We present the automated techniques we have developed for new software that optimally detects, deblends, measures and classifies sources from astronomical images: SExtractor ( Source Extractor  ). We show that a very reliable star/galaxy separation can be achieved on most images using a neural network trained with simulated images. Salient features of SExtractor include its ability to work on very large images, with minimal human intervention, and to deal with a wide variety of object shapes and magnitudes. It is therefore particularly suited to the analysis of large extragalactic surveys.

/pdf/sextractor-software-for-source-extraction-3zgg2qv8fh.pdf

SExtractor: Software for source extraction

▪ Abstract The Universe is in transition. At early times, galactic evolution was dominated by hierarchical clustering and merging, processes that are violent and rapid. In the far future, evolution will mostly be secular—the slow rearrangement of energy and mass that results from interactions involving collective phenomena such as bars, oval disks, spiral structure, and triaxial dark halos. Both processes are important now. This review discusses internal secular evolution, concentrating on one important consequence, the buildup of dense central components in disk galaxies that look like classical, merger-built bulges but that were made slowly out of disk gas. We call these pseudobulges. We begin with an “existence proof”—a review of how bars rearrange disk gas into outer rings, inner rings, and stuff dumped onto the center. The results of numerical simulations correspond closely to the morphology of barred galaxies. In the simulations, gas is transported to small radii, where it reaches high densities and...

Secular Evolution and the Formation of Pseudobulges in Disk Galaxies

The aim of this paper is to set constraints on the epochs of early-type galaxy formation through the archaeology of the stellar populations in local galaxies. Using our models of absorption-line indices that account for variable abundance ratios, we derive ages, total metallicities, and element ratios of 124 early-type galaxies in high- and low-density environments. The data are analyzed by comparison with mock galaxy samples created through Monte Carlo simulations taking the typical average observational errors into account, in order to eliminate artifacts caused by correlated errors. We find that all three parameters, age, metallicity, and ?/Fe ratio, are correlated with velocity dispersion. We show that these results are robust against recent revisions of the local abundance pattern at high metallicities. To recover the observed scatter we need to assume an intrinsic scatter of about 20% in age, 0.08?dex in [Z/H], and 0.05?dex in [?/Fe]. All low-mass objects with M* 1010 M? (? 130 km s-1) show evidence for the presence of intermediate-age stellar populations with low ?/Fe ratios. About 20% of the intermediate-mass objects with 1010 M*/M? 1011 [110 ?/(km s-1) 230; both elliptical and lenticular galaxies] must have either a young subpopulation or a blue horizontal branch. On the basis of the above relationships, valid for the bulk of the sample, we show that the Mg-? relation is mainly driven by metallicity, with similar contributions from the ?/Fe ratio (23%) and age (17%). We further find evidence for an influence of the environment on the stellar population properties. Massive early-type galaxies in low-density environments seem on average ~2?Gyr younger and slightly (~0.05-0.1?dex) more metal-rich than their counterparts in high-density environments. No offsets in the ?/Fe ratios are instead detected. With the aid of a simple chemical evolution model, we translate the derived ages and ?/Fe ratios into star formation histories. We show that most star formation activity in early-type galaxies is expected to have happened between redshifts ~3 and 5 in high-density environments and between redshifts 1 and 2 in low-density environments. We conclude that at least 50% of the total stellar mass density must have already formed at z ~ 1, in good agreement with observational estimates of the total stellar mass density as a function of redshift. Our results suggest that significant mass growth in the early-type galaxy population below z ~ 1 must be restricted to less massive objects, and a significant increase of the stellar mass density between redshifts 1 and 2 should be present, caused mainly by the field galaxy population. The results of this paper further imply the presence of vigorous star formation episodes in massive objects at z ~ 2-5 and evolved elliptical galaxies around z ~ 1, both observationally identified as SCUBA galaxies and extremely red objects, respectively.

