Combes F.,Paris Observatory |
Boquien M.,French National Center for Scientific Research |
Kramer C.,Instituto Radioastronomia Milimetrica |
Xilouris E.M.,National institute for astrophysics |
And 17 more authors.
Astronomy and Astrophysics | Year: 2012
Power spectra of deprojected images of late-type galaxies in gas or dust emission are very useful diagnostics of the dynamics and stability of their interstellar medium. Previous studies have shown that the power spectra can be approximated as two power laws, a shallow one on large scales (larger than 500 pc) and a steeper one on small scales, with the break between the two corresponding to the line-of-sight thickness of the galaxy disk. The break separates the 3D behavior of the interstellar medium on small scales, controlled by star formation and feedback, from the 2D behavior on large scales, driven by density waves in the disk. The break between these two regimes depends on the thickness of the plane, which is determined by the natural self-gravitating scale of the interstellar medium. We present a thorough analysis of the power spectra of the dust and gas emission at several wavelengths in the nearby galaxy M 33. In particular, we use the recently obtained images at five wavelengths by PACS and SPIRE onboard Herschel. The wide dynamical range (2-3 dex in scale) of most images allows us to clearly determine the change in slopes from -1.5 to -4, with some variations with wavelength. The break scale increases with wavelength from 100 pc at 24 and 100 μm to 350 pc at 500 μm, suggesting that the cool dust lies in a thicker disk than the warm dust, perhaps because of star formation that is more confined to the plane. The slope on small scales tends to be steeper at longer wavelength, meaning that the warmer dust is more concentrated in clumps. Numerical simulations of an isolated late-type galaxy, rich in gas and with no bulge, such as M 33, are carried out to better interpret these observed results. Varying the star formation and feedback parameters, it is possible to obtain a range of power spectra, with two power-law slopes and breaks, that nicelybracket the data. The small-scale power-law does indeed reflect the 3D behavior of the gas layer, steepening strongly while the feedback smoothes the structures by increasing the gas turbulence. M 33 appears to correspond to a fiducial model with an SFR of ~ 0.7 Mo/yr, with 10% supernovae energy coupled to the gas kinematics. © ESO, 2012.
Yang Y.,Max Planck Institute for Astronomy |
Decarli R.,Max Planck Institute for Astronomy |
Dannerbauer H.,CEA Saclay Nuclear Research Center |
Dannerbauer H.,University of Vienna |
And 14 more authors.
Astrophysical Journal | Year: 2012
In order to constrain the bolometric luminosities, dust properties, and molecular gas content of giant Lyα nebulae, the so-called Lyα blobs, we have carried out a study of dust continuum and CO line emission in two well-studied representatives of this population at z ∼ 3: an Lyα blob discovered by its strong Spitzer Multiband Infrared Photometer 24 μm detection (LABd05) and the Steidel blob 1 (SSA22-LAB01). We find that the spectral energy distribution of LABd05 is well described by an active-galactic-nucleus-starburst composite template with L FIR = (4.0 0.5) × 1012 L, comparable to high-z submillimeter galaxies and ultraluminous infrared galaxies. New Large APEX Bolometer Camera 870 μm measurements rule out the reported Submillimeter Common-User Bolometer Array detection of the SSA22-LAB01 (S 850 μm = 16.8mJy) at the >4σ level. Consistent with this, ultradeep Plateau de Bure Interferometer observations with 2″ spatial resolution also fail to detect any 1.2mm continuum source down to 0.45mJy beam-1 (3σ). Combined with the existing (sub)millimeter observations in the literature, we conclude that the FIR luminosity of SSA22-LAB01 remains uncertain. No CO line is detected in either case down to integrated flux limits of S νΔV ≲ 0.25-1.0Jykms-1, indicating a modest molecular gas reservoir, M(H2) < (1-3) × 1010M. The non-detections exclude, with high significance (12σ), the previous tentative detection of a CO J=4-3 line in the SSA22-LAB01. The increased sensitivity afforded by the Atacama Large Millimeter/submillimeter Array will be critical in studying molecular gas and dust in these interesting systems. © 2012 The American Astronomical Society. All rights reserved.
