121 research outputs found
The Arp 220 merger on kpc scales
For the first time we study the Eastern nucleus in greater detail and search
for the more extended emission in the molecular gas in different CO line
transitions of the famous ULIRG Arp 220. Furthermore we present a model of the
merger in Arp 220 on large scales with the help of the CO data and an optical
and near-infrared composite HST image of the prototypical ULIRG. Using the
Plateau de Bure Interferometer (PdBI) we obtained CO(2-1) and (1-0) data at
wavelengths of 1 and 3 mm in 1994, 1996, 1997 and 2006 at different beam sizes
and spatial resolutions. The simulations of the merger in Arp 220 were
performed with the Identikit modeling tool. The model parameters that describe
the galaxy merger best give a mass ratio of 1:2 and result in a merger of
~6x10^8 yrs. The low resolution CO(1-0) PdBI observations suggest that there
are indications for emission ~10" towards the south, as well as to the north
and to the west of the two nuclei.Comment: accepted for publication in ApJ, 14 pages 10 figure
Is IRAS 01072+4954 a True-Seyfert 2? Hints from Near Infrared Integral Field Spectroscopy
In contrast to the predictions of the unified model, some X-ray unobscured
Seyfert 2 galaxies have been discovered in the last decade. One of them, the
starburst/Seyfert composite galaxy IRAS 01072+4954 (z=0.0236), has a typical
Type~1 X-ray emission, while its optical spectrum resembles an HII galaxy and
lacks the expected broad lines. We performed near-infrared integral-field
observations of this object with the aim to determine the nature of its nuclear
emission and to find indications for the existence or absence of a broad-line
region. Several reasons have been proposed to explain such peculiar emission.
We studied the validity of such hypotheses, including the possibility for it to
be True-Seyfert~2. We found little obscuration towards the nucleus A_V = 2.5
mag, and a nuclear star-formation rate Sigma_SFR < 11.6 Msun yr^{-1} kpc^{-2},
which is below the average in Seyferts. Unresolved hot-dust emission with T ~
1150 K seems to indicate the presence of a torus with its axis close to the
line of sight. We found that IRAS 01072+4954 hosts a low mass black hole with
an estimated mass of M_BH ~ 10^5 Msun and an upper limit of 2.5x10^6 Msun. Its
bolometric luminosity is L_bol ~ 2.5x10^{42} erg/s, which yields a high
accretion rate with an Eddington ratio ~ 0.2. If the relations found in more
massive systems also apply to this case, then IRAS 01072+4954 should show broad
emission lines with FWHM_{broad} ~(400-600) km/s. Indeed, some indications for
such narrow broad-line components are seen in our data, but the evidence is not
yet conclusive. This source thus seems not to be a True-Seyfert 2, but an
extreme case of a narrow line Seyfert 1, which, due to the faintness of the
active nucleus, does not have strong FeII emission in the optical.Comment: 16 pages, 11 figures. A&A Accepted versio
First direct detection of an exoplanet by optical interferometry; Astrometry and K-band spectroscopy of HR8799 e
To date, infrared interferometry at best achieved contrast ratios of a few
times on bright targets. GRAVITY, with its dual-field mode, is now
capable of high contrast observations, enabling the direct observation of
exoplanets. We demonstrate the technique on HR8799, a young planetary system
composed of four known giant exoplanets. We used the GRAVITY fringe tracker to
lock the fringes on the central star, and integrated off-axis on the HR8799e
planet situated at 390 mas from the star. Data reduction included
post-processing to remove the flux leaking from the central star and to extract
the coherent flux of the planet. The inferred K band spectrum of the planet has
a spectral resolution of 500. We also derive the astrometric position of the
planet relative to the star with a precision on the order of 100as. The
GRAVITY astrometric measurement disfavors perfectly coplanar stable orbital
solutions. A small adjustment of a few degrees to the orbital inclination of HR
8799 e can resolve the tension, implying that the orbits are close to, but not
strictly coplanar. The spectrum, with a signal-to-noise ratio of
per spectral channel, is compatible with a late-type L brown dwarf. Using
Exo-REM synthetic spectra, we derive a temperature of \,K and a
surface gravity of cm/s. This corresponds to a radius
of and a mass of , which is an independent confirmation of mass estimates from evolutionary
models. Our results demonstrate the power of interferometry for the direct
detection and spectroscopic study of exoplanets at close angular separations
from their stars.Comment: published in A&
Adaptive Optics: Observations and Prospects for Studies of Active Galactic Nuclei
These lectures take a look at how observations with adaptive optics (AO) are
beginning to influence our understanding of active galactic nuclei (AGN). By
focussing on a few specific topics, the aim is to highlight the different ways
in which enhanced spatial resolution from AO can aid the scientific analysis of
AGN data. After presenting some background about how AO works, I will describe
a few recent observations made with AO of QSO host galaxies, the Galactic
Center, and nearby AGN, and show how they have contributed to our knowledge of
these enigmatic objects.Comment: Accepted for NewAR in proceedings of "Active Galactic Nuclei at the
highest angular resolution: theory and observations", 2007 summer school,
Torun, Poland. A version with high resolution colour figures is available
from http://www.mpe.mpg.de/~davies/Davies_AGN_AO.pd
Using the motion of S2 to constrain vector clouds around SgrA*
The dark compact object at the centre of the Milky Way is well established to
be a supermassive black hole with mass , but the nature of its environment is still under debate. In this
work, we used astrometric and spectroscopic measurements of the motion of the
star S2, one of the closest stars to the massive black hole, to determine an
upper limit on an extended mass composed of a massive vector field around
Sagittarius A*. For a vector with effective mass , our Markov Chain Monte Carlo analysis shows
no evidence for such a cloud, placing an upper bound at confidence level. We show that dynamical
friction exerted by the medium on S2 motion plays no role in the analysis