/pdf/the-epochs-of-early-type-galaxy-formation-as-a-function-of-1xuxfqwp3q.pdf

The Epochs of Early-Type Galaxy Formation as a Function of Environment

IRAS flux densities, redshifts, and infrared luminosities are reported for all sources identified in the IRAS Revised Bright Galaxy Sample (RBGS), a complete flux-limited survey of all extragalactic objects with total 60 μm flux density greater than 5.24 Jy, covering the entire sky surveyed by IRAS at Galactic latitudes |b| > 5°. The RBGS includes 629 objects, with median and mean sample redshifts of 0.0082 and 0.0126, respectively, and a maximum redshift of 0.0876. The RBGS supersedes the previous two-part IRAS Bright Galaxy Samples (BGS1+BGS2), which were compiled before the final (Pass 3) calibration of the IRAS Level 1 Archive in 1990 May. The RBGS also makes use of more accurate and consistent automated methods to measure the flux of objects with extended emission. The RBGS contains 39 objects that were not present in the BGS1+BGS2, and 28 objects from the BGS1+BGS2 have been dropped from RBGS because their revised 60 μm flux densities are not greater than 5.24 Jy. Comparison of revised flux measurements for sources in both surveys shows that most flux differences are in the range ~5%–25%, although some faint sources at 12 and 25 μm differ by as much as a factor of 2. Basic properties of the RBGS sources are summarized, including estimated total infrared luminosities, as well as updates to cross identifications with sources from optical galaxy catalogs established using the NASA/IPAC Extragalactic Database. In addition, an atlas of images from the Digitized Sky Survey with overlays of the IRAS position uncertainty ellipse and annotated scale bars is provided for ease in visualizing the optical morphology in context with the angular and metric size of each object. The revised bolometric infrared luminosity function, (Lir), for infrared-bright galaxies in the local universe remains best fit by a double power law, (L) ∝ Lα, with α = -0.6(±0.1) and α = -2.2(±0.1) below and above the "characteristic" infrared luminosity L ~ 1010.5 L⊙, respectively. A companion paper provides IRAS High Resolution (HIRES) processing of over 100 RBGS sources where improved spatial resolution often provides better IRAS source positions or allows for deconvolution of close galaxy pairs.

The IRAS Revised Bright Galaxy Sample

A new X-ray-selected and X-ray flux-limited galaxy cluster sample is presented. Based on the ROSAT All-Sky Survey, the 63 brightest clusters with galactic latitude |bII| ? 20? and flux fX(0.1-2.4keV) ? 2 ? 10-11ergss-1cm-2 have been compiled. Gravitational masses have been determined utilizing intracluster gas density profiles, derived mainly from ROSAT PSPC pointed observations, and gas temperatures, as published mainly from ASCA observations, assuming hydrostatic equilibrium. This sample and an extended sample of 106 galaxy clusters is used to establish the X-ray luminosity-gravitational mass relation. From the complete sample the galaxy cluster mass function is determined and used to constrain the mean cosmic matter density and the amplitude of mass fluctuations. Comparison to Press-Schechter type model mass functions in the framework of cold dark matter cosmological models and a Harrison-Zeldovich initial density fluctuation spectrum yields the constraints ?m = 0.12 and ?8 = 0.96 (90% c.l.). Various possible systematic uncertainties are quantified. Adding all identified systematic uncertainties to the statistical uncertainty in a worst-case fashion results in an upper limit ?m < 0.31. For comparison to previous results a relation ?8 = 0.43? is derived. The mass function is integrated to show that the contribution of mass bound within virialized cluster regions to the total matter density is small; i.e., ?cluster = 0.012 for cluster masses larger than 6.4 ? 1013 h M?.

https://iopscience.iop.org/article/10.1086/338753/pdf

The Mass Function of an X-Ray Flux-Limited Sample of Galaxy Clusters

The surface photometry catalogue of the ESO-Uppsala galaxies

We are happy to announce that most of the results of our extensive project on the surface photometry of the 16,000 ESO-Uppsala galaxies are now publicly available.

https://www.eso.org/sci/publications/messenger/archive/no.56-jun89/messenger-no56-31-34.pdf

The data of the surface photometry catalogue of the ESO-Uppsala galaxies are now available.

We have compiled a catalogue of all presently available UBVRI aperture photometry for galaxies in the ESO/Uppsala catalogue. It comprises a total of about 1000 galaxies south of -17° declination.

A compilation of UBVRI photometry for galaxies in the ESO/Uppsala catalogue

Under a restriction for minimum angular diameter of not less than 1 arcmin, corresponding to the 15th magnitude and allowing morphological classification of structure, 16,000 galaxies have been brought together in the single volume of the ESO/Uppsala catalog (1982) Attention is given to the automatic parameter extraction methods employed, and detailed information is presented for preliminary results on test field No 358, which covers the Fornax cluster The data for the 70 galaxies in this test field yield results which are of general interest, such as estimates of total magnitude from a combination of major and minor diameters that yields angular size

Automatic parameter extraction for the 16,000 galaxies in the ESO/Uppsala catalogue

An ongoing photometric survey of 16,000 galaxies on ESO red and blue plates is described. The galaxies of the ESO/Uppsala Catalog (Lauberts, 1982) are being PDS scanned, and the results are combined with existing photometry and supplementary observational data obtained at the 1-m ESO telescope to form a catalog for paper, magnetic-tape, and possibly video-disk publication. Details of the plate digitization, photometric calibration, and automatic parameter extraction are discussed, and a flow chart of the extraction operation and graphs of sample data are provided.

Andris Lauberts

Papers

The surface photometry catalogue of the ESO-Uppsala galaxies

The data of the surface photometry catalogue of the ESO-Uppsala galaxies are now available.

A compilation of UBVRI photometry for galaxies in the ESO/Uppsala catalogue

Automatic parameter extraction for the 16,000 galaxies in the ESO/Uppsala catalogue

Photographic photometry of 16000 galaxies on ESO blue and red survey plates