The final product of galaxy evolution through cosmic time is the population of galaxies in the local universe. These galaxies are also those that can be studied in most detail, thus providing a stringent benchmark for our understanding of galaxy evolution. Through the huge success of spectroscopic single-fiber, statistical surveys of the Local Universe in the last decade, it has become clear, however, that an authoritative observational description of galaxies will involve measuring their spatially resolved properties over their full optical extent for a statistically significant sample. We present here the Calar Alto Legacy Integral Field Area (CALIFA) survey, which has been designed to provide a first step in this direction. We summarize the survey goals and design, including sample selection and observational strategy. We also showcase the data taken during the first observing runs (June/July 2010) and outline the reduction pipeline, quality control schemes and general characteristics of the reduced data. This survey is obtaining spatially resolved spectroscopic information of a diameter selected sample of ∼600 galaxies in the Local Universe (0.005 < z < 0.03). CALIFA has been designed to allow the building of two-dimensional maps of the following quantities: (a) stellar populations: ages and metallicities; (b) ionized gas: distribution, excitation mechanism and chemical abundances; and (c) kinematic properties: both from stellar and ionized gas components. CALIFA uses the PPAK integral field unit (IFU), with a hexagonal field-of-view of ∼1.3 , with a 100% covering factor by adopting a three-pointing dithering scheme. The optical wavelength range is covered from 3700 to 7000 Å, using two overlapping setups (V500 and V1200), with different resolutions: R ∼ 850 and R ∼ 1650, respectively. CALIFA is a legacy survey, intended for the community. The reduced data will be released, once the quality has been guaranteed. The analyzed data fulfill the expectations of the original observing proposal, on the basis of a set of quality checks and exploratory analysis: (i) the final datacubes reach a 3σ limiting surface brightness depth of ∼23.0 mag/arcsec 2 for the V500 grating data (∼22.8 mag/arcsec 2 for V1200); (ii) about ∼70% of the covered field-of-view is above this 3σ limit; (iii) the data have a blue-to-red relative flux calibration within a few percent in most of the wavelength range; (iv) the absolute flux calibration is accurate within ∼8% with respect to SDSS; (v) the measured spectral resolution is ∼85 km s −1 for V1200 (∼150 km s −1 for V500); (vi) the estimated accuracy of the wavelength calibration is ∼5 km s −1 for the V1200 data (∼10 km s −1 for the V500 data); (vii) the aperture matched CALIFA and SDSS spectra are qualitatively and quantitatively similar. Finally, we show that we are able to carry out all measurements indicated above, recovering the properties of the stellar populations, the ionized gas and the kinematics of both components. The associated maps illustrate the spatial variation of...

Gas deficiency in cluster spirals is well known and ram‐pressure stripping is considered the main gas removal mechanism. In some compact groups too gas deficiency is reported. However, gas deficiency in loose groups is not yet well established. Lower dispersion of the member velocities and the lower density of the intragroup medium in small loose groups favour tidal stripping as the main gas removal process in them. Recent releases of data from the H i Parkes All‐Sky Survey (HIPASS) and catalogues of nearby loose groups with associated diffuse X‐ray emission have allowed us to test this notion. In this paper, we address the following questions: (i) do galaxies in groups with diffuse X‐ray emission statistically have lower gas content compared to the ones in groups without diffuse X‐ray emission? (ii) does H i deficiency vary with the X‐ray luminosity, LX, of the loose group in a systematic way? We find that (i) galaxies in groups with diffuse X‐ray emission, on average, are H i deficient, and have lost more gas compared to those in groups without X‐ray emission; the latter are found not to have significant H i deficiency; (ii) no systematic dependence of the H i deficiency with LX is found. Ram‐pressure‐assisted tidal stripping and evaporation by thermal conduction are the two possible mechanisms to account for this excess gas loss.

Context. Pre-merger tidal interactions between pairs of galaxies are known to induce significant changes in the morphologies and kinematics of the stellar and interstellar medium components. Large amounts of gas and stars are often found to be disturbed or displaced as tidal debris. This debris then evolves, sometimes forming stars and occasionally forming tidal dwarf galaxies. Here we present results from our H i study of Arp 65, an interacting pair hosting extended H i tidal debris.Aims. In an effort to understand the evolution of tidal debris produced by interacting pairs of galaxies, including in situ star and tidal dwarf galaxy formation, we are mapping H i in a sample of interacting galaxy pairs. The Arp 65 pair is the latest member of this sample to be mapped. Methods.Our resolved H i 21 cm line survey is being carried out using the Giant Metrewave Radio Telescope. We used our H i survey data as well as available SDSS optical, Spitzer infra-red and GALEX UV data to study the evolution of the tidal debris and the correlation of H i with the star-forming regions within it.Results. In Arp 65 we see a high impact pre-merger tidal interaction involving a pair of massive galaxies (NGC 90 and NGC 93) that have a stellar mass ratio of ∼1:3. The interaction, which probably occurred ∼1.0-2.5 × 10 8 yr ago, appears to have displaced a large fraction of the H i in NGC 90 (including the highest column density H i) beyond its optical disk. We also find extended on-going star formation in the outer disk of NGC 90. In the major star-forming regions, we find the H i column densities to be ∼4.7 × 10 20 cm −2 or lower. But no signature of star formation was found in the highest column density H i debris SE of NGC 90. This indicates conditions within the highest density H i debris remain hostile to star formation and it reaffirms that high H i column densities may be a necessary but not sufficient criterion for star formation.

