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El-Badry K, Bland-Hawthorn J, Wetzel A, Quataert E, Weisz DR, Boylan-Kolchin M, Hopkins PF, Faucher-Giguère CA, Kereš D, Garrison-Kimmel S. Where are the most ancient stars in the Milky Way? Mon Not R Astron Soc 2018; 480:652-668. [PMID: 30581239 PMCID: PMC6301095 DOI: 10.1093/mnras/sty1864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The oldest stars in the Milky Way (MW) bear imprints of the Galaxy's early assembly history. We use FIRE cosmological zoom-in simulations of three MW-mass disc galaxies to study the spatial distribution, chemistry, and kinematics of the oldest surviving stars (z form ≳ 5) in MW-like galaxies. We predict the oldest stars to be less centrally concentrated at z = 0 than stars formed at later times as a result of two processes. First, the majority of the oldest stars are not formed in situ but are accreted during hierarchical assembly. These ex situ stars are deposited on dispersion-supported, halo-like orbits but dominate over old stars formed in situ in the solar neighbourhood, and in some simulations, even in the galactic centre. Secondly, old stars formed in situ are driven outwards by bursty star formation and energetic feedback processes that create a time-varying gravitational potential at z ≳ 2, similar to the process that creates dark matter cores and expands stellar orbits in bursty dwarf galaxies. The total fraction of stars that are ancient is more than an order of magnitude higher for sight lines away from the bulge and inner halo than for inward-looking sight lines. Although the task of identifying specific stars as ancient remains challenging, we anticipate that million-star spectral surveys and photometric surveys targeting metal-poor stars already include hundreds of stars formed before z = 5. We predict most of these targets to have higher metallicity (-3 < [Fe/H] < -2) than the most extreme metal-poor stars.
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Affiliation(s)
- Kareem El-Badry
- Department of Astronomy and Theoretical Astrophysics Center, University of California Berkeley, Berkeley, CA 94720, USA
| | - Joss Bland-Hawthorn
- Miller Institute, University of California Berkeley, Berkeley, CA 94720, USA
- Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO-3D), Sydney, NSW 2006, Australia
- Sydney Institute for Astronomy, School of Physics, University of Sydney, Sydney, NSW 2006, Australia
| | - Andrew Wetzel
- Department of Physics, University of California, Davis, CA 95616, USA
| | - Eliot Quataert
- Department of Astronomy and Theoretical Astrophysics Center, University of California Berkeley, Berkeley, CA 94720, USA
| | - Daniel R. Weisz
- Department of Astronomy and Theoretical Astrophysics Center, University of California Berkeley, Berkeley, CA 94720, USA
| | | | - Philip F. Hopkins
- TAPIR, Mailcode 350-17, California Institute of Technology, Pasadena, CA 91125, USA
| | | | - Dušan Kereš
- Department of Physics, Center for Astrophysics and Space Sciences, University of California at San Diego, La Jolla, CA 92093, USA
| | - Shea Garrison-Kimmel
- TAPIR, Mailcode 350-17, California Institute of Technology, Pasadena, CA 91125, USA
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Zick TO, Weisz DR, Boylan-Kolchin M. Globular clusters in high-redshift dwarf galaxies: a case study from the Local Group. Mon Not R Astron Soc 2018; 477:480-490. [PMID: 30598557 PMCID: PMC6310024 DOI: 10.1093/mnras/sty662] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We present the reconstructed evolution of rest-frame ultraviolet (UV) luminosities of the most massive Milky Way dwarf spheroidal satellite galaxy, Fornax, and its five globular clusters (GCs) across redshift, based on analysis of the stellar fossil record and stellar population synthesis modelling. We find that (1) Fornax's (proto-)GCs can generate 10-100 times more UV flux than the field population, despite comprising <~ 5 per cent of the stellar mass at the relevant redshifts; (2) due to their respective surface brightnesses, it is more likely that faint, compact sources in the Hubble Frontier Fields (HFFs) are GCs hosted by faint galaxies, than faint galaxies themselves. This may significantly complicate the construction of a galaxy UV luminosity function at z > 3. (3) GC formation can introduce order-of-magnitude errors in abundance matching. We also find that some compact HFF objects are consistent with the reconstructed properties of Fornax's GCs at the same redshifts (e.g. surface brightness, star formation rate), suggesting we may have already detected proto-GCs in the early Universe. Finally, we discuss the prospects for improving the connections between local GCs and proto-GCs detected in the early Universe.
