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Title: Chemical Composition of Young Stars in the Leading Arm of the Magellanic System

Abstract

Chemical abundances of eight O- and B-type stars are determined from high-resolution spectra obtained with the MIKE instrument on the Magellan 6.5 m Clay telescope. The sample is selected from 42 candidates for membership in the Leading Arm (LA) of the Magellanic System. Stellar parameters are measured by two independent grids of model atmospheres and analysis procedures, confirming the consistency of the stellar parameter results. Abundances of seven elements (He, C, N, O, Mg, Si, and S) are determined for the stars, as are their radial velocities and estimates of distances and ages. Among the seven B-type stars analyzed, the five that have radial velocities compatible with membership of the LA have an average [Mg/H] of −0.42 ± 0.16, significantly lower than the average of the remaining two, [Mg/H] = −0.07±0.06, which are kinematical members of the Galactic disk. Among the five LA members, four have individual [Mg/H] abundance compatible with that in the LMC. Within errors, we cannot exclude the possibility that one of these stars has an [Mg/H] consistent with the more metal-poor, SMC-like material. The remaining fifth star has an [Mg/H] close to Milky Way values. Distances to the LA members indicate that they are at themore » edge of the Galactic disk, while ages are of the order of ∼50–70 Myr, lower than the dynamical age of the LA, suggesting a single star-forming episode in the LA. V {sub LSR} of the LA members decreases with decreasing Magellanic longitude, confirming the results of previous LA gas studies.« less

Authors:
;  [1];  [2];  [3];  [4];  [5];  [6]; ;  [7]
  1. Key Lab. of Optical Astronomy, National Astronomical Observatories, CAS, 20A Datun Road, Chaoyang District, 100012 Beijing (China)
  2. Instituto de Astronomía, Universidad Católica del Norte, Av. Angomos 0610, Antofagasta (Chile)
  3. Department of Physics, Southern Connecticut State University, 501 Crescent Street, New Haven, CT 06515 (United States)
  4. Departamento de Astronomia Universidad de Chile, Camino El Observatorio #1515, Las Condes, Santiago (Chile)
  5. 14 Dunn Rd, Hamden, Connecticut, CT 06518 (United States)
  6. Institute of Physics, Southern Federal University, Stachki st/194, 344090, Rostov-on-Don (Russian Federation)
  7. Centro de Investigaciones de Astronomiá, Apartado Postal 264, Mérida 5101-A (Venezuela, Bolivarian Republic of)
Publication Date:
OSTI Identifier:
22663961
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 835; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; CHEMICAL COMPOSITION; CONCENTRATION RATIO; DISTANCE; GRIDS; METALS; MILKY WAY; RADIAL VELOCITY; RESOLUTION; SPECTRA; STARS; TELESCOPES

