Full two-photon downconversion of just a single photon

We demonstrate, both numerically and analytically, that it is possible to generate two photons from one and only one photon. We characterize the output two photon field and make our calculations close to reality by including losses. Our proposal relies on real or artificial three-level atoms with a cyclic transition strongly coupled to a one-dimensional waveguide. We show that close to perfect downconversion with efficiency over 99% is reachable using state-of-the-art Waveguide QED architectures such as photonic crystals or superconducting circuits. In particular, we sketch an implementation in circuit QED, where the three level atom is a transmon

Tracing high density gas in M 82 and NGC 4038

We present the first detection of CS in the Antennae galaxies towards the NGC 4038 nucleus, as well as the first detections of two high-J (5-4 and 7-6) CS lines in the center of M 82. The CS(7-6) line in M 82 shows a profile that is surprisingly different to those of other low-J CS transitions we observed. This implies the presence of a separate, denser and warmer molecular gas component. The derived physical properties and the likely location of the CS(7-6) emission suggests an association with the supershell in the centre of M 82.Comment: 10 pages, 3 figures, ApJ Letter - ACCEPTE

The Structure, Kinematics and Physical Properties of the Molecular Gas in the Starburst Nucleus of NGC 253

We present 5.2" x 2.6" resolution interferometry of CO J=1-0 emission from the starburst galaxy NGC 253. The high spatial resolution of these new data, in combination with recent high resolution maps of 13CO, HCN and near-infrared emission, allow us for the first time to link unambiguously the gas properties in the central starburst of NGC 253 with its bar dynamics. We confirm that the star formation results from bar-driven gas flows as seen in "twin peaks" galaxies. Two distinct kinematic features are evident from the CO map and position-velocity diagram: a group of clouds rotating as a solid body about the kinematic center of the galaxy, and a more extended gas component associated with the near-infrared bar. We model the line intensities of CO, HCN and 13CO to infer the physical conditions of the gas in the nucleus of NGC 253. The results indicate increased volume densities around the radio nucleus in a twin-peaks morphology. Compared with the CO kinematics, the gas densities appear highest near the radius of a likely inner Linblad resonance, and slightly lead the bar minor axis. This result is similar to observations of the face-on, twin-peaks galaxy NGC 6951, and is consistent with models of starburst generation due to gas inflow along a bar.Comment: To appear in the ApJ, 28 pages, 12 figure file

Signos radiológicos y ecográficos asociados al síndrome de hiperadrenocorticismo en perros

Aunque el diagnostico de hiperadrenocorticalismo se confirma habitualmente por test endocrinos, radiologia y ecografia aportan datos en los pacientes que permiten realizar una valoracion clinica mas concreta. Este articulo revisa los cambios radiográficos y ecográficos que pueden aparecer en perros con hiperadrenocorticalismo

Optical integral field spectroscopy of intermediate redshift infrared bright galaxies

The extreme infrared (IR) luminosity of local luminous and ultra-luminous IR galaxies (U/LIRGs; 11 12, respectively) is mainly powered by star-formation processes triggered by mergers or interactions. While U/LIRGs are rare locally, at z > 1, they become more common, they dominate the star-formation rate (SFR) density, and a fraction of them are found to be normal disk galaxies. Therefore, there must be an evolution of the mechanism triggering these intense starbursts with redshift. To investigate this evolution, we present new optical SWIFT integral field spectroscopic H{\alpha}+[NII] observations of a sample of 9 intermediate-z (0.2 < z < 0.4) U/LIRG systems selected from Herschel 250{\mu}m observations. The main results are the following: (a) the ratios between the velocity dispersion and the rotation curve amplitude indicate that 10-25% (1-2 out of 8) might be compatible with being isolated disks while the remaining objects are interacting/merging systems; (b) the ratio between un-obscured and obscured SFR traced by H{\alpha} and LIR, respectively, is similar in both local and these intermediate-z U/LIRGs; and (c) the ratio between 250{\mu}m and the total IR luminosities of these intermediate-z U/LIRGs is higher than that of local U/LIRGs with the same LIR . This indicates a reduced dust temperature in these intermediate-z U/LIRGs. This, together with their already measured enhanced molecular gas content, suggests that the interstellar medium conditions are different in our sample of intermediate-z galaxies when compared to local U/LIRGs.Comment: Accepted for publication in MNRA

New insights on the dense molecular gas in NGC253 as traced by HCN and HCO+

We have imaged the central ~1kpc of the circumnuclear starburst disk in the galaxy NGC253 in the HCN(1-0), HCO+(1-0), and CO(1-0) transitions at 60pc resolution using the Owens Valley Radio Observatory Millimeter-Wavelength Array (OVRO). We have also obtained Atacama Pathfinder Experiment (APEX) observations of the HCN(4-3) and the HCO+(4-3) lines of the starburst disk. We find that the emission from the HCN(1-0) and HCO+(1-0) transitions, both indicators of dense molecular gas, trace regions which are non-distinguishable within the uncertainties of our observations. Even though the continuum flux varies by more than a factor 10 across the starburst disk, the HCN/HCO+ ratio is constant throughout the disk, and we derive an average ratio of 1.1+/-0.2. From an excitation analysis we find that all lines from both molecules are subthermally excited and that they are optically thick. This subthermal excitation implies that the observed HCN/HCO+ line ratio is sensitive to the underlying chemistry. The constant line ratio thus implies that there are no strong abundance gradients across the starburst disk of NGC253. This finding may also explain the variations in L'(HCN)/L'(HCO+) between different star forming galaxies both nearby and at high redshifts.Comment: 9 pages, 12 figures, ApJ in press (volume 666 September

