B. F. Madore

Ultraluminous infrared galaxies and the origin of quasars

An evolutionary connection between ultraluminous infrared galaxies and quasars is deduced from the observations nof all 10 infrared galaxies with luminosities L(8-1000 μm) ≥ 10^(12) L⊙, taken from a flux-limited sample of infrared bright galaxies. Images of the infrared galaxies show that nearly all are strongly interacting merger systems with exceptionally luminous nuclei. Millimeter-wave CO observations show that these objects typically contain 0.5-2 x 10^(10) M⊙ of H_2. Optical spectra indicate a mixture of starburst and active galactic nucleus (AGN) energy sources, both of which are apparently fueled by the tremendous reservoir of molecular gas. It is proposed that these ultraluminous infrared galaxies represent the initial, dust-enshrouded stages of quasars. Once these nuclei shed their obscuring dust, allowing the AGN to visually dominate the decaying starburst, they become optically selected quasars. The origin of quasars through the merger of molecular gas-rich spiral galaxies can account for both the increased number of high-luminosity quasars at large redshift, when the universe was smaller and gas supplies less depleted, and the observed redshift-cutoff of quasars which represents the epoch after galaxy formation when the first collisions occur.

Galaxy and Mass Assembly (GAMA): survey diagnostics and core data release

The Galaxy and Mass Assembly (GAMA) survey has been operating since 2008 February on the 3.9-m Anglo-Australian Telescope using the AAOmega fibre-fed spectrograph facility to acquire spectra with a resolution of R ≈ 1300 for 120 862 Sloan Digital Sky Survey selected galaxies. The target catalogue constitutes three contiguous equatorial regions centred at 9h (G09), 12h (G12) and 14.5h (G15) each of 12 × 4 deg2 to limiting fluxes of rpet < 19.4, rpet < 19.8 and rpet <19.4 mag, respectively (and additional limits at other wavelengths). Spectra and reliable redshifts have been acquired for over 98 per cent of the galaxies within these limits. Here we present the survey footprint, progression, data reduction, redshifting, re-redshifting, an assessment of data quality after 3 yr, additional image analysis products (including ugrizYJHK photometry, S´ersic profiles and photometric redshifts), observing mask and construction of our core survey catalogue (GamaCore). From this we create three science-ready catalogues: GamaCoreDR1 for public release, which includes data acquired during year 1 of operations within specified magnitude limits (2008 February to April); GamaCoreMainSurvey containing all data above our survey limits for use by the GAMA Team and collaborators; and GamaCore-AtlasSV containing year 1, 2 and 3 data matched to Herschel-ATLAS science demonstration data. These catalogues along with the associated spectra, stamps and profiles can be accessed via the GAMA website: http://www.gama-survey.org/

The IRAS bright galaxy sample. II - The sample and luminosity function

A complete sample of 324 extragalactic objects with 60 μm flux densities greater than 5.4 Jy has been selected from the IRAS catalogs. Only one of these objects can be classified morphologically as a Seyfert nucleus; the others are all galaxies. The median distance of the galaxies in the sample is ~ 30 Mpc, and the median luminosity vL,(60 μm) is ~ 2 x 10^(10) L_☉ . This infrared selected sample is much more infrared active than optically selected galaxy samples. The range in far-infrared luminosities of the galaxies in the sample is 10^8 L_☉ -2 x 10^(12) L_☉ The far-infrared luminosities of the sample galaxies appear to be independent of the optical luminosities, suggesting a separate luminosity component. As previously found, a correlation exists between 60 μm/100 μm flux density ratio and nfar-infrared luminosity. The mass of interstellar dust required to produce the far-infrared radiation corresponds to a mass of gas of 108-10^(10) M_☉ for normal gas to dust ratios. This is comparable to the mass of the interstellar medium in most galaxies. The infrared luminous galaxies are found to be an important component of extraglactic objects, being the nmost numerous objects in the local universe at luminosities L > 10^(11) L_☉, and producing a luminosity density of ~ that of the observed starlight in normal galaxies. Approximately 60%-80% of the far-infrared luminosity of the local universe is likely attributed to recent or ongoing star formation. If the infrared active phase (L_(FIR) > 10^(11) L_☉ ) is a nonrecurring event of duration less than 108 yr in galaxy evolution, then more than n 10%, and perhaps all of the galaxies with blue luminosities greater than 10^(10) L_☉ must undergo such an event.

