424 research outputs found
The overmassive black hole in NGC 1277: new constraints from molecular gas kinematics
We report the detection of CO(1-0) emission from NGC 1277, a lenticular
galaxy in the Perseus Cluster. NGC 1277 has previously been proposed to host an
overmassive black hole (BH) compared to the galaxy bulge luminosity (mass),
based on stellar-kinematic measurements. The CO(1-0) emission, observed with
the IRAM Plateau de Bure Interferometer (PdBI) using both, a more compact
(2.9-arcsec resolution) and a more extended (1-arcsec resolution)
configuration, is likely to originate from the dust lane encompassing the
galaxy nucleus at a distance of 0.9 arcsec (~320 pc). The double-horned CO(1-0)
profile found at 2.9-arcsec resolution traces of
molecular gas, likely orbiting in the dust lane at $\sim 550\ \mathrm{km\
s^{-1}}\sim 2\times 10^{10}\
M_\odot\sim
1.7\times 10^{10}\ M_\odotM/L_V=6.3\sim 5\times 10^{9}\ M_\odotM/L_V=10$. While the molecular gas reservoir
may be associated with a low level of star formation activity, the extended
2.6-mm continuum emission is likely to originate from a weak AGN, possibly
characterized by an inverted radio-to-millimetre spectral energy distribution.
Literature radio and X-ray data indicate that the BH in NGC 1277 is also
overmassive with respect to the Fundamental Plane of BH activity.Comment: 15 pages, 13 figures; accepted for publication in MNRAS on 20 January
2016; updated version including minor changes and note added in proo
Structure analysis of interstellar clouds: II. Applying the Delta-variance method to interstellar turbulence
The Delta-variance analysis is an efficient tool for measuring the structural
scaling behaviour of interstellar turbulence in astronomical maps. In paper I
we proposed essential improvements to the Delta-variance analysis.
In this paper we apply the improved Delta-variance analysis to i) a
hydrodynamic turbulence simulation with prominent density and velocity
structures, ii) an observed intensity map of rho Oph with irregular boundaries
and variable uncertainties of the different data points, and iii) a map of the
turbulent velocity structure in the Polaris Flare affected by the intensity
dependence on the centroid velocity determination.
The tests confirm the extended capabilities of the improved Delta-variance
analysis. Prominent spatial scales were accurately identified and artifacts
from a variable reliability of the data were removed. The analysis of the
hydrodynamic simulations showed that the injection of a turbulent velocity
structure creates the most prominent density structures are produced on a scale
somewhat below the injection scale. The new analysis of a rho Oph continuum map
reveals an intermediate stage in the molecular cloud evolution showing both
signatures of the typical molecular cloud scaling behaviour and the formation
of condensed cores. When analysing the velocity structure of the Polaris Flare
we show that a universal power law connects scales from 0.03 pc to 3 pc.
However, a plateau in the Delta-variance spectrum around 5 pc indicates that
the visible large-scale velocity gradient is not converted directly into a
turbulent cascade.Comment: Accepted for publication in A&A, Section
Molecular gas in QSO host galaxies
We present the results of a survey for CO line emission from a sample of
nearby QSO hosts taken from the Hamburg/ESO survey (HES) and the Veron-Cetty
and Veron quasar catalogue. From a total of 39 observed sources we clearly
detected 5 objects with >10sigma signals (HE 0108-4743, HE 0224-2834,
J035818.7-612407, HE 1029-1831, HE 2211-3903). Further 6 sources show marginal
detections on the 2sigma level.Comment: 4 pages, 1 figure, submitted to "QSO Hosts: Evolution and
Environment", P.D. Barthel, D.B. Sanders, eds., August 2005, Leiden
University (The Netherlands), New Astr. Re
Major impact from a minor merger - The extraordinary hot molecular gas flow in the Eye of the NGC 4194 Medusa galaxy
Minor mergers are important processes contributing significantly to how
galaxies evolve across the age of the Universe. Their impact on supermassive
black hole growth and star formation is profound. The detailed study of dense
molecular gas in galaxies provides an important test of the validity of the
relation between star formation rate and HCN luminosity on different galactic
scales. We use observations of HCN, HCO+1-0 and CO3-2 to study the dense gas
properties in the Medusa merger. We calculate the brightness temperature ratios
and use them in conjunction with a non-LTE radiative line transfer model. The
HCN and HCO+1-0, and CO3-2 emission do not occupy the same structures as the
less dense gas associated with the lower-J CO emission. The only emission from
dense gas is detected in a 200pc region within the "Eye of the Medusa". No HCN
or HCO+ is detected for the extended starburst. The CO3-2/2-1 brightness
temperature ratio inside "the Eye" is ~2.5 - the highest ratio found so far.
The line ratios reveal an extreme, fragmented molecular cloud population inside
"the Eye" with large temperatures (>300K) and high gas densities (>10^4 cm^-3).
"The Eye" is found at an interface between a large-scale minor axis inflow and
the Medusa central region. The extreme conditions inside "the Eye" may be the
result of the radiative and mechanical feedback from a deeply embedded, young,
massive super star cluster, formed due to the gas pile-up at the intersection.
Alternatively, shocks from the inflowing gas may be strong enough to shock and
fragment the gas. For both scenarios, however, it appears that the HCN and HCO+
dense gas tracers are not probing star formation, but instead a post-starburst
and/or shocked ISM that is too hot and fragmented to form new stars. Thus,
caution is advised in linking the detection of emission from dense gas tracers
to evidence of ongoing or imminent star formation.Comment: 10 pages, 5 figures, 2 tables, accepted for publication in A&
A Redline Starburst: Co(2-1) Observations of an Eddington-Limited Galaxy Reveal Star Formation at its Most Extreme
We report observations of the CO(2-1) emission of SDSSJ1506+54, a compact (r_e~135pc) starburst galaxy at z=0.6. SDSSJ1506+54 appears to be forming stars close to the limit allowed by stellar radiation pressure feedback models: the measured L_IR/L\u27_CO 1500 is one of the highest measured for any galaxy. With its compact optical morphology but extended low surface brightness envelope, post-starburst spectral features, high infrared luminosity (L_IR\u3e10^12.5 L_Sun), low gas fraction (M_H2/M_stars~15%), and short gas depletion time (tens of Myr), we speculate that this is a feedback- limited central starburst episode at the conclusion of a major merger. Taken as such, SDSSJ1504+54 epitomizes the brief closing stage of a classic model of galaxy growth: we are witnessing a key component of spheroid formation during what we term a \u27redline\u27 starburst
NIR Observations of the QSO 3C 48 Host Galaxy
In this paper we present new near infrared (NIR) imaging and spectroscopic
data of the quasar 3C 48 and its host galaxy. The data were obtained with the
ESO-VLT camera ISAAC.We report the first detection of the apparent second
nucleus 3C 48A about 100NE of the bright QSO nucleus in the NIR bands J, H, and
Ks. 3C 48A is highly reddened with respect to the host, which could be due to
warm dust, heated by enhanced star formation or by interstellar material
intercepting the radio jet. In fact, all colors on the host galaxy are reddened
by several magnitudes of visual extinction. Imaging and initial spectroscopy
also reveal a stellar content of about 30% to the overall QSO-light in the NIR.
These results are important input parameters for future models of the stellar
populations by taking extinction into account.Comment: 8 pages, 8 figures, accepted by A&
Resolving the Bright HCN(1–0) Emission toward the Seyfert 2 Nucleus of M51: Shock Enhancement by Radio Jets and Weak Masing by Infrared Pumping?
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