TY - JOUR A1 - Cioni, Maria-Rosa L. A1 - Bekki, Kenji A1 - Girardi, Leo A1 - de Grijs, Richard A1 - Irwin, Mike J. A1 - Ivanov, Valentin D. A1 - Marconi, Marcella A1 - Oliveira, Joana M. A1 - Piatti, Andres E. A1 - Ripepi, Vincenzo A1 - van Loon, Jacco Th. T1 - XVII. Proper motions of the Small Magellanic Cloud and the Milky Way globular cluster 47 Tucanae JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - Aims. In this study we use multi-epoch near-infrared observations from the VISTA survey of the Magellanic Cloud system (VMC) to measure the proper motions of different stellar populations in a tile of 1.5 deg2 in size in the direction of the Galactic globular cluster 47 Tuc. We obtain the proper motion of the cluster itself, of the Small Magellanic Cloud (SMC), and of the field Milky Way stars. Methods. Stars of the three main stellar components are selected according to their spatial distributions and their distributions in colour−magnitude diagrams. Their average coordinate displacement is computed from the difference between multiple Ks-band observations for stars as faint as Ks = 19 mag. Proper motions are derived from the slope of the best-fitting line among ten VMC epochs over a time baseline of ~1 yr. Background galaxies are used to calibrate the absolute astrometric reference frame. Results. The resulting absolute proper motion of 47 Tuc is (μαcos(δ), μδ) = (+7.26 ± 0.03, −1.25 ± 0.03) mas yr-1. This measurement refers to about 35 000 sources distributed between 10′ and 60′ from the cluster centre. For the SMC we obtain (μαcos(δ), μδ) = (+1.16 ± 0.07, −0.81 ± 0.07) mas yr-1 from about 5250 red clump and red giant branch stars. The absolute proper motion of the Milky Way population in the line of sight (l = 305.9, b = −44.9) of this VISTA tile is (μαcos(δ), μδ) = (+10.22 ± 0.14, −1.27 ± 0.12) mas yr-1 and has been calculated from about 4000 sources. Systematic uncertainties associated with the astrometric reference system are 0.18 mas yr-1. Thanks to the proper motion we detect 47 Tuc stars beyond its tidal radius. KW - proper motions KW - surveys KW - Magellanic Clouds KW - globular clusters: individual: 47 Tucanae Y1 - 2016 U6 - https://doi.org/10.1051/0004-6361/201527004 SN - 1432-0746 VL - 586 SP - 67 EP - 75 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Evans, Chris J. A1 - van Loon, Jacco Th. A1 - Hainich, Rainer A1 - Bailey, M. T1 - 2dF-AAOmega spectroscopy of massive stars in the Magellanic Clouds The north-eastern region of the Large Magellanic Cloud JF - Astronomy and astrophysics : an international weekly journal N2 - We present spectral classifications from optical spectroscopy of 263 massive stars in the north-eastern region of the Large Magellanic Cloud. The observed two-degree field includes the massive 30 Doradus star-forming region, the environs of SN1987A, and a number of star-forming complexes to the south of 30 Dor. These are the first classifications for the majority (203) of the stars and include eleven double-lined spectroscopic binaries. The sample also includes the first examples of early OC-type spectra (AA Omega 30 Dor 248 and 280), distinguished by the weakness of their nitrogen spectra and by C IV lambda 4658 emission. We propose that these stars have relatively unprocessed CNO abundances compared to morphologically normal O-type stars, indicative of an earlier evolutionary phase. From analysis of observations obtained on two consecutive nights, we present radial-velocity estimates for 233 stars, finding one apparent single-lined binary and nine (>3 sigma) outliers compared to the systemic velocity; the latter objects could be runaway stars or large-amplitude binary systems and further spectroscopy is required to investigate their nature. KW - Magellanic Clouds KW - stars: early-type KW - stars: fundamental parameters KW - open clusters and associations: general Y1 - 2015 U6 - https://doi.org/10.1051/0004-6361/201525882 SN - 1432-0746 VL - 584 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Fox, Andrew J. A1 - Barger, Kathleen A. A1 - Wakker, Bart P. A1 - Richter, Philipp A1 - Antwi-Danso, Jacqueline A1 - Casetti-Dinescu, Dana I. A1 - Howk, J. Christopher A1 - Lehner, Nicolas A1 - Crowther, Paul A. A1 - Lockman, Felix J. T1 - Chemical Abundances in the Leading Arm of the Magellanic Stream JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - The Leading Arm (LA) of the Magellanic Stream is a vast debris field of H I clouds connecting the Milky Way and the Magellanic Clouds. It represents an example of active gas accretion onto the Galaxy. Previously, only one chemical abundance measurement had been made in the LA. Here we present chemical abundance measurements using Hubble Space Telescope/Cosmic Origins Spectrograph and Green Bank Telescope spectra of four AGN sightlines passing through the LA and three nearby sightlines that may trace outer fragments of the LA. We find low oxygen abundances, ranging from 4.0+(2.0)(2.0)% 12.6(4.1)(6.0)% solar, in the confirmed LA directions, with the lowest values found in the region known as LA III, farthest from the LMC. These abundances are substantially lower than the single previous measurement, S/H = 35 +/- 7% solar, but are in agreement with those reported in the SMC filament of the trailing Stream, supporting a common origin in the SMC (not the LMC) for the majority of the LA and trailing Stream. This provides important constraints for models of the formation of the Magellanic System. Finally, two of the three nearby sightlines show high-velocity