Connecting the First Galaxies with Ultrafaint Dwarfs in the Local Group: Chemical Signatures of Population III Stars
AffiliationUniv Arizona, Dept Astron
MetadataShow full item record
PublisherIOP PUBLISHING LTD
CitationConnecting the First Galaxies with Ultrafaint Dwarfs in the Local Group: Chemical Signatures of Population III Stars 2017, 848 (2):85 The Astrophysical Journal
JournalThe Astrophysical Journal
Rights© 2017. The American Astronomical Society. All rights reserved.
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at firstname.lastname@example.org.
AbstractWe investigate the star formation history (SFH) and chemical evolution of isolated analogs of Local Group (LG) ultrafaint dwarf galaxies (UFDs; stellar mass range of 10(2)M(circle dot) < M-*< 10(5) M-circle dot) and gas-rich, low-mass dwarfs (Leo P analogs; stellar mass range of 10(5)M(circle dot) < M-*< 10(6) M-circle dot). We perform a suite of cosmological hydrodynamic zoom-in simulations to follow their evolution from the era of the first generation of stars down to z=0. We confirm that reionization, combined with supernova (SN) feedback, is primarily responsible for the truncated star formation in UFDs. Specifically, halos with a virial mass of M-vir less than or similar to 2 x 10(9) M-circle dot form greater than or similar to 90% of stars prior to reionization. Our work further demonstrates the importance of Population. III stars, with their intrinsically high [C/Fe] yields and the associated external metal enrichment, in producing low-metallicity stars ([Fe/H] less than or similar to -4) and carbon-enhanced metal-poor (CEMP) stars. We find that UFDs are composite systems, assembled from multiple progenitor halos, some of which hosted only Population. II stars formed in environments externally enriched by SNe in neighboring halos, naturally producing extremely low metallicity Population II stars. We illustrate how the simulated chemical enrichment may be used to constrain the SFHs of true observed UFDs. We find that Leo P analogs can form in halos with M-vir similar to 4 x 10(9) M-circle dot 9 (z = 0). Such systems are less affected byreionization and continue to form stars until z = 0, causing higher-metallicity tails. Finally, we predict the existence of extremely low metallicity stars in LG UFD galaxies that preserve the pure chemical signatures of Population III nucleosynthesis.
VersionFinal published version
SponsorsNational Science Foundation ; NSF [AST-1413501]
Showing items related by title, author, creator and subject.
The Apache Point Observatory Galactic Evolution Experiment (APOGEE)Majewski, Steven R.; Schiavon, Ricardo P.; Frinchaboy, P. M.; Prieto, Carlos Allende; Barkhouser, Robert; Bizyaev, Dmitry; Blank, Basil; Brunner, Sophia; Burton, Adam; Carrera, R.; et al. (IOP PUBLISHING LTD, 2017-08-14)The Apache Point Observatory Galactic Evolution Experiment (APOGEE), one of the programs in the Sloan Digital Sky Survey III (SDSS-III), has now completed its systematic, homogeneous spectroscopic survey sampling all major populations of the Milky Way. After a three-year observing campaign on the Sloan 2.5 m Telescope, APOGEE has collected a half million high-resolution (R similar to 22,500), high signal-to-noise ratio (>100), infrared (1.51-1.70 mu m) spectra for 146,000 stars, with time series information via repeat visits to most of these stars. This paper describes the motivations for the survey and its overall design-hardware, field placement, target selection, operations-and gives an overview of these aspects as well as the data reduction, analysis, and products. An index is also given to the complement of technical papers that describe various critical survey components in detail. Finally, we discuss the achieved survey performance and illustrate the variety of potential uses of the data products by way of a number of science demonstrations, which span from time series analysis of stellar spectral variations and radial velocity variations from stellar companions, to spatial maps of kinematics, metallicity, and abundance patterns across the Galaxy and as a function of age, to new views of the interstellar medium, the chemistry of star clusters, and the discovery of rare stellar species. As part of SDSS-III Data Release 12 and later releases, all of the APOGEE data products are publicly available.