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Affiliation(s)
- Tom O. Zick
- Department of Astronomy, University of California Berkeley, Berkeley, CA 94720, USA
- Lawrence Livermore National Laboratory, PO Box 808 L-210, Livermore, CA 94551, USA
| | - Daniel R. Weisz
- Department of Astronomy, University of California Berkeley, Berkeley, CA 94720, USA
| | - Michael Boylan-Kolchin
- Department of Astronomy, The University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712, USA
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El-Badry K, Bradford J, Quataert E, Geha M, Boylan-Kolchin M, Weisz DR, Wetzel A, Hopkins PF, Chan TK, Fitts A, Kereš D, Faucher-Giguére CA. Gas kinematics in FIRE simulated galaxies compared to spatially unresolved HI observations. Mon Not R Astron Soc 2018; 477:1536-1548. [PMID: 30713356 PMCID: PMC6350816 DOI: 10.1093/mnras/sty730] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The shape of a galaxy's spatially unresolved, globally integrated 21-cm emission line depends on its internal gas kinematics: galaxies with rotationally supported gas discs produce double-horned profiles with steep wings, while galaxies with dispersion-supported gas produce Gaussian-like profiles with sloped wings. Using mock observations of simulated galaxies from the FIRE project, we show that one can therefore constrain a galaxy's gas kinematics from its unresolved 21-cm line profile. In particular, we find that the kurtosis of the 21-cm line increases with decreasing V/σ and that this trend is robust across a wide range of masses, signal-to-noise ratios, and inclinations. We then quantify the shapes of 21-cm line profiles from a morphologically unbiased sample of ~2000 low-redshift, HI-detected galaxies with Mstar = 107-11 M☉ and compare to the simulated galaxies. At Mstar ≳ 1010 M☉, both the observed and simulated galaxies produce double-horned profiles with low kurtosis and steep wings, consistent with rotationally supported discs. Both the observed and simulated line profiles become more Gaussian like (higher kurtosis and less-steep wings) at lower masses, indicating increased dispersion support. However, the simulated galaxies transition from rotational to dispersion support more strongly: at Mstar 108-10 M, most of the simulations produce more Gaussian-like profiles than typical observed galaxies with similar mass, indicating that gas in the low-mass simulated galaxies is, on average, overly dispersion supported. Most of the lower-mass-simulated galaxies also have somewhat lower gas fractions than the median of the observed population. The simulations nevertheless reproduce the observed line-width baryonic Tully-Fisher relation, which is insensitive to rotational versus dispersion support.
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Affiliation(s)
- Kareem El-Badry
- Department of Astronomy and Theoretical Astrophysics Center, University of California Berkeley, Berkeley, CA 94720, USA
| | - Jeremy Bradford
- Department of Astronomy, Yale University, New Haven, CT 06520, USA
| | - Eliot Quataert
- Department of Astronomy and Theoretical Astrophysics Center, University of California Berkeley, Berkeley, CA 94720, USA
| | - Marla Geha
- Department of Astronomy, Yale University, New Haven, CT 06520, USA
| | | | - Daniel R. Weisz
- Department of Astronomy and Theoretical Astrophysics Center, University of California Berkeley, Berkeley, CA 94720, USA
| | - Andrew Wetzel
- Department of Physics, University of California, Davis, CA 95616, USA
| | - Philip F. Hopkins
- TAPIR, Mailcode 350-17, California Institute of Technology, Pasadena, CA 91125, USA
| | - T. K. Chan
- Department of Physics, Center for Astrophysics and Space Sciences, University of California at San Diego, La Jolla, CA 92093, USA
| | - Alex Fitts
- Department of Astronomy, The University of Texas at Austin, Austin, TX 78712, USA
| | - Dušan Kereš
- Department of Physics, Center for Astrophysics and Space Sciences, University of California at San Diego, La Jolla, CA 92093, USA
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Johnson LC, Seth AC, Dalcanton JJ, Wallace ML, Simpson RJ, Lintott CJ, Kapadia A, Skillman ED, Caldwell N, Fouesneau M, Weisz DR, Williams BF, Beerman LC, Gouliermis DA, Sarajedini A. PHAT STELLAR CLUSTER SURVEY. II. ANDROMEDA PROJECT CLUSTER CATALOG. ACTA ACUST UNITED AC 2015. [DOI: 10.1088/0004-637x/802/2/127] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Jennings ZG, Williams BF, Murphy JW, Dalcanton JJ, Gilbert KM, Dolphin AE, Weisz DR, Fouesneau M. THE SUPERNOVA PROGENITOR MASS DISTRIBUTIONS OF M31 AND M33: FURTHER EVIDENCE FOR AN UPPER MASS LIMIT. ACTA ACUST UNITED AC 2014. [DOI: 10.1088/0004-637x/795/2/170] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Weisz DR, Johnson BD, Conroy C. THE VERY FAINT END OF THE UV LUMINOSITY FUNCTION OVER COSMIC TIME: CONSTRAINTS FROM THE LOCAL GROUP FOSSIL RECORD. ACTA ACUST UNITED AC 2014. [DOI: 10.1088/2041-8205/794/1/l3] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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