Far infrared properties of Hickson compact groups of galaxies. I. High resolution IRAS maps and fluxes

Abstract

Abstract. -The Far Infrared (FIR) properties of galaxies which are members of compact groups bear relevant information on the dynamical status and the physical properties of these structures. All studies published so far have been undermined by the poor sensitivity and spatial resolution of the IRAS-PSC and IRAS Sky Survey data. We used the HIRAS software available at the IRAS server at the Laboratory for Space Research in Groningen to fully exploit the redundancy of the IRAS data and to approach the theoretical diffraction limit of IRAS. Among the 97 groups which were observed by IRAS, 62 were detected in at least one band, while reliable upper limits were derived for all the others. Among the detected groups, 49 were fully or partially resolved, i.e. it was possible to discriminate which member or members emit most of the FIR light. At 60 µm, for instance, 87 individual sources were detected in 62 groups. In order to ease the comparison with data obtained at other wavelengths -and in particular in the X and radio domains -we give co-added and HIRAS maps for all the detected groups.

Star formation in the intragroup medium and other diagnostics of the evolutionary stages of compact groups of galaxies

“…HCG 7a and HCG 7c are strong FIR sources (Allam et al 1996;Verdes-Montenegro et al 1998). Shimada et al (2000) classified the nuclear activity in HCG 7a as an HII type.…”

“…According to the NED 5 database and the RC3 catalogue (de Vaucouleurs et al 1991), the brightest galaxy of the system, HCG 2a, is classified as a late-type barred SBd galaxy. HCG 2b is classified as a cI (compact Irr) by Hickson (1993) and it is the strongest FIR source in this group (Allam et al 1996). HCG 2c is an SBc-type galaxy.…”

“…Our detected region at the end of the tidal tail is only 45 Myr old. Bournaud & Duc (2006) performed simulations in order to relate TDGs and Allam et al (1996), Verdes-Montenegro et al (1998) and Gallagher et al (2008). The indicator "Central Activity" was taken from: Shimada et al (2000), de Carvalho et al (1997), Coziol et al (1998 and Xu et al (2003).…”

A mid-IR study of Hickson compact groups

“…The only far-IR data available for our sample are based on IRAS (see Allam et al 1996), since the Akari all-sky maps have not yet been released. However, the IRAS data suffer from poor spatial resolution and in nearly all cases one cannot resolve the emission of individual group members.…”

“…Using the mid-IR imaging and extrapolating to the far-IR by the SED fits in this work, we can estimate the fraction of the farinfrared luminosity that is contributed by each group member to the total far-IR luminosity of the whole group. We can calculate the "synthetic" IRAS 60 μm and 100 μm flux densities of each group and compare them to the ones deduced by Allam et al (1996). The results are presented in Table 3 and Fig.…”