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|Red giant branch in near-infrared colour-magnitude diagrams - I. Calibration of photometric indices|
We present new high-quality near-infrared photometry of 10 Galacticglobular clusters spanning a wide metallicity range (-2.12<=[Fe/H]<=- 0.49): five clusters belong to the halo (NGC 288, 362,6752, M15 and M30) and five (NGC 6342, 6380, 6440, 6441 and 6624) to thebulge. By combining J, H and K observations with optical data, weconstructed colour-magnitude diagrams in various planes: (K, J-K), (K,V-K), (H, J-H) and (H, V-H). A set of photometric indices (colours,magnitudes and slopes) describing the location and the morphology of thered giant branch (RGB) have been measured. We have combined this newdata set with those collected by our group over the last 5 years, andhere we present an updated calibration of the various RGB indices in theTwo-Micron All-Sky Survey photometric system, in terms of the clustermetallicity.
|The ISOPHOT 170 μm Serendipity Survey II. The catalog of optically identified galaxies%|
The ISOPHOT Serendipity Sky Survey strip-scanning measurements covering≈15% of the far-infrared (FIR) sky at 170 μm were searched forcompact sources associated with optically identified galaxies. CompactSerendipity Survey sources with a high signal-to-noise ratio in at leasttwo ISOPHOT C200 detector pixels were selected that have a positionalassociation with a galaxy identification in the NED and/or Simbaddatabases and a galaxy counterpart visible on the Digitized Sky Surveyplates. A catalog with 170 μm fluxes for more than 1900 galaxies hasbeen established, 200 of which were measured several times. The faintest170 μm fluxes reach values just below 0.5 Jy, while the brightest,already somewhat extended galaxies have fluxes up to ≈600 Jy. For thevast majority of listed galaxies, the 170 μm fluxes were measured forthe first time. While most of the galaxies are spirals, about 70 of thesources are classified as ellipticals or lenticulars. This is the onlycurrently available large-scale galaxy catalog containing a sufficientnumber of sources with 170 μm fluxes to allow further statisticalstudies of various FIR properties.Based on observations with ISO, an ESA project with instruments fundedby ESA Member States (especially the PI countries: France, Germany, TheNetherlands and the UK) and with the participation of ISAS and NASA.Members of the Consortium on the ISOPHOT Serendipity Survey (CISS) areMPIA Heidelberg, ESA ISO SOC Villafranca, AIP Potsdam, IPAC Pasadena,Imperial College London.Full Table 4 and Table 6 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (18.104.22.168) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/422/39
|The Dwarf Irregular/Wolf-Rayet Galaxy NGC 4214. I. A New Distance, Stellar Content, and Global Parameters|
We present the results of a detailed optical and near-IR study of thenearby star-forming dwarf galaxy NGC 4214. We discuss the stellarcontent, drawing particular attention to the intermediate-age and/or oldfield stars, which are used as a distance indicator. On images obtainedwith the Hubble Space Telescope Wide Field Planetary Camera 2 andNear-Infrared Camera and Multi-Object Spectrometer (NICMOS) instrumentsin the equivalents of the V, R, I, J and H bands, the galaxy is wellresolved into stars. We achieve limiting magnitudes of F814W~27 in theWF chips and F110W~25 in the NICMOS 2 camera. The optical andnear-infrared color-magnitude diagrams confirm a core-halo galaxymorphology: an inner, high surface brightness, young population within~1.5′ (~1 kpc) from the center of the galaxy, where the stars areconcentrated in bright complexes along a barlike structure, and arelatively low surface brightness, field star population extending outto at least 8' (7 kpc). The color-magnitude diagrams of the core regionshow evidence of blue and red supergiants, main-sequence stars,asymptotic giant branch stars, and blue loop stars. We identify somecandidate carbon stars from their extreme near-IR color. The field-starpopulation is dominated by the ``red tangle,'' which contains the redgiant branch. We use the I-band luminosity function to determine thedistance based on the tip of the red giant branch method: 2.7+/-0.3 Mpc.This is much closer than the values usually assumed in the literature,and we provide revised distance-dependent parameters such as physicalsize, luminosity, H I mass, and star formation rate. From the mean colorof the red giant branch in V and I, we estimate the mean metal abundanceof this population to be [Fe/H]~=-1.7 dex, with a large internalabundance spread characterized by σint([Fe/H])~1 dex.Based on observations made with the NASA/ESA Hubble Space Telescope,obtained at the Space Telescope Science Institute, which is operated bythe Association of Universities for Research in Astronomy, Inc., underNASA contract NAS 5-26555.
