Multi-wavelength landscape of the young galaxy cluster RX J1257.2+4738 atz= 0.866

Abstract

Context. Many studies have shown how galaxy properties (e.g. colours, morphology, star-forming (SF) activity, active galactic nuclei population) change not only with redshift, but also with local galaxy density, revealing the important effect of the stellar/halo mass and the environment in the evolution of galaxies. A detailed analysis of the star formation activity in a representative sample of clusters will help us to understand the physical processes that cause the observed changes. Aims. We performed a thorough analysis of the star formation activity in the young massive galaxy cluster RX J1257+4738 at z = 0.866, with emphasis on the relationship between the local environment of the cluster galaxies and their star formation activity. We present an optical and infrared (IR) study that benefited from the large amount of data available for this cluster, including new OSIRIS/GTC and Herschel imaging observations. Methods. Using a multi-wavelength catalogue from the optical to the near-infrared, we measured photometric redshifts through a χ 2 spectral energy distribution fitting procedure. We implemented a reliable and carefully chosen cluster membership selection criterion including Monte Carlo simulations and derived a sample of 292 reliable cluster member galaxies for which we measured the following properties: optical colours, stellar masses, ages, ultraviolet luminosities and local densities. Using the MIPS 24 µm and Herschel data, we measured total IR luminosities and star formation rates (SFRs). Results. Of the sample of 292 cluster galaxies, 38 show far-infrared (FIR) emission with an SFR between 0.5 and 45 M yr −1 . The spatial distribution of the FIR emitters within the cluster density map and the filament-like overdensities observed suggest that RX J1257 is not virialised, but is in the process of assembly. The average star formation as a function of the cluster environment parametrised by the local density of galaxies does not show any clear trend. However, the fraction of SF galaxies unveils that the cluster intermediatedensity regions is preferred for the SF activity to enhance, since we observe a significant increase of the FIR-emitter fraction in this environment. The analysis of the extinction distributions of the optically red and blue SF galaxies supports the assumption of the red SF galaxies as a dusty population.

COSMIC WEB AND STAR FORMATION ACTIVITY IN GALAXIES ATz∼ 1

“…It is unlikely that the observed distributions of SFRs, stellar masses and sSFRs in different environments are extracted from different parent populations, with the evaluated p-value > 0.01 in all cases. The results in this section are consistent with other independent studies at different redshifts (Peng et al 2010;Geach et al 2011;Wijesinghe et al 2012;Koyama et al 2010Koyama et al , 2013bKoyama et al ,a, 2014Feruglio et al 2010;Ideue et al 2012;Muzzin et al 2012;Pintos-Castro et al 2013;Bouché & Lowenthal 2005;Grützbauch et al 2011;Brodwin et al 2013;Hayashi et al 2014;Santos et al 2014;Smail et al 2014). Here, we found no significant evidence that the cosmic web affects the stellar mass, SFR & sSFR of the observed star-forming galaxies at z∼1; a result that might be partially explained by selection biases.…”

“…These results hold at low-z (z 0.5, Fadda et al 2008;Tran et al 2009;Biviano et al 2011;Geach et al 2011;Koyama et al 2011;Mahajan et al 2012 Koyama et al 2008Koyama et al , 2010Sobral et al 2011;Pintos-Castro et al 2013) and high-z (z 1.5, Koyama et al 2014;Santos et al 2014). At z∼1, the closest work to our study in terms of sample selection is that of Sobral et al 2011 who showed that at z∼0.85, the fraction of Hα emitters from both COSMOS-& UDS-HiZELS surveys, when compared to the underlying population of galaxies at the same redshift, peaks at intermediate environments, in agreement with our result.…”

SPECTROSCOPIC STUDY OF STAR-FORMING GALAXIES IN FILAMENTS AND THE FIELD ATz∼ 0.5: EVIDENCE FOR ENVIRONMENTAL DEPENDENCE OF ELECTRON DENSITY

“…Although they are expected to occupy 10% of the volume of the cosmic web, simulations have shown that galaxy filaments contain most of the mass in the universe (∼40%;Aragón-Calvo et al 2010) and host a significant fraction of baryons in the form of a warm-hot intergalactic medium gas in the temperature range 10 5 -10 7 K (Cen & Ostriker 1999Davé et al 2001Davé et al , 2010Klar & Mücket 2012). Filaments are seen in the optical wavelengths as the large-scale thread-like concentration of galaxies (e.g., Pimbblet et al 2004;Scoville et al 2007aScoville et al , 2013Kovač et al 2010;Guzzo & The Vipers Team 2013;Alpaslan et al 2014;Darvish et al 2014Darvish et al , 2015Tempel et al 2014), in X-ray as a warm-hot gas in emission and absorption (e.g., Scharf et al 2000;Zappacosta et al 2002Zappacosta et al , 2010Finoguenov et al 2003;Kaastra et al 2003;Nicastro et al 2005aNicastro et al , 2005bNicastro et al , 2010Werner et al 2008;Danforth et al 2010), in the infrared as possible sites of enhanced star-formation activity, linking clusters (e.g., Koyama et al 2008;Biviano et al 2011;Coppin et al 2012;Pintos-Castro et al 2013), and in the weak-lensing studies as a bridging distribution of dark matter, connecting galaxy clusters (e.g., Dietrich et al 2012;Jauzac et al 2012;Higuchi et al 2015).…”

“…Nevertheless, the limited number of studies in this field has already highlighted the importance of filaments as regions with an enhanced fraction of star-forming galaxies and/or star-formation activity (Porter & Raychaudhury 2007;Fadda et al 2008;Koyama et al 2008;Porter et al 2008;Biviano et al 2011;Coppin et al 2012;Pintos-Castro et al 2013;Darvish et al 2014). There are also some systematic surveys/works trying to expand galaxy evolution studies beyond the cluster realm by probing the much larger scale structures (of the order of ∼10 Mpc and beyond) around massive galaxy cluster candidates (see, e.g., Kodama et al 2005;Kartaltepe et al 2008;Lubin et al 2009;Sobral et al 2011).…”

DUSTY STARBURSTS AND THE FORMATION OF ELLIPTICAL GALAXIES: A SCUBA-2 SURVEY OF Az= 1.46 CLUSTER

“…Indeed, mid-infrared and sub-millimeter wavelength observations have revealed populations of strongly star-forming (ultra-)luminous infrared galaxies (U/LIRGs) in more distant clusters (e.g. Brodwin et al 2013;Pintos-Castro et al 2013;Smail et al 2014;Alberts et al 2014;Santos et al 2014Santos et al , 2015. This enhanced activity means that the mass-normalized integrated star-formation rate for massive clusters evolves rapidly with redshift, Σ(SFR)/M cl ∝ (1+z) α with α as high as seven (e.g.…”