The Baryon Content of Extremely Low Mass Dwarf Galaxies

By M. Geha, M. Blanton, M. Masjedi, Andrew A. West. 2006

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We investigate the gas content and baryonic Tully-Fisher relationship for extremely low luminosity dwarf galaxies in the absolute magnitude range -13.5 > Mr - 5 log h70 > -16. The sample is selected from the Sloan Digital Sky Survey and consists of 101 galaxies for which we have obtained follow-up H I observations using the Arecibo Observatory and Green Bank Telescope. This represents the largest homogeneous sample of dwarf galaxies at low luminosities with well-measured H I and optical properties. The sample spans a range of environments, from dense groups to truly isolated galaxies. The average neutral gas fraction is ⟨fgas⟩ = 0.6, significantly exceeding that of typical gas-rich galaxies at higher luminosities. Dwarf galaxies are therefore less efficient at turning gas into stars over their lifetimes. The strong environmental dependence of the gas fraction distribution demonstrates that while internal processes can reduce the gas fractions to roughly fgas = 0.4, external processes are required to fully remove gas from a dwarf galaxy. The average rotational velocity of our sample is ⟨vrot⟩ = ⟨W20i,t/2⟩ = 50 km s-1, based on H I line widths. In this luminosity range, the optical Tully-Fisher relationship has significantly more scatter compared to the baryonic relationship. By including more massive galaxies from the literature, we fit a baryonic Tully-Fisher slope of Mbary ∝ v. This slope compares well with CDM models that assume an equal baryon-to-dark matter ratio at all masses. While gas stripping or other processes may modify the baryon-to-dark matter ratio for dwarfs in the densest environments, the majority of dwarf galaxies in our sample have not preferentially lost significant baryonic mass relative to more massive galaxies.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/6a3042cd53e9ef6fa18d39bf269436a2811f73f4

