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The cores of clusters at 0 ≲ z ≲ 1 are dominated by quiescent early-type galaxies, whereas the field is dominated by star-forming late-type galaxies. Clusters grow through the accretion of galaxies and groups from the surrounding field, which implies that galaxy properties, notably the star formation ability, are altered as they fall into overdense regions. The critical issues for understanding this evolution are how the truncation of star formation is connected to the morphological transformation and what physical mechanism is responsible for these changes. The GaLAxy Cluster Evolution Survey (GLACE) is conducting a thorough study of the variations in galaxy properties (star formation, AGN activity, and morphology) as a function of environment in a representative and well-studied sample of clusters. To address these questions, the GLACE survey is making a deep panoramic survey of emission line galaxies (ELG), mapping a set of optical lines ([O ii], [O iii], Hβ andHα/[N ii] when possible) in several galaxy clusters at z ~ 0.40, 0.63, and 0.86. Using the tunable filters (TF) of the OSIRIS instrument at the 10.4 m GTC telescope, the GLACE survey applies the technique of TF tomography: for each line, a set of images are taken through the OSIRIS TF, each image tuned at a different wavelength (equally spaced), to cover a rest frame velocity range of several thousand km s-1 centred on the mean cluster redshift, and scanned for the full TF field of view of an 8 arcmin diameter. Here we present the first results of the GLACE project, targeting the Hα/[N ii] lines in the intermediate-redshift cluster ZwCl 0024.0+1652 at z = 0.395. Two pointings have been performed that cover ~2 × rvir. We discuss the specific techniques devised to process the TF tomography observations in order to generate the catalogue of cluster Hα emitters, which contains more than 200 sources down to a star formation rate (SFR) ≲1 M⊙/yr. An ancillary broadband catalogue is constructed, allowing us to discriminate line interlopers by means of colour diagnostics. The final catalogue contains 174 unique cluster sources. The AGN population is distinguished using different diagnostics and found to be ~37% of the ELG population. The median SFR of the star-forming population is 1.4 M⊙/yr. We studied the spatial distribution of ELG and confirm the existence of two components in the redshift space. Finally, we exploited the outstanding spectral resolution of the TF, attempting to estimate the cluster mass from ELG dynamics, finding M200 = (4.1 ± 0.2) × 1014 M⊙ h-1, in agreement with previous weak-lensing estimates. [ABSTRACT FROM AUTHOR]

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 e ect 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 X2 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. [ABSTRACT FROM AUTHOR]

The GaLAxy Cluster Evolution survey (GLACE) is aimed to study the evolution of emission line galaxies in clusters across the cosmic time. It takes advantage of the tunable filter mode of OSIRIS (first light instrument of GTC) to scan H α /[N II], H β, [O II]3727 and [O III]5007 searching for star formation activity and AGNs in clusters in three different redshift windows ( z ∼ 0.40, 0.63, and 0.86), providing a unique view of the evolution of cluster galaxies along such redshift range. Moreover, the OSIRIS large field of view (8×8 arcmin2) together with GTC large collective area ( D ∼ 10 m) make it possible to detect SFR ∼ 2 M⊙ yr-1 in an angular area up to 2 Rvir. We present here the first results of the program together with a brief description of this novel technique focusing in the cluster CL0024+1654 ( z ∼ 0.39). (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Context. Computational techniques are essential for mining large databases produced in modern surveys with value-added products. Aims. This paper presents a machine learning procedure to carry out a galaxy morphological classification and photometric redshift estimates simultaneously. Currently, only a spectral energy distribution (SED) fitting has been used to obtain these results all at once. Methods. We used the ancillary data gathered in the OTELO catalog and designed a nonsequential neural network that accepts optical and near-infrared photometry as input. The network transfers the results of the morphological classification task to the redshift fitting process to ensure consistency between both procedures. Results. The results successfully recover the morphological classification and the redshifts of the test sample, reducing catastrophic redshift outliers produced by an SED fitting and avoiding possible discrepancies between independent classification and redshift estimates. Our technique may be adapted to include galaxy images to improve the classification. [ABSTRACT FROM AUTHOR]

Microvariability (intranight variability) is a low amplitude flux change at short time-scales (i.e. hours). It has been detected in unobscured type 1 active galactic nuclei (AGN) and blazars. However in type 2AGN, the detection is hampered by the lowcontrast between the presumably variable nucleus and the host galaxy. In this paper, we present a search for microvariability in a sample of four type 2 quasars as an astrostatistical problem. We are exploring the use of a newly introduced enhanced F-test, proposed by Diego. The presented results show that out of four observed target, we are able to apply this statistical method to three of them. Evidence of microvariations is clear in the case of quasar J0802+2552 in all used filters (g', r' and i') during both observing nights, and they are present in one of the nights of observations, J1258+5239 in one filter (i'), while for the J1316+4452, there is evidence for microvariability within our detection levels during one night and two filters (r' and i'). We demonstrate the feasibility of the enhanced F-test to detect microvariability in obscured type 2 quasars. At the end of this paper, we discuss possible causes of microvariability. One of the options is the misclassification of the targets. A likely scenario for explanation of the phenomenon involves optically thin gaps in a clumpy obscuring medium, in accordance with the present view of the circumnuclear medium. There is a possible interesting connection between the merging state of the targets and detection of microvariability. [ABSTRACT FROM AUTHOR]

