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تسجيل مستخدم جديدSpectacular HST observations of the Coma galaxy D100 and star formation in its ram pressure stripped tail
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We present new HST F275W, F475W, and F814W imaging of the region of the Coma cluster around D100, a spiral galaxy with a remarkably long and narrow ($60 times 1.5$ kpc) ram pressure stripped gas tail. We find blue sources coincident with the H$alpha$ tail, which we identify as young stars formed in the tail. We also determine they are likely to be unbound stellar complexes with sizes of $sim$ $50-100$ pc, likely to disperse as they age. From a comparison of the colors and magnitudes of the young stellar complexes with simple stellar population models, we find ages ranging from $sim$ $1-50$ Myr, and masses ranging from $10^3$ to $sim$ $10^5$ M$_{odot}$. We find the overall rate and efficiency of star formation are low, $sim$ $6.0 times , 10^{-3}$ $M_{odot}$ yr$^{-1}$ and $sim$ $6 , times$ 10$^{-12}$ yr$^{-1}$ respectively. The total H$alpha$ flux of the tail would correspond to a star formation rate $7$ times higher, indicating some other mechanism for H$alpha$ excitation is dominant. From analysis of colors, we track the progression of outside-in star formation quenching in the main body of D100, as well as its apparent companion the S0 D99. Finally, we observe the dust extinction in the base of the tail has an outer envelope with remarkably smooth and straight edges, and linear filamentary substructure strongly suggestive of magnetic fields. These features and the small amount of tail broadening strongly suggest gas cooling restricting broadening, and the influence of magnetic fields inhibiting turbulence.
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We have discovered large amounts of molecular gas, as traced by CO emission, in the ram pressure stripped gas tail of the Coma cluster galaxy D100 (GMP 2910), out to large distances of about 50 kpc. D100 has a 60 kpc long, strikingly narrow tail whic
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of H_2 in three Ha bright regions along the tail of the Norma cluster galaxy ESO 137-001, out to a projected distance of 40 kpc from the disk. ESO 137-001 has an 80 kpc long and bright X-ray tail associated with a shorter (40 kpc) and broader tail of numerous star-forming H II regions. The amount of about 1.5x10^8 Msun of H_2 found in the most distant region is similar to molecular masses of tidal dwarf galaxies, though the standard Galactic CO-to-H_2 factor could overestimate the H_2 content. Along the tail, we find the amount of molecular gas to drop, while masses of the X-ray emitting and diffuse ionized components stay roughly constant. Moreover, the amounts of hot and cold gas are large and similar, and together nearly account for the missing gas from the disk. We find a very low star formation efficiency (tau > 10^10 yr) in the stripped gas in ESO 137-001 and suggest that this is due to a low average gas density in the tail, or turbulent heating of the interstellar medium that is induced by a ram pressure shock. The unprecedented bulk of observed H_2 in the ESO 137-001 tail suggests that some stripped gas may survive ram pressure stripping in the molecular phase.
Previous studies have revealed a population of galaxies in galaxy clusters with ram pressure stripped (RPS) tails of gas and embedded young stars. We observed 1.4 GHz continuum and HI emission with the Very Large Array in its B-configuration in two f
ields of the Coma cluster to study the radio properties of RPS galaxies. The best continuum sensitivities in the two fields are 6 and 8 $mu$Jy per 4 beam respectively, which are 4 and 3 times deeper than those previously published. Radio continuum tails are found in 10 (8 are new) out of 20 RPS galaxies, unambiguously revealing the presence of relativistic electrons and magnetic fields in the stripped tails. Our results also hint that the tail has a steeper spectrum than the galaxy. The 1.4 GHz continuum in the tails is enhanced relative to their H$alpha$ emission by a factor of $sim$7 compared to the main bodies of the RPS galaxies. The 1.4 GHz continuum of the RPS galaxies is also enhanced relative to their IR emission by a factor of $sim$2 compared to star-forming galaxies. The enhancement is likely related to ram pressure and turbulence in the tail. We furthermore present HI detections in three RPS galaxies and upper limits for the other RPS galaxies. The cold gas in D100s stripped tail is dominated by molecular gas, which is likely a consequence of the high ambient pressure. No evidence of radio emission associated with ultra-diffuse galaxies is found in our data.
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