clouds with H I columns, kinematics, and oxygen abundances consistent with LA membership. This suggests that the LA is larger than traditionally thought, extending at least 20 degrees further to the Galactic northwest. KW - Galaxy: evolution KW - Galaxy: halo KW - ISM: abundances KW - Magellanic Clouds KW - quasars: absorption lines Y1 - 2018 U6 - https://doi.org/10.3847/1538-4357/aaa9bb SN - 0004-637X SN - 1538-4357 VL - 854 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Fox, Andrew J. A1 - Richter, Philipp A1 - Wakker, Bart P. A1 - Lehner, Nicolas A1 - Howk, J. Christopher A1 - Ben Bekhti, Nadya A1 - Bland-Hawthorn, Joss A1 - Lucas, Stephen T1 - The COS/UVES absorption survey of the magellanic stream - I. One-tenth solar abundances along the body of the stream JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - The Magellanic Stream (MS) is a massive and extended tail of multi-phase gas stripped out of the Magellanic Clouds and interacting with the Galactic halo. In this first paper of an ongoing program to study the Stream in absorption, we present a chemical abundance analysis based on HST/COS and VLT/UVES spectra of four active galactic nuclei (RBS 144, NGC 7714, PHL 2525, and HE 0056-3622) lying behind the MS. Two of these sightlines yield good MS metallicity measurements: toward RBS 144 we measure a low MS metallicity of [S/H] = [S II/H I] = -1.13 +/- 0.16 while toward NGC 7714 we measure [O/H] = [O I/H I] = -1.24 +/- 0.20. Taken together with the published MS metallicity toward NGC 7469, these measurements indicate a uniform abundance of approximate to 0.1 solar along the main body of the Stream. This provides strong support to a scenario in which most of the Stream was tidally stripped from the SMC approximate to 1.5-2.5 Gyr ago (a time at which the SMC had a metallicity of approximate to 0.1 solar), as predicted by several N-body simulations. However, in Paper II of this series, we report a much higher metallicity (S/H = 0.5 solar) in the inner Stream toward Fairall 9, a direction sampling a filament of the MS that Nidever et al. claim can be traced kinematically to the Large Magellanic Cloud, not the Small Magellanic Cloud. This shows that the bifurcation of the Stream is evident in its metal enrichment, as well as its spatial extent and kinematics. Finally we measure a similar low metallicity [O/H] = [O I/H I] = -1.03 +/- 0.18 in the v(LSR) = 150 km s(-1) cloud toward HE 0056-3622, which belongs to a population of anomalous velocity clouds near the south Galactic pole. This suggests these clouds are associated with the Stream or more distant structures (possibly the Sculptor Group, which lies in this direction at the same velocity), rather than tracing foreground Galactic material. KW - Galaxy: evolution KW - Galaxy: halo KW - ISM: abundances KW - Magellanic Clouds KW - ultraviolet: ISM Y1 - 2013 U6 - https://doi.org/10.1088/0004-637X/772/2/110 SN - 0004-637X VL - 772 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Fox, Andrew J. A1 - Wakker, Bart P. A1 - Barger, Kathleen A. A1 - Hernandez, Audra K. A1 - Richter, Philipp A1 - Lehner, Nicolas A1 - Bland-Hawthorn, Joss A1 - Charlton, Jane C. A1 - Westmeier, Tobias A1 - Thom, Christopher A1 - Tumlinson, Jason A1 - Misawa, Toru A1 - Howk, J. Christopher A1 - Haffner, L. Matthew A1 - Ely, Justin A1 - Rodriguez-Hidalgo, Paola A1 - Kumari, Nimisha T1 - The COS/UVES absorption survey of the magellanic stream. III. Ionization, total mass, and inflow rate onto the milky way JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - Dynamic interactions between the two Magellanic Clouds have flung large quantities of gas into the halo of the Milky Way. The result is a spectacular arrangement of gaseous structures, including the Magellanic Stream, the Magellanic Bridge, and the Leading Arm (collectively referred to as the Magellanic System). In this third paper of a series studying the Magellanic gas in absorption, we analyze the gas ionization level using a sample of 69 Hubble Space Telescope/Cosmic Origins Spectrograph sightlines that pass through or within 30 degrees of the 21 cm emitting regions. We find that 81% (56/69) of the sightlines show UV absorption at Magellanic velocities, indicating that the total cross-section of the Magellanic System is approximate to 11,000 deg(2), or around one-quarter of the entire sky. Using observations of the Si III/Si II ratio together with Cloudy photoionization modeling, we calculate the total gas mass (atomic plus ionized) of the Magellanic System to be approximate to 2.0 x 10(9) M-circle dot (d/55 kpc)(2), with the ionized gas contributing around three times as much mass as the atomic gas. This is larger than the current-day interstellar H I mass of both Magellanic Clouds combined, indicating that they have lost most of their initial gas mass. If the gas in the Magellanic System survives to reach the Galactic disk over its inflow time of similar to 0.5-1.0 Gyr, it will represent an average inflow rate of similar to 3.7-6.7 M-circle dot yr(-1), potentially raising the Galactic star formation rate. However, multiple signs of an evaporative interaction with the hot Galactic corona indicate that the Magellanic gas may not survive its journey to the disk fully intact and will instead add material to (and cool) the corona. KW - Galaxy: evolution KW - Galaxy: halo KW - ISM: abundances KW - Magellanic Clouds KW - quasars: absorption lines Y1 - 2014 U6 - https://doi.org/10.1088/0004-637X/787/2/147 SN - 0004-637X SN - 1538-4357 VL - 787 