Wings-Spe

Abstract

Context. Cluster galaxies are the ideal sites to look at when studying the influence of the environment on the various aspects of the evolution of galaxies, such as the changes in their stellar content and morphological transformations. In the framework of wings, the WIde-field Nearby Galaxy-cluster Survey, we have obtained optical spectra for ∼6000 galaxies selected in fields centred on 48 local (0.04 < z < 0.07) X-ray selected clusters to tackle these issues. Aims. By classifying the spectra based on given spectral lines, we investigate the frequency of the various spectral types as a function of both the clusters' properties and the galaxies' characteristics. In this way, using the same classification criteria adopted for studies at higher redshift, we can consistently compare the properties of the local cluster population to those of their more distant counterparts. Methods. We describe a method that we have developed to automatically measure the equivalent width of spectral lines in a robust way, even in spectra with a non optimal signal-to-noise ratio. This way, we can derive a spectral classification reflecting the stellar content, based on the presence and strength of the [Oii] and Hδ lines. Results. After a quality check, we are able to measure 4381 of the ∼6000 originally observed spectra in the fields of 48 clusters, of which 2744 are spectroscopically confirmed cluster members. The spectral classification is then analysed as a function of galaxies' luminosity, stellar mass, morphology, local density, and host cluster's global properties and compared to higher redshift samples (MORPHS and EDisCS). The vast majority of galaxies in the local clusters population are passive objects, being also the most luminous and massive. At a magnitude limit of M V < −18, galaxies in a post-starburst phase represent only ∼11% of the cluster population, and this fraction is reduced to ∼5% at M V < −19.5, which compares to the 18% at the same magnitude limit for high-z clusters. "Normal" star-forming galaxies (e(c)) are proportionally more common in local clusters. Conclusions. The relative occurrence of post-starbursts suggests a very similar quenching efficiency in clusters at redshifts in the 0 to ∼1 range. Furthermore, more important than the global environment, the local density seems to be the main driver of galaxy evolution in local clusters at least with respect to their stellar populations content.

Jellyfish Galaxy Candidates at Low Redshift

“…In the following we distinguish between "star-forming galaxies" (all those with emission lines) and "post-starburst" (k+a) and "passive" (k) galaxies that lack emission lines and have a strong and a weak Hδ line in absorption, respectively. The post-starburst signature testifies the presence of recent SF activity that ended sometime during the last ∼1 Gyr, while k galaxies are those that have been devoid of any SF for a longer time (Poggianti et al 1999, Fritz et al 2014.…”

“…Galaxies were assigned a spectral type on the basis of the strength of their main emission and absorption lines, as done in Fritz et al (2014). In the following we distinguish between "star-forming galaxies" (all those with emission lines) and "post-starburst" (k+a) and "passive" (k) galaxies that lack emission lines and have a strong and a weak Hδ line in absorption, respectively.…”

Structural and dynamical modeling of WINGS clusters

“…Detailed information about spectral features are available for a subset of these galaxies (Fritz et al 2007(Fritz et al , 2011(Fritz et al , 2014. Follow-up spectroscopy of a subset of the WINGS clusters has been obtained using the Anglo Australian Telescope (AAT) AAOmega spectrograph (Moretti et al 2017), to extend the spectroscopic coverage of the WINGS clusters in their outer regions.…”

WINGS Data Release: a database of galaxies in nearby clusters

“…Line equivalent widths were measured in the WINGS spectra using an automated method described in detail in Fritz et al (2014). Among the original spectroscopic sample consisting of ∼6000 galaxies, we discarded those having unrecoverable difficulties in the wavelength calibration shortward of ∼4300 Å.…”

“…The measured spectral lines are listed in Table 1 of Fritz et al (2014) and are listed in the database columns that we make publicly available (see Table 8). Following the WINGS ID with its sky coordinates, we list equivalent widths of OII, H θ , H ζ , H η , Ca(K), Ca(H)+H , H δ , Gband, H γ , H β , OIII, Mg, Na, H α , D4000, D n 4000.…”