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Aumont J.,Institut Universitaire de France | Aumont J.,Roche Holding AG | Conversi L.,European Space Astronomy Center | Thum C.,Iram Institute Of Radioastronomie Millimetrique | And 10 more authors.
Astronomy and Astrophysics | Year: 2010

Context. CMB experiments aiming at a precise measurement of the CMB polarization, such as the Planck satellite, need a strong polarized absolute calibrator on the sky to accurately set the detectors polarization angle and the cross-polarization leakage. As the most intense polarized source in the microwave sky at angular scales of few arcminutes, the Crab nebula will be used for this purpose. Aims. Our goal was to measure the Crab nebula polarization characteristics at 90 GHz with unprecedented precision. Methods. The observations were carried out with the IRAM 30 m telescope employing the correlation polarimeter XPOL and using two orthogonally polarized receivers. Results. We processed the Stokes I, Q, and U maps from our observations in order to compute the polarization angle and linear polarization fraction. The first is almost constant in the region of maximum emission in polarization with a mean value of αSky = 152.1±0.3° in equatorial coordinates, and the second is found to reach a maximum of Π = 30% for the most polarized pixels. We find that a CMB experiment having a 5 arcmin circular beam will see a mean polarization angle of αSky = 149.9±0.2° and a mean polarization fraction of Π = 8.8±0.2%. © 2010 ESO.

Feruglio C.,Iram Institute Of Radioastronomie Millimetrique | Feruglio C.,National institute for astrophysics | Bongiorno A.,National institute for astrophysics | Fiore F.,National institute for astrophysics | And 12 more authors.
Astronomy and Astrophysics | Year: 2014

Context. Understanding the relationship between the formation and evolution of galaxies and their central super-massive black holes (SMBH) is one of the main topics in extragalactic astrophysics. Links and feedback may reciprocally affect both black hole and galaxy growth. Aims. Observations of the CO line at the main epoch of galaxy and SMBH assembly (z = 2-4) are crucial to investigating the gas mass, star formation, and accretion onto SMBHs, and the effect of AGN feedback. Potential correlations between AGN and host galaxy properties can be highlighted by observing extreme objects. Methods. We targeted CO(3-2) in ULAS J1539+0557, a hyper-luminous quasar (Lbol > 1048 erg/s) at z = 2.658, selected through its unusual red colour in the UKIDSS Large Area Survey (ULAS). Results. We find a molecular gas mass of 4.1 ± 0.8 × 1010 M⊙, by adopting a conversion factor α = 0.8 M⊙ K-1 km s -1 pc2, and a gas fraction of ~0.4-0.1, depending mostly on the assumed source inclination. We also find a robust lower limit to the star-formation rate (SFR = 250-1600 M⊙/yr) and star-formation efficiency (SFE = 25-350 L⊙/(K kms-1pc2) by comparing the observed optical-near-infrared spectral energy distribution with AGN and galaxy templates. The black hole gas consumption timescale, M(H2)/acc, is ~160 Myr, similar to or higher than the gas consumption timescale. Conclusions. The gas content and the star formation efficiency are similar to those of other high-luminosity, highly obscured quasars, and at the lower end of the star-formation efficiency of unobscured quasars, in line with predictions from AGN-galaxy co-evolutionary scenarios. Further measurements of the (sub)mm continuum in this and similar sources are mandatory to obtain a robust observational picture of the AGN evolutionary sequence. © 2014 ESO.

Silverman J.D.,University of Tokyo | Daddi E.,University Paris Diderot | Rodighiero G.,University of Padua | Rujopakarn W.,University of Tokyo | And 19 more authors.
Astrophysical Journal Letters | Year: 2015

