- ID:
- ivo://CDS.VizieR/J/AJ/147/155
- Title:
- BV photometry in and around 5 globular clusters
- Short Name:
- J/AJ/147/155
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Homogeneous B, V photometry is presented for 19324 stars in and around 5 Magellanic Cloud globular clusters: NGC 1466, NGC 1841, NGC 2210, NGC 2257, and Reticulum. The photometry is derived from eight nights of CCD imaging with the Cerro Tololo Inter-American Observatory 0.9m SMARTS telescope. Instrumental magnitudes were transformed to the Johnson B, V system using accurate calibration relations based on a large sample of Landolt-Stetson equatorial standard stars, which were observed on the same nights as the cluster stars. Residual analysis of the equatorial standards used for the calibration, and validation of the new photometry using Stetson's sample of secondary standards in the vicinities of the five Large Magellanic Cloud clusters, shows excellent agreement with our values in both magnitudes and colors. Color-magnitude diagrams reaching to the main-sequence turnoffs at V~22mag, sigma-magnitude diagrams, and various other summaries are presented for each cluster to illustrate the range and quality of the new photometry. The photometry should prove useful for future studies of the Magellanic Cloud globular clusters, particularly studies of their variable stars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/572/A10
- Title:
- (BV) photometry in Carina dSph
- Short Name:
- J/A+A/572/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep photometry of the Carina dwarf Spheroidal galaxy in the B,V filters from CTIO/MOSAIC, out to and beyond the tidal radius of r_ell_~0.48{deg}. The accurately calibrated photometry is combined with spectroscopic metallicity distributions of Red Giant Branch stars to determine the detailed star formation and chemical evolution history of Carina. The star formation history confirms the episodic formation history of Carina and quantifies the duration and strength of each episode in great detail, as a function radius from the centre. Two main episodes of star formation occurred at old (>8Gyr) and intermediate (2-8Gyr) ages, both enriching stars starting from low metallicities ([Fe/H]<-2dex). By dividing the SFH into two components, we determine that 60+/-9 percent of the total number of stars formed within the intermediate age episode. Furthermore, within the tidal radius (0.48{deg} or 888pc) a total mass in stars of 1.07+/-0.08x10^6^M_{sun}_ was formed, giving Carina a stellar mass-to-light ratio of 1.8+/-0.8. Combining the detailed star formation history with spectroscopic observations of RGB stars, we are able to determine the detailed age-metallicity relation of each episode and the timescale of alpha-element evolution of Carina from individual stars. The oldest episode displays a tight age-metallicity relation during ~6Gyr with steadily declining alpha-element abundances and a possible alpha-element knee visible at [Fe/H]~-2.5dex. The intermediate age sequence displays a more complex age-metallicity relation starting from low metallicity and a sequence in alpha-element abundances with a slope much steeper than observed in the old episode, starting from [Fe/H]=-1.8dex and [Mg/Fe]~0.4dex and declining to Mg-poor values ([Mg/Fe]<-0.5dex). This indicates clearly that both episodes of star formation formed from gas with different abundance patterns , inconsistent with simple evolution in an isolated system.
- ID:
- ivo://CDS.VizieR/J/AJ/115/1840
- Title:
- BV photometry in Carina dwarf galaxy
- Short Name:
- J/AJ/115/1840
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have analyzed deep B and V photometry of the Carina dwarf spheroidal galaxy reaching below the old main-sequence turnoff to V~25. Using simulated color-magnitude diagrams to model a range of star formation scenarios, we have extracted a detailed, global star formation history. Carina experienced three significant episodes of star formation at ~15, 7, and 3Gyr. Contrary to the generic picture of galaxy evolution, however, the bulk of star formation, at least 50%, occurred during the episode 7Gyr ago, which may have lasted as long as 2Gyr. For unknown reasons, Carina formed only 10%-20% of its stars at an ancient epoch and then remained quiescent for more than 4 Gyr. The remainder (~30%) formed relatively recently, only 3Gyr ago. Interest in the local population of dwarf galaxies has increased lately because of their potential importance in the understanding of faint galaxy counts. We surmise that objects like Carina, which exhibits the most extreme episodic behavior of any of the dwarf spheroidal companions to the Galaxy, are capable of contributing to the observed excess of blue galaxies at B~24 only if the star formation occurred instantaneously.
