- ID:
- ivo://CDS.VizieR/J/A+AS/71/297
- Title:
- CCD UBV photometry of stars in Sex A
- Short Name:
- J/A+AS/71/297
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD UBV photometry of 2279 stars in Sextans A is presented. Differences with the photometric scales of Sandage and Carlson (1985AJ.....90.1019S) and Hoessel et al. (1983ApJ...274..577H) are discussed; recalibration of the Sandage and Carlson data for Cepheids in Sextans A results in a smaller value for the distance modulus, {mu}=25.6. A similar value for the distance modulus is obtained from the colour-colour diagram. Colour-colour and colour-magnitude diagrams for the whole galaxy and for different parts are presented indicating a general star formation activity all over Sextans A. The contribution of stars brighter than M_pg_=-3 to the total blue light of the galaxy amounts to 25%, a much higher value than what is found for other dwarf irregular galaxies in the Local Group. The integrated birthrate per unit mass of massive stars for the galaxy is found to be much higher than in the Magellanic Clouds, suggesting that the rate in Sextans A was probably smaller in the past. Different slopes for high mass and low mass IMF parts are needed to account for its low surface brightness. The formation of massive stars seems to be favoured for systems of decreasing mass or, given the relation between total mass and metal content, for galaxies of decreasing metallicity.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/127/1014
- Title:
- CCD UBVRIHa photometry in NGC 3603
- Short Name:
- J/AJ/127/1014
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present UBVRI and H{alpha} photometry of the extremely compact, starburst cluster NGC 3603. Ground-based images, Hubble Space Telescope (HST) archival data, as well as Chandra X-ray data have been used for this study. We present, for the first time, optical color-magnitude diagrams (CMDs) for the stars in the cluster core down to V=22mag. A well-defined main sequence (MS) as well as low-mass pre-main-sequence (PMS) stars can clearly be seen in the CMDs. This result confirms the finding by Eisenhauer et al. (1998ApJ...498..278E) that low-mass stars are forming in the starburst cluster. We also derive an age (1+/-1Myr) and distance of the cluster (V_0_-M_V_=14.2+/-0.2mag, i.e., d=6.9+/-0.6kpc).
- ID:
- ivo://CDS.VizieR/J/AJ/116/2415
- Title:
- CCD UBVRI Photometry of M80
- Short Name:
- J/AJ/116/2415
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The table photom.dat contains the first multicolour (UVBRI) CCD photometry of 4899 stars in a 4'x7' field of the poorly studied globular cluster M80. The observations were acquired on 1994 June 13-16 using the 2.5m telescope of the Las Campanas Observatory, with a 2x1024x1024 pixel CCD. Two observing 4'x4' fields were observed, the first one at the cluster center, and the second one centered at approximately 3' to the East of the cluster center. The limiting magnitude was deeper in the the second frame by approximately DV=2.5mag. The exposures were 8 to 500s, with a total of 7 frames in U, 17 frames in B, 20 frames in V, and 18 frames in I.
- ID:
- ivo://CDS.VizieR/J/A+AS/122/9
- Title:
- CCD UBVRI Photometry of 4 open clusters
- Short Name:
- J/A+AS/122/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD observations in the U, B, V, R and I passbands have been used to generate colour-colour and deep colour-magnitude diagrams for the young open star clusters NGC 3228, NGC 4103, NGC 5662 and NGC 6087. The sample consists of about 2000 stars reaching down to V=20mag. The interstellar extinction across the face of the imaged cluster regions seems to be uniform with average values of E(B-V)=0.31, 0.34 and 0.22mag for NGC 4103, NGC 5662 and NGC 6087 respectively. The distances to the clusters NGC 3228, NGC 4103, NGC 5662 and NGC 6087 have been estimated as 0.5+/-0.05, 2.0+/-0.3, 0.8+/-0.1 and 1.0+/-0.1kpc respectively, while the corresponding ages estimated from the theoretical stellar evolutionary isochrones fitted to the bright proper motion cluster members are ~100, 30, 80 and 65Myr respectively. Present data are consistent with the membership of the Cepheid variable V Cen to NGC 5662 and of S Norm to NGC 6087. Heavy contamination by foreground and background field stars has unfortunately made it impossible to reach definite conclusions about the faint luminosity function, and the data do not reach faint enough limits to investigate pre-main sequence stars.
- ID:
- ivo://CDS.VizieR/J/other/BASI/32.295
- Title:
- CCD UBVRI photometry of 3 open clusters
- Short Name:
- J/other/BASI/32.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD photometric observations of three open clusters Berkeley 15 (= OCl 414), Czernik 18 (= OCl 426) and NGC 2401 (= OCl 588), obtained for the first time in UBVRI filters down to V=20mag, are presented here. They are located at distances of 1259, 955 and 3467 parsecs with their respective ages estimated as ~5x10^9^years, ~0.8 to 1x10^9^years and ~1x10^9^years. While OCl 414 and OCl 426 are in the direction of the Auriga - Perseus constellations, OCl 588 is placed in the direction of Ophiuchus constellation in our Galaxy. The clusters studied here are of intermediate and old age category.
- ID:
- ivo://CDS.VizieR/J/MNRAS/327/23
- Title:
- CCD UBVRI photometry of 7 open star clusters
- Short Name:
- J/MNRAS/327/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive cluster parameters and mass functions from new UBVRI CCD photometric observations of ~3500 stars reaching down to V~20mag for the distant southern open star clusters NGC 3105, NGC 3603, Melotte 105, Hogg 15, NGC 4815, Pismis 20 and NGC 6253. For NGC 3105 and Hogg 15, CCD data are presented for the first time. The observations were carried out in 1992 between February 28 and March 8, June 5 and 9, and July 9 and 12 in the Cousins U, B, V, R and I photometric bands using CCD detector at the 1.0-m Elizabeth Telescope at the South African Astronomical Observatory (SAAO), Sutherland.
