Andromeda IV, a solitary gas-rich dwarf galaxy

Abstract

Observations are presented of the isolated dwarf irregular galaxy And IV made with the Hubble Space Telescope Advanced Camera for Surveys and the Giant Metrewave Radio Telescope in the 21 cm HI line. We determine the galaxy distance of $7.17\pm 0.31$ Mpc using the Tip of Red Giant Branch method. The galaxy has a total blue absolute magnitude of -12.81 mag, linear Holmberg diameter of 1.88 kpc and an HI-disk extending to 8.4 times the optical Holmberg radius. The HI mass-to-blue luminosity ratio for And IV amounts $12.9M_{\odot }/L_{\odot }$. From the GMRT data we derive the rotation curve for the HI and fit it with different mass models. We find that the data are significantly better fit with an iso-thermal dark matter halo, than by an NFW halo. We also find that MOND rotation curve provides a very poor fit to the data. The fact that the iso-thermal dark matter halo provides the best fit to the data supports models in which star formation feedback results in the formation of a dark matter core in dwarf galaxies. The total mass-to-blue luminosity ratio of $162M_{\odot }/L_{\odot }$ makes And IV among the darkest dIrr galaxies known. However, its baryonic-to-dark mass ratio ($M_{gas}+M^{\ast })/M_T=0.11$ is close to the average cosmic baryon fraction, 0.15.

9 pages, 10 figures, 2 tables, accepted in Astronomische Nachrichten

References in corpus (10)

• The GALEX Ultraviolet Atlas of Nearby Galaxies
• Updated Nearby Galaxy Catalog
• FIGGS: Faint Irregular Galaxies GMRT Survey - Overview, observations and first results
• Tip of the Red Giant Branch Distances. I. Optimization of a Maximum Likelihood Algorithm
• The molecular gas reservoir of 6 low-metallicity galaxies from the Herschel Dwarf Galaxy Survey: A ground-based follow-up survey of CO(1-0), CO(2-1), and CO(3-2)
• The ALFALFA "Almost Darks" Campaign: Pilot VLA HI Observations of Five High Mass-to-Light Ratio Systems
• The Minimum Amount of Stars a Galaxy Will Form
• The distribution of dark and luminous matter inferred from extended rotation curves
• The Geometry of PSR B0031-07
• Andromeda IV: a new Local Volume very metal-poor galaxy

Cited by in corpus (8)

• Galaxy Groups within 3500 km s${}^{-1}$
• The universal rotation curve of dwarf disk galaxies
• Angular momentum of dwarf galaxies
• Void galaxies in the nearby Universe. I. Sample description
• Angular Momentum Content in Gas Rich Dwarf Galaxies
• The insight into the dark side. I. The pitfalls of the dark halo parameters estimation
• Comparing rotation curve observations to hydrodynamic ΛCDM simulations of galaxies
• On a Generalized Mass-Velocity Relation for Disk Galaxies and Galaxy Clusters