Environment plays an important role in the evolution of the gas contents of galaxies. Gas deficiency of cluster spirals and the role of the hot intracluster medium in stripping gas from these galaxies is a well-studied subject. Loose groups with diffuse X-ray emission from the intragroup medium (IGM) offer an intermediate environment between clusters and groups without a hot IGM. These X-ray bright groups have smaller velocity dispersion and lower temperature than clusters, but higher IGM density than loose groups without diffuse X-ray emission. A single-dish comparative study of loose groups with and without diffuse X-ray emission from the IGM, showed that the galaxies in X-ray bright groups have lost more gas on average than the galaxies in non X-ray bright groups. In this paper we present GMRT H I observations of 13 galaxies from four X-ray bright groups: NGC 5044, 720, 1550 and IC1459. The aim of this work is to study the morphology of H I in these galaxies and to see if the hot IGM has in any way affected their H I content or distribution. In addition to disturbed H I morphology, we find that most galaxies have shrunken H I discs compared to the field spirals. This indicates that IGM-assisted stripping processes like ram pressure may have stripped gas from the outer edges of the galaxies.

ABSTRACT Our GMRT (Giant Metrewave Radio Telescope) H i observations of the ultra-diffuse galaxy (UDG) UGC 2162, projected ∼ 300 kpc from the centre of the M 77 group, reveal it to a have an extended H i disc ($R_{\rm H\,{\small I}}/R_{25}$ ∼ 3.3) with a moderate rotational velocity (Vrot ∼ 31 km s−1). This Vrotis in line with that of dwarf galaxies with similar H i mass. We estimate an Mdyn of ∼1.14 × 109 M⊙ within the galaxy’s $R_ \rm {H\,{\small I}}$ ∼ 5.2 kpc. Additionally, our estimates of M200 for the galaxy from NFW models are in the range of 5.0–8.8 × 1010 M⊙. Comparing UGC 2162 to samples of UDGs with H i detections show it to have amongst the smallest Re with its MH i/M* being distinctly higher and g – icolour slightly bluer than typical values in those samples. We also compared H i and dark matter (DM) halo properties of UGC 2162 with dwarf galaxies in the LITTLE THINGS sample and find its DM halo mass and profile are within the range expected for a dwarf galaxy. While we were unable to determine the origin of the galaxy’s present-day optical form from our study, its normal H i rotation velocity in relation to its H i mass, H i morphology, environment, and dwarf mass DM halo ruled out some of the proposed ultra-diffuse galaxy formation scenarios for this galaxy.

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We present results from GMRT Hi 21 cm line observations of the interacting galaxy pair Arp 181 (NGC 3212 and NGC 3215) at z =0.032. We find almost all of the detected Hi (90%) displaced well beyond the optical disks of the pair with the highest density Hi located ∼70 kpc west of the pair. An Hi bridge extending between the optical pair and the bulk of the Hi together with their Hi deficiencies provide strong evidence that the interaction between the pair has removed most of their Hi to THE current projected position. Hi to the west of the pair has two approximately equal intensity peaks. The Hi intensity maximum furthest to the west coincides with a small spiral companion SDSS J102726.32+794911.9 which shows enhanced mid-infrared (Spitzer), UV (GALEX) and Hα emission indicating intense star forming activity. The Hi intensity maximum close to the Arp 181 pair, coincides with a diffuse optical cloud detected in UV (GALEX) at the end of the stellar and Hi tidal tails originating at NGC 3212 and, previously proposed to be a tidal dwarf galaxy in formation. Future sensitive Hi surveys by telescopes like ASKAP should prove to be powerful tools for identifying tidal dwarfs at moderate to large redshifts to explore in detail the evolution of dwarf galaxies in the Universe.

We present the results of Giant Metrewave Radio Telescope (GMRT) observations of the interacting system Arp86 in both neutral atomic hydrogen, H I, and in radio continuum at 240 606 and 1394 MHz. In addition to H I emission from the two dominant galaxies, NGC 7752 and NGC 7753, these observations show a complex distribution of H I tails and bridges due to tidal interactions. The regions of highest column density appear related to the recent sites of intense star formation. H I column densities ∼1-1.5 × 10 21 cm −2 have been detected in the tidal bridge which is bright in Spitzer image as well. We also detect H I emission from the galaxy 2MASX J23470758+2926531, which is shown to be a part of this system. We discuss the possibility that this could be a tidal dwarf galaxy. The radio continuum observations show evidence of a non-thermal bridge between NGC 7752 and NGC 7753, and a radio source in the nuclear region of NGC 7753 consistent with it having a low-ionization nuclear emission region nucleus.