281 research outputs found
The supermassive black hole in the Seyfert 2 galaxy NGC 5252
We present results from HST/STIS long-slit spectroscopy of the gas motions in
the nuclear region of the Seyfert 2 galaxy NGC 5252. The observed velocity
field is consistent with gas in regular rotation with superposed localized
patches of disturbed gas. The dynamics of the circumnuclear gas can be
accurately reproduced by adding to the stellar mass component a compact dark
mass of MBH = 0.95 (-0.45;+1.45) 10E9 M(sun), very likely a supermassive black
hole. Contrarily to results obtained in similar studies rotational broadening
is sufficient to reproduce also the behaviour of line widths. The MBH estimated
for NGC 5252 is in good agreement with the correlation between MBH and bulge
mass. The comparison with the MBH vs sigma relationship is less stringent
(mostly due to the relatively large error in sigma); NGC 5252 is located above
the best fit line by between 0.3 and 1.2 dex, i.e. 1 - 4 times the dispersion
of the correlation. Both the galaxy's and MBH of NGC 5252 are substantially
larger than those usually estimated for Seyfert galaxies but, on the other
hand, they are typical of radio-quiet quasars. Combining the determined MBH
with the hard X-ray luminosity, we estimate that NGC 5252 is emitting at a
fraction ~ 0.005 of L(Edd). In this sense, this active nucleus appears to be a
quasar relic, now probably accreting at a low rate, rather than a low black
hole mass counterpart of a QSO.Comment: Accepted for publication in A&
Relation between dust and radio luminosity in optically selected early type galaxies
We have surveyed an optical/IR selected sample of nearby E/S0 galaxies with
and without nuclear dust structures with the VLA at 3.6 cm to a sensitivity of
100 Jy. We can construct a Radio Luminosity Function (RLF) of these
galaxies to ~10^19 W/Hz and find that ~50% of these galaxies have AGNs at this
level. The space density of these AGNs equals that of starburst galaxies at
this luminosity. Several dust-free galaxies have low luminosity radio cores,
and their RLF is not significantly less than that of the dusty galaxies.Comment: 8 pages, 5 figures, accepted for publication in A&
HST/ACS observations of shell galaxies: inner shells, shell colours and dust
AIM:Learn more about the origin of shells and dust in early type galaxies.
METHOD: V-I colours of shells and underlying galaxies are derived, using HST
Advanced Camera for Surveys (ACS) data. A galaxy model is made locally in
wedges and subtracted to determine shell profiles and colours. We applied
Voronoi binning to our data to get smoothed colour maps of the galaxies.
Comparison with N-body simulations from the literature gives more insight to
the origin of the shell features. Shell positions and dust characteristics are
inferred from model galaxy subtracted images. RESULT: The ACS images reveal
shells well within the effective radius in some galaxies (at 1.7 kpc in the
case of NGC 5982). In some cases, strong nuclear dust patches prevent detection
of inner shells. Most shells have colours which are similar to the underlying
galaxy. Some inner shells are redder than the galaxy. All six shell galaxies
show out of dynamical equilibrium dust features, like lanes or patches, in
their central regions. Our detection rate for dust in the shell ellipticals is
greater than that found from HST archive data for a sample of normal early-type
galaxies, at the 95% confidence level. CONCLUSIONS: The merger model describes
better the shell distributions and morphologies than the interaction model. Red
shell colours are most likely due to the presence of dust and/or older stellar
populations. The high prevalence and out of dynamical equilibrium morphologies
of the central dust features point towards external influences being
responsible for visible dust features in early type shell galaxies. Inner
shells are able to manifest themselves in relatively old shell systems.Comment: accepted by A&A; 36 Figures, 25 pages. A version with full resolution
Figures can be found here: http://www.astro.rug.nl/~sikkema/shells.p
Star formation in z>1 3CR host galaxies as seen by Herschel
We present Herschel (PACS and SPIRE) far-infrared (FIR) photometry of a
complete sample of z>1 3CR sources, from the Herschel GT project The Herschel
Legacy of distant radio-loud AGN (PI: Barthel). Combining these with existing
Spitzer photometric data, we perform an infrared (IR) spectral energy
distribution (SED) analysis of these landmark objects in extragalactic research
to study the star formation in the hosts of some of the brightest active
galactic nuclei (AGN) known at any epoch. Accounting for the contribution from
an AGN-powered warm dust component to the IR SED, about 40% of our objects
undergo episodes of prodigious, ULIRG-strength star formation, with rates of
hundreds of solar masses per year, coeval with the growth of the central
supermassive black hole. Median SEDs imply that the quasar and radio galaxy
hosts have similar FIR properties, in agreement with the orientation-based