performed in this and previous works, and can be neglected thus.Comment: 9 pages, 5 figures, accepted to MNRA
Polarimetry and Astrometry of NIR Flares as Event Horizon Scale, Dynamical Probes for the Mass of Sgr A*
We present new astrometric and polarimetric observations of flares from Sgr
A* obtained with GRAVITY, the near-infrared interferometer at ESO's Very Large
Telescope Interferometer (VLTI), bringing the total sample of well-covered
astrometric flares to four and polarimetric ones to six, where we have for two
flares good coverage in both domains. All astrometric flares show clockwise
motion in the plane of the sky with a period of around an hour, and the
polarization vector rotates by one full loop in the same time. Given the
apparent similarities of the flares, we present a common fit, taking into
account the absence of strong Doppler boosting peaks in the light curves and
the EHT-measured geometry. Our results are consistent with and significantly
strengthen our model from 2018: We find that a) the combination of polarization
period and measured flare radius of around nine gravitational radii (, innermost stable circular orbit) is consistent with
Keplerian orbital motion of hot spots in the innermost accretion zone. The mass
inside the flares' radius is consistent with the measured from stellar orbits at several thousand . This
finding and the diameter of the millimeter shadow of Sgr A* thus support a
single black hole model. Further, b) the magnetic field configuration is
predominantly poloidal (vertical), and the flares' orbital plane has a moderate
inclination with respect to the plane of the sky, as shown by the non-detection
of Doppler-boosting and the fact that we observe one polarization loop per
astrometric loop. Moreover, c) both the position angle on sky and the required
magnetic field strength suggest that the accretion flow is fueled and
controlled by the winds of the massive, young stars of the clockwise stellar
disk 1-5 arcsec from Sgr A*, in agreement with recent simulations.Comment: 10 pages, 12 figures. Submitted to A&
A dynamical measure of the black hole mass in a quasar 11 billion years ago
Tight relationships exist in the local universe between the central stellar
properties of galaxies and the mass of their supermassive black hole. These
suggest galaxies and black holes co-evolve, with the main regulation mechanism
being energetic feedback from accretion onto the black hole during its quasar
phase. A crucial question is how the relationship between black holes and
galaxies evolves with time; a key epoch to probe this relationship is at the
peaks of star formation and black hole growth 8-12 billion years ago (redshifts
1-3). Here we report a dynamical measurement of the mass of the black hole in a
luminous quasar at a redshift of 2, with a look back time of 11 billion years,
by spatially resolving the broad line region. We detect a 40 micro-arcsecond
(0.31 pc) spatial offset between the red and blue photocenters of the H
line that traces the velocity gradient of a rotating broad line region. The
flux and differential phase spectra are well reproduced by a thick, moderately
inclined disk of gas clouds within the sphere of influence of a central black
hole with a mass of 3.2x10 solar masses. Molecular gas data reveal a
dynamical mass for the host galaxy of 6x10 solar masses, which indicates
an under-massive black hole accreting at a super-Eddington rate. This suggests
a host galaxy that grew faster than the supermassive black hole, indicating a
delay between galaxy and black hole formation for some systems.Comment: 5 pages Main text, 8 figures, 2 tables, to be published in Nature,
under embargo until 29 January 2024 16:00 (London
The GRAVITY+ Project: Towards All-sky, Faint-Science, High-Contrast Near-Infrared Interferometry at the VLTI
The GRAVITY instrument has been revolutionary for near-infrared
interferometry by pushing sensitivity and precision to previously unknown
limits. With the upgrade of GRAVITY and the Very Large Telescope Interferometer
(VLTI) in GRAVITY+, these limits will be pushed even further, with vastly
improved sky coverage, as well as faint-science and high-contrast capabilities.
This upgrade includes the implementation of wide-field off-axis
fringe-tracking, new adaptive optics systems on all Unit Telescopes, and laser
guide stars in an upgraded facility. GRAVITY+ will open up the sky to the
measurement of black hole masses across cosmic time in hundreds of active
galactic nuclei, use the faint stars in the Galactic centre to probe General
Relativity, and enable the characterisation of dozens of young exoplanets to
study their formation, bearing the promise of another scientific revolution to
come at the VLTI.Comment: Published in the ESO Messenge
Identification of regulatory variants associated with genetic susceptibility to meningococcal disease.
Non-coding genetic variants play an important role in driving susceptibility to complex diseases but their characterization remains challenging. Here, we employed a novel approach to interrogate the genetic risk of such polymorphisms in a more systematic way by targeting specific regulatory regions relevant for the phenotype studied. We applied this method to meningococcal disease susceptibility, using the DNA binding pattern of RELA - a NF-kB subunit, master regulator of the response to infection - under bacterial stimuli in nasopharyngeal epithelial cells. We designed a custom panel to cover these RELA binding sites and used it for targeted sequencing in cases and controls. Variant calling and association analysis were performed followed by validation of candidate polymorphisms by genotyping in three independent cohorts. We identified two new polymorphisms, rs4823231 and rs11913168, showing signs of association with meningococcal disease susceptibility. In addition, using our genomic data as well as publicly available resources, we found evidences for these SNPs to have potential regulatory effects on ATXN10 and LIF genes respectively. The variants and related candidate genes are relevant for infectious diseases and may have important contribution for meningococcal disease pathology. Finally, we described a novel genetic association approach that could be applied to other phenotypes
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