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Citations in the corpus

Implementing molecular hydrogen in hydrodynamic simulations of galaxy formation (2012, methodology): “When comparing the galaxies to the baryonic Tully-Fisher relationship, wefollowed the same method as Geha et al. (2006) to find the baryonic mass: the total gas mass was assumed to be 1.4 times the HI mass and the stellar mass was determined from the SDSSi-band magnitudes and g - r colors…”
Scaling Relations of Spiral Galaxies (2007, background): “Our observations are also corroborated by the study of low mass dwarf galaxies of Geha et al. (2006) who finds no break in the TF relations of very faint and brighter spiral galaxies.”
REPRODUCING THE STELLAR MASS/HALO MASS RELATION IN SIMULATED ΛCDM GALAXIES: THEORY VERSUS OBSERVATIONAL ESTIMATES (2012, background): “As other works have highlighted the importance of having a representative sample before drawing general conclusions (Brooks et al. 2011; Sales et al. 2012; McCarthy et al. 2012), the halos in our sample span a representative range of halo spin values and accretion histories (Geha et al. 2006).”
THE DUAL ORIGIN OF STELLAR HALOS (2009, background): “G07 and Governato et al. (2009) showed that disk galaxies naturally form in a cosmological context in simulations such as those studied here, and have sizes that place them on the I-band Tully–Fisher relation (TF, e.g., Giovanelli et al. 1997; McGaugh 2005; Geha et al. 2006).”
Small scale problems of the $\Lambda$CDM model: a short review (2016, background): “the APOSTLE project [119,142] — claimed to have successfully reproduced the BTFR over four decades [143], even reproducing its break-down at the faint end, as was indeed observed [68,144].”
THE ARECIBO LEGACY FAST ALFA SURVEY. X. THE H i MASS FUNCTION AND FROM THE 40% ALFALFA SURVEY (2010, background): “Since neutral gas fractions become large for dwarf galaxies, dominating the stellar mass, HI surveys are efficient at finding the extremely low-baryon-mass systems locally (Schombert et al. 2001; Geha et al. 2006), and the HIMF is a better measure of baryon content at the lowest masses.”
A DIRECT MEASUREMENT OF THE BARYONIC MASS FUNCTION OF GALAXIES AND IMPLICATIONS FOR THE GALACTIC BARYON FRACTION (2012, background): “The triangles correspond to disc galaxies for which Mh was determined from their rotation speed (Geha et al. 2006; Pizagno et al. 2007; Springob et al. 2007).”
The effect of galaxy mass ratio on merger-driven starbursts (2007, methodology): “To determine the mass of gas, we use the observed trend that systems with lower total/stellar mass have a higher gas fraction (Bell et al. 2003; Geha et al. 2006).”
Molecular Hydrogen and Global Star Formation Relations in Galaxies (2007, background): “This connection between SFE and molecular hydrogen abundance may explain why dwarf galaxies are still gas rich today compared to larger mass galaxies (Geha et al. 2006), without relying on mediation of star formation or gas blowout by supernovae.”
THE CLUSTERING CHARACTERISTICS OF H i-SELECTED GALAXIES FROM THE 40% ALFALFA SURVEY (2012, background): “Additionally, such surveys are sensitive to low-luminosity dwarf systems, which tend to be gas-dominated (Geha et al. 2006).”
The ATLAS3D project - XXIX. The new look of early-type galaxies and surrounding fields disclosed by extremely deep optical images (2014, background): “…adopted definition, streams trace past minor mergers, with a possible bias towards dry ones, given that the satellites of early-type galaxies tend to be gas–poor, having lost their gas by internal – feedback – or external – ram pressure – processes before they were accreted (e.g. Geha et al. 2006).”
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THE ACS NEARBY GALAXY SURVEY TREASURY. VIII. THE GLOBAL STAR FORMATION HISTORIES OF 60 DWARF GALAXIES IN THE LOCAL VOLUME (2011, background): “This same morphology–density relationship has been found for dwarf galaxies (e.g., Einasto et al. 1974; Mateo 1998; van den Bergh 2000; Skillman et al. 2003a; Geha et al. 2006).”
Merger Histories of Galaxy Halos and Implications for Disk Survival (2007, background): “While dark halo merger histories are approximately self-similar in M0, gas fractions are known to decrease systematically with halo mass (at least at z = 0, see e.g. Geha et al. 2006; Kaufmann et al. 2007b, and references therein).”
NEW CONSTRAINTS ON THE EVOLUTION OF THE STELLAR-TO-DARK MATTER CONNECTION: A COMBINED ANALYSIS OF GALAXY–GALAXY LENSING, CLUSTERING, AND STELLAR MASS FUNCTIONS FROM z = 0.2 to z = 1 (2011, background): “The agreement between the extrapolation of our SHMR to lower masses and the Geha et al. (2006) sample is encouraging.”
The Origin and Evolution of the Mass-Metallicity Relationship for Galaxies: Results from Cosmological N-Body Simulations (2006, background): “Z∗ SN feedback as a function of galaxy mass has been investigated by various groups, with results that are still debated (Veilleux et al. 2005; Geha et al. 2006; Dalcanton 2007; E06).”
MaGICC discs: matching observed galaxy relationships over a wide stellar mass range (2012, background): “…feedback had the trouble of ejecting their gas in high-redshift starbursts, resulting in isolated dwarf spheroidal galaxies (Sawala et al. 2010), rather than dwarfs with prolonged star formation histories and significant amounts of H I gas at z = 0, as observed in the field (e.g. Geha et al. 2006).”
Galaxies in a simulated ΛCDM universe – II. Observable properties and constraints on feedback (2009, background): “Only at lower masses does the gas begin to dominate the baryonic mass of galaxies (e.g. Geha et al. 2006), and hence begin to alleviate the differences between the observed and simulated SMFs.”
The role of dwarf galaxy interactions in shaping the Magellanic System and implications for Magellanic Irregulars (2012, methodology): “The gas fractions of isolated dwarf galaxies are known to be large (e.g. Geha et al. 2006). cThe total mass of the LMC/SMC at infall is determined using the observed stellar mass of the LMC (SMC) M∗ = 3 × 109 M (3 × 108 M ) (van der Marel et al. 2002; Stanimirović, Staveley-Smith & Jones 2004) and…”