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The Lazy Giants : APOGEE Abundances Reveal Low Star Formation Efficiencies in the Magellanic Clouds

Nidever, David L. ; Hasselquist, Sten ; Hayes, Christian R. ; Hawkins, Keith ; Povick, Joshua ; Majewski, Steven R. ; Smith, Verne V. ; Anguiano, Borja ; Stringfellow, Guy S. and Sobeck, Jennifer S. , et al. (2020) In Astrophysical Journal 895(2).
Abstract

We report the first APOGEE metallicities and α-element abundances measured for 3600 red giant stars spanning a large radial range of both the Large (LMC) and Small Magellanic Clouds, the largest Milky Way (MW) dwarf galaxies. Our sample is an order of magnitude larger than that of previous studies and extends to much larger radial distances. These are the first results presented that make use of the newly installed southern APOGEE instrument on the du Pont telescope at Las Campanas Observatory. Our unbiased sample of the LMC spans a large range in metallicity, from [Fe/H] = -0.2 to very metal-poor stars with [Fe/H] ≈ -2.5, the most metal-poor Magellanic Cloud (MC) stars detected to date. The LMC [α/Fe]-[Fe/H] distribution is very flat... (More)

We report the first APOGEE metallicities and α-element abundances measured for 3600 red giant stars spanning a large radial range of both the Large (LMC) and Small Magellanic Clouds, the largest Milky Way (MW) dwarf galaxies. Our sample is an order of magnitude larger than that of previous studies and extends to much larger radial distances. These are the first results presented that make use of the newly installed southern APOGEE instrument on the du Pont telescope at Las Campanas Observatory. Our unbiased sample of the LMC spans a large range in metallicity, from [Fe/H] = -0.2 to very metal-poor stars with [Fe/H] ≈ -2.5, the most metal-poor Magellanic Cloud (MC) stars detected to date. The LMC [α/Fe]-[Fe/H] distribution is very flat over a large metallicity range but rises by ∼0.1 dex at -1.0 < [Fe/H] ≲ -0.5. We interpret this as a sign of the known recent increase in MC star formation activity and are able to reproduce the pattern with a chemical evolution model that includes a recent "starburst." At the metal-poor end, we capture the increase of [α/Fe] with decreasing [Fe/H] and constrain the "α-knee" to [Fe/H] ≲ -2.2 in both MCs, implying a low star formation efficiency of ∼0.01 Gyr-1. The MC knees are more metal-poor than those of less massive MW dwarf galaxies such as Fornax, Sculptor, or Sagittarius. One possible interpretation is that the MCs formed in a lower-density environment than the MW, a hypothesis that is consistent with the paradigm that the MCs fell into the MW's gravitational potential only recently.

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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Astrophysical Journal
volume
895
issue
2
article number
88
publisher
American Astronomical Society
external identifiers
  • scopus:85086259241
ISSN
0004-637X
DOI
10.3847/1538-4357/ab7305
language
English
LU publication?
yes
id
d6dcd59b-81fa-471b-8b38-5120ad16c177
date added to LUP
2020-12-18 13:20:31
date last changed
2024-04-17 21:25:12
@article{d6dcd59b-81fa-471b-8b38-5120ad16c177,
  abstract     = {{<p>We report the first APOGEE metallicities and α-element abundances measured for 3600 red giant stars spanning a large radial range of both the Large (LMC) and Small Magellanic Clouds, the largest Milky Way (MW) dwarf galaxies. Our sample is an order of magnitude larger than that of previous studies and extends to much larger radial distances. These are the first results presented that make use of the newly installed southern APOGEE instrument on the du Pont telescope at Las Campanas Observatory. Our unbiased sample of the LMC spans a large range in metallicity, from [Fe/H] = -0.2 to very metal-poor stars with [Fe/H] ≈ -2.5, the most metal-poor Magellanic Cloud (MC) stars detected to date. The LMC [α/Fe]-[Fe/H] distribution is very flat over a large metallicity range but rises by ∼0.1 dex at -1.0 &lt; [Fe/H] ≲ -0.5. We interpret this as a sign of the known recent increase in MC star formation activity and are able to reproduce the pattern with a chemical evolution model that includes a recent "starburst." At the metal-poor end, we capture the increase of [α/Fe] with decreasing [Fe/H] and constrain the "α-knee" to [Fe/H] ≲ -2.2 in both MCs, implying a low star formation efficiency of ∼0.01 Gyr<sup>-1</sup>. The MC knees are more metal-poor than those of less massive MW dwarf galaxies such as Fornax, Sculptor, or Sagittarius. One possible interpretation is that the MCs formed in a lower-density environment than the MW, a hypothesis that is consistent with the paradigm that the MCs fell into the MW's gravitational potential only recently.</p>}},
  author       = {{Nidever, David L. and Hasselquist, Sten and Hayes, Christian R. and Hawkins, Keith and Povick, Joshua and Majewski, Steven R. and Smith, Verne V. and Anguiano, Borja and Stringfellow, Guy S. and Sobeck, Jennifer S. and Cunha, Katia and Beers, Timothy C. and Bestenlehner, Joachim M. and Cohen, Roger E. and Garcia-Hernandez, D. A. and Jönsson, Henrik and Nitschelm, Christian and Shetrone, Matthew and Lacerna, Ivan and Allende Prieto, Carlos and Beaton, Rachael L. and Dell'Agli, Flavia and Fernández-Trincado, José G. and Feuillet, Diane and Gallart, Carme and Hearty, Fred R. and Holtzman, Jon and Manchado, Arturo and Mu&ntilde;oz, Ricardo R. and O'Connell, Robert and Rosado, Margarita}},
  issn         = {{0004-637X}},
  language     = {{eng}},
  number       = {{2}},
  publisher    = {{American Astronomical Society}},
  series       = {{Astrophysical Journal}},
  title        = {{The Lazy Giants : APOGEE Abundances Reveal Low Star Formation Efficiencies in the Magellanic Clouds}},
  url          = {{http://dx.doi.org/10.3847/1538-4357/ab7305}},
  doi          = {{10.3847/1538-4357/ab7305}},
  volume       = {{895}},
  year         = {{2020}},
}