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Register a new userCO in late-type galaxies within the central region of Abell 1367
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We present CO (J = 1 - 0) and CO (J = 2 - 1) spectra for 19 bright, late-type galaxies (spirals) in the central region of the galaxy cluster Abell 1367 (z = 0.02) from observations made with the IRAM 30 - m telescope. All 19 spirals were observed at the position of their optical center and for a subset, at multiple positions. For each spiral the integrated CO (J = 1 - 0) intensity from the central pointing, in few cases supplemented with intensities from offset pointings, was used to estimate its molecular hydrogen mass and H_2 deficiency. Accepting the considerable uncertainties involved in determining H_2 deficiencies, spirals previously identified by us to have redder colours and higher HI deficiencies as a result of environmental influence, were found to be more H_2 deficient compared to members of the sample in less advanced evolutionary states. For eight of the observed spirals multiple pointing observations were made to investigate the distribution of their molecular gas. For these spirals we fitted Gaussians to the CO intensities projected in a line across the galaxy. In two cases, CGCG 097-079 and CGCG 097-102(N), the offset between the CO and optical intensity maxima was significantly larger than the pointing uncertainty and the FWHMs of the fits were significantly greater than those of the other spirals, irrespective of optical size. Both signatures are indicators of an abnormal molecular gas distribution. In the case of CGCG 097-079, which is considered an archetype for ram pressure stripping, our observations indicate the CO intensity maximum lies ~ 15.6 +/- 8.5 arcsec (6 kpc) NW of the optical centre at the same projected position as the HI intensity maximum.
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To investigate the effects the cluster environment has on Late-Type Galaxies (LTGs) we studied HI perturbation signatures for all Abell 1367 LTGs with HI detections. We used new VLA HI observations combined with AGES single dish blind survey data. Our study indicates that the asymmetry between the high-and low-velocity wings of the characteristic double-horn integrated HI spectrum as measured by the asymmetry parameter, Aflux, can be a useful diagnostic for ongoing and/or recent HI stripping. 26% of A1367 LTGs have an Aflux ratio, more asymmetrical than 3 times the 1{sigma} spread in the Aflux ratio distribution of an undisturbed sample of isolated galaxies (2%) and samples from other denser environments (10% to 20%). Over half of the A 1367 LTGs, which are members of groups or pairs, have an Aflux ratio larger than twice the 1 {sigma} spread found in the isolated sample. This suggests inter-group/pair interactions could be making a significant contribution to the LTGs displaying such Aflux ratios. The study also demonstrates that the definition of the HI offset from the optical centre of LTGs is resolution dependent, suggesting that unresolved AGES HI offsets that are significantly larger than the pointing uncertainties (> 2 {sigma}) reflect interactions which have asymmetrically displaced significant masses of lower density HI, while having minimal impact on the location of the highest density HI in resolved maps. The distribution of Aflux from a comparable sample of Virgo galaxies provides a clear indication that the frequency of HI profile perturbations is lower than in A 1367.
We present VLA D-array HI observations of the RSCG42 and FGC1287 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 HI extending over as much as 200kpc in both groups. Our new, higher resolution observations reveal that the complex HI features detected by Arecibo are in reality two extraordinary long HI tails extending for ~160 and 250 kpc, respectively, i.e., among the longest HI structures ever observed in groups of galaxies. Although in the case of RSCG42 the morphology and dynamics of the HI 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 FGC1287. This galaxy displays an exceptionally long dog leg HI 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 FGC1287. 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 HI tail remains to be determined, our discovery highlights how little we know about environmental effects in galaxy groups.
Using wide baseline broad-band photometry, we analyse the stellar population properties of a sample of 72 galaxies, spanning a wide range of stellar masses and morphological types, in the nearby spiral-rich and dynamically young galaxy cluster Abell 1367. The sample galaxies are distributed from the cluster centre out to approximately half the cluster Abell radius. The optical/near-infrared colours are compared with simple stellar population synthesis models from which the luminosity-weighted stellar population ages and metallicities are determined. The locus of the colours of elliptical galaxies traces a sequence of varying metallicity at a narrow range of luminosity-weighted stellar ages. Lenticular galaxies in the red sequence, however, exhibit a substantial spread of luminosity-weighted stellar metallicities and ages. For red sequence lenticular galaxies and blue cloud galaxies, low mass galaxies tend to be on average dominated by stellar populations of younger luminosity-weighted ages. Sample galaxies exhibit a strong correlation between integrated stellar mass and luminosity-weighted stellar metallicity. Galaxies with signs of morphological disturbance and ongoing star formation activity, tend to be underabundant with respect to passive galaxies in the red sequence of comparable stellar masses. We argue that this could be due to tidally-driven gas flows toward the star-forming regions, carrying less enriched gas and diluting the pre-existing gas to produce younger stellar populations with lower metallicities than would be obtained prior to the interaction. Finally, we find no statistically significant evidence for changes in the luminosity-weighted ages and metallicities for either red sequence or blue cloud galaxies, at fixed stellar mass, with location within the cluster.
Multi-wavelength observations show that Abell 1367 (A1367) is a dynamically young cluster, with at least two subclusters merging along the SE-NW direction. With the wide-field XMM-Newton mosaic of A1367, we discover a previously unknown merger shock at the NW edge of the cluster. We estimate the shock Mach number from the density and temperature jumps as $M_{rho}=1.21pm0.08$ and $M_T=1.60pm0.07$, respectively. This shock region also corresponds to a radio relic discovered with the VLA and GBT, which could be produced by the shock re-acceleration of pre-existing seed relativistic electrons. We suggest that some of the seed relativistic electrons originate from late-type, star-forming galaxies in this region.
We combine observations of spiral galaxies in the [CII] line at 158 micron, made with the Long Wavelength Spectrometer aboard ISO, with previous data from the Kuiper Airborne Observatory to study the origin of this line, which is the main coolant of the interstellar medium at relatively low temperatures. We also use HI and CO(1-0) observations of these galaxies and estimate the respective line fluxes in the same beam as the [CII] observations. We confirm the existence of a linear relation between the [CII] line intensity and the CO(1-0) line intensity, that we extend to intrinsically fainter galaxies. The dispersion around this relation is significant and due to variations in the far-UV flux, thus in the star formation rate. We find that for the least active galaxies of our sample, in terms of star formation, the rate of [CII] line emission per interstellar hydrogen atom is similar to that in the Solar neighbourhood. For those galaxies, most of the [CII] line emission comes probably from the diffuse cold atomic medium. In more active galaxies, considered globally, the average [CII] line emission is dominated by dense photodissociation regions and to some extent by the warm ionized diffuse medium. This is true in the central region of many spiral galaxies, and probably even in the interarm regions of the most actively star-forming ones.
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