|NIR Census of the Stellar Content of Nearby Blue Compact Dwarf Galaxies with HST|
We resolved the brightest stars in 5 nearby blue compact dwarf galaxieswith NICMOS aboard HST in J and H. In all galaxies, RGB stars weredetected. This finding allows an improved estimate of the distances ofthese galaxies and sets a lower limit to the age of the old stellarcomponent of 1 Gyr. Further, we detected a pronounced AGB population,including - in all but one - also TP-AGB stars. Our data do not supportthe hypothesis that very low metallicity BCD galaxies may have formedtheir first stars only recently.
|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 Near-Infrared Stellar Census of the Blue Compact Dwarf Galaxy VII ZW 403|
We present near-infrared single-star photometry for the low-metallicityblue compact dwarf galaxy VII Zw 403. We achieve limiting magnitudes ofF110W~25.5 and F160W~24.5 using one of the NICMOS cameras with theHubble Space Telescope equivalents of the ground-based J and H filters.The data have a high photometric precision (0.1 mag) and are more than95% complete down to magnitudes of about 23, far deeper than previousground-based studies in the near-IR. The color-magnitude diagramcontains about 1000 point sources. We provide a preliminarytransformation of the near-IR photometry into the ground system. Weinvestigate the tip of the red giant branch method in the J and H bandsto provide an empirical distance calibration. Combining our result withglobular cluster data as well as stellar-evolution models, we recommendMH,TRGB=-5.5(+/-0.1) for -2.3<[Fe/H]<-1.5. We proceed todiscuss the stellar content of VII Zw 403 using evolutionary tracks aswell as a classification scheme based on optical and near-IR colors, andwe comment on the detection of asymptotic giant branch stars and theblue Hertzprung gap. We use MH as an indicator ofMbol for red stars after evaluating BCH at lowmetallicity. We calculate the fractional contribution of individualstars from our color-magnitude diagram to the integrated light of VII Zw403 and determine which red stellar population dominates the integratedcolors. We find that young red supergiants, and young andintermediate-age asymptotic giants, together provide about 50% of thelight in I, J, and H bands, whereas the old red giant stars contributeless than 15%. Young, main-sequence stars and blue supergiants accountfor the remaining light and dominate in V. This explains thedifficulties in discerning the nature of blue compact dwarf galaxieswhen only integrated photometry is available.
|Large-Scale Structure at Low Galactic Latitude|
We have extended the CfA Redshift Survey to low galactic latitudes toinvestigate the relation between the Great Wall in the North GalacticCap and the Perseus-Pisces chain in the South Galactic Cap. We presentredshifts for 2020 galaxies in the Catalogue of Galaxies and of Clustersof Galaxies (Zwicky et al. 1961-68, CGCG) in the following regions: 4^h^<= α <= 8^h^, 17^h^ <= α <= 20^h^, 0^deg^ <=δ <= 45^deg^. In these regions, the redshift catalogue includes1664 galaxies with B(0) <= 15.5 (of which 820 are newly measured) andis 97% complete. We also include redshifts for an additional 356galaxies in these regions with B(O) > 15.5; of these, 148 werepreviously unmeasured. The CGCG samples the galaxy distribution down tob_II_ = 10^deg^. In this paper, we discuss the acquisition and reductionof the spectra, and we examine the qualitative features of the redshiftdistribution. The Great Wall and the Perseus-Pisces chain are not simplyconnected across the Zone of Avoidance. These structures, which at firstappear to be coherent on scales of ~100 h^-1^ Mpc or more, actually formthe boundaries of neighboring voids of considerably smaller scale,approximately 50h^-1^ Mpc. The structures delineated by ouroptically-selected sample are qualitatively similar to those detected bythe far-infrared-selected IRAS 1.2 Jansky Survey (Fisher et al. 1995).Although the IRAS survey probes more deeply into the Zone of Avoidance,our optically-selected survey provides better sampling of structures atb_II_ >= 10^deg^.
|Neutral hydrogen observations of galaxies in the Hercules supercluster. III. CGCG fields at the edge of the void.|
The third installment of a HI redshift survey in the region of theHercules supercluster is presented. This part of the survey presents HIspectra of 84 galaxies selected from the UGC and CGCG which extends thepreviously begun survey of late-type spiral galaxies in that region.Measured HI parameters from the spectra are given. For about 20% of thesample, these parameters are compared to those measured previously byother workers.
|Preliminary photometry of the X-ray globular cluster NGC 6624|
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