2,916 research outputs found
Transient receptor potential canonical type 3 channels control the vascular contractility of mouse mesenteric arteries
Transient receptor potential canonical type 3 (TRPC3) channels are non-selective cation channels and regulate intracellular Ca2+ concentration. We examined the role of TRPC3 channels in agonist-, membrane depolarization (high K+)-, and mechanical (pressure)-induced vasoconstriction and vasorelaxation in mouse mesenteric arteries. Vasoconstriction and vasorelaxation of endothelial cells intact mesenteric arteries were measured in TRPC3 wild-type (WT) and knockout (KO) mice. Calcium concentration ([Ca2+]) was measured in isolated arteries from TRPC3 WT and KO mice as well as in the mouse endothelial cell line bEnd.3. Nitric oxide (NO) production and nitrate/nitrite concentrations were also measured in TRPC3 WT and KO mice. Phenylephrine-induced vasoconstriction was reduced in TRPC3 KO mice when compared to that of WT mice, but neither high K+- nor pressure-induced vasoconstriction was altered in TRPC3 KO mice. Acetylcholine-induced vasorelaxation was inhibited in TRPC3 KO mice and by the selective TRPC3 blocker pyrazole-3. Acetylcholine blocked the phenylephrine-induced increase in Ca2+ ratio and then relaxation in TRPC3 WT mice but had little effect on those outcomes in KO mice. Acetylcholine evoked a Ca2+ increase in endothelial cells, which was inhibited by pyrazole-3. Acetylcholine induced increased NO release in TRPC3 WT mice, but not in KO mice. Acetylcholine also increased the nitrate/nitrite concentration in TRPC3 WT mice, but not in KO mice. The present study directly demonstrated that the TRPC3 channel is involved in agonist-induced vasoconstriction and plays important role in NO-mediated vasorelaxation of intact mesenteric arteries.Fil: Yeon, Soo-In. Yonsei University College of Medicine; Corea del SurFil: Kim, Joo Young. Yonsei University College Of Medicine; . Yonsei University College of Medicine; Corea del SurFil: Yeon, Dong-Soo. Kwandong University College of Medicine; Corea del SurFil: Abramowitz, Joel. National Institute of Environmental Health Sciences; Estados UnidosFil: Birnbaumer, Lutz. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; Argentina. National Institute of Environmental Health Sciences; Estados UnidosFil: Muallem, Shmuel. National Institutes of Health; Estados UnidosFil: Lee, Young-Ho. Yonsei University College of Medicine; Corea del Su
High-ionization mid-infrared lines as black hole mass and bolometric luminosity indicators in active galactic nuclei
We present relations of the black hole mass and the optical luminosity with
the velocity dispersion and the luminosity of the [Ne V] and the [O IV]
high-ionization lines in the mid-infrared (MIR) for 28 reverberation-mapped
active galactic nuclei. We used high-resolution Spitzer Infrared Spectrograph
and Infrared Space Observatory Short Wavelength Spectrometer data to fit the
profiles of these MIR emission lines that originate from the narrow-line region
of the nucleus. We find that the lines are often resolved and that the velocity
dispersion of [Ne V] and [O IV] follows a relation similar to that between the
black hole mass and the bulge stellar velocity dispersion found for local
galaxies. The luminosity of the [Ne V] and the [O IV] lines in these sources is
correlated with that of the optical 5100A continuum and with the black hole
mass. Our results provide a means to derive black hole properties in various
types of active galactic nuclei, including highly obscured systems.Comment: accepted for publication in ApJ
Cosmic Train Wreck by Massive Black Holes: Discovery of a kpc-Scale Triple Active Galactic Nucleus
Hierarchical galaxy mergers will lead to the formation of binary and, in the
case of a subsequent merger before a binary coalesce, triple supermassive black
holes (SMBHs), given that most massive galaxies harbor SMBHs. A triple of SMBHs
becomes visible as a triple active galactic nucleus (AGN) when the BHs accrete
large amounts of gas at the same time. Here we report the discovery of a
kpc-scale triple AGN, SDSSJ1027+1749 at z = 0.066, from our systematic search
for hierarchical mergers of AGNs. The galaxy contains three emission-line
nuclei, two of which are offset by ~ 450 and 110 km/s in velocity and by 2.4
and 3.0 kpc in projected separation from the central nucleus. All three nuclei
are classified as obscured AGNs based on optical diagnostic emission line
ratios, with black hole mass estimates M_BH ~> 10^8 M_sun from stellar velocity
dispersions measured in the associated stellar components. Based on dynamical
friction timescale estimates, the three stellar components in SDSSJ1027+1749
will merge in ~ 40 Myr, and their associated SMBHs may evolve into a
gravitationally interacting triple system in ~< 200 Myr. Our result sets a
lower limit of ~ 5 x 10^(-5) for the fraction of kpc-scale triples in optically
selected AGNs at z ~ 0.1.Comment: minor revisions; to appear in ApJ
Hubble Space Telescope H-Band Imaging Survey of Massive Gas-Rich Mergers
We report the results from a deep HST NICMOS H-band imaging survey of a
carefully selected sample of 33 luminous, late-stage galactic mergers at z <
0.3. Signs of a recent galactic interaction are seen in all of the objects in
the HST sample, including all 7 IR-excess Palomar-Green (PG) QSOs in the
sample. Unsuspected double nuclei are detected in 5 ULIRGs. A detailed
two-dimensional analysis of the surface brightness distributions in these
objects indicates that the great majority (81%) of the single-nucleus systems
show a prominent early-type morphology. However, low-surface-brightness
exponential disks are detected on large scale in at least 4 of these sources.
