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Optical and Near-Infrared Color Profiles in Nearby Early-Type Galaxies and the Implied Age and Metallicity Gradients
We present results of an age and metallicity gradient analysis inferredfrom both optical and near-infrared surface photometry. The analysis isbased on a sample of 36 nearby early-type galaxies, obtained from theEarly Data Release of the Sloan Digital Sky Survey and the Two MicronAll Sky Survey. Surface brightness profiles were derived in each bandand used to study the color gradients of the galaxies. Using simplestellar population models with both optical and near-infrared colors, wemay interpret the color gradients in terms of age and metallicitygradients of galaxies. UsinggZ≡dlogZmet/dlogR andgA=dlog(age)/dlogR to represent the metallicity and agegradients, we found a median value of gZ=-0.25+/-0.03 for themetallicity gradient, with a dispersionσgZ=0.19+/-0.02. The corresponding valuesfor the age gradients were gA=0.02+/-0.04 andσgA=0.25+/-0.03. These results are in goodagreement with recent observational results, as well as with recentsimulations that suggest that both monolithic collapse and major mergershave played important roles in the formation of early-type galaxies. Ourresults demonstrate the potential of using multi-wave band colorsobtained from current and future optical and infrared surveys inconstraining the age and metallicity gradients of early-type galaxies.
| The 2dF galaxy redshift survey: clustering properties of radio galaxies
The clustering properties of local, S1.4 GHz>= 1 mJy,radio sources are investigated for a sample of 820 objects drawn fromthe joint use of the Faint Images of the Radio Sky at 20 cm (FIRST) and2dF Galaxy Redshift surveys. To this aim, we present 271 newbJ<= 19.45 spectroscopic counterparts of FIRST radiosources to be added to those already introduced in our previous paper.The two-point correlation function for the local radio population isfound to be entirely consistent with estimates obtained for the wholesample of 2dFGRS galaxies. From measurements of the redshift-spacecorrelation function ξ(s) we derive a redshift-space clusteringlength s0= 10.7+0.8-0.7 Mpc, while fromthe projected correlation function Ξ(rT) we estimate theparameters of the real-space correlation function ξ(r) =(r/r0)-γ, r0=6.7+0.9-1.1 Mpc and γ= 1.6 +/- 0.1, where h=0.7 is assumed. Different results are instead obtained if we onlyconsider sources that present signatures of active galactic nucleus(AGN) activity in their spectra. These objects are shown to be verystrongly correlated, with r0=10.9+1.0-1.2 Mpc and γ= 2 +/- 0.1, a steeperslope than has been claimed in other recent works. No difference isfound in the clustering properties of radio-AGNs of different radioluminosity. Comparisons with models for ξ(r) show that AGN-fuelledsources reside in dark matter haloes more massive than~1013.4 Msolar, higher than the correspondingfigure for radio-quiet quasi-stellar objects. This value can beconverted into a minimum black hole mass associated with radio-loud,AGN-fuelled objects of MminBH~ 109Msolar. The above results then suggest - at least forrelatively faint radio objects - the existence of a threshold black holemass associated with the onset of significant radio activity such asthat of radio-loud AGNs; however, once the activity is triggered, thereappears to be no evidence for a connection between black hole mass andlevel of radio output.
| The Millennium Galaxy Catalogue: 16 <=BMGC < 24 galaxy counts and the calibration of the local galaxy luminosity function
The Millennium Galaxy Catalogue (MGC) is a 37.5 deg2,medium-deep, B-band imaging survey along the celestial equator, takenwith the Wide Field Camera on the Isaac Newton Telescope. The surveyregion is contained within the regions of both the Two Degree FieldGalaxy Redshift Survey (2dFGRS) and the Sloan Digital Sky Survey EarlyData Release (SDSS-EDR). The survey has a uniform isophotal detectionlimit of 26 mag arcsec-2 and it provides a robust,well-defined catalogue of stars and galaxies in the range 16<=BMGC < 24 mag.Here we describe the survey strategy, the photometric and astrometriccalibration, source detection and analysis, and present the galaxynumber counts that connect the bright and faint galaxy populationswithin a single survey. We argue that these counts represent the stateof the art and use them to constrain the normalizations (φ*) of anumber of recent estimates of the local galaxy luminosity function. Wefind that the 2dFGRS, SDSS Commissioning Data (CD), ESO Slice Project,Century Survey, Durham/UKST, Mt Stromlo/APM, SSRS2 and NOG luminosityfunctions require a revision of their published φ* values by factorsof 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 localbJ luminosity density of .1
| Nearby Optical Galaxies: Selection of the Sample and Identification of Groups
In this paper we describe the Nearby Optical Galaxy (NOG) sample, whichis a complete, distance-limited (cz<=6000 km s-1) andmagnitude-limited (B<=14) sample of ~7000 optical galaxies. Thesample covers 2/3 (8.27 sr) of the sky (|b|>20deg) andappears to have a good completeness in redshift (97%). We select thesample on the basis of homogenized corrected total blue magnitudes inorder to minimize systematic effects in galaxy sampling. We identify thegroups in this sample by means of both the hierarchical and thepercolation ``friends-of-friends'' methods. The resulting catalogs ofloose groups appear to be similar and are among the largest catalogs ofgroups currently available. Most of the NOG galaxies (~60%) are found tobe members of galaxy pairs (~580 pairs for a total of ~15% of objects)or groups with at least three members (~500 groups for a total of ~45%of objects). About 40% of galaxies are left ungrouped (field galaxies).We illustrate the main features of the NOG galaxy distribution. Comparedto previous optical and IRAS galaxy samples, the NOG provides a densersampling of the galaxy distribution in the nearby universe. Given itslarge sky coverage, the identification of groups, and its high-densitysampling, the NOG is suited to the analysis of the galaxy density fieldof the nearby universe, especially on small scales.
