12 research outputs found
A study of the compact group of galaxies Shahbazian 4
The radial velocities of members of Shakhbazian 4 are determined. It is found that the dispersion of the radial velocities is 440 km/s. The apparent and absolute magnitudes of galaxies in V color are obtained. It is found that the M/L ratio of the group is about 220 solar mass/solar luminosity. The crossing time for the Shakhbazian 4 group is equal to 47 Myr
Intrinsic Absorption Lines in Seyfert 1 Galaxies. I. Ultraviolet Spectra from the Hubble Space Telescope
We present a study of the intrinsic absorption lines in the ultraviolet
spectra of Seyfert 1 galaxies. We find that the fraction of Seyfert 1 galaxies
that show absorption associated with their active nuclei is more than one-half
(10/17), which is much higher than previous estimates (3 - 10%) . There is a
one-to-one correspondence between Seyferts that show intrinsic UV absorption
and X-ray ``warm absorbers''. The intrinsic UV absorption is generally
characterized by high ionization: C IV and N V are seen in all 10 Seyferts with
detected absorption (in addition to Ly-alpha), whereas Si IV is present in only
four of these Seyferts, and Mg II absorption is only detected in NGC 4151. The
absorption lines are blueshifted (or in a few cases at rest) with respect to
the narrow emission lines, indicating that the absorbing gas is undergoing net
radial outflow. At high resolution, the absorption often splits into distinct
kinematic components that show a wide range in widths (20 - 400 km/s FWHM),
indicating macroscopic motions (e.g., radial velocity subcomponents or
turbulence) within a component. The strong absorption components have cores
that are much deeper than the continuum flux levels, indicating that the
regions responsible for these components lie completely outside of the broad
emission-line regions. The covering factor of the absorbing gas in the line of
sight, relative to the total underlying emission, is C > 0.86, on average. The
global covering factor, which is the fraction of emission intercepted by the
absorber averaged over all lines of sight, is C > 0.5.Comment: 56 pages, Latex, includes 4 figures (encapsulated postscript), Fig. 1
has 2 parts and Fig. 2 has 3 parts, to appear in the Astrophysical Journa
Resolved Spectroscopy of the Narrow-Line Region in NGC 1068. II. Physical Conditions Near the NGC 1068 ``Hot-Spot''
The physical conditions near the optical continuum peak (``hot spot'') in the
inner narrow line region (NLR) of the Seyfert 2 galaxy, NGC 1068. Spectra were
taken with HST/STIS through the 0.1X52 arcsec slit, covering the full STIS 1200
to 10000 Angstrom waveband, and are from a region that includes the hot spot,
extending 0.2, or ~ 14 pc (for H= 75 km/sec/Mpc). Perhaps the most striking
feature of these spectra is the presence of strong coronal emission lines,
including [S XII] 7611 which has hitherto only been identified in spectra of
the solar corona. There is an apparent correlation between ionization energy
and velocity of the emission lines with respect to the systemic velocity of the
host galaxy, with the coronal lines blueshifted, most other high excitation
lines near systemic, and some of the low ionization lines redshifted. From the
results of our modeling, we find that the emission-line gas consists of three
principal components: 1) one in which most of the strong emission-lines, such
as [O III] 5007, [Ne V] 3426, C IV 1550, arise, 2) a more tenuous, highly
ionized component, which is the source of the coronal-line emission, and 3) a
component, which is not co-planar with the other two, in which the low
ionization and neutral lines, such as [N II] 6548 and [O I] 6300, are formed.
The first two components are directly ionized by the EUV-Xray continuum emitted
by the central source, while the low ionization gas is ionized by a combination
of highly absorbed continuum radiation and a small fraction of unabsorbed
continuum scattered by free electrons associated with the hot spot. The
combination of covering factor and Thomson optical depth of the high ionization
components is insufficient to scatter the observed fraction of continuum
radiation into our line-of-sight.Comment: 42 pages, Latex, includes 5 figures (postscript), to appear in the
Astrophysical Journa
Investigation of Dual Active Nuclei, Outflows, Shock-Heated Gas, and Young Star Clusters in Markarian 266
Results of observations with the Spitzer, Hubble, GALEX, Chandra, and
XMM-Newton space telescopes are presented for the Luminous Infrared Galaxy
(LIRG) merger Mrk 266. The SW (Seyfert 2) and NE (LINER) nuclei reside in
galaxies with Hubble types SBb (pec) and S0/a (pec), respectively. Both
galaxies have L > L*, and they are inferred to each contain a ~2.5x10^8 M_sun
black hole. Mrk 266 SW is likely the primary source of a bright Fe K-alpha line
detected from the system, consistent with the reflection-dominated X-ray
spectrum of a heavily obscured AGN. Optical knots embedded in an arc with
aligned radio continuum radiation, combined with luminous H_2 line emission,
provide evidence for a radiative bow shock in an AGN-driven outflow surrounding
the NE nucleus. Soft X-ray emission modeled as shock-heated plasma is
co-spatial with radio continuum emission between the galaxies. Mid-IR
diagnostics indicate roughly equal contributions of AGN and starburst radiation
powering the bolometric luminosity. Approximately 120 star clusters have been
detected, with most having estimated ages < 50 Myr. Detection of 24 micron
emission extending ~34 arcsec (20 kpc) north of the galaxies is interpreted as
~2x10^7 M_sun of dust entrained in an outflowing superwind; at optical
wavelengths this region is resolved into a fragmented morphology indicative of
Rayleigh-Taylor instabilities in an expanding shell of ionized gas. Mrk 266
demonstrates that the dust "blow-out" phase can begin in a LIRG well before the
galaxies fully coalesce during a subsequent ULIRG phase, and rapid gas
consumption in luminous dual AGNs (kpc scale separations) early in the merger
process may explain the paucity of detected binary QSOs (sub-pc scale orbits)
in large surveys. An evolutionary sequence is proposed representing a
progression from dual to binary AGNs, accompanied by an increase in observed
L_x/L_ir ratios by 10^4 or more.Comment: Accepted for publication in the Astronomical Journal, 40 pages, 31
figures, 15 table
A Classic Type 2 QSO
In the Chandra Deep Field South 1Msec exposure we have found, at redshift
3.700 +- 0.005, the most distant Type 2 AGN ever detected. It is the source
with the hardest X-ray spectrum with redshift z>3. The optical spectrum has no
detected continuum emission to a 3sigma detection limit of ~3 10^{-19}
ergs/s/cm^2/AA and shows narrow lines of Ly_alpha, CIV, NV, HeII, OVI, [OIII],
and CIII]. Their FWHM line widths have a range of ~700-2300 km/s with an
average of approximately ~1500 km/s. The emitting gas is metal rich (Z ~2.5-3
Z_solar). In the X-ray spectrum of 130 counts in the 0.5-7 keV band there is
evidence for intrinsic absorption with N_H > 10^{24} cm^{-2}. An iron K_alpha
line with rest frame energy and equivalent width of ~6.4 keV and ~1 keV,
respectively, in agreement with the obscuration scenario, is detected at a
2sigma level. If confirmed by our forthcoming XMM observations this would be
the highest redshift detection of FeK_alpha. Depending on the assumed cosmology
and the X-ray transfer model, the 2-10 keV rest frame luminosity corrected for
absorption is ~10^{45 +- 0.5} ergs/s, which makes our source a classic example
of the long sought Type 2 QSOs. From standard population synthesis models,
these sources are expected to account for a relevant fraction of the
black-hole-powered QSO distribution at high redshift.Comment: 24 LaTeX pages including 6 postscript figures. Revised version,
accepted by Ap