The Arecibo Galaxy Environment Survey XII : Optically dark HI clouds in the Leo I Group

Abstract

Using data from the Arecibo Galaxy Environment Survey, we report the discovery of five HI clouds in the Leo I group without detected optical counterparts. Three of the clouds are found midway between M96 and M95, one is only 10${}^{\prime }$ from the south-east side of the well-known Leo Ring, and the fifth is relatively isolated. HI masses range from 2.6$\times$10${}^6$ - 9.0$\times$10${}^6$M${}_{\odot }$ and velocity widths (W50) from 16 - 42 km/s. Although a tidal origin is the most obvious explanation, this formation mechanism faces several challenges. For the most isolated cloud, the difficulties are its distance from neighbouring galaxies and the lack of any signs of disturbance in the HI discs of those systems. Some of the clouds also appear to follow the baryonic Tully-Fisher relation between mass and velocity width for normal, stable galaxies which is not expected if they are tidal in origin. Three clouds are found between M96 and M95 which have no optical counterparts, but have otherwise similar properties and location to the optically detected galaxy LeG 13. While overall we favour a tidal debris scenario to explain the clouds, we cannot rule out a primordial origin. If the clouds were produced in the same event that gave rise to the Leo Ring, they may provide important constraints on any model attempting to explain that structure

16 pages (plus 4 page appendix), 1 table, 7 figures, accepted for publication in AJ

References in corpus (22)

• The Arecibo Legacy Fast ALFA Survey: IV. Strategies for Signal Identification and Survey Catalog Reliability
• Robust HI kinematics of gas-rich ultra-diffuse galaxies: hints of a weak-feedback formation scenario
• NGC 4254: An Act of Harassment Uncovered by the Arecibo Legacy Fast ALFA Survey
• Tidal debris from high-velocity collisions as fake dark galaxies: A numerical model of VirgoHI21
• The Arecibo Galaxy Environment Survey: Precursor Observations of the NGC 628 group
• The ALFALFA-SDSS Galaxy Catalog
• A collisional origin for the Leo ring
• 21-cm synthesis observations of VIRGOHI 21 - a possible dark galaxy in the Virgo Cluster
• Statistical Analysis of H I Profile Asymmetry and Shape for Nearby Galaxies
• A diffuse tidal dwarf galaxy destined to fade out as a "dark galaxy"
• On the Determination of Rotation Velocity and Dynamical Mass of Galaxies Based on Integrated H I Spectra
• ALFALFA and WSRT Imaging of Extended HI Features in the Leo Cloud of Galaxies
• The Arecibo Ultra-Deep Survey
• Hydrodynamic simulations of an isolated star-forming gas cloud in the Virgo cluster
• Gaseous Tidal Debris found in the NGC 3783 Group
• Faint and fading tails : the fate of stripped HI gas in Virgo cluster galaxies
• Kinematic clues to the origins of starless HI clouds : dark galaxies or tidal debris ?
• WALLABY pre-pilot survey: Two dark clouds in the vicinity of NGC 1395
• Heavy elements unveil the non primordial origin of the giant HI ring in Leo
• The detection of a massive chain of dark HI clouds in the GAMA G23 Field
• Unravelling the Mysteries of the Leo Ring: An Absorption Line Study of an Unusual Gas Cloud
• The Arecibo Galaxy Environment Survey VIII : Discovery of an Isolated Dwarf Galaxy in the Local Volume

Cited by in corpus (2)

• On the completeness and reliability of visual source extraction : an examination of eight thousand data cubes by eye
• Ultra Diffuse Galaxies in clusters : the peculiar gas loss of VCC 1964