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The Luminosity and Mass Functions of Low-Mass Stars in the Galactic Disk. I. The Calibration Region
We present measurements of the luminosity and mass functions of low-massstars constructed from a catalog of matched Sloan Digital Sky Survey(SDSS) and Two Micron All Sky Survey (2MASS) detections. Thisphotometric catalog contains more than 25,000 matched SDSS and 2MASSpoint sources spanning ~30 deg2 on the sky. We have obtainedfollow-up spectroscopy, complete to J = 16, of more than 500 low-massdwarf candidates within a 1 deg2 subsample, and thousands ofadditional dwarf candidates in the remaining 29 deg2. Thisspectroscopic sample verifies that the photometric sample is complete,uncontaminated, and unbiased at the 99% level globally, and at the 95%level in each color range. We use this sample to derive the luminosityand mass functions of low-mass stars over nearly a decade in mass (0.7 Msun > M * > 0.1 M sun). Theluminosity function of the Galactic disk is statistically consistentwith that measured from volume-complete samples in the solarneighborhood. We find that the logarithmically binned mass function isbest fit with an Mc = 0.29 log-normal distribution, with a90% confidence interval of Mc = 0.20-0.50. These 90%confidence intervals correspond to linearly binned mass functionspeaking between 0.27 M sun and 0.12 M sun, wherethe best fit MF turns over at 0.17 M sun. A power-law fit tothe entire mass range sampled here, however, returns a best fit ofα = 1.1 (where the Salpeter slope is α = 2.35); a brokenpower law returns α = 2.04 at masses greater than log M =-0.5 (M = 0.32 M sun), and α = 0.2 at lowermasses. These results agree well with most previous investigations,though differences in the analytic formalisms adopted to describe thosemass functions, as well as the range over which the data are fit, cangive the false impression of disagreement. Given the richness ofmodern-day astronomical data sets, we are entering the regime wherebystronger conclusions can be drawn by comparing the actual datapointsmeasured in different mass functions, rather than the results ofanalytic analyses that impose structure on the data a priori. Havingvalidated this method to generate a low-mass luminosity function frommatched SDSS/2MASS data sets, future studies will extend this techniqueto the entirety of the SDSS footprint.Based in part on observations obtained with the Apache Point Observatory3.5 m telescope, which is owned and operated by the AstrophysicalResearch Consortium.
| Photoelectric photometry of stars near the north Galactic pole. II
UBV photometric observations of about 700 stars near the north Galacticpole, obtained using single-channel photometers on the 40-cm and 60-cmCassegrain telescopes at Kvistaberg Observatory (during 1976-1983) andthe Spanish International Observatory (during 1984), respectively, aspart of a program including the stars to be observed by the Hipparcosspacecraft, are reported. The data are presented in a series of tablesand briefly characterized.
| The space distribution of late type stars in a North galactic pole region.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1962AJ.....67...37U&db_key=AST
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Observation and Astrometry data
| Constellation: | Chiens de chasse |
| Right ascension: | 12h56m39.23s |
| Declination: | +36°51'57.3" |
| Apparent magnitude: | 10.055 |
| Distance: | 40.016 parsecs |
| Proper motion RA: | 65 |
| Proper motion Dec: | 10.2 |
| B-T magnitude: | 11.437 |
| V-T magnitude: | 10.17 |
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