unification for radio-loud AGN. The star-forming properties of the AGN hosts
are similar to those of the general population of equally massive non-AGN
galaxies at comparable redshifts, thus there is no strong evidence of universal
quenching of star formation (negative feedback) within this sample. Massive
galaxies at high redshift may be forming stars prodigiously, regardless of
whether their supermassive black holes are accreting or not.Comment: 30 pages, 13 figures, 4 tables. Accepted for publication in A&
Spectroscopy of the near-nuclear regions of Cygnus A: estimating the mass of the supermassive black hole
We use a combination of high spatial resolution optical and near-IR
spectroscopic data to make a detailed study of the kinematics of the NLR gas in
the near-nuclear regions of the powerful, FRII radio galaxy Cygnus A
(z=0.0560), with the overall goal of placing limits on the mass of any
supermassive black hole in the core. Our K-band infrared observations (0.75
arcsec seeing) -- taken with NIRSPEC on the Keck II telescope -- show a smooth
rotation pattern across the nucleus in the Paschen alpha and H_2 emission lines
along a slit position (PA180) close to perpendicular to the radio axis,
however, there is no evidence for such rotation along the radio axis (PA105).
Higher spatial resolution observations of the [OIII]5007 emission line -- taken
with STIS on the Hubble Space Telescope (HST) -- confirm the general rotation
pattern of the gas in the direction perpendicular to the radio axis, and
provide evidence for steep velocity gradients within a radius of 0.1 arcsec of
the core. The circular velocities measured from both the Keck and HST data lead
to an estimate of the mass of the supermassive black hole of 2.5+/-0.7x10^9
solar masses. For the host galaxy properties of Cygnus A, this mass is
consistent with the global correlations between black hole mass and host galaxy
properties deduced for non-active galaxies. Therefore, despite the extreme
power of its radio source and the quasar-like luminosity of its AGN, the black
hole in Cygnus A is not unusually massive considering theluminosity of its host
galaxy. Indeed, the estimated mass of the black hole in Cygnus A is similar to
that inferred for the supermassive black hole in the FRI radio galaxy M87,
despite the fact that the AGN and radio jets of Cygnus A are 2 -- 3 orders of
magnitude more powerful.Comment: 17 pages, 12 figure
EnzymeâActivatable Chemokine Conjugates for In Vivo Targeting of TumorâAssociated Macrophages
Increased levels of tumorâassociated macrophages (TAMs) are indicators of poor prognosis in most cancers. Although antibodies and small molecules blocking the recruitment of macrophages to tumors are under evaluation as anticancer therapies, these strategies are not specific for macrophage subpopulations. Herein we report the first enzymeâactivatable chemokine conjugates for effective targeting of defined macrophage subsets in live tumors. Our constructs exploit the high expression of chemokine receptors (e.g., CCR2) and the activity of cysteine cathepsins in TAMs to target these cells selectively over other macrophages and immune cells (e.g., neutrophils, T cells, B cells). Furthermore, we demonstrate that cathepsinâactivatable chemokines are compatible with both fluorescent and therapeutic cargos, opening new avenues in the design of targeted theranostic probes for immune cells in the tumor microenvironment
Target and (Astro-)WISE technologies - Data federations and its applications
After its first implementation in 2003 the Astro-WISE technology has been
rolled out in several European countries and is used for the production of the
KiDS survey data. In the multi-disciplinary Target initiative this technology,
nicknamed WISE technology, has been further applied to a large number of
projects. Here, we highlight the data handling of other astronomical
applications, such as VLT-MUSE and LOFAR, together with some non-astronomical
applications such as the medical projects Lifelines and GLIMPS, the MONK
handwritten text recognition system, and business applications, by amongst
others, the Target Holding. We describe some of the most important lessons
learned and describe the application of the data-centric WISE type of approach
to the Science Ground Segment of the Euclid satellite.Comment: 9 pages, 5 figures, Proceedngs IAU Symposium No 325 Astroinformatics
201
Astro-WISE: Chaining to the Universe
The recent explosion of recorded digital data and its processed derivatives
threatens to overwhelm researchers when analysing their experimental data or
when looking up data items in archives and file systems. While current hardware
developments allow to acquire, process and store 100s of terabytes of data at
the cost of a modern sports car, the software systems to handle these data are
lagging behind. This general problem is recognized and addressed by various
scientific communities, e.g., DATAGRID/EGEE federates compute and storage power
over the high-energy physical community, while the astronomical community is
building an Internet geared Virtual Observatory, connecting archival data.