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Hainich, Rainer A1 - Pasemann, Diana A1 - Todt, Helge Tobias A1 - Shenar, Tomer A1 - Sander, Andreas Alexander Christoph A1 - Hamann, Wolf-Rainer T1 - Wolf-Rayet stars in the Small Magellanic Cloud I. Analysis of the single WN stars JF - Astronomy and astrophysics : an international weekly journal N2 - Context. Wolf-Rayet (WR) stars have a severe impact on their environments owing to their strong ionizing radiation fields and powerful stellar winds. Since these winds are considered to be driven by radiation pressure, it is theoretically expected that the degree of the wind mass-loss depends on the initial metallicity of WR stars. Aims. Following our comprehensive studies of WR stars in the Milky Way, M31, and the LMC, we derive stellar parameters and mass-loss rates for all seven putatively single WN stars known in the SMC. Based on these data, we discuss the impact of a low-metallicity environment on the mass loss and evolution of WR stars. Methods. The quantitative analysis of the WN stars is performed with the Potsdam Wolf-Rayet (PoWR) model atmosphere code. The physical properties of our program stars are obtained from fitting synthetic spectra to multi-band observations. Results. In all SMC WN stars, a considerable surface hydrogen abundance is detectable. The majority of these objects have stellar temperatures exceeding 75 kK, while their luminosities range from 10(5.5) to 10(6.1) L-circle dot. The WN stars in the SMC exhibit on average lower mass-loss rates and weaker winds than their counterparts in the Milky Way, M31, and the LMC. Conclusions. By comparing the mass-loss rates derived for WN stars in different Local Group galaxies, we conclude that a clear dependence of the wind mass-loss on the initial metallicity is evident, supporting the current paradigm that WR winds are driven by radiation. A metallicity effect on the evolution of massive stars is obvious from the HRD positions of the SMC WN stars at high temperatures and high luminosities. Standard evolution tracks are not able to reproduce these parameters and the observed surface hydrogen abundances. Homogeneous evolution might provide a better explanation for their evolutionary past. KW - stars: Wolf-Rayet KW - Magellanic Clouds KW - stars: early-type KW - stars: atmospheres KW - stars: winds, outflows KW - stars: mass-loss Y1 - 2015 U6 - https://doi.org/10.1051/0004-6361/201526241 SN - 1432-0746 VL - 581 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Hainich, Rainer A1 - Ruehling, Ute A1 - Todt, Helge Tobias A1 - Oskinova, Lida A1 - Liermann, A. A1 - Graefener, G. A1 - Foellmi, C. A1 - Schnurr, O. A1 - Hamann, Wolf-Rainer T1 - The Wolf-Rayet stars in the Large Magellanic Cloud - A comprehensive analysis of the WN class JF - Astronomy and astrophysics : an international weekly journal N2 - Context. Massive stars, although being important building blocks of galaxies, are still not fully understood. This especially holds true for Wolf-Rayet (WR) stars with their strong mass loss, whose spectral analysis requires adequate model atmospheres. Aims. Following our comprehensive studies of the WR stars in the Milky Way, we now present spectroscopic analyses of almost all known WN stars in the LMC. Methods. For the quantitative analysis of the wind-dominated emission-line spectra, we employ the Potsdam Wolf-Rayet (PoWR) model atmosphere code. By fitting synthetic spectra to the observed spectral energy distribution and the available spectra (ultraviolet and optical), we obtain the physical properties of 107 stars. Results. We present the fundamental stellar and wind parameters for an almost complete sample of WN stars in the LMC. Among those stars that are putatively single, two different groups can be clearly distinguished. While 12% of our sample are more luminous than 10(6) L-circle dot and contain a significant amount of hydrogen, 88% of the WN stars, with little or no hydrogen, populate the luminosity range between log (L/L-circle dot) = 5.3 ... 5.8. Conclusions. While the few extremely luminous stars (log (L/L-circle dot) > 6), if indeed single stars, descended directly from the main sequence at very high initial masses, the bulk of WN stars have gone through the red-supergiant phase. According to their luminosities in the range of log (L/L-circle dot) = 5.3 ... 5.8, these stars originate from initial masses between 20 and 40 M-circle dot. This mass range is similar to the one found in the Galaxy, i.e. the expected metallicity dependence of the evolution is not seen. Current stellar evolution tracks, even when accounting for rotationally induced mixing, still partly fail to reproduce the observed ranges of luminosities and initial masses. Moreover, stellar radii are generally larger and effective temperatures correspondingly lower than predicted from stellar evolution models, probably due to subphotospheric inflation. KW - stars: Wolf-Rayet KW - Magellanic Clouds KW - stars: early-type KW - stars: atmospheres KW - stars: winds, outflows KW - stars: mass-loss Y1 - 2014 U6 - https://doi.org/10.1051/0004-6361/201322696 SN - 0004-6361 SN - 1432-0746 VL - 565 PB - EDP Sciences CY - Les Ulis ER - TY - THES A1 - Haupt, Maria T1 - The Magellanic Clouds in VHE gamma rays as seen by H.E.S.S. N2 - Das Gebiet der Gammastrahlungsastronomie hat ein neues Fenster in das nicht-thermische Universum geöffnet, welches erlaubt, die Beschleunigungsorte der kosmischen Strahlung und ihrer Rolle in evolutionären Prozessen in Galaxien zu