UV-optical colors as probes of early-type galaxy evolution

We have studied ~2100 early-type galaxies in the SDSS DR3 which have been detected by the GALEX Medium Imaging Survey (MIS), in the redshift range 0 < z < 0.11. Combining GALEX UV photometry with corollary optical data from the SDSS, we find that, at a 95% confidence level, at least ~30% of galaxies in this sample have UV to optical colors consistent with some recent star formation within the last Gyr. In particular, galaxies with an NUV − r color less than 5.5 are very likely to have experienced such recent star formation, taking into account the possibility of a contribution to NUV flux from the UV upturn phenomenon. We find quantitative agreement between the observations and the predictions of a semianalytical ΛCDM hierarchical merger model and deduce that early-type galaxies in the redshift range 0 < z < 0.11 have ~1%-3% of their stellar mass in stars less than 1 Gyr old. The average age of this recently formed population is ~300-500 Myr. We also find that monolithically evolving galaxies, where recent star formation can be driven solely by recycled gas from stellar mass loss, cannot exhibit the blue colors (NUV − r < 5.5) seen in a significant fraction (~30%) of our observed sample.

The effect of environment on the ultraviolet color-magnitude relation of early-type galaxies

We use GALEX near-UV (NUV) photometry of a sample of early-type galaxies selected in the SDSS (Sloan Digital Sky Survey) to study the UV color-magnitude relation (CMR). NUV − r color is an excellent tracer of even small amounts (~1% mass fraction) of recent (≲1 Gyr) star formation, and so the NUV − r CMR allows us to study the effect of environment on the recent star formation history. We analyze a volume-limited sample of 839 visually inspected early-type galaxies in the redshift range 0.05 < z < 0.10 brighter than M_r of –21.5 with any possible emission-line or radio-selected active galactic nuclei (AGNs) removed to avoid contamination. We find that contamination by AGN candidates and late-type interlopers highly bias any study of recent star formation in early-type galaxies and that, after removing those, our lower limit to the fraction of massive early-type galaxies showing signs of recent star formation is roughly 30% ± 3% . This suggests that residual star formation is common even among the present day early-type galaxy population. We find that the fraction of UV-bright early-type galaxies is 25% higher in low-density environments. However, the density effect is clear only in the lowest density bin. The blue galaxy fraction for the subsample of the brightest early-type galaxies, however, shows a very strong density dependence, in the sense that the blue galaxy fraction is lower in a higher density region.

Herschel-ATLAS: counterparts from the ultraviolet-near-infrared in the science demonstration phase catalogue

We present a technique to identify optical counterparts of 250-μm-selected sources from theu2002Herschel–ATLAS survey. Of the 6621 250 μm > 32-mJy sources in our science demonstration catalogue we find that ∼60 per cent have counterparts brighter thanu2002ru2002 = 22.4 mag in the Sloan Digital Sky Survey. Applying a likelihood ratio technique we are able to identify 2423 of the counterparts with a reliabilityu2002Ru2002> 0.8. This is approximately 37 per cent of the full 250-μm catalogue. We have estimated photometric redshifts for each of these 2423 reliable counterparts, while 1099 also have spectroscopic redshifts collated from several different sources, including the GAMA survey. We estimate the completeness of identifying counterparts as a function of redshift, and present evidence that 250-μm-selectedu2002Herschel–ATLAS galaxies have a bimodal redshift distribution. Those with reliable optical identifications have a redshift distribution peaking atu2002zu2002≈ 0.25 ± 0.05, while submillimetre colours suggest that a significant fraction with no counterpart above theu2002r-band limit haveu2002zu2002 > 1. We also suggest a method for selecting populations of strongly lensed high-redshift galaxies. Our identifications are matched to UV–NIR photometry from the GAMA survey, and these data are available as part of theu2002Herschel–ATLAS public data release.

The luminosity function and space density of the most luminous galaxies in the IRAS survey

The local space density of galaxies with 60 μm luminosity greater than VL_v (60 μm) ≳ 10^(10) L_☉ is derived from a sample of bright galaxies detected in the IRAS survey. The sample is complete to 5 Jy at 60 μm and covers one-quarter of the sky. With a maximum redshift in the sample of 0.081, this sample represents a survey of the infrared characteristics for infrared bright galaxies in the local universe. The space density is described by p(L) ≈ 1.7 X 10^(-3) (L/10^(10) L_☉)-2 Mpc^(-3) over the range 10^(10) L_☉ 10^(10) L_☉ undergo a period of extreme infrared activity.

