4,961 research outputs found
Keck Observations of the Hidden Quasar IRAS P09104+4109
We present imaging and spectro- polarimetric observations of the
ultraluminous infrared galaxy IRAS P09104+4109 using the Keck 10-m Telescope.
We detect the clear presence of broad Hb, Hg, and MgII 2800 emission lines in
the polarized flux spectra of the nucleus and of an extranuclear emission
region ~ 4" away, confirming the presence of a hidden central quasar. The
polarization of the broad Mg II emission line is high (~ 29%), consistent with
the remarkably high polarization (~ 30%-40%) observed in the extended continuum
emission. The narrow emission lines are polarized in a stratified fashion, with
the high ionization lines being polarized 0.7%-1.7% and [O II] essentially
unpolarized. The line polarizations are positively correlated with critical
density, ionization potential, and velocity width of the emission lines. This
indicates that the NLR may be partially shadowed by the putative torus, with
the higher ionization lines originating closer to the nucleus. One notable
characteristic of the extranuclear knot is that all species of Fe are markedly
absent in its spectrum, while they appear prominently in the nucleus. Our
favored interpretation is that there is a large amount of dust in the
extranuclear regions, allowing gaseous refractory metals to deposit. The
extended emission regions are most likely material shredded from nearby cluster
members and not gas condensed from the cooling flow or expelled from the
obscured quasar. Our data provide strong evidence for matter-bounded clouds in
addition to ionization-bounded clouds in the NLR. Ionization by pure velocity
shocks can be ruled out. Shocks with photoionizing precursors may be present,
but are probably not a dominant contributor to the energy input.Comment: 32 pages, including 9 figs and 2 tables, to be published in the
Astronomical Journa
Revisiting the location and environment of the central engine in NGC1068
We revisit in this paper the location of the various components observed in
the AGN of NGC1068. Discrepancies between previously published studies are
explained, and a new measurement for the absolute location of the K-band
emission peak is provided. It is found to be consistent with the position of
the central engine as derived by Gallimore (1997), Capetti (1997) and Kishimoto
(1999). A series of map overlays is then presented and discussed. Model
predictions of dusty tori show that the nuclear unresolved NIR-MIR emission is
compatible with a broad range of models: the nuclear SED alone does not
strongly constrain the torus geometry, while placing reasonable constraints on
its size and thickness. The extended MIR emission observed within the ionizing
cone is shown to be well explained by the presence of optically thick dust
clouds exposed to the central engine radiation and having a small covering
factor. Conversely, a distribution of diffuse dust particles within the
ionizing cone is discarded. A simple model for the H2 and CO emission observed
perpendicularly to the axis of the ionizing cone is proposed. We show that a
slight tilt between the molecular disc and the Compton thick central absorber
naturally reproduces the observed distribution of H2 of CO emission.Comment: 17 pages, 11 figures, revised version for A&
Low-Ionization Emission Regions in Quasars: Gas Properties Probed with Broad O I and Ca II Lines
We have compiled the emission-line fluxes of O I 8446, O I 11287, and the
near-IR Ca II triplet (8579) observed in 11 quasars. These lines are considered
to emerge from the same gas as do the Fe II lines in the low-ionized portion of
the broad emission line region (BELR). The compiled quasars are distributed
over wide ranges of redshift (0.06 < z < 1.08) and of luminosity (-29.8 < M_B <
-22.1), thus representing a useful sample to investigate the line-emitting gas
properties in various quasar environments. The measured line strengths and
velocities, as functions of the quasar properties, are analyzed using
photoionization model calculations. We found that the flux ratio between Ca II
and O I 8446 is hardly dependent on the redshift or luminosity, indicating
similar gas density in the emission region from quasar to quasar. On the other
hand, a scatter of the O I 11287/8446 ratios appears to imply the diversity of
the ionization parameter. These facts invoke a picture of the line-emitting
gases in quasars that have similar densities and are located at regions exposed
to various ionizing radiation fluxes. The observed O I line widths are found to
be remarkably similar over more than 3 orders of magnitude in luminosity, which
indicates a kinematically determined location of the emission region and is in
clear contrast to the well-studied case of H I lines. We also argue about the
dust presence in the emission region since the region is suggested to be
located near the dust sublimation point at the outer edge of the BELR.Comment: Accepted for publication in ApJ; minor rewordings mad
Ionized gas outflows and global kinematics of low-z luminous star forming galaxies
We study the kinematic properties of the ambient ionized ISM and ionized gas
outflows in a large and representative sample of local luminous and
ultraluminous infrared galaxies (U/LIRGs) (58 systems, 75 galaxies), on the
basis of integral field spectroscopy (IFS)-based high S/N integrated spectra at
galactic and sub-galactic, i.e. star forming (SF) clumps, scales.
Ambient ionized gas. The velocity dispersion of the ionized ISM in U/LIRGs
( ~ 70 kms-1) is larger than in lower luminosity local star forming
galaxies ( ~ 25 kms-1). While for isolated disc LIRGs star formation
appears to sustain turbulence, gravitational energy release associated to
interactions and mergers plays an important role driving sigma in the U/LIRG
range. We also find that the impact of an AGN in ULIRGs is strong, increasing
sigma by a factor 1.5 on average. The observed weak dependency of sigma with
SFR surface density for local U/LIRGs is in very good agreement with that
measured in some high-z samples.
Ionized outflows. The presence of ionized gas outflows in U/LIRGs seems
universal based on the detection of a broad, usually blueshifted, Halpha line.
AGNs in U/LIRGs are able to generate faster (x2) and more massive (x1.4)
ionized gas outflows than pure starbursts. The derived ionized mass loading
factors are in general below one, with only a few AGNs above this limit. Only a
small fraction of the ionized material from low mass LIRGs (log(Mdyn/Msun) <
10.4) could reach the intergalactic medium, with more massive galaxies
retaining the gas. The observed average outflow properties in U/LIRGs are
similar to high-z galaxies of comparable SFR. In the bright SF clumps found in
LIRGs, ionized gas outflows appear to be very common. For a given SFR surface
density, outflows in LIRG clumps would be about one to two orders of magnitude
less energetic than those launched by clumps in high-z SF galaxies.Comment: 36 pages, 20 figures, 6 tables. Accepted for publication in A&
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