- ID:
- ivo://CDS.VizieR/J/A+A/364/712
- Title:
- BV photometry in Draco molecular cloud
- Short Name:
- J/A+A/364/712
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To investigate the distance and linear dimensions of the Draco Molecular Cloud (MBM 41) we have obtained new CCD photometry for a selection of stars in 20 selected areas toward the cores of the cloud. The selected areas were chosen to coincide with the brightest IRAS emitting portions of the cloud, and also with dense ^12^CO emission from the cloud. For each area we have obtained V and B photometry, and a subset of the fields has also been observed through a narrow-band H{alpha} filter and in the U band. We present V and B magnitudes for the 362 stars which have high-quality observations in both bands. The observations were made during the nights of June 29 and June 30, 1993 at the Palomar Observatory, using the 1.5-meter telescope and Palomar 6 Tektronix CCD camera with 24 micron pixels.
- ID:
- ivo://CDS.VizieR/J/PASP/99/739
- Title:
- BV photometry in 4 fields of 47 Tuc
- Short Name:
- J/PASP/99/739
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD photometry in B and V, taken with the RCA camera at the CTIO 4-meter telescope, is reported for 8800 stars in the field of 47 Tuc (= NGC 104 = C0021-723). Our data, reduced through the DAOPHOT code, comprise results from two long-exposure frame pairs in which the photometry extends from the cluster turnoff down to V~24, and two other short-exposure fields nearer to the cluster center which precisely define the giant and horizontal branches. Color-magnitude diagrams are presented, statistically corrected for background contamination from the Small Magellanic Cloud halo, and a composite CMD and luminosity function are constructed for the entire cluster, covering an 11-magnitude range in luminosity.
- ID:
- ivo://CDS.VizieR/J/AJ/116/2395
- Title:
- BV photometry in five SMC clusters
- Short Name:
- J/AJ/116/2395
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present our analysis of archival Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2) observations in F450W (~B) and F555W (~V) of the intermediate-age populous star clusters NGC 121, NGC 339, NGC 361, NGC 416, and Kron 3 in the Small Magellanic Cloud. We use published photometry of two other SMC populous star clusters, Lindsay 1 and Lindsay 113, to investigate the age sequence of these seven star clusters in order to improve our understanding of the formation chronology of the SMC. We analyzed the V versus B-V and M_V_ versus (B-V)_0_ color-magnitude diagrams of these populous Small Magellanic Cloud star clusters using a variety of techniques and determined their ages, metallicities, and reddenings. These new data enable us to improve the age-metallicity relation of star clusters in the Small Magellanic Cloud. In particular, we find that a closed-box continuous star formation model does not reproduce the age-metallicity relation adequately. However, a theoretical model punctuated by bursts of star formation is in better agreement with the observational data presented herein.
- ID:
- ivo://CDS.VizieR/J/AJ/111/1596
- Title:
- BV photometry in Fornax globulars
- Short Name:
- J/AJ/111/1596
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report new color-magnitude diagrams for Fornax globular clusters 1 and 5 where our data reaches V=24, below the horizontal branch. Using the index B-R/(B+V+R), a measure of the horizontal branch color, we find cluster 1 has a red (-0.50+/-0.10) and cluster 5 an intermediate color (-0.09+/-0.12) horizontal branch confirming the first extragalactic second parameter pair. The HB types are markedly redder than the Galactic globular clusters at [Fe/H]=-2. In globular cluster 1, we find 21 possible variable stars out of 41 horizontal branch stars. Cluster 1 has an anomalously low ratio of horizontal branch to red giant stars, which formally gives a helium abundance of 0.16<Y<0.22, depending on the assumptions used. For both clusters 1 and 5, and for the red horizontal branch in the field adjacent to cluster 5, V_HB = 21.25 +/- 0.05. We give calibrated surface brightness profiles and measure new core and tidal radii for cluster 1 of 17.6" and 104" and for cluster 5 of <2" and 91", respectively.