Ladu A.,National institute for astrophysics |
Pisanu T.,National institute for astrophysics |
Navarrini A.,Iram Institute Of Radio Astronomie Millimetrique |
Marongiu P.,National institute for astrophysics |
Valente G.,National institute for astrophysics
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014
We present the optical and mechanical design of a 3mm band SIS receiver for the Gregorian focus of the Sardinia Radio Telescope (SRT). The receiver, was designed and built at IRAM and deployed on the IRAM for the Plateau de Bure Interferometer antennas until 2006. Following its decommissioning the receiver was purchased by the INAFAstronomical Observatory of Cagliari with the aim to adapt its optics for test of the performance of the new 64-m diameter Sardinia Radio Telescope (SRT) in the 3 mm band (84-116 GHz). The instrument will be installed in the rotating turret inside of the Gregorian focal room of SRT. The dimensions of the focal room, the horn position in the lower side of the cryostat and the vessel for the liquid helium impose very hard constraints to the optical and mechanical mounting structure of the receiver inside the cabin. We present the receiver configuration and how we plan to install it on SRT. © 2014 SPIE.
Lis D.C.,California Institute of Technology |
Neufeld D.A.,Johns Hopkins University |
Phillips T.G.,California Institute of Technology |
Gerin M.,Ecole Normale Superieure de Paris |
Neri R.,Iram Institute Of Radio Astronomie Millimetrique
Astrophysical Journal Letters | Year: 2011
We report a detection of the excited 220-211 rotational transition of para-H2O in APM 08279+5255 using the IRAM Plateau de Bure Interferometer. At z = 3.91, this is the highest-redshift detection of interstellar water to date. From large velocity gradient modeling, we conclude that this transition is predominantly radiatively pumped and on its own does not provide a good estimate of the water abundance. However, additional water transitions are predicted to be detectable in this source, which would lead to an improved excitation model. We also present a sensitive upper limit for the hydrogen fluoride (HF) J = 1-0 absorption toward APM 08279+5255. While the face-on geometry of this source is not favorable for absorption studies, the lack of HF absorption is still puzzling and may be indicative of a lower fluorine abundance at z = 3.91 compared with the Galactic interstellar medium. © 2011. The American Astronomical Society. All rights reserved.
Casasola V.,National institute for astrophysics |
Hunt L.K.,National institute for astrophysics |
Combes F.,Paris Observatory |
Garcia-Burillo S.,Observatorio Astronomico Nacional OAN |
Neri R.,Iram Institute Of Radio Astronomie Millimetrique
Astronomy and Astrophysics | Year: 2011
We present 12CO(1-0) and 12CO(2-1) maps of the interacting barred LINER/Seyfert 2 galaxy NGC 3627 obtained with the IRAM interferometer at resolutions of 2.″ × 1.″ and 0.″ × 0.″6, respectively. We also present single-dish IRAM 30m 12CO(1-0) and 12CO(2-1) observations used to compute short spacings and complete interferometric measurements. These observations are complemented by IRAM 30 m measurements of HCN(1-0) emission detected in the center of NGC 3627. The molecular gas emission shows a nuclear peak, an elongated bar-like structure of ∼18″ (∼900 pc) diameter in both 12CO maps and, in 12CO(1-0), a two-arm spiral feature from r ∼ 9″ (∼450 pc) to r ∼ 16″ (∼800 pc). The inner ∼18″ bar-like structure, with a north/south orientation (PA = 14°), forms two peaks at the extremes of this elongated emission region. The kinematics of the inner molecular gas shows signatures of non-circular motions associated both with the 18″ bar-like structure and the spiral feature detected beyond it. The 1.6 μm H-band 2MASS image of NGC 3627 shows a stellar bar with a PA = - 21°, different from the PA (= 14°) of the 12CO bar-like structure, indicating that the gas is leading the stellar bar. The far-infrared Spitzer-MIPS 70 and 160 μm images of NGC 3627 show that the dust emission is intensified at the nucleus and at the ansae at the ends of the bar, coinciding with the 12CO peaks. The GALEX far-ultraviolet (FUV) morphology of NGC 3627 displays an inner elongated (north/south) ring delimiting a hole around the nucleus, and the 12CO bar-like structure is contained in the hole observed in the FUV. The torques computed with the HST-NICMOS F160W image and our PdBI maps are negative down to the resolution limit of our images, ∼60 pc in 12CO(2-1). If the bar ends at ∼3 kpc, coincident with corotation (CR), the torques are negative between the CR of the bar and the nucleus, down to the resolution limit of our observations. This scenario is compatible with a recently-formed rapidly rotating bar which has had insufficient time to slow down because of secular evolution, and thus has not yet formed an inner Lindblad resonance (ILR). The presence of molecular gas inside the CR of the primary bar, where we expect that the ILR will form, makes NGC 3627 a potential smoking gun of inner gas inflow. The gas is fueling the central region, and in a second step could fuel directly the active nucleus. © 2011 ESO.