We describe the construction of MegaZ-LRG, a photometric redshift catalogue of over one million luminous red galaxies (LRGs) in the redshift range 0.4<z<0.7 with limiting magnitude i<20. The catalogue is selected from the imaging data of the Sloan Digital Sky Survey (SDSS) Data Release 4. The 2dF-SDSS LRG and Quasar (2SLAQ) spectroscopic redshift catalogue of 13000 intermediate-redshift LRGs provides a photometric redshift training set, allowing use of ANNZ, a neural network-based photometric-redshift estimator. The rms photometric redshift accuracy obtained for an evaluation set selected from the 2SLAQ sample is z=0.049 averaged over all galaxies, and z=0.040 for a brighter subsample (i<19.0). The catalogue is expected to contain ~5 per cent stellar contamination. The ANNZ code is used to compute a refined star/galaxy probability based on a range of photometric parameters; this allows the contamination fraction to be reduced to 2 per cent with negligible loss of genuine galaxies. The MegaZ-LRG catalogue is publicly available on the World Wide Web from http://www.2slaq.info .
We present the largest publicly available catalog of interacting dwarf galaxies. It includes 177 nearby merging dwarf galaxies of stellar mass M*<10^10^M_{sun}_ and redshifts z<0.02. These galaxies are selected by visual inspection of publicly available archival imaging from two wide-field optical surveys (SDSS-III and the Legacy Survey), and they possess low-surface-brightness features that are likely the result of an interaction between dwarf galaxies. We list UV and optical photometric data that we use to estimate stellar masses and star formation rates. So far, the study of interacting dwarf galaxies has largely been done on an individual basis, and lacks a sufficiently large catalog to give statistics on the properties of interacting dwarf galaxies, and their role in the evolution of low-mass galaxies. We expect that this public catalog can be used as a reference sample to investigate the effects of the tidal interaction on the evolution of star formation, and the morphology/structure of dwarf galaxies. Our sample is overwhelmingly dominated by star-forming galaxies, and they are generally found significantly below the red sequence in the color-magnitude relation. The number of early-type galaxies is only 3 out of 177. We classify them, according to observed low-surface-brightness features, into various categories including shells, stellar streams, loops, antennae, or simply interacting. We find that dwarf-dwarf interactions tend to prefer the low-density environment. Only 41 out of the 177 candidate dwarf-dwarf interaction systems have giant neighbors within a sky-projected distance of 700kpc and a line-of-sight radial velocity range +/-700km/s, and compared to the LMC-SMC, they are generally located at much larger sky-projected distances from their nearest giant neighbors.
We studied the r'-, z'-, and y'-band images of merging galaxies from the observations of the Panoramic Survey Telescope & Rapid Response System (Pan-STARRS). The merging galaxies were selected from our merging catalog that was created by checking the images of the Red-Sequence Cluster Survey 2 from the observations of the Canada France Hawaii Telescope By using the homomorphic-aperture, we determined the photometric results of these merging systems. To obtain accurate photometry, we calibrated the Pan-STARRS r'-, z'-, and y'-band data to match the results of Sloan Digital Sky Survey Data Release 9. We also investigated the stellar masses of the merging galaxies by comparing the Wide-field Infrared Survey Explorer 3.4um emission with the calibrated y'-band data. We present a catalog of the r'-, z'-, and y'-band photometric results for 4698 merging galaxies. For extended sources, our results suggest that the homomorphic-aperture method can obtain more reasonable results than the Desktop Virtual Observatory photometry. We derived new relations between the Pan-STARRS y'-band luminosities and the stellar masses of the merging galaxies. Our results show that the stellar masses of the merging galaxies range from 10^8^ to 10^13^M_{sun}_; some of the dry mergers could be as massive as 10^13^M_{sun}_.
Galaxy groups and clusters are the main tools to test cosmological models and to study the environmental effect of galaxy formation. This work aims to provide a catalogue of galaxy groups/clusters and potentially merging systems based on the SDSS main galaxy survey. We identify galaxy groups and clusters using the modified friends-of-friends (FoF) group finder that is designed specifically for flux-limited galaxy surveys. FoF group membership is refined by multimodality analysis to find subgroups and by using the group virial radius and escape velocity to expose unbound galaxies. We look for merging systems by comparing distances between group centres with group radii. The analysis results in a catalogue of 88 662 galaxy groups with at least two members. Among them are 6873 systems with at least 6 members which we consider as more reliable groups. We find 498 group mergers with up to six groups.
This paper introduces the Multi-wavelength Extreme Starburst Sample (MESS), a new catalog of 138 star-forming galaxies (0.1<z<0.3) optically selected from the Sloan Digital Sky Survey using emission line strength diagnostics to have a high absolute star formation rate (SFR; minimum 11M_{sun}_/yr with median SFR~61M_{sun}_/yr based on a Kroupa initial mass function). The MESS was designed to complement samples of nearby star-forming galaxies such as the luminous infrared galaxies (LIRGs) and ultraviolet luminous galaxies (UVLGs). Observations using the Multi-band Imaging Photometer (24, 70, and 160um channels) on the Spitzer Space Telescope indicate that the MESS galaxies have IR luminosities similar to those of LIRGs, with an estimated median total IR luminosity L_IR_=~3x10^11^L_{sun}_.
