and a one with a disk-like pseudo bulge (Triangulum Galaxy; bottom). The authors find that for galaxies hosting low-mass SMBHs, those with more disk-like bulges appear to have more powerful radio jets. [Top: NASA/Hubble Heritage Team (STScI), Bottom: Hewholooks]From this sample, the authors then selected 31 galaxies that have low-mass SMBHs at their centers, as measured using the surrounding stellar dynamics. Wang and collaborators cataloged radio information revealing properties of the powerful jets launched by the SMBHs, and they analyzed the host galaxies properties by modeling their brightness profiles.Spin-Up From Accreting GasBy examining this sample, the authors discovered an intriguing relationship: the radio power of jets launched by an SMBH appears to be dependent upon its host galaxys bulge surface brightness. Specifically, Wang and collaborators found that more powerful radio emission comes from SMBHs associated with less-concentrated bulges, i.e. those that are more disk-like.The authors findings allow them to rule out many common explanations for the radio-loudness of such galaxies with small SMBH masses. Instead, they argue that the tendency for galaxies with more disk-like bulges to host SMBHs with more powerful jets is evidence that low-mass SMBHs are spun up by the accretion of surrounding gas.In this scenario, the angular momentum of gas with significant disk-like rotational dynamics provides the spin to the SMBH, and this rotational energy can then be extracted to launch the powerful jets. If this explanation is correct, it strengthens the dichotomy between low-mass and high-mass SMBHs, supporting the idea that the two categories of black holes are indeed formed and spun up via completely different mechanisms.CitationJ. Wang et al 2016 ApJL 833 L2.doi:10.3847/2041-8205/833/1/L2

The Milky Way's Tiny but Tough Galactic Neighbour

NASA Astrophysics Data System (ADS)

2009-10-01

Today ESO announces the release of a stunning new image of one of our nearest galactic neighbours, Barnard's Galaxy, also known as NGC 6822. The galaxy contains regions of rich star formation and curious nebulae, such as the bubble clearly visible in the upper left of this remarkable vista. Astronomers classify NGC 6822 as an irregular dwarf galaxy because of its odd shape and relatively diminutive size by galactic standards. The strange shapes of these cosmic misfits help researchers understand how galaxies interact, evolve and occasionally "cannibalise" each other, leaving behind radiant, star-filled scraps. In the new ESO image, Barnard's Galaxy glows beneath a sea of foreground stars in the direction of the constellation of Sagittarius (the Archer). At the relatively close distance of about 1.6 million light-years, Barnard's Galaxy is a member of the Local Group, the archipelago of galaxies that includes our home, the Milky Way. The nickname of NGC 6822 comes from its discoverer, the American astronomer Edward Emerson Barnard, who first spied this visually elusive cosmic islet using a 125-millimetre aperture refractor in 1884. Astronomers obtained this latest portrait using the Wide Field Imager (WFI) attached to the 2.2-metre MPG/ESO telescope at ESO's La Silla Observatory in northern Chile. Even though Barnard's Galaxy lacks the majestic spiral arms and glowing, central bulge that grace its big galactic neighbours, the Milky Way, the Andromeda and the Triangulum galaxies, this dwarf galaxy has no shortage of stellar splendour and pyrotechnics. Reddish nebulae in this image reveal regions of active star formation, where young, hot stars heat up nearby gas clouds. Also prominent in the upper left of this new image is a striking bubble-shaped nebula. At the nebula's centre, a clutch of massive, scorching stars send waves of matter smashing into the surrounding interstellar material, generating a glowing structure that appears ring-like from our perspective. Other similar ripples of heated matter thrown out by feisty young stars are dotted across Barnard's Galaxy. At only about a tenth of the Milky Way's size, Barnard's Galaxy fits its dwarfish classification. All told, it contains about 10 million stars - a far cry from the Milky Way's estimated 400 billion. In the Local Group, as elsewhere in the Universe, however, dwarf galaxies outnumber their larger, shapelier cousins. Irregular dwarf galaxies like Barnard's Galaxy get their random, blob-like forms from close encounters with or "digestion" by other galaxies. Like everything else in the Universe, galaxies are in motion, and they often make close passes or even go through one another. The density of stars in galaxies is quite low, meaning that few stars physically collide during these cosmic dust-ups. Gravity's fatal attraction, however, can dramatically warp and scramble the shapes of the passing or crashing galaxies. Whole bunches of stars are pulled or flung from their galactic home, in turn forming irregularly shaped dwarf galaxies like NGC 6822. More information ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".