135 research outputs found
The Cataclysmic Variable CW 1045+525: A Secondary-Dominated Dwarf Nova?
We present spectroscopic and photometric observations of the cataclysmic variable CW 1045+525. Both the optical spectrum and the photometric lightcurve show a strong contribution of a K5V–M0V secondary. We derive an orbital period Porb = 0.271278(1) d by measuring the radial velocities of the absorption lines of the secondary. The period and spectral type of the secondary suggest a distance of 350–700 pc. There is evidence for additional sources of line- and continuum emission, but no direct evidence of an accretion disc. We discuss several scenarios for the nature of CW 1045+525 on the basis of our results, finding a dwarf nova classification to be the most probable, although not completely satisfying, explanation for the observed characteristics
Spatially-Resolved Spectra of the "Teacup" AGN: Tracing the History of a Dying Quasar
The Sloan Digital Sky Survey (SDSS) Galaxy Zoo project has revealed a number
of spectacular galaxies possessing Extended Emission-Line Regions (EELRs), the
most famous being Hanny's Voorwerp galaxy. We present another EELR object
discovered in the SDSS endeavor: the Teacup Active Galactic Nucleus (AGN),
nicknamed for its EELR, which has a handle like structure protruding 15 kpc
into the northeast quadrant of the galaxy. We analyze physical conditions of
this galaxy with long-slit ground based spectroscopy from Lowell, Lick, and
KPNO observatories. With the Lowell 1.8m Perkin's telescope we took multiple
observations at different offset positions, allowing us to recover spatially
resolved spectra across the galaxy. Line diagnostics indicate the ionized gas
is photoionized primarily by the AGN. Additionally we are able to derive the
hydrogen density from the [S II] 6716/6731 ratio. We generated two-component
photoionization models for each spatially resolved Lowell spectrum. These
models allow us to calculate the AGN bolometric luminosity seen by the gas at
different radii from the nuclear center of the Teacup. Our results show a drop
in bolometric luminosity by more than two orders of magnitude from the EELR to
the nucleus, suggesting that the AGN has decreased in luminosity by this amount
in a continuous fashion over 46,000 years, supporting the case for a dying AGN
in this galaxy independent of any IR based evidence. We demonstrate that
spatially resolved photoionization modeling could be applied to EELRs to
investigate long time scale variability.Comment: 38 pages, 11 figures, accepted for publication in the Astrophysical
Journa
The cataclysmic variable CW 1045+525: a secondary-dominated dwarf nova?
We present spectroscopic and photometric observations of the cataclysmic
variable CW 1045+525. Both the optical spectrum and the photometric lightcurve
show a strong contribution of a K5V - M0V secondary. We derive an orbital
period P_orb = 0.271278(1) d by measuring the radial velocities of the
absorption lines of the secondary. The period and spectral type of the
secondary suggest a distance of 350 - 700 pc. There is evidence for additional
sources of line- and continuum emission, but no direct evidence of an accretion
disc. We discuss several scenarios for the nature of CW 1045+525 on the basis
of our results, finding a dwarf nova classification the most probable, although
not completely satisfying, explanation for the observed characteristics.Comment: 11 pages, including 10 figures, accepted for publication in A&A; only
cosmetic changes: some text accidentally was in boldfac
X-ray Absorption and Optical Extinction in the Partially Obscured Seyfert Nucleus in Mrk 1393
We present a detailed study of the X-ray and optical spectra of the luminous
Seyfert galaxy Mrk 1393, which revealed variable partial obscuration of the
active nucleus. The X-ray spectra obtained by XMM-Newton and Swift show
moderate absorption with a column density around 3x10^21 cm^-2, consistent with
a dust-reddening interpretation of the steep Balmer decrement seen in recent
optical spectra. The X-ray flux in the 0.5 to 2 keV band during the XMM-Newton
observation in 2005 and Swift observation in 2006 was a factor 6 brighter than
that of the ROSAT All Sky Survey in 1991. In the past 4 years, the broad
H\alpha line brightened by a factor of 4 accompanied by a decrease in the
Balmer decrement. A comparison with literature spectra reveals variations in
the dust extinction on time scales of several years, suggesting that the
obscuring material is very close to the active nucleus. These observations
indicate that a dust-to-gas ratio as high as the Galactic value can be present
in moderately thick gas in the vicinity of the central engine within a few
parsecs. We suggest that the obscuring material may be debris disrupted from
the dusty torus.Comment: 25 pages, 5 figures, accepted to A
Resolving the dynamical mass of a z~1.3 QSO host galaxy using SINFONI and Laser Guide Star assisted Adaptive Optics
Recent studies of the tight scaling relations between the masses of
supermassive black holes and their host galaxies have suggested that in the
past black holes constituted a larger fraction of their host galaxies' mass.