Gas flows play a fundamental role in galaxy formation and evolution, providing the fuel for the star formation process. These mechanisms leave an imprint in the amount of heavy elements that enrich the interstellar medium (ISM). Thus, the analysis of this metallicity signature provides additional constraint on the galaxy formation scenario. We aim to discriminate between four different galaxy formation models based on two accretion scenarios and two different star formation recipes. We address the impact of a bimodal accretion scenario and a strongly regulated star formation recipe on the metal enrichment process of galaxies. We present a new extension of the eGalICS model, which allows us to track the metal enrichment process in both stellar populations and in the gas phase. Based on stellar metallicity bins from 0 to 2.5Z_{sun}_, our new chemodynamical model is applicable for situations ranging from metal-free primordial accretion to very enriched interstellar gas contents. We use this new tool to predict the metallicity evolution of both the stellar populations and gas phase. We compare these predictions with recent observational measurements. We also address the evolution of the gas metallicity with the star formation rate (SFR). We then focus on a sub-sample of Milky Way-like galaxies. We compare both the cosmic stellar mass assembly and the metal enrichment process of such galaxies with observations and detailed chemical evolution models.
A method is proposed for the determination of the position and inclination angles of the plane of a spiral galaxy based on the assumption that every spiral arm is a monotonic function of the radius against azimuthal angle. This method may yield more accurate results than the more commonly employed isophote method, which is subject to a number of drawbacks. Analytical study, calibration against other methods and examples of application of the proposed method to real galaxies are presented.
We present 210 new measurements of the central absorption line-strength Mg_2_ index for 87 early-type galaxies drawn from the Prugniel & Simien (1996, Cat. <J/A+A/309/749>) sample. 28 galaxies were not observed before. The results are compared to measurements published previously as available in HYPERCAT, and rescaled to the Lick system. The mean individual internal error on these measurements is 0.009mag+/-0.003mag and the mean external error is 0.012mag+/-0.002mag for this series of measurements. These data are also available from HYPERCAT.
At the faintest radio flux densities (S1.4<10mJy), conflicting results have arisen regarding whether there is a flattening of the average spectral index between a low radio frequency (325 or 610MHz) and, for example, 1.4GHz. We present a new catalogue of 843-MHz radio sources in the European Large Area ISO Survey-South 1 field, which contains the sources, their Australia Telescope Large Area Survey (ATLAS) counterparts and the spectral index distribution of the sources as a function of flux density.
The Millennium Galaxy Catalogue (MGC) is a 37.5deg^2^, medium-deep, B-band imaging survey along the celestial equator, taken with the Wide Field Camera on the Isaac Newton Telescope. The survey region is contained within the regions of both the Two Degree Field Galaxy Redshift Survey (2dFGRS) and the Sloan Digital Sky Survey Early Data Release (SDSS-EDR). The survey has a uniform isophotal detection limit of 26mag.arcsec^-2^ and it provides a robust, well-defined catalogue of stars and galaxies in the range 16<=B_MGC_<24 mag. Here we describe the survey strategy, the photometric and astrometric calibration, source detection and analysis, and present the galaxy number counts that connect the bright and faint galaxy populations within a single survey. We argue that these counts represent the state of the art and use them to constrain the normalizations ({phi}*) of a number of recent estimates of the local galaxy luminosity function. We find that the 2dFGRS, SDSS Commissioning Data (CD), ESO Slice Project, Century Survey, Durham/UKST, Mt Stromlo/APM, SSRS2 and NOG luminosity functions require a revision of their published {phi}* values by factors of 1.05+/-0.05, 0.76+/-0.10, 1.02+/-0.22, 1.02+/-0.16, 1.16+/-0.28, 1.75+/-0.37, 1.40+/-0.26 and 1.01+/-0.39, respectively. After renormalizing the galaxy luminosity functions we find a mean local b_J_ luminosity density of 1.986+/-0.031x10^8^h L_{sun}_.Mpc^-3^
![UCDC is licensed under the `Creative Commons Attribution 4.0 License <http://creativecommons.org/licenses/by/4.0/>`_ .. image:: /static/img/ccby.png :alt: [CC-BY]](/registry-search/?f%5BcontentLevel_facet%5D%5B%5D=Research&f%5Brights_facet%5D%5B%5D=UCDC+is+licensed+under+the+%60Creative+Commons+Attribution+4.0+License+%3Chttp%3A%2F%2Fcreativecommons.org%2Flicenses%2Fby%2F4.0%2F%3E%60_%0A%0A..+image%3A%3A+%2Fstatic%2Fimg%2Fccby.png%0A+++%3Aalt%3A+%5BCC-BY%5D%0A%0A&f%5Bsubject_facet_lc%5D%5B%5D=catalogs){kind=link}