European Southern Observatory

About: European Southern Observatory is a facility organization based out in Garching bei München, Germany. It is known for research contribution in the topics: Galaxy & Stars. The organization has 3594 authors who have published 16157 publications receiving 823095 citations. The organization is also known as: The European Southern Observatory，ESO & ESO.

The properties of the peculiar type Ia supernova 1991bg — I. Analysis and discussion of two years of observations

Abstract: Observations of the peculiar type Ia SN 1991bg in NGC 4374 collected at ESO–La Silla and Asiago are presented and discussed. The photometric coverageextends for 530 days and the spectroscopy for the first seven months after the explosion. The broad– band light curves in the early months have a narrower peak and a luminosity decline faster than other SNIa (14.6 and 11.7 mag×(100d) 1 in B and V respectively). The R and I light curves do not show the secondary peak typical of normal SNIa. The SN is intrinsically very red ((B V )max = 0.74) and faint (Bmax = 16.54). The light curves flatten with age but remain significantly steeper (2.0 and 2.7 mag×(100d) 1 in B and V between 70 and 200 day) than the average. Consequently the uvoir bolometric light curve of SN 1991bg is fainter with a steeper decline than that of the normal SNIa (e.g. 1992A). This object enhances the correlation which exists between the peak luminosity of SNIa, the decline rate and the kinetic energy. Peculiarities are evident in the spectra at various phases. The continuum at maximum is very red and the photospheric expansion velocity extremely low. There are a number of unusual spectral features, in particular a broad absorption between 4200 and 4500 u which is attributed to TiII and the appearance, as early as one month after maximum, of nebular emission of possibly [CoIII] �5890 5908. Nevertheless, contrary to previous claims (Ruiz-Lapuente et al 1993), the spectral evolution retains a general resemblance to that of other SNIa until the latest available observation (day 203). At this epoch one sees the typical emission features of SNIa at late times although they are significantly narrower (FWHM� 2300 km s 1 ). This facilitates the identification of most lines with forbidden emission of [FeII], [FeIII] and [CoIII]. The emission feature centered at about �6590 is difficult to reconcile with the previous identification as H�, unless asymmetries in the ejecta or ad hoc binary configurations are invoked. This work suggests that the explosion energy was probably a factor 3 to 5 lower than in normal SNIa. Whether this resulted from an explosion of a sub–Chandrasekhar mass WD is not unambiguously established.

The Millennium Galaxy Catalogue: the space density and surface-brightness distribution(s) of galaxies

Abstract: We recover the joint and individual space density and surface-brightness distribution(s) of galaxies from the Millennium Galaxy Catalogue (MGC). The MGC is a local survey spanning 30.9 deg 2 and probing approximately 1-2 mag arcsec -2 deeper than either the Two-Degree Field Galaxy Redshift Survey (2dFGRS) or the Sloan Digital Sky Survey (SDSS). The MGC contains 10095 galaxies to B MGC < 20 mag with 96 per cent spectroscopic completeness. For each galaxy we derive individual K-corrections and seeing-corrected sizes. We implement a joint luminosity-surface-brightness step-wise maximum-likelihood method to recover the bivariate brightness distribution (BBD) inclusive of most selection effects. Integrating the BBD over surface brightness we recover the following Schechter function parameters: Φ* = (0.0177 ± 0.0015)h 3 Mpc -3 , M* BMGC - 5 log h = (-19.60 ± 0.04) mag and a = -1.13 ± 0.02. Compared to the 2dFGRS we find a consistent M* value but a slightly flatter faint-end slope and a higher normalization, resulting in a final luminosity density j bJ = (1.99 ± 0.17) x 10 8 h L ○. Mpc -3 - marginally higher than, but consistent with, the earlier 2dFGRS, ESP, and SDSS z = 0.1 results. The MGC is inconsistent with the SDSS z = 0.0 result (+3σ) if one adopts the derived SDSS evolution. The MGC surface-brightness distribution is a well-bounded Gaussian at the M* point with Φ* = (3.5 ± 0.1) x 10 -2 h 3 Mpc -3 , μ e * = (21.90 ± 0.01) mag arcsec -2 and σ InRe = 0.35 ± 0.01. The characteristic surface brightness for luminous systems is invariant to M BMGC -5 log h -19 mag faintwards of which it moves to lower surface brightness. The surface-brightness distribution also broadens (σ lnRe 0.5 - 0.7) towards lower luminosities. The luminosity dependence of σ lnRe provides a new constraint for both the theoretical development and numerical simulations, which typically predict a mass-independent σ ln Re 0.56 ± 0.04. Higher resolution (FWHM « 1 arcsec) and deeper (μ lim » 26 mag arcsec -2 in the B-band) observations of the local Universe are now essential to probe to lower luminosity and lower surface-brightness levels.

