Search

We report on CO (J = 2 → 1) mapping with the IRAM 30-m HEtrodyne Receiver Array (HERA) of CGCG 97-079, an irregular galaxy in the merging galaxy cluster Abell 1367 (z = 0.022). We find that â80 per cent of the detected CO (J = 2 → 1) is projected within a 16 arcsec2 (6.5 kpc2) region to the north and west of the optical/NIR centre, with the intensity maximum offset â10 arcsec (4 kpc) NW of the optical/NIR centre and â7 arcsec (3 kpc) south-east of the HI intensity maximum. Evolutionary synthesis models indicate CGCG 97- 079 experienced a burst of star formation â108 yr ago, most likely triggered by a tidal interaction with CGCG 97-073. For CGCG 97-079 we deduce an infall velocity to the cluster of â1000 km sâ'1 and moderate ram pressure (Pram â 10â'11 dyne cmâ'2). The observed offset in CGCG 97-079 of the highest density HI and CO (J = 2→1) from the stellar components has not previously been observed in galaxies currently undergoing ram pressure stripping, although previous detailed studies of gas morphology and kinematics during ram pressure stripping were restricted to significantly more massive galaxies with deeper gravitational potential wells. We conclude the observed cold gas density maxima offsets are most likely the result of ram pressure and/or the high-speed tidal interaction with CGCG 97-073. However ram pressure stripping is likely to be playing a major role in the perturbation of lower density gas. [ABSTRACT FROM AUTHOR]

ABSTRACT We present VLA D-array H i observations of the RSCG 42 and FGC 1287 galaxy groups, in the outskirts of the Abell 1367 cluster. These groups are projected ∼1.8 and 2.7 Mpc west from the cluster centre. The Arecibo Galaxy Environment Survey provided evidence for H i extending over as much as 200 kpc in both groups. Our new, higher resolution observations reveal that the complex H i features detected by Arecibo are in reality two extraordinary long H i tails extending for ∼160 and 250 kpc, respectively, i.e. among the longest H i structures ever observed in groups of galaxies. Although in the case of RSCG 42 the morphology and dynamics of the H i tail, as well as the optical properties of the group members, support a low-velocity tidal interaction scenario, less clear is the origin of the unique features associated with FGC 1287. This galaxy displays an exceptionally long 'dog leg' H i tail, and the large distance from the X-ray-emitting region of Abell 1367 makes a ram-pressure stripping scenario highly unlikely. At the same time, a low-velocity tidal interaction seems unable to explain the extraordinary length of the tail and the lack of any sign of disturbance in the optical properties of FGC 1287. An intriguing possibility could be that this galaxy might have recently experienced a high-speed interaction with another member of the Coma-Abell 1367 Great Wall. We searched for the interloper responsible for this feature and, although we find a possible candidate, we show that without additional observations it is impossible to settle this issue. While the mechanism responsible for this extraordinary H i tail remains to be determined, our discovery highlights how little we know about environmental effects in galaxy groups. [ABSTRACT FROM AUTHOR]