Fast brightness variations are a unique tool to probe the innermost regions of active galactic nuclei (AGN). These variations are called microvariability or intra-night variability, and this phenomenon has been monitored in samples of blazars and unobscured AGNs. Detecting optical microvariations in targets hidden by the obscuring torus is a challenging task because the region responsible for the variations is hidden from our sight. However, there have been reports of fast variations in obscured Seyfert galaxies in X-rays, which rises the question whether microvariations can also be detected in obscured AGNs in the optical regime. Because the expected variations are very small and can easily be lost within the noise, the analysis requires a statistical approach. We report the use of a one-way analysis of variance, ANOVA, with which we searched for microvariability. ANOVA was successfully employed in previous studies of unobscured AGNs. As a result, we found microvariable events during three observing blocks: in two we observed the same object (Mrk 477), and in another, J0759+5050. The results on Mrk 477 confirm previous findings. However, since Mrk 477 is quite a peculiar target with hidden broad-line regions, we cannot rule out the possibility that we have serendipitously chosen a target prone to variations. [ABSTRACT FROM AUTHOR]

In this work we analyse the physical properties of a sample of 56 spectroscopically selected star-forming (SF) Lyα emitting galaxies at 2.0 ≲ z ≲ 3.5 using both a spectral energy distribution (SED) fitting procedure from rest-frame UV to mid-IR and direct 160 μm FIR observations taken with the Photodetector Array Camera and Spectrometer (PACS) instrument onboard the Herschel Space Observatory. We define LAEs as those Lyα-emitting galaxies whose rest-frame Lyα equivalent widths (LyαEWrest-frame) are above 20Å, the typical threshold in narrow-band searches. Lyα-emitting galaxies with LyαEWrest-frame < 20Å are called non-LAEs. As a result of an individual SED fit for each object, we find that the studied sample of LAEs contains galaxies with ages mostly below 100 Myr and a wide variety of dust attenuations, SFRs, and stellar masses. The heterogeneity of the physical properties is also seen in the morphology, ranging from bulge-like galaxies to highly clumpy systems. In this way, we find that LAEs at 2.0 ≲ z ≲ 3.5 are very diverse, and do not have a bimodal nature, as suggested in previous studies. Furthermore, the main difference between LAEs and non-LAEs is their dust attenuation, because LAEs are not as dusty as non-LAEs. On the FIR side, four galaxies of the sample (two LAEs and two non-LAEs) have PACS detections. Their total IR luminosities place all of them in the ULIRG regime, and all are dusty objects, with A1200 ≳ 4mag. This is an indication from direct FIR measurements that dust and Lyα emission are not mutually exclusive. This population of red and dusty LAEs is not seen at z ∼ 0.3, which suggests an evolution with redshift of the IR nature of galaxies selected via their Lyα emission. [ABSTRACT FROM AUTHOR]

The analysis of the physical properties of low-redshift Lyα emitters (LAEs) can provide clues in the study of their high-redshift analogs. At z ∼ 0.3, LAEs are bright enough to be detected over almost the entire electromagnetic spectrum and it is possible to carry out a more precise and complete study than at higher redshifts. In this work, we examine the UV and IR emission, dust attenuation, star formation rate (SFR), and morphology of a sample of 23 GALEX-discovered star-forming LAEs at z ∼ 0.3 with direct UV (GALEX), optical (ACS), and FIR (PACS and MIPS) data. Using the same UV and IR limiting luminosities, we find that LAEs at z ∼ 0.3 tend to be less dusty, have slightly higher total SFRs, have bluer UV continuum slopes, and are much smaller than other galaxies that do not exhibit Lyα emission in their spectrum (non-LAEs). These results suggest that at z ∼ 0.3, Lyα photons tend to escape from small galaxies with low dust attenuation. Regarding their morphology, LAEs belong to Irr/merger classes, unlike non-LAEs. Size and morphology represent the most noticeable difference between LAEs and non-LAEs at z ∼ 0.3. Furthermore, the comparison of our results with those obtained at higher redshifts indicates either that the Lyα technique picks up different kind of galaxies at different redshifts or that the physical properties of LAEs are evolving with redshift. [ABSTRACT FROM AUTHOR]