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.Comment: to appear in PASP; 17 pages, including 7 embedded, postscript figures and 1 embedded table; uses AAS LaTeX style files (not included); also available at http://astro.caltech.edu/~map/map.bibliography.htm

Dust during the Reionization

The possibility that population III stars have reionized the Universe at redshifts greater than 6 has recently gained momentum with WMAP polarization results. Here we analyse the role of early dust produced by these stars and ejected into the intergalactic medium. We show that this dust, heated by the radiation from the same population III stars, produces a submillimetre excess. The electromagnetic spectrum of this excess could account for a significant fraction of the FIRAS (Far Infrared Absolute Spectrophotometer) cosmic far infrared background above 700 micron. This spectrum, a primary anisotropy ($\Delta T$) spectrum times the $\nu^2$ dust emissivity law, peaking in the submillimetre domain around 750 micron, is generic and does not depend on other detailed dust properties. Arcminute--scale anisotropies, coming from inhomogeneities in this early dust, could be detected by future submillimetre experiments such as Planck HFI.Comment: 6 pages, 8 figures, accepted by A&A; clarifications made, typos fixed, results more exactly calculate

HEROES: The Hawaii eROSITA Ecliptic Pole Survey Catalog

We present a seven band (g, r, i, z, y, NB816, NB921) catalog derived from a Subaru Hyper Suprime-Cam (HSC) imaging survey of the North Ecliptic Pole (NEP). The survey, known as HEROES, consists of 44 sq. deg of contiguous imaging reaching median 5-sigma depths of g: 26.5, r: 26.2, i: 25.7, z: 25.1, y: 23.9, NB816: 24.4, NB921: 24.4 mag. We reduced these data with the HSC pipeline software hscPipe, and produced a resulting multiband catalog containing over 25 million objects. We provide the catalog in three formats: (1) a collection of hscPipe format forced photometry catalogs, (2) a single combined catalog containing every object in that dataset with selected useful columns, and (3) a smaller variation of the combined catalog with only essential columns for basic analysis or low memory machines. The catalog uses all the available HSC data on the NEP and may serve as the primary optical catalog for current and future NEP deep fields from instruments and observatories such as SCUBA-2, eROSITA, Spitzer, Euclid, and JWST.Comment: 10 pages, 6 figures, 2 tables. Submitted to ApJS. v2: 11 pages, 6 figures, 2 tables. Accepted to ApJ

Physical properties and small-scale structure of the Lyman-alpha forest: Inversion of the HE 1122-1628 UVES spectrum

We study the physical properties of the Lyman-alpha forest by applying the inversion method described by Pichon et al. (2001) to the high resolution and high S/N ratio spectrum of the z_em=2.40 quasar HE 1122-1628 obtained during Science Verification of UVES at the VLT. We compare the column densities obtained with the new fitting procedure with those derived using standard Voigt profile methods. The agreement is good and gives confidence in the new description of the Lyman-alpha forest as a continuous field as derived from our method. We show that the observed number density of lines with logN>13 and 14 is, respectively, 50 and 250 per unit redshift at z~2. We study the physical state of the gas, neglecting peculiar velocities, assuming a relation between the overdensity and the temperature. T=Tbar * rho^(2beta). There is an intrinsic degeneracy between the parameters beta and Tbar. We demonstrate that, at a fixed beta, the temperature at mean density, Tbar, can be uniquely extracted however. While applying the method to HE 1122-1628, we conclude that for 0.2<beta<0.3, 6000<Tbar<15000 K at z~2. We investigate the small scale structure of strong absorption lines using the information derived from the Lyman-beta, Lyman-gamma and Civ profiles. Introducing the Lyman-beta line in the fit allows us to reconstruct the density field up to rho~10 instead of 5 for the Lyman-alpha line only. There may be small velocity shifts ~10km.s^{-1} between the peaks in the Civ and Hi density profiles. Although the statistics is small, it seems that Civ/Hi and n_HI are anti-correlated. This could be a consequence of the high sensitivity of the Civ/Hi ratio to temperature. The presence of associated Ovi absorption, with similar profile, confirms that the gas is photo-ionized and at a temperature of T~10^5 K.Comment: 15 pages, 21 figures, accepted for publication in A&A. Quoted results from other papers in section 4.2 have been modifie