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|The UZC-SSRS2 Group Catalog|
We apply a friends-of-friends algorithm to the combined Updated ZwickyCatalog and Southern Sky Redshift Survey to construct a catalog of 1168groups of galaxies; 411 of these groups have five or more members withinthe redshift survey. The group catalog covers 4.69 sr, and all groupsexceed the number density contrast threshold, δρ/ρ=80. Wedemonstrate that the groups catalog is homogeneous across the twounderlying redshift surveys; the catalog of groups and their membersthus provides a basis for other statistical studies of the large-scaledistribution of groups and their physical properties. The medianphysical properties of the groups are similar to those for groupsderived from independent surveys, including the ESO Key Programme andthe Las Campanas Redshift Survey. We include tables of groups and theirmembers.
|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.
|Galaxy coordinates. II. Accurate equatorial coordinates for 17298 galaxies|
Using images of the Digitized Sky Survey we measured coodinates for17298 galaxies having poorly defined coordinates. As a control, wemeasured with the same method 1522 galaxies having accurate coordinates.The comparison with our own measurements shows that the accuracy of themethod is about 6 arcsec on each axis (RA and DEC).
|Infrared stellar absorption lines around 1.6μm: a new metallicity scale for old stellar populations.|
A new metallicity scale (accurate to within +/-0.3dex) for old stellarsystems is derived and discussed. It is particularly useful in coolobjects with [Fe/H]>-1.3 and is based on medium resolution (R~2000)near infrared spectra of a deep and relatively isolated feature at1.62μm which is mostly due to the CO(6,3) second overtone band-head.The value of [Fe/H] can be determined using handy interpolation formulae(Eqs. 1a, 1b and Eq. 2) and is little influenced by anomalies of thecarbon abundance, [C/Fe], since the growth of Wlambda_(1.62)with metallicity primarily tracks variations of stellar temperature andgravity, rather than the increase of the total carbon abundance. Themethod is tested using IRSPEC observations of 13 well known globularclusters where the derived [Fe/H] values are in good agreement with theresults of Zinn (1985ApJ...293..324Z) for all but two objects, namelyNGC 6624 and Terzan 5, which we find much less (=~0.9dex) metallic(first two columns of Table 1 and Fig. 5). Ellipticals are found to have[Fe/H]=~-0.4 and ~0.5dex below estimates based on the Mg_2_ index, thisindicates that Mg may be overabundant by a similar amount. A ~0.5dexenhancement of Si (another α element) is also suggested by thestrength of the 1.59μm line in our spectra. The only object with[Fe/H]>0.0 is the globular cluster Terzan 1.
|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.
|Red supergiants as starburst tracers in galactic nuclei.|
We present infrared spectral observations of CO (1.62, 2.29μm) and Si(1.59μm) stellar absorption features in 23 galaxies including 14calibrators (normal ellipticals/spirals and well known HII galaxies) and9 Seyferts. Our main aim was to define and calibrate an observationalmethod for tracing red supergiants (i.e. starbursts) in active galaxies.Additional spectra were also obtained around the Brγ hydrogenrecombination line. The measured equivalent widths of the absorptionfeatures in old stellar systems and HII galaxies are found to beremarkably similar and the CO and Si indices do not therefore providereliable diagnostics for distinguishing red supergiants (i.e.starbursts) from metallic red giants (i.e. old stellar systems). A moresensitive quantity is found to be the light to mass ratio (L_H_/M) asinferred from the observed 1.65μm stellar luminosities and velocitydispersions. All HII galaxies and several of the Seyfert 2's exhibitL_H_/M values a factor =~5 larger than normal ellipticals and spirals.Both the L_H_/M ratios and the Brγ equivalent widths in Sy2's areconsistent with the presence of starbursts which are older than those inHII galaxies. A large fraction of the near infrared (<2μm)continuum in Sy1's also appears to be stellar but associated with evenolder starburst activity or normal red giants in the galaxy bulge. Theseresults therefore provide additional support for evolutionary models inwhich Seyfert activity is related to the presence of a black hole whichis formed/fueled by the remnants of a pre-cursor starburst. The originof the non-stellar 2μm continuum in Seyferts and the metallicity ofellipticals are also discussed.
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