HI Observations of two New Dwarf Galaxies: Pisces A & B with the SKA Pathfinder KAT-7

Abstract

Context. Pisces A & Pisces B are the only two galaxies found via optical imaging and spectroscopy out of 22 HI clouds identified in the GALFAHI survey as dwarf galaxy candidates. Aims. Derive the HI content and kinematics of Pisces A & B. Methods. Aperture synthesis HI observations using the seven dish Karoo Array Telescope (KAT-7), which is a pathfinder instrument for MeerKAT, the South African precursor to the mid-frequency Square Kilometre Array (SKA-MID). Results. The small rotation velocities detected of ~5 km/sec and ~10 km/sec in Pisces A & B respectively, and their HI content show that they are really dwarf irregular galaxies (dIrr). Despite that small rotation component, it is more the random motions ~9-11 km/sec that provide most of the gravitational support, especially in the outer parts. The study of their kinematics, especially the strong gradients of random motions, suggest that those two dwarf galaxies are not yet in equilibrium. Conclusions. These HI rich galaxies may be indicative of a large population of dwarfs at the limit of detectability. However, such gas-rich dwarf galaxies will most likely never be within the virial radius of MW-type galaxies and become sub-halo candidates. Systems such as Pisces A & B are more likely to be found at a few Mpc.s from MW-type galaxies.

4 pages, 4 figures, accepted for publication in A&A Letters

References in corpus (12)

• Beasts of the Southern Wild: Discovery of nine Ultra Faint satellites in the vicinity of the Magellanic Clouds
• Sagittarius II, Draco II and Laevens 3: three new Milky Way satellites discovered in the Pan-STARRS 1 3pi Survey
• The Northern HIPASS catalogue - Data presentation, completeness and reliability measures
• The Dearth of Neutral Hydrogen in Galactic Dwarf Spheroidal Galaxies
• The discovery of seven extremely low surface brightness galaxies in the field of the nearby spiral galaxy M101
• A Catalog of Ultra-compact High Velocity Clouds from the ALFALFA Survey: Local Group Galaxy Candidates?
• The ALFALFA "Almost Darks" Campaign: Pilot VLA HI Observations of Five High Mass-to-Light Ratio Systems
• (Almost) Dark HI Sources in the ALFALFA Survey: The Intriguing Case of HI1232+20
• Two Local Volume Dwarf Galaxies Discovered in 21 cm Emission: Pisces A and B
• KAT-7 Science Verification: Cold Gas, Star Formation, and Substructure in the Nearby Antlia Cluster
• On the neutral gas content of nine new Milky Way satellite galaxy candidates
• AGC198606: A gas-bearing dark matter minihalo?

Cited by in corpus (5)

• WALLABY -- An SKA Pathfinder HI Survey
• Neutral hydrogen and magnetic fields in M83 observed with the SKA Pathfinder KAT-7
• Identifying galaxy candidates in WSRT HI imaging of ultra-compact high velocity clouds
• HI Kinematics, Mass Distribution, and Star Formation Threshold in NGC 6822, using the SKA pathfinder KAT-7
• The HI Structure of the Local Volume Dwarf Galaxy Pisces A