- ID:
- ivo://CDS.VizieR/J/ApJ/710/1664
- Title:
- BV photometry in Leo IV and Leo V dSphs
- Short Name:
- J/ApJ/710/1664
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained deep photometry in two 1{deg}x1{deg} fields covering the close pair of dwarf spheroidal galaxies Leo IV and Leo V and part of the area in between. From the distribution of likely red giant branch (RGB) and horizontal-branch (HB) stars in the data set, we find that both Leo IV and Leo V are significantly larger than indicated by previous measurements based on shallower data. With a half-light radius of r_h_=4.6'+/-0.8' (206+/-36pc) and r_h_=2.6'+/-0.6' (133+/-31pc), respectively, both systems are now well within the physical size bracket of typical dwarf spheroidal Milky Way satellites. Both are also found to be significantly elongated with an ellipticity of {epsilon}~0.5, a characteristic shared by many of the fainter (M_V_>-8) Milky Way dwarf spheroidals. The large spatial extent of our survey allows us to search for extra-tidal features in the area between the two dwarf galaxies with unprecedented sensitivity. The spatial distribution of candidate RGB and HB stars in this region is found to be non-uniform at the ~3{sigma} level. We investigate different scenarios to explain the close proximity of Leo IV and Leo V, and the possible tidal bridge between them.
- ID:
- ivo://CDS.VizieR/J/AJ/117/2868
- Title:
- BV photometry in M2 (NGC 7089)
- Short Name:
- J/AJ/117/2868
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present BV CCD photometry for 30 RR Lyrae variables, including 13 newly discovered, in the Oosterhoff type II globular cluster M2. New light curves and ephemerides are presented. Our observations cover magnitudes ranging from the red giant branch tip to ~3mag below the turnoff, allowing us to determine accurate fundamental photometric parameters. With the discovery of new RR Lyrae variables, the mean periods of the RRab and RRc variables are <P_ab_>=0.685+/-0.022days and <P_c_>=0.333+/-0.013days, respectively. The number ratio of the RRc type variables to the total number of RR Lyrae type variables is n(c)/n(ab+c)=0.40. The RR Lyrae pulsational mode transition occurs between the fundamental period of 0.528-days and 0.556-days. From star counts along the horizontal branch (HB), we obtain two HB color distribution indices, (B-R)/(B+V+R)=0.92 and B2/(B+V+R)=0.46. The period-change rates are also derived. The mean period-change rate from six RRab variables is <{beta}>=0.06+/-0.04days/Myr, which agrees well with the predictions of Lee's 1991 model. Our color-magnitude diagram shows a very extended blue HB tail, and there are no significant blue HB gaps in M2.
- ID:
- ivo://CDS.VizieR/J/AJ/121/318
- Title:
- BV photometry in NGC 5986
- Short Name:
- J/AJ/121/318
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained new CCD BV photometry of the little-studied southern Galactic globular cluster NGC 5986, including light curves of five of its RR Lyrae variables. The cluster's red giant branch bump is detected for the first time, at V=16.47 +/-0.03. We derive a reddening and true distance modulus of E(B-V)=0.29+/-0.02 and (m-M)_0_=15.15+/-0.10, respectively. The cluster's color-magnitude diagram reveals a mostly blue horizontal branch, like that of M13 or M2, and quite unlike M3; yet all of these clusters have nearly identical metallicities ([Fe/H]_CG97_=-1.35). We show that the RR Lyrae variables in NGC 5986 are about 0.2mag brighter on average than those in M3, an important exception to the often-employed, universal M_V_(RR)-[Fe/H] relation. Finally, we note that NGC 5986 contains two luminous stars with spectral types A-F, which are likely to be post-asymptotic giant branch (PAGB) objects. The V-band luminosity function of such yellow PAGB stars is a promising standard candle. We suggest that the luminosity function is sharply peaked at M_V_(PAGB)=-3.28+/-0.07.
