A UBVR CCD Survey of the Magellanic Clouds

By Philip Massey. 2001

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We present photometry and a preliminary interpretation of a UBVR survey of the Large and Small Magellanic Clouds, which covers 14.5 deg2 and 7.2 deg2, respectively. This study is aimed at obtaining well-calibrated data on the brighter, massive stars, complementing recent, deeper CCD surveys. Our catalog contains 179,655 LMC and 84,995 SMC stars brighter than V ∼ 18.0, and is photometrically complete to U ∼ B ∼ V ∼ 15.7 and R ∼ 15.2, although stars in crowded regions are selectively missed. We compare our photometry to that of others, and describe the need for gravity-dependent corrections to our CCD U-band photometry. We provide a preliminary cross-reference between our catalog stars and the stars with existing spectroscopy. We discuss the population of stars seen toward the two Clouds, identifying the features in the color-magnitude diagram, and using existing spectroscopy to help construct H-R diagrams. We derive improved values for the blue-to-red star ratios in the two Clouds, emphasizing the uncertainties involved in this before additional spectroscopy. We compare the relative number of red supergiants and Wolf-Rayet stars in the LMC and SMC with that of other galaxies in the Local Group, demonstrating a very strong, tight trend with metallicity, with the ratio changing by a factor of 160 from the SMC to M31. We also reinvestigate the initial mass function of the massive stars found outside of the OB associations. With the newer data, we find that the initial mass function (IMF) slope of this field population is very steep, with Γ ∼ -4 ± 0.5, in agreement with our earlier work. This is in sharp contrast to the IMF slope found for the massive stars with OB associations (Γ ∼ -1.3). Although much more spectroscopy is needed to make this result firm, incompleteness can no longer be invoked as an explanation.

Subfields: Astronomy and Astrophysics, Education, Instrumentation

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Citations in the corpus

The Effective Temperatures and Physical Properties of Magellanic Cloud Red Supergiants: The Effects of Metallicity (2006, methodology): “Observationally, the relative number of RSGs andWolf-Rayet stars appear to change by a factor of >100 over 0.8 dex in metallicity (Massey 2002, 2003), in accordance with the suggestion first made by Maeder et al. (1980).”
The Magellanic Clouds Photomtric Survey: The Small Magellanic Cloud Stellar Catalog and Extinction Map (2001, methodology): “Massey (2002) has produced a photometric catalog (U, B, V and R) of bright stars in the LMC.”
The death of massive stars – I. Observational constraints on the progenitors of Type II-P supernovae (2008, result): “Limiting magnitudes for the progenitors of Type Ibc SNe (indicated with arrows), compared to the observed magnitudes of LMC WR stars from Massey (2002).”
The Physical Properties and Effective Temperature Scale of O-Type Stars as a Function of Metallicity. II. Analysis of 20 More Magellanic Cloud Stars and Results from the Complete Sample (2005, methodology): “Unless otherwise noted in the table, the photometry comes from the CCD UBV measurements by Massey (2002) or Massey et al. (2000), except for the R136 stars, which comes from the WFPC2 photometry of Hunter et al. (1997).”
Galactic-Field Initial Mass Functions of Massive Stars (2003, background): “For stars more massive than the Sun, the stellar initial mass function (IMF) can be approximated well by a single power-law function, ðmÞ / m , with the Salpeter index ¼ 2:35, ðmÞ dm being the number of stars in the mass interval m;mþ dm. Massey and collaborators (Massey et al. 1995a, 1995b; Massey ”
Massive Stars in the Local Group: Implications for Stellar Evolution and Star Formation (2003, methodology): “Using preliminary data for the LMC and SMC, Massey (2002a) notes that there is a factor of three difference in the relative number of blue and red supergiants between the LMC and SMC if one counts only M-type stars; if one instead includes potential K-type supergiants, the difference between the…”
SPITZER SAGE INFRARED PHOTOMETRY OF MASSIVE STARS IN THE LARGE MAGELLANIC CLOUD (2009, methodology): “′′6 for the catalog of Massey (2002), ∼1.”
Toward Understanding Massive Star Formation (2007, methodology): “The latter authors do not find the much steeper slope of the IMF (for the range of 25 M to 120 M ) derived by Massey (2002) for the global OB field population in the LMC.”
The Formation of Stellar Clusters in Turbulent Molecular Clouds: Effects of the Equation of State (2002, background): “Massey (2002) also reported finding apparently isolated, massive, field stars in both the Large and Small Magellanic Clouds.”
The relation between the most-massive star and its parental star cluster mass (2009, background): “…0.5 M⊙, being independent of the cluster density and metallicity for metallicities Z >∼ 0.002 (Massey & Hunter 1998; Sirianni et al. 2000, 2002; Parker et al. 2001; Massey 1998, 2002, 2003; Larson 2002a,b; Wyse et al. 2002; Bell et al. 2003; Piskunov et al. 2004; Pflamm-Altenburg & Kroupa 2006).”
Luminosities and mass-loss rates of SMC and LMC AGB stars and red supergiants (2009, methodology): “UBVR data from Massey (2002) for the MCs,BVRI data from Oestreicher et al. (1997) for RSG in the LMC, OGLEBVI data from Udalski et al. (1998),VRI data from Wood, Bessell & Fox (1983, hereafter WBF).”
A Survey of Local Group Galaxies Currently Forming Stars. I. UBVRI Photometry of Stars in M31 and M33 (2006, methodology): “The latter is based on a consideration of the Bahcall-Soneira model (Bahcall & Soneira 1980) updated by G. Da Costa and H. Morrison; see Massey (2002).”
Cluster Mass Functions in the Large and Small Magellanic Clouds: Fading and Size-of-Sample Effects (2003, methodology): “For this, we had available to us images of the Magellanic Clouds taken by Massey (2002) with the Michigan Curtis Schmidt telescope at Cerro Tololo Interamerican Observatory (CTIO) and a Tektronix 2048×2048 CCD. Massey obtained UBVR images and copious Landolt (1992) standard stars.”
Identification of New M Dwarfs in the Solar Neighborhood (2003, background): “Some of these have been identified by previous surveys (Carpenter et al. 2001; Craig et al. 1997; Fuhrmeister & Schmitt 2003; Koehler 2001; Li & Hu 1998; Li et al. 2000;MacConnell 1981;Massey 2002; Preibisch&Zinnecker 1999; Thompson et al. 1998; Zickgraf et al. 2003).”