Strong Far-IR Cooling Lines, Peculiar CO Kinematics and Possible Star Formation Suppression in Hickson Compact Group 57

Abstract

We present [C II] and [O I] observations from Herschel and CO(1-0) maps from the Combined Array for† Research in Millimeter Astronomy (CARMA) of the Hickson Compact Group HCG 57, focusing on the galaxies HCG 57a and HCG 57d. HCG 57a has been previously shown to contain enhanced quantities of warm molecular hydrogen consistent with shock and/or turbulent heating. Our observations show that HCG 57d has strong [C II] emission compared to L${}_{\mathrm{FIR}}$ and weak CO(1-0), while in HCG 57a, both the [C II] and CO(1-0) are strong. HCG 57a lies at the upper end of the normal distribution of [C II]/CO and [C II]/FIR ratios, and its far-IR cooling supports a low density warm diffuse gas that falls close to the boundary of acceptable PDR models. However, the power radiated in the [C II] and warm H${}_2$ emission have similar magnitudes, as seen in other shock-dominated systems and predicted by recent models. We suggest that shock-heating of the [C II] is a viable alternative to photoelectric heating in violently disturbed diffuse gas. The existence of shocks is also consistent with peculiar CO kinematics in the galaxy, indicating highly non-circular motions are present. These kinematically disturbed CO regions also show evidence of suppressed star formation, falling a factor of 10-30 below normal galaxies on the Kennicutt-Schmidt relation. We suggest that the peculiar properties of both galaxies are consistent with a highly dissipative off-center collisional encounter between HCG 57d and 57a, creating ring-like morphologies in both systems. Highly dissipative gas-on-gas collisions may be more common in dense groups because of the likelihood of repeated multiple encounters. The possibility of shock-induced SF suppression may explain why a subset of these HCG galaxies have been found previously to fall in the mid-infrared green valley.

ApJ accepted, 16 pages, 12 figures, 3 tables

References in corpus (12)

• The Host Galaxies and Classification of Active Galactic Nuclei
• Star Formation in the Central 400 pc of the Milky Way: Evidence for a Population of Massive YSOs
• Powerful High Velocity-Dispersion Molecular Hydrogen Associated with an Intergalactic Shock Wave in Stephan's Quintet
• Low velocity shocks: signatures of turbulent dissipation in diffuse irradiated gas
• Galaxy Evolution in Hickson Compact Groups: The Role of Ram Pressure Stripping and Strangulation
• The Infrared Properties of Hickson Compact Groups
• Shocked Molecular Hydrogen in the 3C 326 Radio Galaxy System
• The SINS Survey: Broad Emission Lines in High-Redshift Star-Forming Galaxies
• Gas and Dust in the Taffy Galaxies: Ugc12914/15
• Herschel observations of Hickson compact groups of galaxies: Unveiling the properties of cold dust
• The H$\alpha$ kinematics of interacting galaxies in 12 compact groups
• CO in Hickson Compact Group galaxies with enhanced warm \htwo\ emission: Evidence for galaxy evolution?

Cited by in corpus (14)

• Suppression of Star Formation in NGC 1266
• Powerful H2 Line Cooling in Stephan's Quintet II. Group-wide Gas and Shock Modeling of the Warm H2 and a Comparison with [CII]157.7um Emission and Kinematics
• Exceptional AGN-driven turbulence inhibits star formation in the 3C 326N radio-galaxy
• After The Fall: Resolving the Molecular Gas in Post-Starburst Galaxies
• The role of molecular gas in galaxy transition in compact groups
• Accretion-Inhibited Star Formation in the Warm Molecular Disk of the Green-valley Elliptical Galaxy NGC 3226
• Studying the evolution of galaxies in compact groups over the past 3 Gyr. I. The nuclear activity
• Resolved Molecular Gas Observations of MaNGA Post-starbursts Reveal a Tumultuous Past
• NOEMA Observations of CO Emission in Arp 142 and Arp 238
• The ALMA-CRISTAL survey: Extended [CII] emission in an interacting galaxy system at z ~ 5.5
• Bright [CII]158$\mu$m Streamers as a Beacon for Giant Galaxy Formation in SPT2349$-$56 at $z=4.3$
• Measuring the ISM Content of Nearby, Luminous, Type 1 and Type 2 QSOs through CO and [C II]
• Properties of Interstellar Medium in the S0 Galaxy NGC 1222: Evidence for Shocked-enhanced Line Emission
• A Herschel and CARMA view of CO and [C II] in Hickson Compact groups