HST Imaging of the Local Volume Dwarf Galaxies Pisces A&B: Prototypes for Local Group Dwarfs

Abstract

We present observations of the Pisces A and B galaxies with the Advanced Camera for Surveys on the Hubble Space Telescope. Photometry from these images clearly resolve a Red Giant Branch for both objects, demonstrating that they are nearby dwarf galaxies. We describe a Bayesian inferential approach to determining the distance to these galaxies using the magnitude of the tip of the RGB, and then apply this approach to these galaxies. We also provide the full probability distributions for parameters derived using this approach. This reveals the distance to these galaxies as $5.64_{-0.15}^{+0.13}\mathrm{Mpc}$ and $8.89_{-0.85}^{+0.75}\mathrm{Mpc}$ for Pisces A and B, respectively, placing both within the Local Volume but not the Local Group. We estimate the star formation histories of these galaxies, which suggests that they have recently undergone an increase in their star formation rates. Together these yield luminosities for Pisces A and B of $M_V=-11.57_{-0.05}^{+0.06}$ and $-12.9\pm 0.2$, respectively, and estimated stellar masses of $\log (M_{\ast }/M_{\odot })=7.0_{-1.7}^{+0.4}$ and $7.5_{-1.8}^{+0.3}$. We further show that these galaxies are likely at the boundary between nearby voids and higher-density filamentary structure. This suggests that they are entering a higher-density region from voids, where they would have experienced delayed evolution, consistent with their recent increased star formation rates. If this is indeed the case, they are useful for study as proxies of the galaxies that later evolved into typical Local Group satellite galaxies.

arXiv commentAccepted to ApJ, 14 pages. 3D version of Figure 12 at http://bit.ly/piscdwarfs_3d_fig12, MCMC chains at http://dx.doi.org/10.5281/zenodo.51375

References in corpus (45)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Astropy: A Community Python Package for Astronomy
• emcee: The MCMC Hammer
• The NumPy array: a structure for efficient numerical computation
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• The Seventh Data Release of the Sloan Digital Sky Survey
• Where are the missing galactic satellites?
• The observed properties of dwarf galaxies in and around the Local Group
• Too big to fail? The puzzling darkness of massive Milky Way subhaloes
• The Photometric Performance and Calibration of the HST Advanced Camera For Surveys
• The 6dF Galaxy Survey: Final Redshift Release (DR3) and Southern Large-Scale Structures
• WFPC2 Stellar Photometry with HSTphot
• Numerical Methods of Star Formation History Measurement and Applications to Seven Dwarf Spheroidals
• Improved background subtraction for the Sloan Digital Sky Survey images
• The 6dF Galaxy Survey: Samples, Observational Techniques and the First Data Release
• A comprehensive Maximum Likelihood analysis of the structural properties of faint Milky Way satellites
• The Star Formation Histories of Local Group Dwarf Galaxies I. Hubble Space Telescope / Wide Field Planetary Camera 2 Observations
• The ACS Nearby Galaxy Survey Treasury VIII. The Global Star Formation Histories of 60 Dwarf Galaxies in the Local Volume
• Tip of the Red Giant Branch Distances. II. Zero-Point Calibration
• Why Baryons Matter: The Kinematics of Dwarf Spheroidal Satellites
• The Baryon Content of Extremely Low Mass Dwarf Galaxies
• An Empirical Pixel-Based Correction for Imperfect CTE. I. HST's Advanced Camera for Surveys
• The GALFA-HI Survey: Data Release 1
• Deviations from the Local Hubble Flow. I. The Tip of the Red Giant Branch as a Distance Indicator
• Tip of the Red Giant Branch Distances. I. Optimization of a Maximum Likelihood Algorithm
• Dark matter substructure and dwarf galactic satellites
• The Void Galaxy Survey: Optical Properties and H I Morphology and Kinematics
• The very local Hubble flow
• ALFALFA Discovery of the Nearby Gas-Rich Dwarf Galaxy Leo P. I. HI Observations
• Leo P: An Unquenched Very Low-Mass Galaxy
• Dwarf Galaxies and the Cosmic Web
• Taking Care of Business in a Flash: Constraining the Timescale for Low-Mass Satellite Quenching with ELVIS
• Rapid Environmental Quenching of Satellite Dwarf Galaxies in the Local Group
• The Hierarchical Structure and Dynamics of Voids
• The Survey of HI in Extremely Low-mass Dwarfs (SHIELD)
• A dynamical model of the local cosmic expansion
• Determining the Location of the Tip of the Red Giant Branch in Old Stellar Populations: M33, Andromeda I & II
• On the Estimation of Systematic Uncertainties of Star Formation Histories
• On the Estimation of Random Uncertainties of Star Formation Histories
• The Local Group as a time machine: studying the high-redshift Universe with nearby galaxies
• How Typical Are The Local Group Dwarf Galaxies?
• A Bayesian Approach to Locating the Red Giant Branch Tip Magnitude (Part I)
• A Comprehensive Archival Search for Counterparts to Ultra-Compact High Velocity Clouds: Five Local Volume Dwarf Galaxies
• Two Local Volume Dwarf Galaxies Discovered in 21 cm Emission: Pisces A and B
• Measuring Sizes of Ultra-Faint Dwarf Galaxies

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• Five Gas-rich Ultra-faint Dwarf Galaxy Candidates Discovered in WIYN Imaging of ALFALFA Sources
• The Stellar Kinematics of Void Dwarf Galaxies Using KCWI
• The Distance and Dynamical History of the Virgo Cluster Ultradiffuse Galaxy VCC 615
• Hubble Space Telescope Imaging of Isolated Local Volume Dwarfs GALFA-Dw3 and Dw4
• Millimeter Dust Emission and Planetary Dynamics in the HD 106906 System
• Star Formation in Nearby Dwarf Galaxies
• The HI Structure of the Local Volume Dwarf Galaxy Pisces A
• A Correlated Search for Local Dwarf Galaxies in GALFA-HI and Pan-STARRS
• A Search for Gas-Rich Dwarf Galaxies in the Local Universe with ALFALFA and the WIYN One Degree Imager
• Galaxy Properties at the Faint End of the HI Mass Function
• Pisces VII: Discovery of a possible satellite of Messier 33 in the DESI Legacy Imaging Surveys