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20842. VI photometry in NGC 6352
- ID:
- ivo://CDS.VizieR/J/AJ/110/652
- Title:
- VI photometry in NGC 6352
- Short Name:
- J/AJ/110/652
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The globular cluster NGC 6352, which on the basis of its Galactic position, radial velocity, and [Fe/H] is a member of the (thick) disk system of globular clusters, has been observed to below the main-sequence turnoff (MSTO) using the Hubble Space Telescope. These observations, which were obtained before the repair mission, were analyzed using the flux-conserving iterative/recursive deconvolution algorithm developed at the University of North Carolina. This algorithm can produce more precise photometry than standard PSF-fitting methods with the aberrated images. The V, (V-Ic) color-magnitude diagram constructed from these observations places the cluster turnoff at V=18.80+/-0.10. Observations with the CTIO 0.9m telescope have been used to photometer the brighter stars in the cluster, providing a calibration of the HST data and an estimate of the cluster's reddening, E(B-V)=0.21+/-0.03. From spectroscopic observations of the strengths of the Ca II triplet lines in red giants in the cluster and from previous measurements in the literature, we find that NGC 6352 is only slightly more metal rich (Delta[Fe/H]=0.08+/-0.05) than the prototypical disk globular cluster, 47 Tuc. From the difference in V magnitude between the horizontal branch and the MSTO, we find that NGC 6352 is essentially the same age as 47 Tuc (formally, older by 0.7+/-2.2Gyr). Comparisons with the latest Yale isochrones support this result and yield 14.5+/-2Gyr for the age of 47 Tuc from the photometry of Hesser et al. (1987PASP...99..739H), which is consistent with other determinations. The old age obtained for NGC 6352 provides additional evidence that the disk system of globular clusters is very old and is in fact older or comparable in age to several globular clusters populating the Galactic halo.
- ID:
- ivo://CDS.VizieR/J/A+AS/106/161
- Title:
- (V,I) photometry in NGC 6356 and 47 Tuc
- Short Name:
- J/A+AS/106/161
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD photometry in the VRI and Gunn z bands was obtained for the populous bulge globular cluster NGC 6356. The analysis of the red giant branch indicates that it is metal-rich, intermediate between 47 Tuc and NGC 6528; we estimate [Fe/H]=~-0.4. The red giant clump is clearly detected. The horizontal branch morphology is red and compact. We derive a reddening of E(B-V)=0.2410.04 and a distance d=15.010.4kpc from the Sun. We also present VI colour magnitude diagrams of 47 Tuc for comparison. NGC 6356 and 47 Tuc are important reference objects for studies of more reddened metal-rich bulge clusters.
- ID:
- ivo://CDS.VizieR/J/MNRAS/424/1113
- Title:
- VI photometry in Phoenix dwarf galaxy
- Short Name:
- J/MNRAS/424/1113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a wide-area photometric survey of the Phoenix dwarf galaxy, one of the rare dwarf irregular/dwarf spheroidal transition-type galaxies (dTs) of the Local Group (LG). These objects offer the opportunity to study the existence of possible evolutionary links between the late- and early-type LG dwarf galaxies, since the properties of dTs suggest that they may be dwarf irregulars in the process of transforming into dwarf spheroidals. Using FORS at the Very Large Telescope (VLT), we have acquired VI photometry of Phoenix. The data reach a signal-to-noise ratio (S/N)~10 just below the horizontal branch of the system and consist of a mosaic of images that covers an area of 26x26arcmin^2^ centred on the coordinates of the optical centre of the galaxy.
- ID:
- ivo://CDS.VizieR/J/A+A/390/931
- Title:
- VI photometry in Pismis 23 and Stephenson 2
- Short Name:
- J/A+A/390/931
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Pismis 23 and Stephenson 2 are two very reddened open clusters, projected close to the Galactic plane. We present VI and JH photometry for Pismis 23 and I and Gunn z for Stephenson 2. We derive a relatively old age of ~700Myr for Pismis 23, with a reddening value of E(B-V)=1.73 and a distance d_{sun}_~2.6kpc from the Sun. Stephenson 2 has a clump of red supergiants, indicating a young age of about 20Myr, somewhat younger and more distant (d_{sun}_~6kpc) than recently reported in the literature. The age estimate for such a young object is crucial for the distance estimate. The high reddening of these two clusters relative to predictions from the diffuse interstellar medium at their distances is due to discrete intervening clouds.
- ID:
- ivo://CDS.VizieR/J/AJ/112/772
- Title:
- VI photometry in South Galactic Pole
- Short Name:
- J/AJ/112/772
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Catalogs of V and I photometry for two 20 square degree regions near the South Galactic Pole, containing 30,000 and 19,000 stars, have been constructed using a CCD in time delay integration mode. Internal and external comparisons indicate a characteristic photometric accuracy ranging from 0.02mag at V~12 to 0.05 at V~18-18.5.
