CDROM/APJS/V105/P369 Galactic H I Column Densities (Murphy+ 1996) ================================================================================ Galactic H I Column Densities toward Quasars and Active Galactic Nuclei Edward M. Murphy, Felix J. Lockman, Ari Laor, and Martin Elvis <1996, ApJS, 105, 369> =1996ApJS..105..369M ================================================================================ Abstract: We have determined accurate values of the Galactic neutral hydrogen column density, N_H, toward 220 quasars and active galactic nuclei from 21 cm H I measurements made on the 130 Foot Telescope (42.7 m). Accurate values of N_H have now been obtained for the whole PG bright quasar sample and most quasars that have been observed by ROSAT and the Hubble Space Telescope through mid-1993. The spectra were corrected for stray 21 cm radiation yielding values of N_H with a typical uncertainty of 1x10^19 cm^-2 for high Galactic latitude directions. The H I column densities will be useful for correcting for interstellar opacity at UV and soft X-ray wavelengths, and for estimating the reddening and extinction toward these objects. Keywords: Galaxy: structure -- radio lines: ISM -- X-rays: general Description: The file data.fit contains the data for all 220 objects as FITS IMAGE extensions. The spectrum for each object is written as an image extension in the same order as printed in table 1 (and the FITS table in the first file). The data are written as 1-dimensional spectra and are in units of brightness temperature in Kelvins. In the header, the LSR velocity (CRVAL1), the reference pixel (CRPIX1), and the velocity increment (CRPIX1) can by used to calculate the LSR velocity of a given pixel. Note that the data are linear in frequency, not velocity, and this must be taken into account when calculating the velocity of a given pixel. The FITS files were written using the CFITSIO package written by Dr. William Pence at the GSFC. File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table1.dat 66 220 Summary of 21 cm H I observations table1.fit 2880 9 FITS ASCII table version of table1.dat data.fit 2880 441 FITS IMAGE Extension file of spectra -------------------------------------------------------------------------------- Byte-per-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1-16 A16 --- Object Object name 17-24 F8.3 deg RAdeg Right ascension, 1950 25-32 F8.3 deg DEdeg Declination, 1950 33-40 F8.3 deg GLon Galactic longitude 41-48 F8.3 deg GLat Galactic latitude 49-54 F6.1 cm-2 NH_Thin Optically thin H I column density 55-60 F6.1 cm-2 NH_TS150 Uniform temp 150 K H I column density 61-62 I2 --- Comment *Comment number 63-66 I4 --- Image *Image extension number -------------------------------------------------------------------------------- Notes for file: table1.dat -------------------------------------------------------------------------------- Comment: 1) Data not corrected for stray radiation 2) The listed value of NH includes emission only between LSR velocities -60 km/s and +28 km/s. The H I in NGC 247 itself appears in the spectrum at V_LSR > +28 km/s. Image: The image extension number of the data for each object in the data file, data.fit. -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 22-Oct-96