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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.
| 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.
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