2,662 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
Dynamics of a classical Hall system driven by a time-dependent Aharonov--Bohm flux
We study the dynamics of a classical particle moving in a punctured plane
under the influence of a strong homogeneous magnetic field, an electrical
background, and driven by a time-dependent singular flux tube through the hole.
We exhibit a striking classical (de)localization effect: in the far past the
trajectories are spirals around a bound center; the particle moves inward
towards the flux tube loosing kinetic energy. After hitting the puncture it
becomes ``conducting'': the motion is a cycloid around a center whose drift is
outgoing, orthogonal to the electric field, diffusive, and without energy loss
Conductivity and the current-current correlation measure
We review various formulations of conductivity for one-particle Hamiltonians
and relate them to the current-current correlation measure. We prove that the
current-current correlation measure for random Schr\"odinger operators has a
density at coincident energies provided the energy lies in a localization
regime. The density vanishes at such energies and an upper bound on the rate of
vanishing is computed. We also relate the current-current correlation measure
to the localization length
Non-absorbing high-efficiency counter for itinerant microwave photons
Detecting an itinerant microwave photon with high efficiency is an
outstanding problem in microwave photonics and its applications. We present a
scheme to detect an itinerant microwave photon in a transmission line via the
nonlinearity provided by a transmon in a driven microwave resonator. With a
single transmon we achieve 84% distinguishability between zero and one
microwave photons and 90% distinguishability with two cascaded transmons by
performing continuous measurements on the output field of the resonator. We
also show how the measurement diminishes coherence in the photon number basis
thereby illustrating a fundamental principle of quantum measurement: the higher
the measurement efficiency, the faster is the decoherence
Search for cold and hot gas in the ram pressure stripped Virgo dwarf galaxy IC3418
We present IRAM 30m sensitive upper limits on CO emission in the ram pressure
stripped dwarf Virgo galaxy IC3418 and in a few positions covering HII regions
in its prominent 17 kpc UV/Ha gas-stripped tail. In the central few arcseconds
of the galaxy, we report a possible marginal detection of about 1x10^6 M_sun of
molecular gas (assuming a Galactic CO-to-H_2 conversion factor) that could
correspond to a surviving nuclear gas reservoir. We estimate that there is less
molecular gas in the main body of IC3418, by at least a factor of 20, than
would be expected from the pre-quenching UV-based star formation rate assuming
the typical gas depletion timescale of 2 Gyr. Given the lack of star formation
in the main body, we think the H_2-deficiency is real, although some of it may
also arise from a higher CO-to-H_2 factor typical in low-metallicity, low-mass
galaxies. The presence of HII regions in the tail of IC3418 suggests that there
must be some dense gas; however, only upper limits of < 1x10^6 M_sun were found
in the three observed points in the outer tail. This yields an upper limit on
the molecular gas content of the whole tail < 1x10^7 M_sun, which is an amount
similar to the estimates from the observed star formation rate over the tail.
We also present strong upper limits on the X-ray emission of the stripped gas
in IC3418 from a new Chandra observation. The measured X-ray luminosity of the
IC3418 tail is about 280 times lower than that of ESO 137-001, a spiral galaxy
in a more distant cluster with a prominent ram pressure stripped tail.
Non-detection of any diffuse X-ray emission in the IC3418 tail may be due to a
low gas content in the tail associated with its advanced evolutionary state
and/or due to a rather low thermal pressure of the surrounding intra-cluster
medium.Comment: 15 pages, 11 figures, A&A accepte
New constraints on dust emission and UV attenuation of z=6.5-7.5 galaxies from millimeter observations
We have targeted two recently discovered Lyman break galaxies (LBGs) to
search for dust continuum and [CII] 158 micron line emission. The strongly
lensed z~6.8 LBG A1703-zD1 behind the galaxy cluster Abell 1703, and the
spectroscopically confirmed z=7.508 LBG z8-GND-5296 in the GOODS-N field have
been observed with the Plateau de Bure interferometer (PdBI) at 1.2mm. These
observations have been combined with those of three z>6.5 Lya emitters (named
HCM6A, Himiko, and IOK-1), for which deep measurements were recently obtained
with the PdBI and ALMA. [CII] is undetected in both galaxies, providing a deep
upper limit for Abell1703-zD1, comparable to recent ALMA non-detections. Dust
continuum emission from Abell1703-zD1 and z8-GND-5296 is not detected with an
rms of 0.12 and 0.16 mJy/beam. From these non-detections we derive upper limits
on their IR luminosity and star formation rate, dust mass, and UV attenuation.
Thanks to strong gravitational lensing the limit for Abell1703-zD1 is probing
the sub-LIRG regime ( Lsun) and very low dust
masses ( Msun). We find that all five galaxies are
compatible with the Calzetti IRX- relation, their UV attenuation is
compatible with several indirect estimates from other methods (the UV slope,
extrapolation of the attenuation measured from the IR/UV ratio at lower
redshift, and SED fits), and the dust-to-stellar mass ratio is not incompatible
with that of galaxies from z=0 to 3. For their stellar mass the high-z galaxies
studied here have an attenuation below the one expected from the mean relation
of low redshift (z<1.5) galaxies. More and deeper (sub)-mm data are clearly
needed to directly determine the UV attenuation and dust content of the
dominant population of high-z star-forming galaxies and to establish more
firmly their dependence on stellar mass, redshift, and other properties.Comment: 10 pages, 7 figures. Minor revisions. Accepted for publication in A&
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