Abundant Molecular Gas and Inefficient Star Formation in Intracluster Regions: Ram Pressure Stripped Tail of the Norma Galaxy Eso137-001

Abstract

For the first time, we reveal large amounts of cold molecular gas in a ram pressure stripped tail, out to a large, "intracluster" distance from the galaxy. With the APEX telescope we have detected 12 CO(2-1) emission corresponding to more than 10 9 M ⊙ of H 2 in three Hα 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 ∼ 1.5 × 10 8 M ⊙ 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 (τ dep > 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.

Neutral hydrogen in galaxy clusters: impact of AGN feedback and implications for intensity mapping

“…gas stripping by the ICM; see for instance Jáchym et al 2014;Sun et al 2007), a numerical artifact of our hy-drodynamic solver, where residual errors in our SPH scheme prevents the disruption of those HI blobs, or a mix of the two. In order to address this issue one could run simulations with different SPH methods or with grid methods, and investigate how results change.…”

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

“…Given the uncertainty of the X-factor (see the discussion in Section 5.3), it is possible that the molecular gas fraction is somewhat smaller, however, very likely still exceeding the fraction of the other gas components. For comparison, in the tail of the Norma galaxy ESO 137-001, the amounts of cold molecular and hot ionized gas are similar (∼ 1×10 9 M ⊙ ; Jáchym et al 2014;Sun et al 2006).…”

“…In the inner tail of ESO 137-001 elevated ratios of warm-to-cold molecular gas of 0.1 were observed (Sivanandam et al 2010;Jáchym et al 2014), indicating that some part of CO emission is coming from a warmer, more diffuse molecular component. Also in several Virgo spirals, higher ratios of warm H 2 /PAH were found (Wong et al 2014).…”

“…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.…”

The Cosmic Skidmark: witnessing galaxy transformation at z = 0.19

“…The evolution of the CMD into a progressively pronounced "red sequence" (Bower, Lucey & Ellis 1992) at early times, indications of a transitional CM "green valley" and a lack of high-mass blue spirals point to the transformation of latetype spirals into early-type ellipticals within cluster environments. Examples of such transformations (most recently Jáchym et al 2014) are valuable case-studies that deepen our understanding of galaxy evolution. To this end, we present a preliminary look at the "Cosmic Skidmark" -an example of galaxy transformation in action.…”