The UV–optical colour dependence of galaxy clustering in the local universe

We measure the UV-optical colour dependence of galaxy clustering in the local Universe. Using the clean separation of the red and blue sequences made possible by the NUV - r colour-magnitude diagram, we segregate the galaxies into red, blue and intermediate `green classes. We explore the clustering as a function of this segregation by removing the dependence on luminosity and by excluding edge-on galaxies as a means of a non-model dependent veto of highly extincted galaxies. We find that xi(r(p), pi) for both red and green galaxies shows strong redshift-space distortion on small scales - the `finger-of-God effect, with green galaxies having a lower amplitude than is seen for the red sequence, and the blue sequence showing almost no distortion. On large scales, xi(r(p), pi) for all three samples show the effect of large-scale streaming from coherent infall. On scales of 1 h-1 Mpc textless r(p) textless 10 h-1 Mpc, the projected auto-correlation function w(p)(r(p)) for red and green galaxies fits a power law with slope gamma similar to 1.93 and amplitude r(0) similar to 7.5 and 5.3, compared with gamma similar to 1.75 and r(0) similar to 3.9 h-1 Mpc for blue sequence galaxies. Compared to the clustering of a fiducial L* galaxy, the red, green and blue have a relative bias of 1.5, 1.1 and 0.9, respectively. The w(p)(r(p)) for blue galaxies display an increase in convexity at similar to 1 h-1 Mpc, with an excess of large-scale clustering. Our results suggest that the majority of blue galaxies are likely central galaxies in less massive haloes, while red and green galaxies have larger satellite fractions, and preferentially reside in virialized structures. If blue sequence galaxies migrate to the red sequence via processes like mergers or quenching that take them through the green valley, such a transformation may be accompanied by a change in environment in addition to any change in luminosity and colour.

H-ATLAS/GAMA: Dusty early-type galaxies and passive spirals

We present the dust properties and star-formation histories of local submillimetre-selected galaxies in Herschel-ATLAS, classified by optical morphology. The early-type galaxies (ETGs) that are detected contain as much dust as typical spirals, and form a unique sample that has been blindly selected at submillimetre wavelengths. nComparing H-ATLAS galaxies to a control sample of optically selected galaxies, we find 5.5% of luminous ETGs are detected in H-ATLAS. The H-ATLAS ETGs contain a significant mass of cold dust: the mean dust mass is 5.5x10^7 Msun, with individual galaxies ranging from 9x10^5-4x10^8 Msun. This is comparable to that of spirals in our sample, and is an order of magnitude more dust than that found for the control ETGs, which have a median dust mass inferred from stacking of (0.8-4.0)x10^6 Msun. The ETGs detected in H-ATLAS have bluer NUV-r colours, higher specific star-formation rates and younger stellar populations than ETGs which are optically selected, and may be transitioning from the blue cloud to the red sequence. We also find that H-ATLAS and control ETGs inhabit similar low-density environments. We conclude that the dust in H-ATLAS and control ETGs cannot be solely from stellar sources, and a large contribution from dust formed in the ISM or external sources is required. Alternatively, dust destruction may not be as efficient as predicted. nWe also explore the properties of the most passive spiral galaxies in our sample with SSFR<10^-11/yr. We find these passive spirals have lower dust-to-stellar mass ratios, higher stellar masses and older stellar population ages than normal spirals. The passive spirals inhabit low density environments similar to those of the normal spiral galaxies in our sample. This shows that the processes which turn spirals passive do not occur solely in the intermediate density environments of group and cluster outskirts. (Abridged)

Erratum: “An Ultraviolet-to-Radio Broadband Spectral Atlas of Nearby Galaxies” (ApJ, 655, 863 [2007])

D. A. Dale, A. Gil de Paz, K. D. Gordon, H. M. Hanson, L. Armus, G. J. Bendo, L. Bianchi, M. Block, S. Boissier, A. Boselli, B. A. Buckalew, V. Buat, D. Burgarella, D. Calzetti, J. M. Cannon, C. W. Engelbracht, G. Helou, D. J. Hollenbach, T. H. Jarrett, R. C. Kennicutt, C. Leitherer, A. Li, B. F. Madore, M. J. Meyer, E. J. Murphy, M. W. Regan, H. Roussel, J. D. T. Smith, M. L. Sosey, D. A. Thilker, and F. Walter