- ID:
- ivo://CDS.VizieR/J/ApJ/518/262
- Title:
- CCD VIc Photometry of M30 Stars
- Short Name:
- J/ApJ/518/262
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The file contains VIc data of the globular cluster M30. All frames were taken using a 2048x2048 pixel CCD with pixels covering 0.44 arcseconds on a side, for a total field of approximately 15 arcminutes on a side. Data were taken on 1994 July 78 at the Cerro Tololo Inter-American Observatory (CTIO) 4m telescope. The data were calibrated against Landolt (1983, Cat. <II/118>) standard stars.
- ID:
- ivo://CDS.VizieR/J/AJ/144/100
- Title:
- CCD Washington CT1T2 photometry of stars in LMC
- Short Name:
- J/AJ/144/100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present photometry for an unprecedented database of some 5.5million stars distributed throughout the Large Magellanic Cloud main body, from 21 fields covering a total area of 7.6deg^2^, obtained from Washington CT_1_T_2_ CTIO 4m MOSAIC data. Extensive artificial star tests over the whole mosaic image data set and the observed behavior of the photometric errors with magnitude demonstrate the accuracy of the morphology and clearly delineate the position of the main features in the color-magnitude diagrams (CMDs). The representative T_1_(MS TO) mags are on average ~0.5mag brighter than the T_1_ mags for the 100% completeness level of the respective field, allowing us to derive an accurate age estimate. We have analyzed the CMD Hess diagrams and used the peaks in star counts at the main sequence turnoff and red clump (RC) locations to age date the most dominant sub-population (or "representative" population) in the stellar population mix. The metallicity of this representative population is estimated from the locus of the most populous red giant branch track. We use these results to derive age and metallicity estimates for all of our fields. The analyzed fields span age and metallicity ranges covering most of the galaxy's lifetime and chemical enrichment, i.e., ages and metallicities between ~1 and 13Gyr and ~-0.2 and -1.2dex, respectively. We show that the dispersions associated with the mean ages and metallicities represent in general a satisfactory estimate of the age/metallicity spread (~1-3 Gyr/0.2-0.3 dex), although a few subfields have a slightly larger age/metallicity spread. Finally, we revisit the study of the vertical structure (VS) phenomenon, a striking feature composed of stars that extend from the bottom, bluest end of the RC to ~0.45mag fainter. We confirm that the VS phenomenon is not clearly seen in most of the studied fields and suggest that its occurrence is linked to some other condition(s) in addition to the appropriate age, metallicity, and the necessary red giant star density.
- ID:
- ivo://CDS.VizieR/J/MNRAS/497/1791
- Title:
- CCD Washington photometry of Antlia cluster
- Short Name:
- J/MNRAS/497/1791
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an extension of our previous research on the early-type galaxy population of the Antlia cluster (d~35Mpc), achieving a total coverage of ~2.6deg^2^ and performing surface photometry for ~300 galaxies, 130 of which are new uncatalogued ones. Such new galaxies mainly fall in the low surface brightness (LSB) regime, but there are also some lenticulars (S0) which support the existence of unique functions that connect bright and dwarf galaxies in the scaling relations. We analyse the projected spatial distribution of galaxies up to a distance of ~800kpc from NGC 3268, the adopted centre, as well as the radial velocity distribution and the correlation between galaxy colour and effective radius with the projected spatial distribution. We also obtain the luminosity function of the early-type galaxies and the distribution of stellar masses using the T1-band magnitudes and adopted mass-luminosity ratios. Additionally, we correlate the central galaxy distribution with an X-ray emission map from the literature. Based on the analysis of the radial velocities and galaxy colour distributions, we find that galaxies redder than the colour-magnitude relation (CMR) have a velocity distribution strongly concentrated towards the values of the dominant galaxies and are homogeneously distributed throughout the cluster. Those bluer than the CMR, in turn, have a much more extended radial velocity distribution and are concentrated towards the centre of the cluster. We also identify 12 candidates to ultra diffuse galaxies (UDG), that seem to be split into two families, and speculate about their origins in the context of the cluster structure.
- ID:
- ivo://CDS.VizieR/J/ApJ/817/34
- Title:
- C-COSMOS Legacy sources multiwavelength catalog
- Short Name:
- J/ApJ/817/34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the catalog of optical and infrared counterparts of the Chandra COSMOS-Legacy Survey, a 4.6Ms Chandra program on the 2.2deg^2^ of the COSMOS field, combination of 56 new overlapping observations obtained in Cycle 14 with the previous C-COSMOS survey. In this Paper we report the i, K, and 3.6{mu}m identifications of the 2273 X-ray point sources detected in the new Cycle 14 observations. We use the likelihood ratio technique to derive the association of optical/infrared (IR) counterparts for 97% of the X-ray sources. We also update the information for the 1743 sources detected in C-COSMOS, using new K and 3.6{mu}m information not available when the C-COSMOS analysis was performed. The final catalog contains 4016 X-ray sources, 97% of which have an optical/IR counterpart and a photometric redshift, while ~54% of the sources have a spectroscopic redshift. The full catalog, including spectroscopic and photometric redshifts and optical and X-ray properties described here in detail, is available online. We study several X-ray to optical (X/O) properties: with our large statistics we put better constraints on the X/O flux ratio locus, finding a shift toward faint optical magnitudes in both soft and hard X-ray band. We confirm the existence of a correlation between X/O and the the 2-10keV luminosity for Type 2 sources. We extend to low luminosities the analysis of the correlation between the fraction of obscured AGNs and the hard band luminosity, finding a different behavior between the optically and X-ray classified obscured fraction.