untersuchen. Der Nachweis von fast einhundert sehr hochenergetischen Gammastrahlungsquellen in unserer Milchstraße zeigt, dass Teilchenbeschleunigung bis in den zweistelligen TeV-Energiebereich ein häufiges Phänomen ist. Darüber hinaus hat der Nachweis von sehr hochenergetischer Gammastrahlung von anderen Galaxien bestätigt, dass die kosmische Strahlung nicht ausschließlich in der Milchstraße beschleunigt wird. Die rasante Entwicklung der Gammastrahlungsastronomie in den letzten zwei Jahrzehnten führte zu einem Übergang von der Detektion und Untersuchung einzelner Quellen hin zu Quellpopulationsstudien. Um die Frage zu beantworten, ob die Quellpopulationen hochenergetischer Gammastrahlung in der Milchstraße einzigartig sind, sind Beobachtungen von anderen Galaxien erforderlich, für die es möglich ist, trotz ihrer Entfernung, einzelne Quellen aufzulösen. Die Magellanschen Wolken, zwei Satellitengalaxien der Milchstraße, sind solche Galaxien, welche im letzten Jahrzehnt durch das H.E.S.S.-Experiment intensiv beobachtet wurden. In dieser Arbeit werden die Daten von insgesamt 450 Stunden H.E.S.S.-Beobachtungen der Großen Magellanschen Wolke und der Kleinen Magellanschen Wolke vorgestellt. Während der Analyse der Datensätze wird besonderer Wert auf die Evaluierung der systematischen Unsicherheiten des Experiments gelegt, um eine unverfälschte Flussabschätzung der potentiellen hochenergetischen Gammastrahlungsquellen der Magellanschen Wolken zu gewährleisten. Die detaillierte Analyse der Beobachtungen führte zur Detektion hochenergetischer Gammastrahlung des Binärsystems LMC P3 in der Großen Magellanschen Wolke und erhöht somit die Anzahl der detektierten Gammastrahlungsquellen in dieser Galaxie auf vier. Dieses neuentdeckte Binärsystem ist das bisher leuchtstärkste in der Quellklasse der Gammastrahlungsbinärsysteme. Für keine andere Quelle in den Magellanschen Wolken wird hochenergetische Gammastrahlung nachgewiesen und es werden Obergrenzen auf den integralen Fluss ermittelt. Diese Flussobergrenzen werden verwendet, um Populationsstudien auf der Grundlage bekannter hochenergetischer Quellklassen sowie bestehender Quellkataloge anderer Wellenlängen durchzuführen. Ein systematischer Vergleich zwischen den Quellpopulationen der Magellanschen Wolken und der Milchstraße ergab, dass keine andere Quelle der Magellanschen Wolken so leuchtstark ist wie die leuchtstärkste hochenergetische Gammastrahlungsquelle in der LMC: der Pulsarwindnebel N157B. Des Weiteren ist ein Drittel der untersuchten Quellpopulation der Magellanschen Wolken weniger leuchtstark als die vier bekannten Gammastrahlungsquellen in der Großen Magellanschen Wolke. Für einige wenige Quellen kann gezeigt werden, dass sie weniger leuchtstark sind als die leuchtstärksten Objekte in der Milchstraße, deren Leuchtkraft um mehr als eine Größenordnung schwächer ist als die der detektierten Quellen in der Großen Magellanschen Wolke. Basierend auf den Flussobergrenzen werden Unterschiede in den Quellpopulationen der Magellanschen Wolken und der Milchstraße sowie die Bedeutung der Quellumgebungen diskutiert. N2 - The field of gamma-ray astronomy opened a new window into the non-thermal universe that allows studying the acceleration sites of cosmic rays and the role of cosmic rays on evolutionary processes in galaxies. The detection of almost one hundred Galactic very-high-energy (VHE: 0.1−100TeV) gamma-ray sources in the Milky Way demonstrates that particle acceleration up to tens of TeV energies is a common phenomenon. Furthermore, the detection of VHE gamma rays from other galaxies has confirmed that cosmic rays are not exclusively accelerated in the Milky Way. The rapid development of gamma-ray astronomy in the past two decades has led to a transition from the detection and study of individual sources to source population studies. To answer the question, whether the VHE gamma-ray source population of the Milky Way is unique, observations of galaxies, for which individual sources can be resolved, are required. Such galaxies are the Magellanic Clouds, two satellite galaxies of the Milky Way, which have been surveyed by the H.E.S.S. experiment in the last decade. In this thesis, data from a total of 450 hours of H.E.S.S. observations towards the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC) are presented. During the analysis of the data sets, special emphasis is put on the evaluation of systematic uncertainties of the experiment in order to assure an unbiased flux estimation of the potential VHE gamma-ray sources of the Magellanic Clouds. A detailed analysis of the survey data revealed the detection of the gamma-ray binary LMCP3, the most powerful gamma-ray binary known so far, that is located in the LMC, and thus, increases the number of known VHE gamma-ray sources in the LMC to four. No other VHE gamma-ray source is detected in the Magellanic Clouds and integral flux upper limits are estimated. These flux upper limits are used to perform a source population study based on known VHE source classes and existing multi-wavelength catalogues. A comparison of the source populations of the Magellanic Clouds and the Milky Way revealed that no other source in the Magellanic Clouds is as bright as the most luminous VHE gamma-ray source in the LMC: the pulsar wind nebula N 157B, and that one-third of the source population of the Magellanic Clouds is less luminous than the other known VHE gamma-ray sources in the LMC. For only a couple of sources luminosity levels of Galactic VHE sources, that are more than one order of magnitude fainter than the detected sources in the LMC, are constrained. Based on the flux upper limits, differences on the TeV source populations in the Magellanic Clouds and the Milky Way as well as the importance of the source environments will be discussed. KW - astroparticle physics KW - gamma-ray astronomy KW - Magellanic Clouds KW - Astroteilchenphysik KW - Gammastrahlungsastronomie KW - Magellansche Wolken Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-474601 ER - TY - JOUR A1 - Henault-Brunet, V. A1 - Oskinova, Lida A1 - Guerrero, Martín A. A1 - Sun, W. A1 - Chu, Y.