The Faint End of the Centaurus A Satellite Luminosity FunctionCrnojević, D.; Sand, D. J.; Bennet, P.; Pasetto, S.; Spekkens, K.; Caldwell, N.; Guhathakurta, P.; McLeod, B.; Seth, A.; Simon, J. D.; et al. (IOP PUBLISHING LTD, 2019-02-10)The Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS) is constructing a wide-field map of the resolved stellar populations in the extended halos of these two nearby, prominent galaxies. We present new Magellan/Megacam imaging of a similar to 3 deg(2) area around Centaurus A (Cen A), which filled in much of our coverage to its south, leaving a nearly complete halo map out to a projected radius of similar to 150 kpc and allowing us to identify two new resolved dwarf galaxies. We have additionally obtained deep Hubble Space Telescope (HST) optical imaging of 11 out of the 13 candidate dwarf galaxies identified around Cen A and presented in Crnojevic et al. 2016a: seven are confirmed to be satellites of Cen A, while four are found to be background galaxies. We derive accurate distances, structural parameters, luminosities, and photometric metallicities for the seven candidates confirmed by our HST/ACS imaging. We further study the stellar population along the similar to 60 kpc long (in projection) stream associated with Dw3, which likely had an initial brightness of M-V similar to -15 and shows evidence for a metallicity gradient along its length. Using the total sample of 11 dwarf satellites discovered by the PISCeS survey, as well as 13 brighter previously known satellites of Cen A, we present a revised galaxy luminosity function for the Cen A group down to a limiting magnitude of M-V similar to -8, which has a slope of -1.14 +/- 0.17, comparable to that seen in the Local Group and in other nearby groups of galaxies.
STELLAR MASS–GAS-PHASE METALLICITY RELATION AT 0.5 ≤ z ≤ 0.7: A POWER LAW WITH INCREASING SCATTER TOWARD THE LOW-MASS REGIMEGuo, Yicheng; Koo, David C.; Lu, Yu; Forbes, John C.; Rafelski, Marc; Trump, Jonathan R.; Amorín, Ricardo; Barro, Guillermo; Davé, Romeel; Faber, S. M.; et al. (IOP PUBLISHING LTD, 2016-05-11)We present the stellar mass (M-*)-gas-phase metallicity relation (MZR) and its scatter at intermediate redshifts (0.5 <= z <= 0.7) for 1381 field galaxies collected from deep spectroscopic surveys. The star formation rate (SFR) and color at a given M-* of this magnitude-limited (R less than or similar to 24 AB) sample are representative of normal star-forming galaxies. For masses below 10(9) M-circle dot, our sample of 237 galaxies is similar to 10 times larger than those in previous studies beyond the local universe. This huge gain in sample size enables superior constraints on the MZR and its scatter in the low-mass regime. We find a power-law MZR at 10(8) M-circle dot < M-* < 10(11) M-circle dot: 12 + log (O/H) = (5.83 +/- 0.19)+(0.30 +/- 0.02) log (M-*/M-circle dot). At 10(9) M-circle dot < M-* < 10(10.5) M-circle dot, our MZR shows agreement with others measured at similar redshifts in the literature. Our power-law slope is, however, shallower than the extrapolation of the MZRs of others to masses below 10(9) M-circle dot. The SFR dependence of the MZR in our sample is weaker than that found for local galaxies (known as the fundamental metallicity relation). Compared to a variety of theoretical models, the slope of our MZR for low-mass galaxies agrees well with predictions incorporating supernova energy-driven winds. Being robust against currently uncertain metallicity calibrations, the scatter of the MZR serves as a powerful diagnostic of the stochastic history of gas accretion, gas recycling, and star formation of low-mass galaxies. Our major result is that the scatter of our MZR increases as M-* decreases. Our result implies that either the scatter of the baryonic accretion rate (sigma((M) over dot)) or the scatter of the M-*-M-halo relation (sigma(SHMR)) increases as M-* decreases. Moreover, our measure of scatter at z = 0.7 appears consistent with that found for local galaxies. This lack of redshift evolution constrains models of galaxy evolution to have both sigma((M) over dot) and sigma(SHMR) remain unchanged from z = 0.7 to z = 0.