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High Galactic Latitudes (high + galactic_latitude)

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Physics and Astronomy100%

Selected Abstracts

Discovery of new nearby L and late-M dwarfs at low Galactic latitude from the DENIS data base

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2008
N. Phan-Bao
ABSTRACT We report on new nearby L and late-M dwarfs (dphot, 30 pc) discovered in our search for nearby ultracool dwarfs (I,J, 3.0, later than M8.0) at low Galactic latitude (|b| < 15°) over 4800 deg2 in the Deep Near Infrared Survey of the Southern Sky (DENIS) data base. We used late-M (, M8.0), L and T dwarfs with accurate trigonometric parallaxes to calibrate the MJ versus I,J colour,luminosity relation. The resulting photometric distances have standard errors of ,15 per cent, which we used to select candidates dphot, 30 pc. We measured proper motions from multi-epoch images found in the public archives ALADIN, DSS, 2MASS and DENIS, with at least three distinct epochs and time baselines of 10,21 yr. We then used a maximum reduced proper motion cut-off to select 28 candidates as ultracool dwarfs (M8.0,L8.0) and to reject one as a distant red star. No T dwarf candidates were found in this search, which required an object to be detected in all three DENIS bands. Our low-resolution optical spectra confirmed that 26 were indeed ultracool dwarfs, with spectral types from M8.0 to L5.5. Two contaminants and one rejected by the maximum reduced proper motion cut-off were all reddened F,K main sequence stars. 20 of these 26 ultracool dwarfs are new nearby ultracool dwarf members, three L dwarfs within 15 pc with one L3.5 at only ,10 pc. We determine a stellar density of dwarfs pc,3 mag,1 over 11.1 ,MJ, 13.1 based on this sample of M8,L3.5 ultracool dwarfs. Our ultracool dwarf density value is in good agreement with the measurement by Cruz et al. of the ultracool dwarf density at high Galactic latitude. [source]

A search for circumstellar material around B-type stars in the Galactic halo

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2002
H. R. M. Magee
Abstract 19 B-type stars, selected from the Palomar,Green Survey, have been observed at infrared wavelengths to search for possible infrared excesses, as part of an ongoing programme to investigate the nature of early-type stars at high Galactic latitudes. The resulting infrared fluxes, along with Strömgren photometry, are compared with theoretical flux profiles to determine whether any of the targets show evidence of circumstellar material, which may be indicative of post-main-sequence evolution. Eighteen of the targets have flux distributions in good agreement with theoretical predictions. However, one star, PG 2120+062, shows a small near-infrared excess, which may be due either to a cool companion of spectral type F5,F7, or to circumstellar material, indicating that it may be an evolved object such as a post-asymptotic giant branch star, in the transition region between the asymptotic giant branch and planetary nebula phase, with the infrared excess due to recent mass loss during giant branch evolution. [source]

The ROSAT Brightest Cluster Sample , IV.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2000
The extended sample
We present a low-flux extension of the X-ray-selected ROSAT Brightest Cluster Sample (BCS) published in Paper I of this series. Like the original BCS and employing an identical selection procedure, the BCS extension is compiled from ROSAT All-Sky Survey (RASS) data in the northern hemisphere (,,0°) and at high Galactic latitudes (|b|,20°). It comprises 99 X-ray-selected clusters of galaxies with measured redshifts z,0.3 (as well as eight more at z>0.3) and total fluxes between 2.8×10,12 and 4.4×10,12 erg cm,2 s,1 in the 0.1,2.4 keV band (the latter value being the flux limit of the original BCS). The extension can be combined with the main sample published in 1998 to form the homogeneously selected extended BCS (eBCS), the largest and statistically best understood cluster sample to emerge from the RASS to date. The nominal completeness of the combined sample (defined with respect to a power-law fit to the bright end of the BCS log N,log S distribution) is relatively low at 75 per cent (compared with 90 per cent for the high-flux sample of Paper I). However, just as for the original BCS, this incompleteness can be accurately quantified, and thus statistically corrected for, as a function of X-ray luminosity and redshift. In addition to its importance for improved statistical studies of the properties of clusters in the local Universe, the low-flux extension of the BCS is also intended to serve as a finding list for X-ray-bright clusters in the northern hemisphere which we hope will prove useful in the preparation of cluster observations with the next generation of X-ray telescopes such as Chandra and XMM-Newton. An electronic version of the eBCS can be obtained from the following URL: http://www.ifa.hawaii.edu/~ebeling/clusters/BCS.html. [source]

Deep H, imagery of the Eridanus shells

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2001
P. Boumis
A deep H, image of interlocking filamentary arcs of nebulosity has been obtained with a wide-field (,30° diameter) narrow-band filter camera combined with a charge-coupled device as a detector. The resultant mosaic of images, extending to a galactic latitude of ,65°, has been corrected for field distortions and had galactic coordinates superimposed on it to permit accurate correlations with the most recent H i (21 cm), X-ray (0.75 keV) and FIR (IRAS 100 ,m) maps. Furthermore, an upper limit of 0.13 arcsec yr,1 to the expansion proper motion of the primary 25° long nebulous arc has been obtained by comparing a recent H, image obtained with the San Pedro Martir telescope of its filamentary edge with that on a Palomar Observatory Sky Survey E plate obtained in 1951. It is concluded that these filamentary arcs are the superimposed images of separate shells (driven by supernova explosions and/or stellar winds) rather than the edges of a single ,superbubble' stretching from Barnard's Arc (and the Orion Nebula) to these high galactic latitudes. The proper motion measurement argues against the primary H,-emitting arc being associated with the giant radio loop (Loop 2) except in extraordinary circumstances. [source]

The source content of low galactic latitude XMM-Newton surveys

ASTRONOMISCHE NACHRICHTEN, Issue 1-2 2003
C. Motch
Abstract We present results from a project conducted by the Survey Science Center of the XMM-Newton satellite and aiming at the identification and characterisation of serendipitous EPIC sources at low galactic latitudes. Deep multi-colour optical imaging and spectroscopic observations have been obtained in the framework of several observing campaigns carried out at ING, CFHT and ESO. These observations have lead to a number of optical identifications, mostly with active stars. We describe the identified source content at low galactic latitudes and compare stellar populations properties at low and high galactic latitudes with those expected from stellar X-ray count models. [source]