These large projects either focus on a specific distribution aspect or aim to
connect many sub-communities and have a relatively long trajectory for setting
standards and a common layer. Here, we report "first light" of a very different
solution to the problem initiated by a smaller astronomical IT community. It
provides the abstract "scientific information layer" which integrates
distributed scientific analysis with distributed processing and federated
archiving and publishing. By designing new abstractions and mixing in old ones,
a Science Information System with fully scalable cornerstones has been
achieved, transforming data systems into knowledge systems. This break-through
is facilitated by the full end-to-end linking of all dependent data items,
which allows full backward chaining from the observer/researcher to the
experiment. Key is the notion that information is intrinsic in nature and thus
is the data acquired by a scientific experiment. The new abstraction is that
software systems guide the user to that intrinsic information by forcing full
backward and forward chaining in the data modelling.Comment: To be published in ADASS XVI ASP Conference Series, 2006, R. Shaw, F.
Hill and D. Bell, ed
The counterrotating core and the black hole mass of IC1459
The E3 giant elliptical galaxy IC1459 is the prototypical galaxy with a fast
counterrotating stellar core. We obtained one HST/STIS long-slit spectrum along
the major axis of this galaxy and CTIO spectra along five position angles. We
present self-consistent three-integral axisymmetric models of the stellar
kinematics, obtained with Schwarzschild's numerical orbit superposition method.
We study the dynamics of the kinematically decoupled core (KDC) in IC1459 and
we find it consists of stars that are well-separated from the rest of the
galaxy in phase space. The stars in the KDC counterrotate in a disk on orbits
that are close to circular. We estimate that the KDC mass is ~0.5% of the total
galaxy mass or ~3*10^9 Msun. We estimate the central black hole mass M_BH of
IC1459 independently from both its stellar and its gaseous kinematics. Some
complications probably explain why we find rather discrepant BH masses with the
different methods. The stellar kinematics suggest that M_BH = (2.6 +/-
1.1)*10^9 Msun (3 sigma error). The gas kinematics suggests that M_BH ~
3.5*10^8 Msun if the gas is assumed to rotate at the circular velocity in a
thin disk. If the observed velocity dispersion of the gas is assumed to be
gravitational, then M_BH could be as high as ~1.0*10^9 Msun. These different
estimates bracket the value M_BH = (1.1 +/- 0.3)*10^9 Msun predicted by the
M_BH-sigma relation. It will be an important goal for future studies to assess
the reliability of black hole mass determinations with either technique. This
is essential if one wants to interpret the correlation between the BH mass and
other global galaxy parameters (e.g. velocity dispersion) and in particular the
scatter in these correlations (believed to be only ~0.3 dex). [Abridged]Comment: 51 pages, LaTeX with 19 PostScript figures. Revised version, with
three new figures and data tables. To appear in The Astrophysical Journal,
578, 2002 October 2
Origin of the X-ray Emission in the Nuclei of FR Is
We investigate the X-ray origin in FRIs using the multi-waveband high
resolution data of eight FR I sources, which have very low Eddington ratios. We
fit their multi-waveband spectrum using a coupled accretion-jet model. We find
that X-ray emission in the source with the highest L_X (~1.8*10^-4 L_Edd) is
from the advection-dominated accretion flow (ADAF). Four sources with moderate
L_X(~several*10^-6 L_Edd) are complicated. The X-ray emission of one FR I is
from the jet, and the other three is from the sum of the jet and ADAF. The
X-ray emission in the three least luminous sources (L_X<1.0*10^-6L_Edd) is
dominated by the jet. These results roughly support the predictions of Yuan and
Cui(2005) where they predict that when the X-ray luminosity of the system is
below a critical value, the X-radiation will not be dominated by the emission
from the ADAF any longer, but by the jet. We also find that the accretion rates
in four sources must be higher than the Bondi rates, which implies that other
fuel supply (e.g., stellar winds) inside the Bondi radius should be important.Comment: 6 pages. To published in Journal of Physics, in proceedings of "The
Universe under the Microscope - Astrophysics at High Angular Resolution" (Bad
Honnef, Germany, April 2008), eds. R. Schoedel, A. Eckart, S. Pfalzner, and
E. Ro
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