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A Predicted Correlation Between Age Gradient and Star Formation History in FIRE Dwarf Galaxies

Graus, Andrew S. and Bullock, James S. and Fitts, Alex and Cooper, Michael C. and Boylan-Kolchin, Michael and Weisz, Daniel R. and Wetzel, Andrew and Feldmann, Robert and Faucher-Giguère, Claude-André and Quataert, Eliot and Hopkins, Philip F. and Kereš, Dušan (2019) A Predicted Correlation Between Age Gradient and Star Formation History in FIRE Dwarf Galaxies. . (Unpublished) http://resolver.caltech.edu/CaltechAUTHORS:20190206-105702036

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Abstract

We explore the radial variation of star formation histories in dwarf galaxies simulated with Feedback In Realistic Environments (FIRE) physics. The sample contains 9 low-mass field dwarfs with M_ star = 10^5 - 10^7 M_sun from previous FIRE results, and a new suite of 17 higher mass field dwarfs with M_star = 10^7 - 10^9 M_sun introduced here. We find that age gradients are common in our dwarfs, with older stars dominant at large radii. The strength of the gradient correlates with overall galaxy age such that earlier star formation produces a more pronounced gradient. The relation between formation time and strength of the gradient is driven by both mergers and star-formation feedback. Mergers can both steepen and flatten the age gradient depending on the timing of the merger and star formation history of the merging galaxy. In galaxies without significant mergers, early feedback pushes stars to the outskirts at early times. Interestingly, among galaxies without mergers, those with large dark matter cores have flatter age gradients because these galaxies have more late-time feedback. If real galaxies have age gradients as we predict, stellar population studies that rely on sampling a limited fraction of a galaxy can give a biased view of its global star formation history. We show that central fields can be biased young by a few Gyrs while outer fields are biased old. Fields positioned near the 2D half-light radius will provide the least biased measure of a dwarf galaxy's global star formation history.


Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription
http://arxiv.org/abs/1901.05487arXivDiscussion Paper
ORCID:
AuthorORCID
Boylan-Kolchin, Michael0000-0002-9604-343X
Weisz, Daniel R.0000-0002-6442-6030
Wetzel, Andrew0000-0003-0603-8942
Feldmann, Robert0000-0002-1109-1919
Faucher-Giguère, Claude-André0000-0002-4900-6628
Quataert, Eliot0000-0001-9185-5044
Hopkins, Philip F.0000-0003-3729-1684
Kereš, Dušan0000-0002-1666-7067
Additional Information:ASG and JSB were supported by NSF AST-1518291, HST-AR-14282, and HST-AR-13888. ASG is further supported by the McDonald Observatory at the University of Texas at Austin, through the Harlan J. Smith fellowship. MBK and AF acknowledge support from NSF grant AST-1517226. MBK also acknowledges support from NSF CAREER grant AST-1752913 and from NASA grants NNX17AG29G and HST-AR-13888, HST-AR-13896, HST-AR-14282, HST-AR-14554, HST-AR-15006, HST-GO-12914, and HST-GO-14191 from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555. MCC was supported by NSF AST-1815475. DRW is supported by a fellowship from the Alfred P. Sloan Foundation. He also acknowledges support from the Alexander von Humboldt Foundation and from HST-GO-13768, HST-GO-15476, HST-AR-13888, HST-AR-13925, HST-AR-15006, and JWST-ERS-01334. AW was supported by NASA through ATP grant 80NSSC18K1097 and grants HST-GO-14734 and HST-AR-15057 from STScI. RF acknowledges support from the Swiss National Science Foundation (grant no. 157591). CAFG was supported by NSF through grants AST-1517491, AST-1715216, and CAREER award AST-1652522, by NASA through grants NNX15AB22G and 17-ATP17-0067, and by a Cottrell Scholar Award from the Research Corporation for Science Advancement. This work used computational resources of the University of Texas at Austin and the Texas Advanced Computing Center (TACC; http://www.tacc.utexas.edu), the NASA Advanced Supercomputing (NAS) Division and the NASA Center for Climate Simulation (NCCS), and the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant number OCI-1053575.
Group:TAPIR
Funders:
Funding AgencyGrant Number
NSFAST-1518291
NASAHST-AR-14282
NASAHST-AR-13888
McDonald ObservatoryUNSPECIFIED
NSFAST-1517226
NSFAST-1752913
NASANNX17AG29G
NASAHST-AR-13896
NASAHST-AR-14282
NASAHST-AR-14554
NASAHST-AR-15006
NASAHST-GO-12914
NASAHST-GO-14191
NASANAS5-26555
NSFAST-1815475
Alfred P. Sloan FoundationUNSPECIFIED
Alexander von Humboldt FoundationUNSPECIFIED
NASAHST-GO-13768
NASAHST-GO-15476
NASAHST-AR-13925
NASAHST-AR-15006
NASAJWST-ERS-01334
NASA80NSSC18K1097
NASAHST-GO-14734
NASAHST-AR-15057
Swiss National Science Foundation (SNSF)157591
NSFAST-1517491
NSFAST-1715216
NSFAST-1652522
NASANNX15AB22G
NASA17-ATP17-0067
Cottrell Scholar of Research CorporationUNSPECIFIED
NSFOCI-1053575
Subject Keywords:galaxies: dwarf - galaxies: formation - galaxies: Local Group - cosmology: theory
Record Number:CaltechAUTHORS:20190206-105702036
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20190206-105702036
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92736
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:06 Feb 2019 20:10
Last Modified:06 Feb 2019 20:10

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