-H. A1 - Evans, C. J. A1 - Gallagher, J. S. A1 - Gruendl, R. A. A1 - Reyes-Iturbide, J. T1 - Discovery of a Be/X-ray pulsar binary and associated supernova remnant in the wing of the small magellanic cloud JF - Monthly notices of the Royal Astronomical Society N2 - We report on a new Be/X-ray pulsar binary located in the Wing of the Small Magellanic Cloud (SMC). The strong pulsed X-ray source was discovered with the Chandra and XMM-Newton X-ray observatories. The X-ray pulse period of 1062 s is consistently determined from both Chandra and XMM-Newton observations, revealing one of the slowest rotating X-ray pulsars known in the SMC. The optical counterpart of the X-ray source is the emission-line star 2dFS 3831. Its B0-0.5(III)e+ spectral type is determined from VLT-FLAMES and 2dF optical spectroscopy, establishing the system as a Be/X-ray binary (Be-XRB). The hard X-ray spectrum is well fitted by a power law with additional thermal and blackbody components, the latter reminiscent of persistent Be-XRBs. This system is the first evidence of a recent supernova in the low-density surroundings of NGC602. We detect a shell nebula around 2dFS 3831 in H alpha and [OIII] images and conclude that it is most likely a supernova remnant. If it is linked to the supernova explosion that created this new X-ray pulsar, its kinematic age of (2-4) x 10(4) yr provides a constraint on the age of the pulsar. KW - stars: emission-line, Be KW - ISM: supernova remnants KW - Magellanic Clouds KW - X-rays: binaries Y1 - 2012 U6 - https://doi.org/10.1111/j.1745-3933.2011.01183.x SN - 0035-8711 VL - 420 IS - 1 SP - L13 EP - L17 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Ivanov, Valentin D. A1 - Cioni, Maria-Rosa L. A1 - Bekki, Kenji A1 - de Grijs, Richard A1 - Emerson, Jim A1 - Gibson, Brad K. A1 - Kamath, Devika A1 - van Loon, Jacco Th. A1 - Piatti, Andres E. A1 - For, Bi-Qing T1 - New quasars behind the Magellanic Clouds. Spectroscopic confirmation of near-infrared selected candidates JF - Current biology N2 - Context. Quasi-stellar objects (quasars) located behind nearby galaxies provide an excellent absolute reference system for astrometric studies, but they are difficult to identify because of fore-and background contamination. Deep wide-field, high angular resolution surveys spanning the entire area of nearby galaxies are needed to obtain a complete census of such quasars. Aims. We embarked on a program to expand the quasar reference system behind the Large and the Small Magellanic Clouds, the Magellanic Bridge, and the Magellanic Stream that connects the Clouds with the Milky Way. Methods. Hundreds of quasar candidates were selected based on their near-infrared colors and variability properties from the ongoing public ESO VISTA Magellanic Clouds survey. A subset of 49 objects was followed up with optical spectroscopy. Results. We confirmed the quasar nature of 37 objects (34 new identifications): four are low redshift objects, three are probably stars, and the remaining three lack prominent spectral features for a secure classification. The bona fide quasars, identified from their broad emisison lines, are located as follows: 10 behind the LMC, 13 behind the SMC, and 14 behind the Bridge. The quasars span a redshift range from z similar to 0.5 to z similar to 4.1. Conclusions. Upon completion the VMC survey is expected to yield a total of similar to 1500 quasars with Y < 19.32 mag, J < 19.09 mag, and K-s < 18.04 mag. KW - surveys KW - infrared: galaxies KW - quasars: general KW - Magellanic Clouds Y1 - 2016 U6 - https://doi.org/10.1051/0004-6361/201527398 SN - 1432-0746 VL - 588 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Martin, Nicolas F. A1 - Jungbluth, Valentin A1 - Nidever, David L. A1 - Bell, Eric F. A1 - Besla, Gurtina A1 - Blum, Robert D. A1 - Cioni, Maria-Rosa L. A1 - Conn, Blair C. A1 - Kaleida, Catherine C. A1 - Gallart, Carme A1 - Jin, Shoko A1 - Majewski, Steven R. A1 - Martinez-Delgado, David A1 - Monachesi, Antonela A1 - Munoz, Ricardo R. A1 - Noel, Noelia E. D. A1 - Olsen, Knut A1 - Stringfellow, Guy S. A1 - van der Marel, Roeland P. A1 - Vivas, A. Katherina A1 - Walker, Alistair R. A1 - Zaritsky, Dennis T1 - SMASH 1: A VERY FAINT GLOBULAR CLUSTER DISRUPTING IN THE OUTER REACHES OF THE LMC? JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters KW - globular clusters: individual: (SMASH 1) KW - Local Group KW - Magellanic Clouds Y1 - 2016 U6 - https://doi.org/10.3847/2041-8205/830/1/L10 SN - 2041-8205 SN - 2041-8213 VL - 830 SP - 92 EP - 98 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Martin, Nicolas F. A1 - Nidever, David L. A1 - Besla, Gurtina A1 - Olsen, Knut A1 - Walker, Alistair R. A1 - Vivas, A. Katherina A1 - Gruendl, Robert A. A1 - Kaleida, Catherine C. A1 - Munoz, Ricardo R. A1 - Blum, Robert D. A1 - Saha, Abhijit A1 - Conn, Blair C. A1 - Bell, Eric F. A1 - Chu, You-Hua A1 - Cioni, Maria-Rosa L. A1 - de Boer, Thomas