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Register a new userA Comprehensive HST BVI Catalogue Of Star Clusters In Five Hickson Compact Groups Of Galaxies
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We present a photometric catalogue of star cluster candidates in Hickson compact groups (HCGs) 7, 31, 42, 59, and 92, based on observations with the Advanced Camera for Surveys and the Wide Field Camera 3 on the Hubble Space Telescope. The catalogue contains precise cluster positions (right ascension and declination), magnitudes, and colours in the BVI filters. The number of detected sources ranges from 2200 to 5600 per group, from which we construct the high-confidence sample by applying a number of criteria designed to reduce foreground and background contaminants. Furthermore, the high-confidence cluster candidates for each of the 16 galaxies in our sample are split into two sub-populations: one that may contain young star clusters and one that is dominated by globular older clusters. The ratio of young star cluster to globular cluster candidates varies from group to group, from equal numbers to the extreme of HCG 31 which has a ratio of 8 to 1, due to a recent starburst induced by interactions in the group. We find that the number of blue clusters with $M_V < -9$ correlates well with the current star formation rate in an individual galaxy, while the number of globular cluster candidates with $M_V < -7.8$ correlates well (though with large scatter) with the stellar mass. Analyses of the high-confidence sample presented in this paper show that star clusters can be successfully used to infer the gross star formation history of the host groups and therefore determine their placement in a proposed evolutionary sequence for compact galaxy groups.
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This study presents the mass distribution for a sample of 18 late-type galaxies in nine Hickson Compact Groups. We used rotation curves from high resolution 2D velocity fields of Fabry-Perot observations and J-band photometry from the 2MASS survey, in order to determine the dark halo and the visible matter distributions. The study compares two halo density profile, an isothermal core-like distribution and a cuspy one. We also compare their visible and dark matter distributions with those of galaxies belonging to cluster and field galaxies coming from two samples: 40 cluster galaxies of Barnes et al (2004) and 35 field galaxies of Spano et al. (2008). The central halo surface density is found to be constant with respect to the total absolute magnitude similar to what is found for the isolated galaxies. This suggests that the halo density is independent to galaxy type and environment. We have found that core-like density profiles fit better the rotation curves than cuspy-like ones. No major differences have been found between field, cluster and compact group galaxies with respect to their dark halo density profiles.
We observed 5 Hickson Compact Groups with the ESO/MPI 2.2m telescope and WFI to investigate the dwarf galaxy content and distribution in these galaxy groups. Our deep imaging and careful selection of the candidate galaxies revealed a rich population of mainly passively evolving dwarf galaxies, which is spatially much more extended than the originally defined Hickson Compact groups. The composite luminosity function of the 5 groups shows a bimodal structure with a very steep rise in the low luminosity regime. The faint end slope is close to the predictions of CDM theory for the slope of the Dark Matter halo mass function.
We have found the atomic gas (HI) reservoirs of the blue ultra diffuse galaxy (UDG) candidates identified by Roman and Trujillo in images near Hickson Compact Groups (HCGs). We confirm that all of the objects are indeed UDGs with effective radii R_e > 1.5 kpc. Three of them are likely to be gravitationally bound to the HCG near which they project, one is plausibly gravitationally bound to the nearest HCG, and one is in the background. We measure HI masses and velocity widths for each object directly from the spectra, and use the widths together with the UDG effective radii to estimate dynamical masses and halo spin parameters. The location of the blue UDGs in the HI mass - stellar mass plane is consistent with that of the broader gas-rich galaxy population, and both their HI masses and gas richnesses are correlated with their effective radii. The blue UDGs appear to be low-mass objects with high-spin halos, although their properties are not as extreme as those of the faintest diffuse objects found in HI searches. The data presented here highlight the potential of single-dish radio observations for measuring the physical properties of blue diffuse objects detected in the optical.
We present 21cm HI observations of four Hickson Compact Groups with evidence for a substantial intragroup medium using the Robert C. Byrd Green Bank Telescope (GBT). By mapping H I emission in a region of 25$^{prime}times$25$^{prime}$ (140-650 kpc) surrounding each HCG, these observations provide better estimates of HI masses. In particular, we detected 65% more HI than that detected in the Karl G. Jansky Very Large Array (VLA) imaging of HCG92. We also identify if the diffuse gas has the same spatial distribution as the high-surface brightness (HSB) HI features detected in the VLA maps of these groups by comparing the HI strengths between the observed and modeled masses based on VLA maps. We found that the HI observed with the GBT to have a similar spatial distribution as the HSB structures in HCGs 31 and 68. Conversely, the observed HI distributions in HCGs44 and 92 were extended and showed significant offsets from the modeled masses. Most of the faint gas in HCG44 lies to the Northeast-Southwest region and in HCG 92 lies in the Northwest region of their respective groups. The spatial and dynamical similarities between the total (faint+HSB) and the HSB HI indicate that the faint gas is of tidal origin. We found that the gas will survive ionization by the cosmic UV background and the escaping ionizing photons from the star forming regions and stay primarily neutral for at least 500 Myrs.
We present deep H{alpha} imaging of seven Hickson Compact Groups (HCGs) using the 4.1m Southern Astrophysics Research (SOAR) Telescope. The high spatial resolution of the observations allow us to study both the integrated star-formation properties of the main galaxies as well as the 2D distribution of star-forming knots in the faint tidal arms that form during interactions between the individual galaxies. We derive star-formation rates and stellar masses for group members and discuss their position relative to the main sequence of star-forming galaxies. Despite the existence of tidal features within the galaxy groups, we do not find any indication for enhanced star-formation in the selected sample of HCGs. We study azimuthally averaged H{alpha} profiles of the galaxy disks and compare them with the g and r surface-brightness profiles. We do not find any truncated galaxy disks but reveal that more massive galaxies show a higher light concentration in H{alpha} than less massive ones. We also see that galaxies that show a high light concentration in r, show a systematic higher light concentration in H{alpha}. TDG candidates have been previously detected in R-band images for 2 groups in our sample but we find that most of them are likely background objects as they do not show any emission in H{alpha}. We present a new tidal dwarf galaxy (TDG) candidate at the tip of the tidal tail in HCG 91.
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