The NARROW X-Ray TAIL AND DOUBLE Hα TAILS OF ESO 137-002 IN A3627

Abstract

We present the analysis of a deep Chandra observation of a ∼ 2L * late-type galaxy, ESO 137-002, in the closest rich cluster A3627. The Chandra data reveal a long ( 40 kpc) and narrow tail with a nearly constant width (∼ 3 kpc) to the southeast of the galaxy, and a leading edge ∼ 1.5 kpc from the galaxy center on the upstream side of the tail. The tail is most likely caused by the nearly edge-on stripping of ESO 137-002's interstellar medium (ISM) by ram pressure, compared to the nearly face-on stripping of ESO 137-001 discussed in our previous work. Spectral analysis of individual regions along the tail shows that the gas throughout it has a rather constant temperature, ∼ 1 keV, very close to the temperature of the tails of ESO 137-001, if the same atomic database is used. The derived gas abundance is low (∼ 0.2 solar with the single-kT model), an indication of the multiphase nature of the gas in the tail. The mass of the X-ray tail is only a small fraction (< 5%) of the initial ISM mass of the galaxy, suggesting that the stripping is most likely at an early stage. However, with any of the single-kT , double-kT and multi-kT models we tried, the tail is always "over-pressured" relative to the surrounding intracluster medium (ICM), which could be due to the uncertainties in the abundance, thermal vs. non-thermal X-ray emission, or magnetic support in the ICM. The Hα data from the Southern Observatory for Astrophysical Research (SOAR) show a ∼ 21 kpc tail spatially coincident with the X-ray tail, as well as a secondary tail (∼ 12 kpc long) to the east of the main tail diverging at an angle of ∼ 23 • and starting at a distance of ∼ 7.5 kpc from the nucleus. At the position of the secondary Hα tail, the X-ray emission is also enhanced at the ∼ 2σ level. We compare the tails of ESO 137-001 and ESO 137-002, and also compare the tails to simulations. Both the similarities and differences of the tails pose challenges to the simulations. Several implications are briefly discussed.

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

“…Molecular gas is the primary fuel of star formation. However, the amount of star formation in CO-abundant tails is different: there is over 30 H II regions in the tail of ESO 137-001 (Sun et al 2007), possibly only a few H II regions in the tail of D100 (this work), but none were revealed in the tail of ESO 137-002 (Zhang et al 2013). The observed correlation thus indicates that different excitation processes are active in the stripped gas.…”

The stripping of a galaxy group diving into the massive cluster A2142

“…During infall, the ram pressure applied by the ambient intracluster medium (ICM) is responsible for stripping the gas from its original halo and heating it up (Gunn & Gott 1972;Vollmer et al 2001;Heinz et al 2003;Roediger & Brüggen 2008), leading to the virialization of the gas in the main dark-matter halo. This A&A 570, A119 (2014) process has been observed in a handful of interacting galaxies in the nearest clusters such as Virgo (e.g., Machacek et al 2004;Randall et al 2008), A3627 (Sun et al 2007;Zhang et al 2013), Pavo (Machacek et al 2005) and A1367 (Sun & Vikhlinin 2005).…”

On the origin of the faint-end of the red sequence in high-density environments

“…They are more frequent in massive clusters such as Coma than in small systems as Virgo. An exception to this rule is the spectacular IC 3418 (VCC 1217) close to the core of the Virgo cluster (Hester et Multifrequency observations have been critical to demonstrate that also the hot X-ray emitting gas in the halo of galaxies can be stripped by ram pressure in cluster (Sun et al 2007(Sun et al , 2010; Ehlert et al 2013;Zhang et al 2013) and group galaxies (Rasmussen et al 2012b). The most evident case is the galaxy ESO 137-001 in A3627 (Sun et al 2007; Fumagalli et al 2014).…”