Citation Formats

Zhang, Lan, Zhao, Gang, Moni Bidin, Christian, Casetti-Dinescu, Dana I., Méndez, Réne A., Girard, Terrence M., Korchagin, Vladimir I., Vieira, Katherine, and Van Altena, William F. Chemical Composition of Young Stars in the Leading Arm of the Magellanic System. United States: N. p., 2017. Web. doi:10.3847/1538-4357/835/2/285.
Zhang, Lan, Zhao, Gang, Moni Bidin, Christian, Casetti-Dinescu, Dana I., Méndez, Réne A., Girard, Terrence M., Korchagin, Vladimir I., Vieira, Katherine, & Van Altena, William F. Chemical Composition of Young Stars in the Leading Arm of the Magellanic System. United States. doi:10.3847/1538-4357/835/2/285.
Zhang, Lan, Zhao, Gang, Moni Bidin, Christian, Casetti-Dinescu, Dana I., Méndez, Réne A., Girard, Terrence M., Korchagin, Vladimir I., Vieira, Katherine, and Van Altena, William F. Wed . "Chemical Composition of Young Stars in the Leading Arm of the Magellanic System". United States. doi:10.3847/1538-4357/835/2/285.
@article{osti_22663961,
title = {Chemical Composition of Young Stars in the Leading Arm of the Magellanic System},
author = {Zhang, Lan and Zhao, Gang and Moni Bidin, Christian and Casetti-Dinescu, Dana I. and Méndez, Réne A. and Girard, Terrence M. and Korchagin, Vladimir I. and Vieira, Katherine and Van Altena, William F.},
abstractNote = {Chemical abundances of eight O- and B-type stars are determined from high-resolution spectra obtained with the MIKE instrument on the Magellan 6.5 m Clay telescope. The sample is selected from 42 candidates for membership in the Leading Arm (LA) of the Magellanic System. Stellar parameters are measured by two independent grids of model atmospheres and analysis procedures, confirming the consistency of the stellar parameter results. Abundances of seven elements (He, C, N, O, Mg, Si, and S) are determined for the stars, as are their radial velocities and estimates of distances and ages. Among the seven B-type stars analyzed, the five that have radial velocities compatible with membership of the LA have an average [Mg/H] of −0.42 ± 0.16, significantly lower than the average of the remaining two, [Mg/H] = −0.07±0.06, which are kinematical members of the Galactic disk. Among the five LA members, four have individual [Mg/H] abundance compatible with that in the LMC. Within errors, we cannot exclude the possibility that one of these stars has an [Mg/H] consistent with the more metal-poor, SMC-like material. The remaining fifth star has an [Mg/H] close to Milky Way values. Distances to the LA members indicate that they are at the edge of the Galactic disk, while ages are of the order of ∼50–70 Myr, lower than the dynamical age of the LA, suggesting a single star-forming episode in the LA. V {sub LSR} of the LA members decreases with decreasing Magellanic longitude, confirming the results of previous LA gas studies.},
doi = {10.3847/1538-4357/835/2/285},
journal = {Astrophysical Journal},
number = 2,
volume = 835,
place = {United States},
year = {Wed Feb 01 00:00:00 EST 2017},
month = {Wed Feb 01 00:00:00 EST 2017}
}
  • We present a catalog of high-velocity clouds in the region of the Magellanic Leading Arm. The catalog is based on neutral hydrogen (H I) observations from the Parkes Galactic All-Sky Survey. Excellent spectral resolution allows clouds with narrow-line components to be resolved. The total number of detected clouds is 419. We describe the method of cataloging and present the basic parameters of the clouds. We discuss the general distribution of the high-velocity clouds and classify the clouds based on their morphological type. The presence of a significant number of head-tail clouds and their distribution in the region is discussed inmore » the context of Magellanic System simulations. We suggest that ram-pressure stripping is a more important factor than tidal forces for the morphology and formation of the Magellanic Leading Arm and that different environmental conditions might explain the morphological difference between the Magellanic Leading Arm and Magellanic Stream. We also discuss a newly identified population of clouds that forms the LA IV and a new diffuse bridge-like feature connecting the LA II and III complexes.« less
  • Strongly interacting galaxies undergo a short-lived but dramatic phase of evolution characterized by enhanced star formation, tidal tails, bridges, and other morphological peculiarities. The nearest example of a pair of interacting galaxies is the Magellanic Clouds, whose dynamical interaction produced the gaseous features known as the Magellanic Stream trailing the pair's orbit about the Galaxy, the bridge between the Clouds, and the leading arm (LA), a wide and irregular feature leading the orbit. Young, newly formed stars in the bridge are known to exist, giving witness to the recent interaction between the Clouds. However, the interaction of the Clouds withmore » the Milky Way (MW) is less well understood. In particular, the LA must have a tidal origin; however, no purely gravitational model is able to reproduce its morphology and kinematics. A hydrodynamical interaction with the gaseous hot halo and disk of the Galaxy is plausible as suggested by some models and supporting neutral hydrogen (H I) observations. Here we show for the first time that young, recently formed stars exist in the LA, indicating that the interaction between the Clouds and our Galaxy is strong enough to trigger star formation in certain regions of the LA—regions in the outskirts of the MW disk (R ∼ 18 kpc), far away from the Clouds and the bridge.« less