Dashing through the cluster: An X-ray to radio view of UGC 10420 undergoing ram-pressure stripping

Abstract

We present multi-wavelength data and analysis, including new FUV AstroSat/UVIT observations of the spiral galaxy UGC 10420 (z = 0.032), a member of the cluster Abell 2199. UGC 10420 is present on the edge of the X-ray emitting region of the cluster at a distance of ∼ 680 kpc from the centre. The far-ultraviolet (FUV) data obtained by the AstroSat mission show intense knots of star formation on the leading edge of the galaxy, accompanied by a tail of the same on the diametrically opposite side. Our analysis shows that the images of the galaxy disk in the optical and mid-infrared are much smaller in size than that in the FUV. While the broadband optical colours of UGC 10420 are typical of a post-starburst galaxy, the star formation rate (SFR) derived from a UV-to-IR spectral energy distribution is at least a factor of nine higher than that expected for a star-forming field galaxy of similar mass at its redshift. A careful removal of the contribution of the diffuse intracluster gas shows that the significant diffuse X-ray emission associated with the inter-stellar medium of UGC 10420 has a temperature, and luminosity, L X = 1.8 ± 0.9 × 1040 erg s−1, which are typical of the X-ray emission from late-type spiral galaxies. Two symmetrically placed X-ray hot spots are observed on either sides of an X-ray weak nucleus. Our analysis favours a scenario where the interaction of a galaxy with the hot intra-cluster medium of the cluster, perturbs the gas in the galaxy causing starburst in the leading edge of the disk. On the other hand, the turbulence thus developed may also push some of the gas out of the disk. Interactions between the gas ejected from the galaxy and the intracluster medium can then locally trigger star formation in the wake of the galaxy experiencing ram-pressure stripping. Our data however does not rule out the possibility of a flyby encounter with a neighbouring galaxy, although no relevant candidates are observed in the vicinity of UGC 10420.

An AstroSat/UVIT study of galaxies in the cluster Abell 2199

“…• Besides UGC 10420 discussed in [16], five new candidates have been identified in the newly acquired UVIT data as galaxies undergoing environment-related gas stripping.…”

“…We centred the 28 ′ UVIT field of view on galaxies known to have higher than average SFR (as estimated using the SDSS spectroscopic data) in [7]. Aided by supplementary data in other wavebands, these newly acquired AstroSat/UVIT data are furthering our understanding of the properties and evolution of the targeted galaxies [16]. These data have also provided an opportunity to study the properties of a variety of galactic…”

“…and LEDA 2153801), which were split into two components each, the total counts estimated by the SE were summed up to get the total flux. For the other two (UGC 10420 and UGC 10429), we used the SAOImageDS9 software package [27] to get the total counts using the method described in [16]. To do so, we chose an aperture size of 1.5 ′ centred at the optical nucleus for UGC 10420, and of 0.8 ′ for UGC 10429, respectively.…”

“…UGC 10420 is a face-on spiral galaxy undergoing ram-pressure stripping in Abell 2199 (figure 8). We have presented detailed multi-wavelength analysis of UGC 10420 in [16],…”