X-ray emission from BL-Lacertae objects. II. The nature of Markarian 421

Journal Article · Fri Sep 01 04:00:00 EDT 1978 · Astron. J.; (United States)

DOI:https://doi.org/10.1086/112286· OSTI ID:6735135

Margon, B; Jones, T W; Wardle, J F.C.

We present optica.l photometry, spectrophotometry, and 3.7- and 11.1-cm radio observations of Markarian 421 (= 38), a object which is a candidate for identification with the highly variable x-ray source. Photometry and radio observations obtained near in time to the large x-ray obutburst of May 1975 show variability, but no clear correlation with the x-ray data. Image tube scanner observations are presented which show stellar absorption features in the blue, with redshift z=0.03, in agreement with previous photographic observations by Ulrich et al. A formalism which interprets the x-ray emission as Compton scattered radio synchrotron radiation is used to derive parameters of the system. The common and distinctive shape of the profile: steeply sloping edges, two maxima or ''horns,'' and a central minimum, can be accounted for in terms of the gradient of the radial velocity field of the galaxy. Because of this gradient the peak rotational value occurs on the edges of the profile, not at the points of H I signal maxima. The intrinsic line width is correlated with absolute magnitude; as a result line widths, though independent of distance, are subject to the same selection bias as any distance dependent property derived from a magnitude limited sample. This effect is illustrated in the strong correlation between line width and systematic velocity for a sample of 215 galaxies having inclination i> or =45/sup 0/ and high signal-to-noise ratio in their profiles. For samples of the same absolute magnitude, late-type galaxies have systematically smaller intrinsic line widths than do early-type systems. For a central spherical mass distribution, the average central density in early-type galaxies is significantly higher than that of the latest-type spirals.on between line width and absolute magnitude. The value of the Hubble constant determined from line widths is similarly subject to both bias and large uncertainty.

• Research Organization: Department of Astronomy, University of California, Los Angeles, California 90024
• OSTI ID: 6735135
• Journal Information: Astron. J.; (United States), Journal Name: Astron. J.; (United States) Vol. 83:9; ISSN ANJOA
• Country of Publication: United States
• Language: English

Related Subjects

640103* -- Astrophysics & Cosmology-- Quasi-Stellar
Radio
& X-Ray Sources-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COSMIC RAY SOURCES
COSMIC X-RAY SOURCES
GALAXIES
INTERFEROMETERS
MARKARIAN GALAXIES
MEASURING INSTRUMENTS
PHOTOMETRY
RADIATION SOURCES
RED SHIFT
SPECTRA
SPECTROPHOTOMETRY
X-RAY EQUIPMENT
X-RAY GALAXIES
X-RAY SOURCES
X-RAY SPECTRA