Local starbursts have a higher efficiency of converting gas into stars, as compared to typical star-forming galaxies at a given stellar mass, possibly indicative of different modes of star formation. With the peak epoch of galaxy formation occurring at z > 1, it remains to be established whether such an efficient mode of star formation is occurring at high redshift. To address this issue, we measure the molecular gas content of seven high-redshift (z ∼ 1.6) starburst galaxies with the Atacama Large Millimeter/submillimeter Array and IRAM/Plateau de Bure Interferometer. Our targets are selected from the sample of Herschel far-infrared-detected galaxies having star formation rates (∼300-800 Mo yr-1) elevated (4×) above the star-forming main sequence (MS) and included in the FMOS-COSMOS near-infrared spectroscopic survey of star-forming galaxies at z ∼ 1.6 with Subaru. We detect CO emission in all cases at high levels of significance, indicative of high gas fractions (∼30%-50%). Even more compelling, we firmly establish with a clean and systematic selection that starbursts, identified as MS outliers, at high redshift generally have a lower ratio of CO to total infrared luminosity as compared to typical MS star-forming galaxies, although with a smaller offset than expected based on past studies of local starbursts. We put forward a hypothesis that there exists a continuous increase in star formation efficiency with elevation from the MS with galaxy mergers as a possible physical driver. Along with a heightened star formation efficiency, our high-redshift sample is similar in other respects to local starbursts, such as being metal rich and having a higher ionization state of the interstellar medium. © 2015. The American Astronomical Society. All rights reserved..

Daddi E.,University Paris Diderot | Dannerbauer H.,University of Vienna | Liu D.,University Paris Diderot | Liu D.,Chinese Academy of Sciences | And 18 more authors.
Astronomy and Astrophysics | Year: 2015

We investigate the CO excitation of normal (near-IR selected BzK) star-forming (SF) disk galaxies at z = 1.5 using IRAM Plateau de Bure observations of the CO[2-1], CO[3-2], and CO[5-4] transitions for four galaxies, including VLA observations of CO[1-0] for three of them, with the aim of constraining the average state of H2 gas. By exploiting previous knowledge of the velocity range, spatial extent, and size of the CO emission, we measure reliable line fluxes with a signal-to-noise ratio >4-7 for individual transitions. While the average CO spectral line energy distribution (SLED) has a subthermal excitation similar to the Milky Way (MW) up to CO[3-2], we show that the average CO[5-4] emission is four times stronger than assuming MW excitation. This demonstrates that there is an additional component of more excited, denser, and possibly warmer molecular gas. The ratio of CO[5-4] to lower-J CO emission is lower than in local (ultra-)luminous infrared galaxies (ULIRGs) and high-redshift starbursting submillimeter galaxies, however, and appears to be closely correlated with the average intensity of the radiation field and with the star formation surface density, but not with the star formation efficiency. The luminosity of the CO[5-4] transition is found to be linearly correlated with the bolometric infrared luminosity over four orders of magnitudes. For this transition, z = 1.5 BzK galaxies follow the same linear trend as local spirals and (U)LIRGs and high-redshift star-bursting submillimeter galaxies. The CO[5-4] luminosity is thus empirically related to the dense gas and might be a more convenient way to probe it than standard high-density tracers that are much fainter than CO. We see excitation variations among our sample galaxies that can be linked to their evolutionary state and clumpiness in optical rest-frame images. In one galaxy we see spatially resolved excitation variations, where the more highly excited part of the galaxy corresponds to the location of massive SF clumps. This provides support to models that suggest that giant clumps are the main source of the high-excitation CO emission in high-redshift disk-like galaxies. © ESO, 2015.

Serres P.,Iram Institute Of Radioastronomie Millimetrique | Navarrini A.,Iram Institute Of Radioastronomie Millimetrique | Bortolotti Y.,Iram Institute Of Radioastronomie Millimetrique | Garnier O.,Iram Institute Of Radioastronomie Millimetrique
ISSTT 2014 - 25th International Sympsoium on Space Terahertz Technology, Proceedings | Year: 2014

We report on the development of a measurement setup to characterize the IF output impedance of a SIS mixer. The measurement method and the details of the test setup are described.

Serres P.,Iram Institute Of Radioastronomie Millimetrique | Navarrini A.,Iram Institute Of Radioastronomie Millimetrique | Bortolotti Y.,Iram Institute Of Radioastronomie Millimetrique | Garnier O.,Iram Institute Of Radioastronomie Millimetrique
IEEE Transactions on Terahertz Science and Technology | Year: 2015

