Related papers: M Subdwarfs: The Population II Luminosity Function

We obtain a new determination of the metallicity distribution function (MDF) of stars within $\sim5$-$10$ kpc of the Sun, based on recently improved co-adds of $ugriz$ photometry for Stripe 82 from the Sloan Digital Sky Survey. Our new…

Ultracool subdwarfs are low luminosity, late-type M and L dwarfs that exhibit spectroscopic indications of subsolar metallicity and halo kinematics. Their recent discovery and ongoing investigation have led to new insights into the role of…

We report dynamical mass measurements for the components of the previously known double-lined spectroscopic subdwarfs G 006-026 B and C using the Fine Guidance Sensors (FGS) on the Hubble Space Telescope. To build the empirical…

Large numbers of low-to-medium resolution spectra of M-type dwarf stars from both the local Galactic disk and halo are available from various surveys. In order to fully exploit these data, we develop a template-fit method using a set of…

Using data from the Sloan Digital Sky Survey Early Data Release and SuperCOSMOS Sky Survey scans of POSS-I plates we identify a sample of 2600 subdwarfs using reduced proper motion methods and strict selection criteria. This forms one of…

We report on the distribution of metallicities, [Fe/H], for very metal-poor stars in the halo of the Galaxy. Although the primary information on the nature of the Metallicity Distribution Function (MDF) is obtained from the two major recent…

Using effective temperature and metallicity derived from SDSS spectra for ~60,000 F and G type main sequence stars (0.2<g-r<0.6), we develop polynomial models for estimating these parameters from the SDSS u-g and g-r colors. We apply this…

We present a statistical parallax study of nearly 2,000 M subdwarfs with photometry and spectroscopy from the Sloan Digital Sky Survey. Statistical parallax analysis yields the mean absolute magnitudes, mean velocities and velocity…

We explore the stellar metallicity distribution function of the Galactic halo based on SDSS ugriz photometry. A set of stellar isochrones is calibrated using observations of several star clusters and validated by comparisons with…

In the past few years, astronomers have uncovered several very low-temperature, metal-poor stars with halo or thick disk kinematics and peculiar spectral and photometric properties, so-called ultracool subdwarfs. These include the first…

We present an analysis of the space motions of 742 subdwarf stars based on the sample of Carney et al. (1994, CLLA). Hipparcos parallaxes, TYC2+HIP proper motions and Tycho2 proper motions were combined with radial velocities and…

We determine the metallicity distribution function (MDF) of the Galactic halo by means of a sample of 1638 metal-poor stars selected from the Hamburg/ESO objective-prism survey (HES). The sample was corrected for minor biases introduced by…

M subdwarfs are low-metallicity M dwarfs that typically inhabit the halo population of the Galaxy. Metallicity controls the opacity of stellar atmospheres; in metal poor stars, hydrostatic equilibrium is reached at a smaller radius, leading…

Recent discoveries from red optical proper motion and wide-field near-infrared surveys have uncovered a new population of ultracool subdwarfs -- metal-poor stars and brown dwarfs extending into the late-type M, L and possibly T spectral…

We analyze a sample of tens of thousands of spectra of halo turnoff stars, obtained with the optical spectrographs of the Sloan Digital Sky Survey (SDSS), to characterize the stellar halo population "in situ" out to a distance of a few tens…

We present the results of an HST snapshot program to search for very-low-mass stellar companions to nearby M subdwarfs. None of our nine targetted metal-poor primaries have companions more massive than the hydrogen burning limit, implying…

A search of the Sloan Digital Sky Survey spectroscopic database has turned up 23 new ultra-cool subdwarfs, low-mass metal-poor stars of spectral subtype M 7.0 or later. Spectra from these red objects all show very strong molecular bands of…

We study a sample of about 1400 disk M dwarfs that are found in 148 fields observed with the Wide Field Camera 2 (WFC2) on the Hubble Space Telescope and 162 fields observed with pre-repair Planetary Camera 1 (PC1), of which 95 of the WFC2…

We determine the metallicity distribution function (MDF) of the Galactic halo based on metal-poor main-sequence turnoff-stars (MSTO) which were selected from the Hamburg/ESO objective-prism survey (HES) database. Corresponding follow-up…

We have searched the Forth Catalogue of Nearby Stars for halo stars and identified 15 subdwarfs and a high velocity white dwarf in the solar neighbourhood. This search was motivated mainly by the recent determinations of MACHO masses of…