J. L. A1 - Gallart, Carme A1 - Jin, Shoko A1 - Kunder, Andrea A1 - Majewski, Steven R. A1 - Martinez-Delgado, David A1 - Monachesi, Antonela A1 - Monelli, Matteo A1 - Monteagudo, Lara A1 - Noel, Noelia E. D. A1 - Olszewski, Edward W. A1 - Stringfellow, Guy S. A1 - van der Marel, Roeland P. A1 - Zaritsky, Dennis T1 - Hydra II: A faint and compact milky way dwarf galaxy found in the survey of the magellanic stellar history JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters N2 - We present the discovery of a new dwarf galaxy, Hydra II, found serendipitously within the data from the ongoing Survey of the Magellanic Stellar History conducted with the Dark Energy Camera on the Blanco 4 m Telescope. The new satellite is compact (r(h) = 68 +/- 11 pc) and faint (MV = -4.8 +/- 0.3), but well within the realm of dwarf galaxies. The stellar distribution of Hydra II in the color-magnitude diagram is well-described by a metal-poor ([Fe/H] = -2.2) and old (13 Gyr) isochrone and shows a distinct blue horizontal branch, some possible red clump stars, and faint stars that are suggestive of blue stragglers. At a heliocentric distance of 134 +/- 10 kpc, Hydra II is located in a region of the Galactic halo that models have suggested may host material from the leading arm of the Magellanic Stream. A comparison with N-body simulations hints that the new dwarf galaxy could be or could have been a satellite of the Magellanic Clouds. KW - galaxies: individual (Hydra II) KW - Local Group KW - Magellanic Clouds Y1 - 2015 U6 - https://doi.org/10.1088/2041-8205/804/1/L5 SN - 2041-8205 SN - 2041-8213 VL - 804 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Moretti, M. I. A1 - Clementini, Gisella A1 - Marconi, V. Ripepi M. A1 - Rubele, S. A1 - Cioni, Maria-Rosa L. A1 - Muraveva, T. A1 - Groenewegen, M. A. T. A1 - Cross, N. J. G. A1 - Ivanov, V. D. A1 - Piatti, A. E. A1 - de Grijs, Richard T1 - The VMC survey - XX. Identification of new Cepheids in the Small Magellanic Cloud JF - Monthly notices of the Royal Astronomical Society N2 - We present K-s-band light curves for 299 Cepheids in the Small Magellanic Cloud (SMC) of which 288 are new discoveries that we have identified using multi-epoch near-infrared photometry obtained by the VISTA survey of the Magellanic Clouds system (VMC). The new Cepheids have periods in the range from 0.34 to 9.1 d and cover the magnitude interval 12.9 <= currency sign < K-s > <= currency sign 17.6 mag. Our method was developed using variable stars previously identified by the optical microlensing survey OGLE. We focus on searching new Cepheids in external regions of the SMC for which complete VMC K-s-band observations are available and no comprehensive identification of different types of variable stars from other surveys exists yet. KW - methods: data analysis KW - surveys KW - stars: variables: Cepheids KW - Magellanic Clouds Y1 - 2016 U6 - https://doi.org/10.1093/mnras/stw716 SN - 0035-8711 SN - 1365-2966 VL - 459 SP - 1687 EP - 1697 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Muraveva, Tatiana A1 - Palmer, Max A1 - Clementini, Gisella A1 - Luri, Xavier A1 - Cioni, Maria-Rosa L. A1 - Moretti, Maria Ida A1 - Marconi, Marcella A1 - Ripepi, Vincenzo A1 - Rubele, Stefano T1 - New near-infrared period-luminosity-metallicity relations for RR lyrae stars and the outlock for GAIA JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We present results of the analysis of 70 RR Lyrae stars located in the bar of the Large Magellanic Cloud (LMC). Combining the spectroscopically determined metallicity of these stars from the literature with precise periods from the OGLE III catalog and multi-epoch K-s photometry from the VISTA survey of the Magellanic Clouds system, we derive a new near-infrared period-luminosity-metallicity (PLKsZ) relation for RR Lyrae variables. In order to fit the relation we use a fitting method developed specifically for this study. The zero-point of the relation is estimated two different ways: by assuming the value of the distance to the LMC and by using Hubble Space Telescope parallaxes of five RR Lyrae stars in the Milky Way (MW). The difference in distance moduli derived by applying these two approaches is similar to 0.2 mag. To investigate this point further we derive the PL(Ks)Z relation based on 23 MW RR Lyrae stars that had been analyzed in Baade-Wesselink studies. We compared the derived PL(Ks)Z relations for RR Lyrae stars in the MW and LMC. Slopes and zero-points are different, but still consistent within the errors. The shallow slope of the metallicity term is confirmed by both LMC and MW variables. The astrometric space mission Gaia is expected to provide a huge contribution to the determination of the RR Lyrae PL(Ks)Z relation; however, calculating an absolute magnitude from the trigonometric parallax of each star and fitting a PL(Ks)Z relation directly to period and absolute magnitude leads to biased results. We present a tool to achieve an unbiased solution by modeling the data and inferring the slope and zero-point of the relation via statistical methods. KW - astrometry KW - distance scale KW - Magellanic Clouds KW - methods: data analysis KW - stars: statistics KW - stars: variables: RR Lyrae Y1 - 2015 U6 - https://doi.org/10.1088/0004-637X/807/2/127 SN - 0004-637X SN - 1538-4357 VL - 807 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Murray, Claire E. A1 - Stanimirovic, Snezana A1 - McClure-Griffiths, Naomi M. A1 - Putman, Mary E. A1 - Liszt, Harvey S. A1 - Wong, Tony A1 - Richter, Philipp