The hosts of 'warm' AGN-like systems are of early type and have less pronounced
merger-induced morphological anomalies than the hosts of cool systems with
LINER or HII region-like nuclear optical spectral types. The host sizes and
luminosities of the 7 PG~QSOs in our sample are statistically indistinguishable
from those of the ULIRG hosts. In comparison, highly luminous quasars, such as
those studied by Dunlop et al. (2003), have hosts which are larger and more
luminous. The hosts of ULIRGs and PG QSOs lie close to the locations of
intermediate-size (about 1 -- 2 L*) spheroids in the photometric projection of
the fundamental plane of ellipticals, although there is a tendency in our
sample for the ULIRGs with small hosts to be brighter than normal spheroids.
Excess emission from a young stellar population in the ULIRG/QSO hosts may be
at the origin of this difference. Our results provide support for a possible
merger-driven evolutionary connection between cool ULIRGs, warm ULIRGs, and
PG~QSOs although this sequence may break down at low luminosity. (abridged)Comment: Paper to be published in the Astrophysical Journal; revised based on
comments from referee. A PDF file combining both text and figures is
available at http://www.astro.umd.edu/~veilleux/pubs/nicmos.pd
Accretion and star formation rates in low redshift type-II active galactic nuclei
Accretion and star formation (SF) rates in low redshift SDSS type-II active
galactic nuclei (AGN) are critically evaluated. Comparison with photoionization
models indicates that bolometric luminosity (Lbol) estimates based on L(oiii
5007A) severely underestimate Lbol in low ionization sources such as LINERs. An
alternative method based on L(hb) is less sensitive to ionization level and a
novel method, based on a combination of L(oiii 5007A) and L(oi 6300A), is
erhaps the best. Using this method I show that low ionization AGN are accreting
faster than assumed until now. Significant related other findings are: 1. Any
type-II AGN property related to the black hole (BH) mass is more reliably
obtained by removing blue galaxies from the sample. 2. Seyfert 2s and LINER 2s
form a continuous sequence of L/Ledd with no indication for a change in
accretion mechanism, or mode of mass supply. There are very few, if any, LINERs
in all type-I samples which results in a much arrower L/Ledd distribution
compared with type-II samples. 3. There is a strong correlation between SF
luminosity, Lsf, and Lbol over more than five orders of magnitude in
luminosity. This leads to a simple relationship between bulge and BH growth
rates, g(bulge)/g(BH) propto Lbol^(-0.2), where g(bulge)/g(BH) = 115 for
Lbol=10^42 erg/sec. Seyfert 2s and LINER 2s follow the same Lsf-Lbol
correlation for all sources with a stellar age indicator, D4000, smaller than
1.8. This suggests that a similar fraction of SF gas finds its way to the
center in all AGN. 4. Lbol, Lsf, L/Ledd and the specific SF rate follow D4000
in a similar way.Comment: 16 pages, 16 figures, accepted for publication in MNRA
Discovery of Nuclear X-ray Sources in SINGS Galaxies
We present the results of a search for nuclear X-ray activity in nearby
galaxies using Chandra archival data in a sample of 62 galaxies from the
Spitzer Infrared Nearby Galaxy Survey (SINGS). We detect 37 nuclear X-ray
sources; seven of these are new detections. Most of the nuclear X-ray sources
are likely to be AGNs. The fraction of galaxies hosting AGNs is thus about 60%,
much higher than that found with optical searches, and demonstrates the
efficacy of X-ray observations to find hidden AGNs in optically normal
galaxies. We find that the nuclear X-ray sources are preferentially present in
earlier type galaxies. Unlike what is observed at high redshift, we do not find
a strong correlation between the AGN luminosity and the 24 micron luminosity of
the host galaxy; we find a strong correlation with the 3.6 micron luminosity
instead. This suggests that at the present epoch the accretion rate depends on
the total mass of the galaxy, as perhaps does the black hole mass.Comment: 35 pages, 10 figures; Accepted for publication in Ap
The Connection between 3.3 {\mu}m PAH Emission and AGN Activity
We investigate the connection between starburst and AGN activity by comparing
the 3.3 {\mu}m PAH eimission with AGN properties. Utilizing the slit-less
spectroscopic capability of the AKARI space telescope, we observe
moderate-luminosity Type I AGN at z~0.4 to measure global starburst activity.