| Arcsecond Positions of UGC Galaxies
We present accurate B1950 and J2000 positions for all confirmed galaxiesin the Uppsala General Catalog (UGC). The positions were measuredvisually from Digitized Sky Survey images with rms uncertaintiesσ<=[(1.2")2+(θ/100)2]1/2,where θ is the major-axis diameter. We compared each galaxymeasured with the original UGC description to ensure high reliability.The full position list is available in the electronic version only.
| A Complete Redshift Survey to the Zwicky Catalog Limit in a 2^h X 15 deg Region around 3C 273
We compile 1113 redshifts (648 new measurements, 465 from theliterature) for Zwicky catalog galaxies in the region (-3.5d <= delta<= 8.5d, 11h5 <= alpha <= 13h5). We include redshifts for 114component objects in 78 Zwicky catalog multiplets. The redshift surveyin this region is 99.5% complete to the Zwicky catalog limit, m_Zw =15.7. It is 99.9% complete to m_Zw = 15.5, the CfA Redshift Survey(CfA2) magnitude limit. The survey region is adjacent to the northernportion of CfA2, overlaps the northernmost slice of the Las CampanasRedshift Survey, includes the southern extent of the Virgo Cluster, andis roughly centered on the QSO 3C 273. As in other portions of theZwicky catalog, bright and faint galaxies trace the same large-scalestructure.
| An image database. II. Catalogue between δ=-30deg and δ=70deg.
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
| Kinematics and dynamics of the MKW/AWM poor clusters
We report 472 new redshifts for 416 galaxies in the regions of the 23poor clusters of galaxies originally identified by Morgan, Kayser, andWhite (MKW), and Albert, White, and Morgan (AWM). Eighteen of the poorclusters now have 10 or more available redshifts within 1.5/h Mpc of thecentral galaxy; 11 clusters have at least 20 available redshifts. Basedon the 21 clusters for which we have sufficient velocity information,the median velocity scale is 336 km/s, a factor of 2 smaller than foundfor rich clusters. Several of the poor clusters exhibit complex velocitydistributions due to the presence of nearby clumps of galaxies. We checkon the velocity of the dominant galaxy in each poor cluster relative tothe remaining cluster members. Significantly high relative velocities ofthe dominant galaxy are found in only 4 of 21 poor clusters, 3 of whichwe suspect are due to contamination of the parent velocity distribution.Several statistical tests indicate that the D/cD galaxies are at thekinematic centers of the parent poor cluster velocity distributions.Mass-to-light ratios for 13 of the 15 poor clusters for which we havethe required data are in the range 50 less than or = M/LB(0)less than or = 200 solar mass/solar luminosity. The complex nature ofthe regions surrounding many of the poor clusters suggests that thesegroupings may represent an early epoch of cluster formation. Forexample, the poor clusters MKW7 and MKWS are shown to be gravitationallybound and likely to merge to form a richer cluster within the nextseveral Gyrs. Eight of the nine other poor clusters for which simpletwo-body dynamical models can be carried out are consistent with beingbound to other clumps in their vicinity. Additional complex systems withmore than two gravitationally bound clumps are observed among the poorclusters.
| Galaxy redshifts in an equatorial field in Virgo and the spatial distribution of local Lyman alpha clouds
New redshifts are presented for 51 galaxies which lie in a narrow stripalong the celestial equator. The redshifts are derived from a mixture ofoptical and H I spectra; for the latter subset (37 galaxies) H I fluxesand line widths are also given. One of the two Ly-alpha clouds in theLocal Supercluster appears to be associated with a spiral galaxy,although the angular and physical separations (42 arcmin and 180 kpc)are large. The other nearby Ly-alpha cloud and the large H I cloudappear to be more isolated. None of the nine Ly-alpha clouds withvelocities between 5000-20,000 km/s are associated with any specificgalaxies, but most appear to fall within or near the large-scalestructures defined by the galaxies.
| Statistics of galaxy orientations - Morphology and large-scale structure
Using the Uppsala General Catalog of bright galaxies and the northernand southern maps of the Lick counts of galaxies, statistical evidenceof a morphology-orientation effect is found. Major axes of ellipticalgalaxies are preferentially oriented along the large-scale features ofthe Lick maps. However, the orientations of the major axes of spiral andlenticular galaxies show no clear signs of significant nonrandombehavior at a level of less than about one-fifth of the effect seen forellipticals. The angular scale of the detected alignment effect forUppsala ellipticals extends to at least theta of about 2 deg, which at aredshift of z of about 0.02 corresponds to a linear scale of about 2/hMpc.
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