- ID:
- ivo://CDS.VizieR/J/AJ/154/85
- Title:
- CTIO/DECam photometry of RR Lyrae stars in M5
- Short Name:
- J/AJ/154/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We characterize the absolute magnitudes and colors of RR Lyrae stars in the globular cluster M5 in the ugriz filter system of the Dark Energy Camera (DECam). We provide empirical period-luminosity (P-L) relationships in all five bands based on 47 RR Lyrae stars of the type ab and 14 stars of the type c. The P-L relationships were found to be better constrained for the fundamental-mode RR Lyrae stars in the riz passbands, with dispersions of 0.03, 0.02 and 0.02mag, respectively. The dispersion of the color at minimum light was found to be small, supporting the use of this parameter as a means to obtain accurate interstellar extinctions along the line of sight up to the distance of the RR Lyrae star. We found a trend of color at minimum light with a pulsational period that, if taken into account, brings the dispersion in color at minimum light to 0.016 mag for the (r-i), (i-z), and (r-z) colors. These calibrations will be very useful for using RR Lyrae stars from DECam observations as both standard candles for distance determinations and color standards for reddening measurements.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/433/43
- Title:
- C-T1 phot. of NGC 4636 globular cluster system
- Short Name:
- J/A+A/433/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Previous smaller-scale studies of the globular cluster system of NGC 4636, an elliptical galaxy in the southern part of the Virgo cluster, have revealed an unusually rich globular cluster system. We re-investigate the cluster system of NGC 4636 with wide-field Washington photometry.
- ID:
- ivo://CDS.VizieR/J/MNRAS/451/3219
- Title:
- CT1 photometry for 11 star fields in the SMC
- Short Name:
- J/MNRAS/451/3219
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from Washington CT_1_ photometry for 11 star fields located in the western outskirts of the Small Magellanic Cloud (SMC), which cover angular distances to its centre from 2{deg} up to 13{deg} (~2.2-13.8 kpc). The colour-magnitude diagrams, cleaned from the unavoidable Milky Way (MW) and background galaxy signatures, reveal that the most distant dominant main-sequence (MS) stellar populations from the SMC centre are located at an angular distance of ~5.7{deg} (6.1 kpc); no sign of farther clear SMC MS is visible other than the residuals from the MW/background field contamination. The derived ages and metallicities for the dominant stellar populations of the western SMC periphery show a constant metallicity level ([Fe/H]=-1.0 dex) and an approximately constant age value (~7-8 Gyr). Their age-metallicity relationship (AMR) do not clearly differ from the most comprehensive AMRs derived for almost the entire SMC main body. Finally, the range of ages of the dominant stellar populations in the western SMC periphery confirms that the major stellar mass formation activity at the very early galaxy epoch peaked ~7-8 Gyr ago.
- ID:
- ivo://CDS.VizieR/J/A+A/501/585
- Title:
- CT1 photometry in five LMC star clusters
- Short Name:
- J/A+A/501/585
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Aims: We present CCD photometry in the Washington system C and T1 passbands down to T1~22.5 in the fields of NGC 1697, SL 133, NGC 1997, SL 663, and OHSC 28, five mostly unstudied star clusters in the LMC. Methods: Cluster radii were estimated from star counts in appropriate-sized boxes distributed throughout the entire observed fields. We perform a detailed analysis of the field star contamination and derive cluster colour-magnitude diagrams (CMDs). Based on the best fits of isochrones computed by the Padova group to the (T1, C-T_1_) CMDs, the {delta}(T1) index and the Standard Giant Branch procedure, we derive metallicities and ages for the five clusters. We combine our sample with clusters with ages and metallicities on a similar scale and examine relationships between position in the LMC, age and metallicity. Results: With the exception of NGC 1697 (age=0.7Gyr, [Fe/H]=0.0dex), the remaining four clusters are of intermediate-age (from 2.2 to 3.0Gyr) and relatively metal-poor ([Fe/H]=0.7dex). The cluster and field age-metallicty realtions show evidence for a metallicity offset but do overlap, particularly on the upper envelope side of the cluster age-metallicity relation. Conclusions: We confirm previous results that clusters younger than ~1Gyr were formed during an outside-in process; this occurred after a bust of cluster formation that took place mainly in the outer disk and peaked at ~2Gyr ago.
- ID:
- ivo://CDS.VizieR/J/MNRAS/367/156
- Title:
- C-T1 photometry in NGC 1374, 1379 and 1387
- Short Name:
- J/MNRAS/367/156
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a photometric study of the globular cluster systems (GCSs) of the Fornax cluster galaxies NGC 1374, NGC 1379 and NGC 1387. The data consist of images from the wide-field MOSAIC imager of the Cerro Tololo Inter-American Observatory (CTIO) 4-m telescope, obtained with Washington C and Kron-Cousins R filters. The images cover a field of 36x36arcmin^2^, corresponding to 200x200kpc^2^ at the Fornax distance. Two of the galaxies, NGC 1374 and NGC 1379, are low-luminosity ellipticals while NGC 1387 is a low-luminosity lenticular. Their cluster systems are still embedded in the cluster system of NGC 1399. Therefore, the use of a large field is crucial and some differences to previous work can be explained by this. The colour distributions of all GCSs are bimodal. NGC 1387 presents a particularly distinct separation between red and blue clusters and an over-proportionally large population of red clusters. The radial distribution is different for blue and red clusters, red clusters being more concentrated towards the respective galaxies. The different colour and radial distributions point to the existence of two globular cluster subpopulations in these galaxies. Specific frequencies are in the range S_N_=1.4-2.4, smaller than the typical values for elliptical galaxies. These galaxies might have suffered tidal stripping of blue globular clusters by NGC 1399.