A1 - Dawson, Joanne R. A1 - Dickey, John M. A1 - Lindner, Robert R. A1 - Babler, Brian L. A1 - Allison, James R. T1 - First detection of HCO+ absorption in the magellanic system JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We present the first detection of HCO+ absorption in the Magellanic System. Using the ATCA, we observed nine extragalactic radio continuum sources behind the Magellanic System and detected HCO+ absorption toward one source located behind the leading edge of the Magellanic Bridge. The detection is located at an LSR velocity of v = 214.0 +/- 0.4 km s(-1), with an FWHM of Delta v = 4.5 +/- 1.0 km s(-1), and an optical depth of tau (HCO+) = 0.10 +/- 0.02. Although there is abundant neutral hydrogen (H I) surrounding the sight line in position-velocity space, at the exact location of the absorber the H I column density is low, <10(20) cm(-2), and there is little evidence for dust or CO emission from Planck observations. While the origin and survival of molecules in such a diffuse environment remain unclear, dynamical events such as H I flows and cloud collisions in this interacting system likely play an important role. KW - ISM: molecules KW - ISM: structure KW - Magellanic Clouds Y1 - 2015 U6 - https://doi.org/10.1088/0004-637X/808/1/41 SN - 0004-637X SN - 1538-4357 VL - 808 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Naze, Yael A1 - Wang, Q. Daniel A1 - Chu, You-Hua A1 - Gruendl, Robert A1 - Oskinova, Lida T1 - A deep chandra observation of the giant HII region N11. I. x-ray sorces in the field JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Supplement series N2 - A very sensitive X-ray investigation of the giant HII region N11 in the Large Megallanic Cloud was performed using the Chandra X-ray Observatory. The 300 ks observation reveals X-ray sources with luminosities down to 10(32) erg s(-1), increasing the number of known point sources in the field by more than a factor of five. Among these detections are 13 massive stars (3 compact groups of massive stars, 9 O stars, and one early B star) with log(L-X/L-BOL) similar to -6.5 to -7, which may suggest that they are highly magnetic or colliding-wind systems. On the other hand, the stacked signal for regions corresponding to undetected O stars yields log(L-X/L-BOL) similar to -7.3, i.e., an emission level comparable to similar Galactic stars despite the lower metallicity. Other point sources coincide with 11 foreground stars, 6 late-B/A stars in N11, and many background objects. This observation also uncovers the extent and detailed spatial properties of the soft, diffuse emission regions, but the presence of some hotter plasma in their spectra suggests contamination by the unresolved stellar population. KW - galaxies: star clusters: general KW - ISM: individual objects (LMC N11) KW - Magellanic Clouds KW - X-rays: stars Y1 - 2014 U6 - https://doi.org/10.1088/0067-0049/213/2/23 SN - 0067-0049 SN - 1538-4365 VL - 213 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Nidever, David L. A1 - Olsen, Knut A1 - Walker, Alistair R. A1 - Katherina Vivas, A. A1 - Blum, Robert D. A1 - Kaleida, Catherine A1 - Choi, Yumi A1 - Conn, Blair C. A1 - Gruendl, Robert A. A1 - Bell, Eric F. A1 - Besla, Gurtina A1 - Munoz, Ricardo R. A1 - Gallart, Carme A1 - Martin, Nicolas F. A1 - Olszewski, Edward W. A1 - Saha, Abhijit A1 - Monachesi, Antonela A1 - Monelli, Matteo A1 - de Boer, Thomas J. L. A1 - Johnson, L. Clifton A1 - Zaritsky, Dennis A1 - Stringfellow, Guy S. A1 - van der Marel, Roeland P. A1 - Cioni, Maria-Rosa L. A1 - Jin, Shoko A1 - Majewski, Steven R. A1 - Martinez-Delgado, David A1 - Monteagudo, Lara A1 - Noel, Noelia E. D. A1 - Bernard, Edouard J. A1 - Kunder, Andrea A1 - Chu, You-Hua A1 - Bell, Cameron P. M. A1 - Santana, Felipe A1 - Frechem, Joshua A1 - Medina, Gustavo E. A1 - Parkash, Vaishali A1 - Seron Navarrete, J. C. A1 - Hayes, Christian T1 - SMASH: Survey of the MAgellanic Stellar History JF - The astronomical journal N2 - The Large and Small Magellanic Clouds are unique local laboratories for studying the formation and evolution of small galaxies in exquisite detail. The Survey of the MAgellanic Stellar History (SMASH) is an NOAO community Dark Energy Camera (DECam) survey of the Clouds mapping 480 deg2 (distributed over similar to 2400 square degrees at similar to 20% filling factor) to similar to 24th. mag in ugriz. The primary goals of SMASH are to identify low surface brightness stellar populations associated with the stellar halos and tidal debris of the Clouds, and to derive spatially resolved star formation histories. Here, we present a summary of the survey, its data reduction, and a description of the first public Data Release (DR1). The SMASH DECam data have been reduced with a combination of the NOAO Community Pipeline, the PHOTRED automated point-spread-function photometry pipeline, and custom calibration software. The astrometric precision is similar to 15 mas and the accuracy is similar to 2 mas with respect to the Gaia reference frame. The photometric precision is similar to 0.5%-0.7% in griz and similar to 1% in u with a calibration accuracy of similar to 1.3% in all bands. The median 5s point source depths in ugriz are 23.9, 24.8, 24.5, 24.2, and 23.5 mag. The SMASH data have already been used to discover the Hydra II Milky Way satellite, the SMASH 1 old globular cluster likely associated with the LMC, and extended stellar populations around the LMC out to R. similar to. 18.4 kpc. SMASH DR1 contains measurements of similar to 