CO Distribution and Kinematics Along the Bar in the Strongly Barred Spiral NGC 7479

We report on the 2.5 arcsec (400 pc) resolution CO (J = 1 -> 0) observations covering the whole length of the bar in the strongly barred late-type spiral galaxy NGC 7479. CO emission is detected only along a dust lane that traverses the whole length of the bar, including the nucleus. The emission is strongest in the nucleus. The distribution of emission is clumpy along the bar outside the nucleus, and consists of gas complexes that are unlikely to be gravitationally bound. The CO kinematics within the bar consist of two separate components. A kinematically distinct circumnuclear disk, < 500 pc in diameter, is undergoing predominantly circular motion with a maximum rotational velocity of 245 km/s at a radius of 1 arcsec (160 pc). The CO-emitting gas in the bar outside the circumnuclear disk has substantial noncircular motions which are consistent with a large radial velocity component, directed inwards. The CO emission has a large velocity gradient across the bar dust lane, ranging from 0.5 to 1.9 km/s/pc after correcting for inclination, and the projected velocity change across the dust lane is as high as 200 km/s. This sharp velocity gradient is consistent with a shock front at the location of the bar dust lane. A comparison of H-alpha and CO kinematics across the dust lane shows that although the H-alpha emission is often observed both upstream and downstream from the dust lane, the CO emission is observed only where the velocity gradient is large. We also compare the observations with hydrodynamic models and discuss star formation along the bar.Comment: 16 pages, including 10 figures. Accepted for publication in Ap

Atomic Hydrogen Properties of AGN Host Galaxies: HI in 16 NUclei of GAlaxies (NUGA) Sources

We present a comprehensive spectroscopic imaging survey of the distribution and kinematics of atomic hydrogen (HI) in 16 nearby spiral galaxies hosting low luminosity AGN, observed with high spectral and spatial resolution (resolution: ~20 arcsec, 5 km/s) using the NRAO Very Large Array (VLA). The sample contains a range of nuclear types, ranging from Seyfert to star-forming nuclei and was originally selected for the NUclei of GAlaxies project (NUGA) - a spectrally and spatially resolved interferometric survey of gas dynamics in nearby galaxies designed to identify the fueling mechanisms of AGN and the relation to host galaxy evolution. Here we investigate the relationship between the HI properties of these galaxies, their environment, their stellar distribution and their AGN type. The large-scale HI morphology of each galaxy is classified as ringed, spiral, or centrally concentrated; comparison of the resulting morphological classification with AGN type reveals that ring structures are significantly more common in LINER than in Seyfert host galaxies, suggesting a time evolution of the AGN activity together with the redistribution of the neutral gas. Dynamically disturbed HI disks are also more prevalent in LINER host galaxies than in Seyfert host galaxies. While several galaxies are surrounded by companions (some with associated HI emission), there is no correlation between the presence of companions and the AGN type (Seyfert/LINER).Comment: 54 pages, 7 figures, accepted for publication in AJ. The full-resolution version is available at http://www.mpia.de/homes/haan/research.htm

First detection of the 448 GHz H2O transition in space

We present the first detection of the ortho-H2O 4_23-3_30 transition at 448 GHz in space. We observed this transition in the local (z = 0.010) luminous infrared (IR) galaxy ESO 320-G030 (IRAS F11506-3851) using the Atacama Large Millimeter/submillimeter Array (ALMA). The water 4_23-3_30 emission, which originates in the highly obscured nucleus of this galaxy, is spatially resolved over a region of ~65 pc in diameter and shows a regular rotation pattern compatible with the global molecular and ionized gas kinematics. The line profile is symmetric and well fitted by a Gaussian with an integrated flux of 37.0 +- 0.7 Jy km s-1 . Models predict this water transition as a potential collisionally excited maser transition. On the contrary, in this galaxy, we find that the 4_23-3_30 emission is primarily excited by the intense far-IR radiation field present in its nucleus. According to our modeling, this transition is a probe of deeply buried galaxy nuclei thanks to the high dust optical depths (tau_100{\mu}m > 1, N_H > 1e24 cm-2) required to efficiently excite it.Comment: Accepted for publication in A&A Letters; 4 pages, 5 figure

Observational Constraints on the Ages of Molecular Clouds and the Star-Formation Timescale: Ambipolar-Diffusion--Controlled or Turbulence-Induced Star Formation?

We revisit the problem of the star formation timescale and the ages of molecular clouds. The apparent overabundance of star-forming molecular clouds over clouds without active star formation has been thought to indicate that molecular clouds are "short-lived" and that star formation is "rapid". We show that this statistical argument lacks self-consistency and, even within the rapid star-formation scenario, implies cloud lifetimes of approximately 10 Myr. We discuss additional observational evidence from external galaxies that indicate lifetimes of molecular clouds and a timescale of star formation of approximately 10 Myr . These long cloud lifetimes in conjunction with the rapid (approximately 1 Myr) decay of supersonic turbulence present severe difficulties for the scenario of turbulence-controlled star formation. By contrast, we show that all 31 existing observations of objects for which the linewidth, the size, and the magnetic field strength have been reliably measured are in excellent quantitative agreement with the predictions of the ambipolar-diffusion theory. Within the ambipolar-diffusion-controlled star formation theory the linewidths may be attributed to large-scale non-radial cloud oscillations (essentially standing large-amplitude, long-wavelength Alfven waves), and the predicted relation between the linewidth, the size, and the magnetic field is a natural consequence of magnetic support of self-gravitating clouds.Comment: 7 pages, 2 figures, uses emulateapj; accepted for publication in Ap