The X-Ray Zurich Environmental Study (X-Zens). Ii. X-Ray Observations of the Diffuse Intragroup Medium in Galaxy Groups

Abstract

We present the results of a pilot XMM-N ewton and Chandra program aimed at studying the diffuse intragroup medium (DIM) of optically-selected nearby groups from the Zurinch ENvironmental Study (ZENS) catalog. The groups are in a narrow mass range about 10 13 M ⊙ , a mass scale at which the interplay between the DIM and the group member galaxies is still largely unprobed. X-ray emission from the DIM is detected in the energy band 0.5-2 keV with flux ≤ 10 −14 erg cm −1 s −1 , which is one order of magnitude fainter than for typical ROSAT groups (RASS). For many groups we set upper limits to the X-ray luminosity, indicating that the detections are likely probing the upper envelope of the X-ray emitting groups. We find evidence for our optically selected groups to be under-luminous with respect to predictions from X-ray scaling relations. X-ray mass determinations are in best agreement with those based on the member galaxies bulge luminosity, followed by their total optical luminosity and velocity dispersion. We measure a stellar mass fraction with a median value of about 1%, with a contribution from the most massive galaxies between 30 to 50 %. Optical and X-ray data give often complementary answers concerning the dynamical state of the groups, and are essential for a complete picture of the system. Extending this pilot program to a larger sample of groups is mandatory to unveil any imprint of interaction between member galaxies and DIM in halo potentials of key importance for environmentally-driven galactic evolution.

The Complete Local Volume Groups Sample – I. Sample selection and X-ray properties of the high-richness subsample

“…Comparison of detection fraction with other samples is not straightforward; the details of the optical selection process, the mass and redshift range targeted and the X-ray data available all influence detection efficiency. Among nearby samples, our detection rate is comparable to that of the handful of groups observed in the XMM/IMACS sample (XI, 50% Rasmussen et al 2006) and somewhat greater than that for the X-ZENS sample (21% Miniati et al 2016), but the latter survey focused on the smallest groups, with masses in the range 1-5×10 13 M , equivalent to temperatures of ∼0.4-0.9 keV. Our detection rate is smaller than the 80% achieved by Pearson et al (2017) for a sample of groups drawn from the Galaxy And Mass Assembly (GAMA) survey.…”

“…Starting from an optically-selected sample avoids the X-ray selection bias toward systems with highly concentrated cool-core haloes, while the X-ray follow-up provides information on the gas content and properties, and confirms that the groups are fully collapsed systems. This approach has been used with some success to identify unbiased samples of groups (Rasmussen et al 2006;Miniati et al 2016;Pearson et al 2017) and clusters (Balogh et al 2011), but these samples have generally targeted more distant systems, either because their goal was to trace the gas halo to large radii, or because they were based on optical surveys whose limited footprint precludes identification of nearby groups with large angular extents. Such samples are well-suited to cosmological studies.…”

The Dawes Review 9: The role of cold gas stripping on the star formation quenching of satellite galaxies

“…However, this is definitely not the case. Indeed, individual groups with halo mass smaller than ∼ 10 13 M are still partially out of reach of current X-ray missions (e.g., Mulchaey 2000;Finoguenov et al 2009;Miniati et al 2016) and can also host dense IGM at lower temperatures (e.g., 10 5-6 K) than larger groups and clusters. Interestingly, indirect proof of the presence of a significant IGM component in X-ray faint groups comes from the work of Freeland & Wilcots (2011), who looked for bent-double radio sources in groups and estimated the density of the IGM, under the assumption that the radio jets are bent by ram pressure (see also the X-ray stacking results of Anderson, Bregman, & Dai 2013;Anderson et al 2015).…”

The Chandra deep fields: Lifting the veil on distant active galactic nuclei and X-ray emitting galaxies

“…However, in terms of detailed observational manifestations, it is still not so clear about the exact role that large-scale structures (LSSs; including galaxy groups, clusters, and superclusters) play regarding AGN triggering and star-formation activities (see, e.g., Mc-Namara & Nulsen 2012 for a review on AGN feedback in LSSs), which is often complicated by additional likely dependencies such as host stellar mass, AGN luminosity, and redshift. Galaxy groups and clusters, lying at the high end of the cosmic density spectrum, have been intensively observed by X-ray observations that are subject to the least observational biases (e.g., Brandt et al 2001;Bauer et al 2002b;Giacconi et al 2002;Finoguenov et al , 2007Silverman et al 2010;Allen, Evrard, & Mantz 2011;Tanaka et al 2012Tanaka et al , 2013Ehlert et al 2013Ehlert et al , 2014Ehlert et al , 2015Patel et al 2015;Koulouridis et al 2016;Miniati et al 2016;Rumbaugh et al 2017), given the utility of extragalactic X-ray surveys (see Section 1.1); but studies based on such observations sometimes obtain inconsistent results. For example, significant suppression of X-ray AGNs in clusters (e.g., lower AGN fractions than in field populations) has been observed by some authors (e.g., Koulouridis & Plionis 2010;Haines et al 2012;Ehlert et al 2013Ehlert et al , 2014, but not seen by other authors (e.g., Martini et al 2013;Melnyk et al 2013;Koulouridis et al 2014).…”