- ID:
- ivo://CDS.VizieR/J/MNRAS/382/1947
- Title:
- CT1 photometry in NGC 1399 and NGC 4486
- Short Name:
- J/MNRAS/382/1947
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper explores the quantitative connection between globular clusters and the diffuse stellar population of the galaxies they are associated with. Both NGC 1399 and NGC 4486 (M87) are well suited for this kind of analysis due to their large globular cluster populations. The main assumption of our Monte Carlo based models is that each globular cluster is formed along with a given diffuse stellar mass that shares the same spatial distribution, chemical composition and age. The main globular cluster subpopulations, that determine the observed bimodal colour distribution, are decomposed avoiding a priori parametric (e.g. Gaussian) fits and using a new colour (C-T1)-metallicity relation. The eventual detectability of a blue tilt in the colour-magnitude diagrams of the blue globular cluster subpopulation is also addressed.
- ID:
- ivo://CDS.VizieR/J/MNRAS/377/300
- Title:
- CT1 photometry in 6 SMC star clusters
- Short Name:
- J/MNRAS/377/300
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD photometry in the Washington C and T1 filters for six star clusters (B 34, NGC 256, NGC 265, NGC 294, IC 1611 and NGC 376) in the Small Magellanic Cloud (SMC) and their surrounding fields. The resultant colour-magnitude diagrams (CMDs) extend from T1~14 to as faint as T1~22 revealing the main-sequence turnoffs of the clusters. Adopting a metallicity of Z=0.004, we compare our cluster photometry with theoretical isochrones in the Washington system in order to derive ages. To facilitate age determination of the surrounding fields, we use the magnitude difference between the helium-burning red clump stars and the main-sequence turnoff. Finally, we estimate mean metallicities for the field stars by comparing the location of the field red giant branch with standard giant branches for Galactic globular clusters of known abundance, corrected for age effects. Combining these results with our previous work, we find a clear trend of younger clusters being located closer to the centre of the SMC. In addition, there is a tendency for the mean metallicity and its dispersion to be greater inside 4{deg} of the SMC's centre as compared to outside this radius. As far as the properties of the field stars are concerned, we find little correlation between the ages of the clusters and those of the field stars against which they are projected. Clearly, more work needs to be done to clarify these trends.
- ID:
- ivo://CDS.VizieR/J/A+A/421/991
- Title:
- CT1 photometry in Tombaugh 1
- Short Name:
- J/A+A/421/991
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD photometry in the Washington system C and T1 passbands down to T1~18.5mag in the field of Tombaugh 1, a little studied open cluster located in the third Galactic quadrant. We measured T1 magnitudes and C-T1 colours for a total of 1351 stars distributed throughout an area of 13.6'x13.6'.
- ID:
- ivo://CDS.VizieR/J/MNRAS/386/2311
- Title:
- CT1 photometry of Antlia early-type galaxies
- Short Name:
- J/MNRAS/386/2311
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first colour-magnitude relation (CMR) of early-type galaxies in the central region of the Antlia cluster, obtained from CCD wide-field photometry in the Washington photometric system. Integrated (C-T1) colours, T1 magnitudes, and effective radii have been measured for 93 galaxies (i.e. the largest galaxies sample in the Washington system till now) from the FS90 Antlia Group catalogue. Membership of 37 objects can be confirmed through new radial velocities and data collected from the literature.
- ID:
- ivo://CDS.VizieR/J/PASP/123/519
- Title:
- C,T1 photometry of 6 LMC clusters
- Short Name:
- J/PASP/123/519
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of an ongoing project to investigate the cluster formation and chemical evolution history in the Large Magellanic Cloud (LMC), we have used the CTIO 0.9m telescope to obtain CCD imaging in the Washington system of NGC 2161, SL 874, and KMHK 1719 - three unstudied star clusters located in the outer region of the LMC. We measured T1 magnitudes and C-T1 colors for a total of 9611 stars distributed throughout cluster areas of 13.6x13.6arcmin^2^. Cluster radii were estimated from star counts distributed throughout the entire observed fields. Careful attention was paid to setting apart the cluster and field star distributions so that statistically cleaned color-magnitude diagrams (CMDs) were obtained. Based on the best fits of isochrones computed by the Padova group to the (T1, C-T1) CMDs, the {delta}T1 index, and the standard giant branch procedure, ages and metallicities were derived for the three clusters.