- ID:
- ivo://CDS.VizieR/J/AJ/110/1649
- Title:
- VI photometry near the M33 nucleus
- Short Name:
- J/AJ/110/1649
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have studied the stellar populations near the nucleus of the nearby spiral galaxy M33 using archival observations of the Hubble Space Telescope Planetary Camera in the F555W and F785LP passbands. The I vs (V-I) color-magnitude diagram reveals a young stellar population with a blue main sequence and red supergiants, and stars in a blue loop that are Cepheid candidates. An old red giant branch is clearly visible, with a break at I=20.7mag which is, within the observational errors, identical to the giant branch termination point of the Mould & Kristian (1986ApJ...305..591M) halo field. However, red giants are seen up to I=19.5mag, and many bright red giants are undetected in the V band. We find evidence for a wide abundance spread of at least 1.5dex from metal-poor (~M15) to metal-rich (>=47Tucanae) in the Population II stars, in sharp contrast to the M33 halo field of Mould & Kristian (1986ApJ...305..591M) which is metal-poor (~M92) with a narrow abundance range. We show that the various stellar populations have different spatial distributions. The Population II stars are more centrally concentrated than the Population I stars. The red giants brighter than I=20.7 (the termination point for a Galactic globular cluster giant branch) are found to be more centrally concentrated than the (presumably) old red giants. The most-centrally concentrated bright Population II giants are probably associated with the many bright red giants that are undetected in the V band. These infrared-bright giants were probably created in an intermediate-age burst of star formation that took place well after the formation of the oldest halo stars but long before the recent burst of star formation seen in nearby OB associations. This stellar population probably corresponds to the bulge identified in the infrared H band by Minniti et al. (1993ApJ...410L..79M).
20848. VI photometry of Berkeley 66
- ID:
- ivo://CDS.VizieR/J/A+AS/121/451
- Title:
- VI photometry of Berkeley 66
- Short Name:
- J/A+AS/121/451
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A colour magnitude diagram (CMD) extending to V=~19mag is given for 444 stars in the region of the galactic cluster Berkeley 66. The V and I photometry of a nearby field is also reported. This object appears very faint, highly contaminated by foreground stars and very reddened. The apparent distance modulus (m-M) and the colour excess E_V-I_ are guessed to be 17.5 and 1.1, respectively, with an uncertainty of at least 30%. Adopting these values the comparison of the CMD with theoretical isochrones from the Padova group provides an age around 1.0Gyr.
- ID:
- ivo://CDS.VizieR/J/AJ/149/66
- Title:
- VI photometry of 8 Cepheid candidates in M31
- Short Name:
- J/AJ/149/66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ultra-long-period Cepheids (ULPCs) are classical Cepheids with pulsation periods exceeding ~80days. The intrinsic brightness of ULPCs are ~1 to ~3mag brighter than their shorter period counterparts. This makes them attractive in future distance scale work to derive distances beyond the limit set by the shorter period Cepheids. We have initiated a program to search for ULPCs in M31, using the single-band data taken from the Palomar Transient Factory, and identified eight possible candidates. In this work, we presented the VI-band follow-up observations of these eight candidates. Based on our VI-band light curves of these candidates and their locations in the color-magnitude diagram and the Period-Wesenheit diagram, we verify two candidates as being truly ULPCs. The six other candidates are most likely other kinds of long-period variables. With the two confirmed M31 ULPCs, we tested the applicability of ULPCs in distance scale work by deriving the distance modulus of M31. It was found to be {mu}_M31,ULPC_=24.30+/-0.76mag. The large error in the derived distance modulus, together with the large intrinsic dispersion of the Period-Wesenheit (PW) relation and the small number of ULPCs in a given host galaxy, means that the question of the suitability of ULPCs as standard candles is still open. Further work is needed to enlarge the sample of calibrating ULPCs and reduce the intrinsic dispersion of the PW relation before re-considering ULPCs as suitable distance indicators.
20850. VI photometry of Cepheids
- ID:
- ivo://CDS.VizieR/J/ApJ/529/723
- Title:
- VI photometry of Cepheids
- Short Name:
- J/ApJ/529/723
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cepheid-based distances to seven Type Ia supernovae (SNe) host galaxies have been derived using the standard Hubble Space Telescope (HST) Key Project on the Extragalactic Distance Scale pipeline. For the first time, this allows for a transparent comparison of data accumulated as part of three different HST projects: the Key Project, the Sandage et al. Type Ia supernovae (SNe) program, and the Tanvir et al. Leo I Group study. Reanalyzing the Tanvir et al. galaxy and six Sandage et al. galaxies, we find a mean (weighted) offset in true distance moduli of 0.12+/-0.07mag; i.e., 6% in linear distance, in the sense of reducing the distance scale or increasing H_0_. Adopting the reddening-corrected Hubble relations of Suntzeff et al. tied to a zero point based on SNe 1990N, 1981B, 1998bu, 1989B, 1972E, and 1960F and the photometric calibration of Hill et al. leads to a Hubble constant of H_0_=68+/-2(random)+/-5(systematic)km/s/Mpc. Adopting the Kennicutt et al. Cepheid period-luminosity-metallicity dependency decreases the inferred H_0_ by 4%. The H0 result from Type Ia SNe is now in good agreement, to within their respective uncertainties, with that from the Tully-Fisher and surface brightness fluctuation relations.