In this paper, we describe a measurement setup to characterize the intermediate frequency (IF) impedance of cryogenically cooled superconductor-insulator-superconductor (SIS) mixers. A setup based on a commercial vector network analyzer (VNA), a circulator and a low noise amplifier (LNA) has allowed to increase the dynamic of the VNA and to perform accurate one-port measurements across a high dynamic range of the SIS mixers IF band. The mixers were biased in three different regions of their unpumped IV curve to obtain three known impedances which are close to the classical calibration SOLT standards (Short, Open, Load, Thru): the reference plane was located at the SIS junction itself and the calibration procedure allowed to calibrate out all IF circuitry of the measurement setup, including the on-chip SIS mixer intrinsic capacitance and inductance without requiring to thermally cycle and open the cryostat to locate and measure the different calibration standards. Thus, the devised method provides a simple and direct measurement of the SIS mixers IF impedance which can be used for quick, accurate and highly repeatable IF characterization of any type of millimeter and sub-millimeter wave SIS mixers. The measurement method is described and the experimental results of the IF output impedances of 3 mm band DSB and SSB mixers with 4 GHz wide IFs (across 4-8 GHz) are presented and compared with simulated predictions obtained from combining Tucker's SIS mixer theory and accurate electromagnetic modeling of the mixer structure. © 2014 IEEE.

Cresci G.,National institute for astrophysics | Mainieri V.,European Southern Observatory | Brusa M.,University of Bologna | Brusa M.,Max Planck Institute for Extraterrestrial Physics | And 16 more authors.
Astrophysical Journal | Year: 2015

Quasar feedback in the form of powerful outflows is invoked as a key mechanism to quench star formation in galaxies, preventing massive galaxies to overgrow and producing the red colors of ellipticals. On the other hand, some models are also requiring "positive" active galactic nucleus feedback, inducing star formation in the host galaxy through enhanced gas pressure in the interstellar medium. However, finding observational evidence of the effects of both types of feedback is still one of the main challenges of extragalactic astronomy, as few observations of energetic and extended radiatively driven winds are available. Here we present SINFONI near infrared integral field spectroscopy of XID2028, an obscured, radio-quiet z = 1.59 QSO detected in the XMM-COSMOS survey, in which we clearly resolve a fast (1500 km s-1) and extended (up to 13 kpc from the black hole) outflow in the [O III] lines emitting gas, whose large velocity and outflow rate are not sustainable by star formation only. The narrow component of Hα emission and the rest frame U-band flux from Hubble Space Telescope/Advanced Camera for Surveys imaging enable to map the current star formation in the host galaxy: both tracers independently show that the outflow position lies in the center of an empty cavity surrounded by star forming regions on its edge. The outflow is therefore removing the gas from the host galaxy ("negative feedback"), but also triggering star formation by outflow induced pressure at the edges ("positive feedback"). XID2028 represents the first example of a host galaxy showing both types of feedback simultaneously at work. © 2015. The American Astronomical Society. All rights reserved.

Feruglio C.,Normal School of Pisa | Feruglio C.,Iram Institute Of Radioastronomie Millimetrique | Feruglio C.,National institute for astrophysics | Fiore F.,National institute for astrophysics | And 11 more authors.
Astronomy and Astrophysics | Year: 2015