100 million objects distributed in 61 fields. A prototype version of the NOAO Data Lab provides data access and exploration tools. KW - galaxies: dwarf KW - galaxies: individual (Large Magellanic Cloud, Small Magellanic Cloud) KW - Local Group KW - Magellanic Clouds KW - surveys Y1 - 2017 U6 - https://doi.org/10.3847/1538-3881/aa8d1c SN - 0004-6256 SN - 1538-3881 VL - 154 SP - 310 EP - 326 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Niederhofer, Florian A1 - Cioni, Maria-Rosa L. A1 - Schmidt, Thomas A1 - Bekki, Kenji A1 - de Grijs, Richard A1 - Ivanov, Valentin D. A1 - Oliveira, Joana M. A1 - Ripepi, Vincenzo A1 - Subramanian, Smitha A1 - van Loon, Jacco Th T1 - The VMC survey – XLVI. Stellar proper motions in the centre of the Large Magellanic Cloud JF - Monthly notices of the Royal Astronomical Society N2 - We present proper motion (PM) measurements within the central region of the Large Magellanic Cloud (LMC), using near-infrared data from the VISTA survey of the Magellanic Cloud system (VMC). This work encompasses 18 VMC tiles covering a total sky area of similar to 28 deg(2). We computed absolute stellar PMs from multiepoch observations in the K-s filter over time baselines between similar to 12 and 47 months. Our final catalogue contains similar to 6322 000 likely LMC member stars with derived PMs. We employed a simple flat-rotating disc model to analyse and interpret the PM data. We found a stellar centre of rotation (alpha(0) = 79.95 degrees(+0.22)(-0.23), delta(0) = -69.31 degrees(+0.12)(-0.11)) that is in agreement with that resulting from Hubble Space Telescope data. The inferred viewing angles of the LMC disc (i = 33.5 degrees(+1.2)(-1.3), Theta = 129.8 degrees(+1.9)(-1.9)) are in good agreement with values from the literature but suggest a higher inclination of the central parts of the LMC. Our data confirm a higher rotation amplitude for the young (less than or similar to 0.5 Gyr) stars compared to the intermediate-age/old (greater than or similar to 1 Gyr) population, which can be explained by asymmetric drift. We constructed spatially resolved velocity maps of the intermediate-age/old and young populations. Intermediate-age/old stars follow elongated orbits parallel to the bar's major axis, providing first observational evidence for x(1) orbits within the LMC bar. In the innermost regions, the motions show more chaotic structures. Young stars show motions along a central filamentary bar structure. KW - surveys KW - proper motion KW - stars: kinematics and dynamics KW - galaxies: individual: LMC KW - Magellanic Clouds Y1 - 2022 U6 - https://doi.org/10.1093/mnras/stac712 SN - 0035-8711 SN - 1365-2966 VL - 512 IS - 4 SP - 5423 EP - 5439 PB - Oxford University Press CY - Oxford ER - TY - JOUR A1 - Oskinova, Lida A1 - Sun, W. A1 - Evans, C. J. A1 - Henault-Brunet, V. A1 - Chu, Y.-H. A1 - Gallagher, J. S. A1 - Guerrero, Martín A. A1 - Gruendl, R. A. A1 - Güdel, M. A1 - Silich, S. A1 - Chen, Y. A1 - Naze, Y. A1 - Hainich, Rainer A1 - Reyes-Iturbide, J. T1 - Discovery of x-ray emission from young suns in the small magellanic cloud JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We report the discovery of extended X-ray emission within the young star cluster NGC 602a in the Wing of the Small Magellanic Cloud (SMC) based on observations obtained with the Chandra X-Ray Observatory. X-ray emission is detected from the cluster core area with the highest stellar density and from a dusty ridge surrounding the H II region. We use a census of massive stars in the cluster to demonstrate that a cluster wind or wind-blown bubble is unlikely to provide a significant contribution to the X-ray emission detected from the central area of the cluster. We therefore suggest that X-ray emission at the cluster core originates from an ensemble of low-and solar-mass pre-main-sequence (PMS) stars, each of which would be too weak in X-rays to be detected individually. We attribute the X-ray emission from the dusty ridge to the embedded tight cluster of the newborn stars known in this area from infrared studies. Assuming that the levels of X-ray activity in young stars in the low-metallicity environment of NGC 602a are comparable to their Galactic counterparts, then the detected spatial distribution, spectral properties, and level of X-ray emission are largely consistent with those expected from low-and solar-mass PMS stars and young stellar objects (YSOs). This is the first discovery of X-ray emission attributable to PMS stars and YSOs in the SMC, which suggests that the accretion and dynamo processes in young, low-mass objects in the SMC resemble those in the Galaxy. KW - Magellanic Clouds KW - ISM: bubbles KW - H II regions KW - stars: winds, outflows KW - stars: pre-main sequence KW - X-rays: stars Y1 - 2013 U6 - https://doi.org/10.1088/0004-637X/765/1/73 SN - 0004-637X VL - 765 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Piatti, Andres E. A1 - de Grijs, Richard A1 - Ripepi, Vincenzo A1 - Ivanov, Valentin D. A1 - Cioni, Maria-Rosa L. A1 - Marconi, Marcella A1 - Rubele, Stefano A1 - Bekki, Kenji A1 - For, Bi-Qing T1 - The VMC survey - XVI. Spatial variation of the cluster formation activity in the innermost regions of the Large Magellanic Cloud JF - Monthly notices of the Royal Astronomical Society KW - techniques: photometric KW - galaxies: individual: LMC KW - Magellanic Clouds Y1 - 2015 U6 - https://doi.org/10.1093/mnras/stv2054 SN - 0035-8711 SN - 1365-2966 VL - 454 IS - 1 SP - 839 EP - 848 PB - Oxford Univ. Press CY - Oxford ER -