Galaxy And Mass Assembly: The G02 field, Herschel-ATLAS target selection and data release 3

Abstract: We describe data release 3 (DR3) of the Galaxy And Mass Assembly (GAMA) survey. The GAMA survey is a spectroscopic redshift and multiwavelength photometric survey in three equatorial regions each of 60.0 deg2 (G09, G12, and G15), and two southern regions of 55.7 deg2 (G02) and 50.6 deg2 (G23). DR3 consists of: the first release of data covering the G02 region and of data on H-ATLAS (Herschel – Astrophysical Terahertz Large Area Survey) sources in the equatorial regions; and updates to data on sources released in DR2. DR3 includes 154 809 sources with secure redshifts across four regions. A subset of the G02 region is 95.5 per cent redshift complete to r < 19.8 mag over an area of 19.5 deg2, with 20 086 galaxy redshifts, that overlaps substantially with the XXL survey (X-ray) and VIPERS (redshift survey). In the equatorial regions, the main survey has even higher completeness (98.5 per cent), and spectra for about 75 per cent of H-ATLAS filler targets were also obtained. This filler sample extends spectroscopic redshifts, for probable optical counterparts to H-ATLAS submillimetre sources, to 0.8 mag deeper (r < 20.6 mag) than the GAMA main survey. There are 25 814 galaxy redshifts for H-ATLAS sources from the GAMA main or filler surveys. GAMA DR3 is available at the survey website (www.gama-survey.org/dr3/).

Cold, clumpy accretion onto an active supermassive black hole

Abstract: The so-called accretion flow that powers the growth of supermassive black holes in galaxy centres is assumed to be dominated by a smooth, steady flow of very hot plasma, but now observations instead reveal a clumpy accretion of very cold molecular clouds onto a supermassive black hole in the nucleus of a nearby giant elliptical galaxy. The so-called accretion flow that powers the growth of supermassive black holes in galaxy centres is often assumed to be dominated by a smooth, steady flow of very hot plasma, but there is little direct evidence to support this idea. New observations of the Abell 2597 galaxy cluster provide evidence for an alternative model, cold accretion onto black holes, recently predicted by simulations and theory, but not directly observed. The data reveal cold, clumpy molecular clouds falling towards an active supermassive black hole in the nucleus of a nearby giant elliptical galaxy. Supermassive black holes in galaxy centres can grow by the accretion of gas, liberating energy that might regulate star formation on galaxy-wide scales1,2,3. The nature of the gaseous fuel reservoirs that power black hole growth is nevertheless largely unconstrained by observations, and is instead routinely simplified as a smooth, spherical inflow of very hot gas4. Recent theory5,6,7 and simulations8,9,10 instead predict that accretion can be dominated by a stochastic, clumpy distribution of very cold molecular clouds—a departure from the ‘hot mode’ accretion model—although unambiguous observational support for this prediction remains elusive. Here we report observations that reveal a cold, clumpy accretion flow towards a supermassive black hole fuel reservoir in the nucleus of the Abell 2597 Brightest Cluster Galaxy (BCG), a nearby (redshift z = 0.0821) giant elliptical galaxy surrounded by a dense halo of hot plasma11,12,13. Under the right conditions, thermal instabilities produce a rain of cold clouds that fall towards the galaxy’s centre14, sustaining star formation amid a kiloparsec-scale molecular nebula that is found at its core15. The observations show that these cold clouds also fuel black hole accretion, revealing ‘shadows’ cast by the molecular clouds as they move inward at about 300 kilometres per second towards the active supermassive black hole, which serves as a bright backlight. Corroborating evidence from prior observations16 of warmer atomic gas at extremely high spatial resolution17, along with simple arguments based on geometry and probability, indicate that these clouds are within the innermost hundred parsecs of the black hole, and falling closer towards it.

The K20 survey. V. The evolution of the near-IR Luminosity Function

Abstract: We present the galaxy rest-frame near-IR Luminosity Function (LF) and its cosmic evolution to z 1:5 based on a spectroscopic survey of a magnitude limited sample of galaxies with Ks < 20 (the K20 survey, Cimatti et al. 2002b). The LFs have been derived in the rest-frame J and Ks bands. Their evolution is traced using three dierent redshift bins (zmean ' 0:5; 1; 1:5) and comparing them to the Local near-IR Luminosity Function. The luminosity functions at dierent redshifts are fairly well fitted by Schechter functions at z< 1:3. The faint-end of the LFs (L< L) is consistent with the local estimates, with no evidence for a change either in the slope or normalization up to z< 1:3. At higher redshift this part of the luminosity function is not well sampled by our data. Viceversa, the density of luminous galaxies ( MKs 5l ogh70< 25:5) is higher than locally at all redshifts and relatively constant or mildly increasing with redshift within our sample. The data are consistent with a mild luminosity evolutionboth in the J -a ndKs -band up toz' 1:5, with an amplitude of aboutMJ ' 0:69 0:12 and MK ' 0:54 0:12 at z 1. Pure density evolution is not consistent with the observed LF at z 1. Moreover, we find that red and early-type galaxies dominate the bright-end of the LF , and that their number density shows at most a small decrease (<30%) up to z' 1, thus suggesting that massive elliptical galaxies were already in place at z' 1a ndthey should have formed their stars and assembled their mass at higher redshift.There appears to be a correlation of the optical/near-IR colors with near-IR luminosities, the most luminous/massive galaxies being red/old, the low-luminous galaxies being instead dominated by blue young stellar populations. We also investigate the evolution of the near-IR comoving luminosity density to z' 1:5, finding a slow evolution with redshift ((z)=(z= 0)(1+z) () with(J)' 0:70 and(Ks)' 0:37). Finally, we compare the observed LFs with the predictions of a set of the most updated hierarchical merging models. Such a comparison shows that the current versions of hierarchical models overpredict significantly the density of low luminosity galaxies at z 1 and underpredict the density of luminous galaxies at z 1, whereas passive evolution models are more consistent with the data up to z 1:5. The GIF model (Kaufmann et al. 1999) shows a clear deficiency of red luminous galaxies at z 1 compared to our observations and predicts a decrease of luminous galaxies with redshift not observed in our sample.