Mrk 231 is a nearby ultra-luminous IR galaxy exhibiting a kpc-scale, multi-phase AGN-driven outflow. This galaxy represents the best target to investigate in detail the morphology and energetics of powerful outflows, as well as their still poorly-understood expansion mechanism and impact on the host galaxy. In this work, we present the best sensitivity and angular resolution maps of the molecular disk and outflow of Mrk 231, as traced by CO(2-1) and (3-2) observations obtained with the IRAM/PdBI. In addition, we analyze archival deep Chandra and NuSTAR X-ray observations. We use this unprecedented combination of multi-wavelength data sets to constrain the physical properties of both the molecular disk and outflow, the presence of a highly-ionized ultra-fast nuclear wind, and their connection. The molecular CO(2-1) outflow has a size of ∼1 kpc, and extends in all directions around the nucleus, being more prominent along the south-west to north-east direction, suggesting a wide-angle biconical geometry. The maximum projected velocity of the outflow is nearly constant out to ∼1 kpc, thus implying that the density of the outflowing material must decrease from the nucleus outwards as ∼r-2. This suggests that either a large part of the gas leaves the flow during its expansion or that the bulk of the outflow has not yet reached out to ∼1 kpc, thus implying a limit on its age of ∼1 Myr. Mapping the mass and energy rates of the molecular outflow yields \hbox{$\rm \dot {\it M}$} OF = [500-1000] M yr-1 and A kin,OF = [7-10] × 1043 erg s-1. The total kinetic energy of the outflow is Ekin,OF is of the same order of the total energy of the molecular disk, Edisk. Remarkably, our analysis of the X-ray data reveals a nuclear ultra-fast outflow (UFO) with velocity -20 000 km s-1, \hbox{$\rm \dot {\it M}$}UFO = [0.3-2.1] M yr-1, and momentum load \hbox{$\rm \dot {\it P}$}UFO/ \hbox{$\dot {\it P}$}rad = [0.2-1.6]. We find A kin,UFO ∼ A kin,OF as predicted for outflows undergoing an energy conserving expansion. This suggests that most of the UFO kinetic energy is transferred to mechanical energy of the kpc-scale outflow, strongly supporting that the energy released during accretion of matter onto super-massive black holes is the ultimate driver of giant massive outflows. The momentum flux \hbox{$\rm \dot {\it P}$}OF derived for the large scale outflows in Mrk 231 enables us to estimate a momentum boost \hbox{$\rm \dot {\it P}$}OF/ \hbox{$\dot {\it P}$} UFO [30-60]. The ratios A kin,UFO/Lbol,AGN = [1-5] % and A kin,OF/Lbol,AGN = [1-3] % agree with the requirements of the most popular models of AGN feedback. © ESO, 2015.

Mattiocco F.,Iram Institute Of Radioastronomie Millimetrique | Garnier O.,Iram Institute Of Radioastronomie Millimetrique | Danneel J.M.,Iram Institute Of Radioastronomie Millimetrique | Berton M.,Iram Institute Of Radioastronomie Millimetrique | And 4 more authors.
26th International Symposium on Space Terahertz Technology, ISSTT 2015 | Year: 2015

We present an overview of the electronically tuned Local Oscillator (LO) system developed at IRAM for the Superconductor-Insulator-Superconductor (SIS) receivers of the NOrthern Extended Millimeter Array interferometer (NOEMA). We have modified and extended the LO designs developed by the National Radio Astronomy Observatory (NRAO) for the Atacama Large Millimeter Array (ALMA) project to the four NOEMA LO frequency ranges 82-108.3 GHz (Band 1), 138.6- 171.3 GHz (Band 2), 207.7-264.4 GHz (Band 3), 283-365 GHz (Band 4). The NOEMA LO system employs commercially available MMICs and GaAs millimeter MMICs from NRAO which are micro-assembled into Active Multiplied Chain (AMC) and Power Amplifier (PA) modules. We discuss the problem of LO spurious harmonics and LO signal directly multiplied by the SIS mixers which add extra noise and result into detection of unwanted spectral lines. A waveguide filter is used in the LO path to suppress the higher order harmonics of the LO at the output of the final frequency multiplier, thus mitigating the undesired effect and improving the system noise temperature.

PubMed | Iram Institute Of Radioastronomie Millimetrique, University of Bordeaux Segalen, Albanova University Center, NASA and 2 more.
Type: Journal Article | Journal: Science advances | Year: 2015

The presence of numerous complex organic molecules (COMs; defined as those containing six or more atoms) around protostars shows that star formation is accompanied by an increase of molecular complexity. These COMs may be part of the material from which planetesimals and, ultimately, planets formed. Comets represent some of the oldest and most primitive material in the solar system, including ices, and are thus our best window into the volatile composition of the solar protoplanetary disk. Molecules identified to be present in cometary ices include water, simple hydrocarbons, oxygen, sulfur, and nitrogen-bearing species, as well as a few COMs, such as ethylene glycol and glycine. We report the detection of 21 molecules in comet C/2014 Q2 (Lovejoy), including the first identification of ethyl alcohol (ethanol, C2H5OH) and the simplest monosaccharide sugar glycolaldehyde (CH2OHCHO) in a comet. The abundances of ethanol and glycolaldehyde, respectively 5 and 0.8% relative to methanol (0.12 and 0.02% relative to water), are somewhat higher than the values measured in solar-type protostars. Overall, the high abundance of COMs in cometary ices supports the formation through grain-surface reactions in the solar system protoplanetary disk.

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