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- ID:
- ivo://CDS.VizieR/J/A+A/615/A96
- Title:
- VI photometry in 3 dwarf galaxies
- Short Name:
- J/A+A/615/A96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The abundance and spatial distribution of dwarf galaxies are excellent empirical benchmarks against which to test models of structure formation on small scales. The nearby Centaurus group, with its two subgroups centered on Cen A and M 83, stands out as an important alternative to the Local Group for scrutinizing cosmological model predictions in a group of galaxies context. We have obtained deep optical images of three recently discovered M 83 satellite galaxy candidates with the FORS2 instrument mounted on the Very Large Telescope. We aim to confirm their group membership and study their stellar population. Deep V I-band photometry was used to resolve the brightest stars in our targets. Artificial star tests are performed to estimate the completeness and uncertainties of the photometry. The color-magnitude diagrams reveal the red giant branch (RGB) stars, allowing us to use the Sobel edge detection method to measure the magnitude of the RGB tip and thus derive distances and group membership for our targets. The mean metallicity of the dwarf galaxies were further determined by fitting BASTI model isochrones to the mean RGB locus.
- ID:
- ivo://CDS.VizieR/J/AJ/128/224
- Title:
- VI photometry in M33 outer regions
- Short Name:
- J/AJ/128/224
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep CCD photometry in the VI passbands using the WIYN 3.5m telescope of a field located approximately 20 southeast of the center of M33; this field includes the region studied by Mould & Kristian in 1986ApJ...305..591M. The color-magnitude diagram (CMD) extends to I~25 and shows a prominent red giant branch (RGB), along with significant numbers of asymptotic giant branch and young main-sequence stars.
- 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/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/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.
- ID:
- ivo://CDS.VizieR/J/ApJ/654/186
- Title:
- VI photometry of Cepheids in NGC 5128
- Short Name:
- J/ApJ/654/186
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss a new distance to NGC 5128 (Centaurus A) based on Cepheid variables observed with the Hubble Space Telescope. Twelve F555W (V) and six F814W (I) epochs of cosmic-ray-split WFPC2 observations were obtained. A total of 56 bona fide Cepheids were discovered, with periods ranging from 5 to ~50 days; five of these are likely Population II Cepheids of the W Virginis class, associated with the bulge or halo of NGC 5128.
- ID:
- ivo://CDS.VizieR/J/MNRAS/346/1143
- Title:
- VI photometry of Collinder 121
- Short Name:
- J/MNRAS/346/1143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a VI photometric catalogue towards the open cluster Cr 121. XMM-Newton and ROSAT data are used to discover a low-mass pre-main sequence (PMS) along this sightline. de Zeeuw et al. (1999, Cat. <J/AJ/117/354>) have identified Cr 121 as a moving group, using Hipparcos data, at a distance of 592pc; we reject the scenario that these low-mass PMS stars are associated with that association. By considering the higher mass main sequence stellar membership of the groups along this sightline, the density of low-mass PMS stars and their age spread we argue that the low-mass PMS stars are associated with a young, compact cluster at a distance of 1050pc.
- ID:
- ivo://CDS.VizieR/J/AJ/124/3222
- Title:
- VI photometry of Draco and UMi galaxies
- Short Name:
- J/AJ/124/3222
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present (V, I) photometry of two wide (~25x25arcmin^2^) fields centered on the low surface brightness dwarf spheroidal galaxies Draco and Ursa Minor. New estimates of the distance to these galaxies are provided [(m-M)_0_(UMi)=19.41+/-0.12 and (m-M)_0_(Dra)=19.84+/-0.14], and a comparative study of their evolved stellar population is presented.
- ID:
- ivo://CDS.VizieR/J/A+A/411/361
- Title:
- VI photometry of extra-galactic Cepheids
- Short Name:
- J/A+A/411/361
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we recalibrate the Cepheid distance to some nearby galaxies observed by the HST Key Project and the Sandage-Tammann-Saha group. We use much of the Key Project methodology in our analysis but apply new techniques, based on Fourier methods to estimate the mean of a sparsely sampled Cepheid light curve, to published extra-galactic Cepheid data. We also apply different calibrating PL relations to estimate Cepheid distances, and investigate the sensitivity of the distance moduli to the adopted calibrating PL relation. We re-determine the OGLE LMC PL relations using a more conservative approach and also study the effect of using Galactic PL relations on the distance scale.
