Searcharxiv⌕ Search

arXiv subjects

A. Songaila

Publications and source records attributed to A. Songaila.

20 records · Page 2Linked to original sources

Faint M-dwarfs and the structure of the Galactic disk

We use broadband photometry and low-resolution spectra of a complete sample of late-K and M dwarfs brighter than I=22 in three fields at high galactic latitude to study issues relating to galactic structure and large scale abundance gradients in the Galaxy. The observed starcounts in each field are a good match to the predictions of models based on deep starcount data in other intermediate-latitude fields, and these models identify the late-type stars as members of the Galactic disk. Abundances for these late type stars are estimated via narrowband indices that measure the strength of the TiO and CaH bands in their spectra. Our results show that the average abundance in the Galactic disk remains close to solar even at heights of more than 2 kpc above the Plane.

astro-ph↗

The Hawaii K-Band Galaxy Survey. II. Bright K-band Imaging

We present the results of a wide-field K-selected galaxy survey with complementary optical I- and B-band imaging in six fields with a total coverage of 9.8 square degrees. This survey establishes the bright-end K-band galaxy number counts in the magnitude range 13<K<16 with high precision. We find that our bright-end counts have a significantly steeper slope than the prediction of a no-evolution model, which cannot be accounted for by known observational or theoretical error. We also argue against the likelihood of sufficient evolution at such low redshifts to account for this effect, we describe an alternative picture in which there is a local deficiency of galaxies by a factor of 2 on scale sizes of around 300 Mpc. Taken at face value, this would imply that local measurements of Ω_0 underestimate the true value of the cosmological mass density by this factor and that local measurements of $H_0$ could be high by as much as 33%.

astro-ph↗