However, these arguments are limited by selection effects and difficulties in
determining robust host galaxy masses at high redshifts. Here we report the
first results of a new, complementary diagnostic route: we directly determine a
dynamical host galaxy mass for the z=1.3 luminous quasar J090543.56+043347.3
through high-spatial-resolution (0.47", 4kpc FWHM) observations of the host
galaxy gas kinematics over 30x40 kpc using ESO/VLT/SINFONI with LGS/AO.
Combining our result of M_dyn = 2.05+1.68_0.74 x 10^11 M_sun (within a radius
5.25 +- 1.05 kpc) with M_BH,MgII = 9.02 \pm 1.43 x 10^8 M_sun, M_BH,Halpha =
2.83 +1.93-1.13 x 10^8 M_sun, we find that the ratio of black hole mass to host
galaxy dynamical mass for J090543.56+043347.3 matches the present-day relation
for M_BH vs. M_Bulge,Dyn, well within the IR scatter, deviating at most a
factor of two from the mean. J090543.56+043347.3 displays clear signs of an
ongoing tidal interaction and of spatially extended star formation at a rate of
50-100 M_sun/yr, above the cosmic average for a galaxy of this mass and
redshift. We argue that its subsequent evolution may move J090543.56+043347.3
even closer to the z=0 relation for M_BH vs. M_Bulge,Dyn. Our results support
the picture where any substantive evolution in these relations must occur prior
to z~1.3. Having demonstrated the power of this modelling approach we are
currently analyzing similar data on seven further objects to better constrain
such evolution.Comment: Accepted for publication in ApJ, 14 pages, 10 Figure
The Close AGN Reference Survey (CARS): Tracing the circumnuclear star formation in the super-Eddington NLS1 Mrk 1044
The host galaxy conditions for rapid supermassive black hole growth are
poorly understood. Narrow-line Seyfert 1 (NLS1) galaxies often exhibit high
accretion rates and are hypothesized to be prototypes of active galactic nuclei
(AGN) at an early stage of their evolution. We present VLT MUSE NFM-AO
observations of Mrk 1044, the nearest super-Eddington accreting NLS1. Together
with archival MUSE WFM data we aim to understand the host galaxy processes that
drive Mrk 1044's black hole accretion. We extract the faint stellar continuum
emission from the AGN-deblended host and perform spatially resolved emission
line diagnostics with an unprecedented resolution. Combining both MUSE WFM and
NFM-AO observations, we use a kinematic model of a thin rotating disk to trace
the stellar and ionized gas motion from 10kpc down to 30pc around the
nucleus. Mrk 1044's stellar kinematics follow circular rotation, whereas the
ionized gas shows tenuous spiral features in the center. We resolve a compact
star forming circumnuclear ellipse (CNE) that has a semi-minor axis of
306pc. Within this CNE, the gas is metal rich and its line ratios are
entirely consistent with excitation by star formation. With an integrated SFR
of the CNE contributes 27% of
the galaxy-wide star formation. We conclude that Mrk 1044's nuclear activity
has not yet affected the circumnuclear star formation. Thus, Mrk 1044 is
consistent with the idea that NLS1s are young AGN. A simple mass budget
consideration suggests that the circumnuclear star formation and AGN phase are
connected and the patterns in the ionized gas velocity field are a signature of
the ongoing AGN feeding.Comment: accepted for publication in A&A, 17 pages, 14 figures, 1 table, for
Fig. 5 associated animation see https://youtube.com/watch?v=H_WSgWJSCf
The Lick AGN Monitoring Project 2011: Spectroscopic Campaign and Emission-Line Light Curves
In the Spring of 2011 we carried out a 2.5 month reverberation mapping
campaign using the 3 m Shane telescope at Lick Observatory, monitoring 15
low-redshift Seyfert 1 galaxies. This paper describes the observations,
reductions and measurements, and data products from the spectroscopic campaign.
