Search for cold and hot gas in the ram pressure stripped Virgo dwarf galaxy IC 3418

Abstract

We present IRAM 30m sensitive upper limits on CO emission in the ram pressure stripped dwarf Virgo galaxy IC3418 and in a few positions covering H ii regions in its prominent 17 kpc UV/Hα gas-stripped tail. In the central few arcseconds of the galaxy, we report a possible marginal detection of about 1 × 10 6 M ⊙ of molecular gas (assuming a Galactic CO-to-H 2 conversion factor) that could correspond to a surviving nuclear gas reservoir. We estimate that there is less molecular gas in the main body of IC3418, by at least a factor of 20, than would be expected from the pre-quenching UV-based star formation rate assuming the typical gas depletion timescale of 2 Gyr. Given the lack of star formation in the main body, we think the H 2 -deficiency is real, although some of it may also arise from a higher CO-to-H 2 factor typical in low-metallicity, low-mass galaxies. The presence of H ii regions in the tail of IC3418 suggests that there must be some dense gas; however, only upper limits of < 1 × 10 6 M ⊙ were found in the three observed points in the outer tail. This yields an upper limit on the molecular gas content of the whole tail < 1 × 10 7 M ⊙ , which is an amount similar to the estimates from the observed star formation rate over the tail. We also present strong upper limits on the X-ray emission of the stripped gas in IC3418 from a new Chandra observation. The measured X-ray luminosity of the IC3418 tail is about 280 times lower than that of ESO 137-001, a spiral galaxy in a more distant cluster with a prominent ram pressure stripped tail. Non-detection of any diffuse X-ray emission in the IC3418 tail may be due to a low gas content in the tail associated with its advanced evolutionary state and/or due to a rather low thermal pressure of the surrounding intra-cluster medium.

GASP. I. Gas Stripping Phenomena in Galaxies with MUSE

“…Many studies lack the multiwavelength data required to know the fate of the different gas phases (molecular gas, neutral and ionized hydrogen, and X-ray gas), but detailed observations are beginning to accumulate for a few galaxies (e.g. Sun et al 2010, Vollmer et al 2012, Yagi et al 2013, Jáchym et al 2013, Abramson et al 2011.…”

Molecular Gas Dominated 50 kpc Ram Pressure Stripped Tail of the Coma Galaxy D100*

“…The warm ionized, Hα emitting gas is on the other hand expected to have a very low volume filling factor (f ∼ 0.05; see Jáchym et al 2013, for details). Its total mass is ∼ 2 × 10 8 f −1/2 M ⊙ ≈ 4.5 × 10 7 M ⊙ , assuming the emission fills a 60 kpc×1 kpc cylinder (Yagi et al 2007).…”

“…CO(2-1) beam area is ∼ 93.3 arcsec 2 ; CO(1-0) beam area is ∼ 369.9 arcsec 2 (1/ ln 2 factor is not included). Jáchym et al 2013) was applied to the ionized gas (Hα) masses. We note that the lines connecting individual points are intended to lead the eye and do not correspond to the actual amount of molecular gas in between the observed regions.…”

“…Moreover, the effects of ram pressure likely have been much stronger on D100 due to its ∼ 5-times lower stellar mass. Solving semi-analytically the equation of motion of gas parcels in a D100-like model galaxy (see Jáchym et al 2013Jáchym et al , 2014, assuming a ∼ 2 × 10 11 M ⊙ dark matter halo and a radial orbit), it is probable that the gas parcels with column densities up to ∼ 50 M ⊙ pc −2 could be completely (directly) stripped from the galaxy, down to 1 kpc radius.…”

“…Moreover, in the tail of ESO 137-001, the observed gas components, including the rich molecular phase, together nearly account for the missing gas in the disk. Other tails were searched for molecular content: In the Virgo cluster, only upper limits on CO emission were measured in the tail of IC 3418 (Jáchym et al 2013), while several regions with molecular gas were recently discovered at large distances in the tail of NGC 4388 (Verdugo et al 2015), but corresponding only to a small fraction of total mass of the gas tail. Also, in the Virgo cluster, regions of off-disk CO emission were detected in NGC 4522, (Vollmer et al 2008), as well as in the long Hα trail that connects M86 with NGC 4438 (Dasyra et al 2012).…”