The 3.3 {\mu}m PAH emissions are detected for 7 out of 26 target galaxies. We
find no strong correlation between the 3.3 {\mu}m PAH emission and AGN
luminosity in the limted range of the observed AGN luminosity, suggesting that
global star formation may not be tightly related with AGN activity. Combining
our measurements with the previous 3.3 {\mu}m measurements of the low redshift
Type I AGN in the literature, we investigate the connection between nuclear
starburst and AGN activity. In contrast to global star formation, the 3.3
{\mu}m PAH luminosity measured from the central part of galaxies correlates
with AGN luminosity, implying that starburst and AGN activity are directly
connected at the nuclear region.Comment: 8 pages, 6 figures, accepted for publication in AJ, minor typos and
references correcte
Dust covering factor, silicate emission and star formation in luminous QSOs
We present Spitzer IRS low resolution, mid-IR spectra of a sample of 25 high
luminosity QSOs at 2<z<3.5. When combined with archival IRS observations of
local, low luminosity type-I AGNs, the sample spans five orders of magnitude in
luminosity. We find that the continuum dust thermal emission at
lambda(rest)=6.7um is correlated with the optical luminosity, following the
non-linear relation L(6.7um) propto L(5100A)^0.82. We also find an anti
correlation between the ratio L(6.7um)/L(5100A) and the [OIII]5007A line
luminosity. These effects are interpreted as a decreasing covering factor of
the circumnuclear dust as a function of luminosity. Such a result is in
agreement with the decreasing fraction of absorbed AGNs as a function of
luminosity recently found in various surveys. We clearly detect the silicate
emission feature in the average spectrum, but also in four individual objects.
These are the Silicate emission in the most luminous objects obtained so far.
When combined with the silicate emission observed in local, low luminosity
type-I AGNs, we find that the silicate emission strength is correlated with
luminosity.
The silicate strength of all type-I AGNs also follows a positive correlation
with the black hole mass and with the accretion rate. The Polycyclic Aromatic
Hydrocarbon (PAH) emission features, expected from starburst activity, are not
detected in the average spectrum of luminous, high-z QSOs. The upper limit
inferred from the average spectrum points to a ratio between PAH luminosity and
QSO optical luminosity significantly lower than observed in lower luminosity
AGNs, implying that the correlation between star formation rate and AGN power
saturates at high luminosities.Comment: accepted for publication in A&A, 17 pages, 9 figure
The Mid-Infrared High-Ionization Lines from Active Galactic Nuclei and Star-Forming Galaxies
We used Spitzer/IRS spectroscopic data on 426 galaxies including quasars,
Seyferts, LINER and HII galaxies to investigate the relationship among the
mid-IR emission lines. There is a tight linear correlation between the [Ne
V]14.3 um and 24.3 um (97.1 eV) and the [O IV]25.9 um (54.9 eV) high-ionization
emission lines. The correlation also holds for these high-ionization emission
lines and the [Ne III]15.56 um (41 eV) emission line, although only for active
galaxies. We used these correlations to calculate the [Ne III] excess due to
star formation in Seyfert galaxies. We also estimated the [O IV] luminosity due
to star formation in active galaxies and determined that it dominates the [O
IV] emission only if the contribution of the active nucleus to the total
luminosity is below 5%. We find that the AGN dominates the [O IV] emission in
most Seyfert galaxies, whereas star-formation adequately explains the observed
[O IV] emission in optically classified HII galaxies. Finally we computed
photoionization models to determine the physical conditions of the narrow line
region where these high-ionization lines originate. The estimated ionization
parameter range is -2.8 < log U < -2.5 and the total hydrogen column density
range is 20 < log nH (cm-2) < 21.Comment: Accepted for Publication in ApJ, 19 pages, 13 figure
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