The reduced spectra were fitted with a multicomponent model in order to isolate
the contributions of various continuum and emission-line components. We present
light curves of broad emission lines and the AGN continuum, and measurements of
the broad H-beta line widths in mean and root-mean square (rms) spectra. For
the most highly variable AGNs we also measured broad H-beta line widths and
velocity centroids from the nightly spectra. In four AGNs exhibiting the
highest variability amplitudes, we detect anticorrelations between broad H-beta
width and luminosity, demonstrating that the broad-line region "breathes" on
short timescales of days to weeks in response to continuum variations. We also
find that broad H-beta velocity centroids can undergo substantial changes in
response to continuum variations; in NGC 4593 the broad H-beta velocity shifted
by ~250 km/s over a one-month duration. This reverberation-induced velocity
shift effect is likely to contribute a significant source of confusion noise to
binary black hole searches that use multi-epoch quasar spectroscopy to detect
binary orbital motion. We also present results from simulations that examine
biases that can occur in measurement of broad-line widths from rms spectra due
to the contributions of continuum variations and photon-counting noise.Comment: 33 pages, 28 figures, accepted for publication in ApJ Supplement
Serie
The Lick AGN Monitoring Project 2011: Reverberation Mapping of Markarian 50
The Lick AGN Monitoring Project 2011 observing campaign was carried out over
the course of 11 weeks in Spring 2011. Here we present the first results from
this program, a measurement of the broad-line reverberation lag in the Seyfert
1 galaxy Mrk 50. Combining our data with supplemental observations obtained
prior to the start of the main observing campaign, our dataset covers a total
duration of 4.5 months. During this time, Mrk 50 was highly variable,
exhibiting a maximum variability amplitude of a factor of 4 in the U-band
continuum and a factor of 2 in the H-beta line. Using standard
cross-correlation techniques, we find that H-beta and H-gamma lag the V-band
continuum by tau_cen = 10.64(-0.93,+0.82) and 8.43(-1.28,+1.30) days,
respectively, while the lag of He II 4686 is unresolved. The H-beta line
exhibits a symmetric velocity-resolved reverberation signature with shorter
lags in the high-velocity wings than in the line core, consistent with an
origin in a broad-line region dominated by orbital motion rather than infall or
outflow. Assuming a virial normalization factor of f=5.25, the virial estimate
of the black hole mass is (3.2+-0.5)*10^7 solar masses. These observations
demonstrate that Mrk 50 is among the most promising nearby active galaxies for
detailed investigations of broad-line region structure and dynamics.Comment: Accepted for publication in ApJ Letters. 6 pages, 4 figure
Discovery of a strong Baldwin effect in mid-infrared AGN lines
We present the discovery of a Baldwin effect in 8 nearby Seyfert galaxies for
the three most prominent mid-infrared forbidden emission lines observable from
the ground that are commonly found in AGN, [ArIII](8.99 micron), [SIV](10.51
micron), and [NeII](12.81 micron). The observations were carried out using the
VLT/VISIR imager and spectroraph at the ESO/Paranal observatory. The bulk of
the observed line emission comes from the inner <0.4 arcsec which corresponds
to spatial scales <100 pc in our object sample. The correlation index is
approximately -0.6 without significant difference among the lines. This is the
strongest anti-correlation between line equivalent width and continuum
luminosity found so far. In the case of Circinus, we show that despite the use
of mid-infrared lines, obscuration by either the host galaxy or the
circumnuclear dust torus might affect the equivalent widths. Given the small
observed spatial scales from which most of the line emission emanates, it is
unclear how these observations fit into the favored "disappearing NLR''
scenario for the narrow-line Baldwin effect.Comment: 5 pages, 4 figures; letter accepted by A&
A Revised Broad-Line Region Radius and Black Hole Mass for the Narrow-Line Seyfert 1 NGC 4051
We present the first results from a high sampling rate, multi-month
reverberation mapping campaign undertaken primarily at MDM Observatory with
supporting observations from telescopes around the world. The primary goal of
this campaign was to obtain either new or improved Hbeta reverberation lag
measurements for several relatively low luminosity AGNs. We feature results for
NGC 4051 here because, until now, this object has been a significant outlier
from AGN scaling relationships, e.g., it was previously a ~2-3sigma outlier on
the relationship between the broad-line region (BLR) radius and the optical
continuum luminosity - the R_BLR-L relationship. Our new measurements of the
lag time between variations in the continuum and Hbeta emission line made from
spectroscopic monitoring of NGC 4051 lead to a measured BLR radius of R_BLR =
1.87 (+0.54 -0.50) light days and black hole mass of M_BH = 1.73 (+0.55 -0.52)
x 10^6 M_sun. This radius is consistent with that expected from the R_BLR-L
relationship, based on the present luminosity of NGC 4051 and the most current
calibration of the relation by Bentz et al. (2009a). We also present a
preliminary look at velocity-resolved Hbeta light curves and time delay
measurements, although we are unable to reconstruct an unambiguous
velocity-resolved reverberation signal.Comment: 38 pages, 7 figures, accepted for publication in ApJ, changes from v1
reflect suggestions from anonymous refere
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