Fuhrmann L.,Max Planck Institute for Radio Astronomy |
Larsson S.,The Oskar Klein Center |
Chiang J.,Kavli Institute for Particle Astrophysics and Cosmology |
Angelakis E.,Max Planck Institute for Radio Astronomy |
And 9 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2014
The exact location of the γ-ray emitting region in blazars is still controversial. In order to attack this problem we present first results of a cross-correlation analysis between radio (11 cm to 0.8mm wavelength, F-GAMMA programme) and γ-ray (0.1-300 GeV) ~3.5 yr light curves of 54 Fermi-bright blazars. We perform a source stacking analysis and estimate significances and chance correlations using mixed source correlations. Our results reveal: (i) the first highly significant multiband radio and γ-ray correlations (radio lagging γ rays) when averaging over the whole sample, (ii) average time delays (source frame: 76 ± 23 to 7 ± 9 d), systematically decreasing from cm to mm/sub-mm bands with a frequency dependence τ r, γ (ν) α ν-1, in good agreement with jet opacity dominated by synchrotron self-absorption, (iii) a bulk γ-ray production region typically located within/upstream of the 3mm core region (τ 3mm, γ = 12 ± 8 d), (iv) mean distances between the region of γ-ray peak emission and the radio 'τ = 1 photosphere' decreasing from 9.8 ± 3.0 pc (11 cm) to 0.9 ± 1.1 pc (2 mm) and 1.4 ± 0.8 pc (0.8 mm), (v) 3 mm/γ-ray correlations in nine individual sources at a significance level where one is expected by chance (probability: 4 × 10-6), (vi) opacity and 'time lag core shift' estimates for quasar 3C 454.3 providing a lower limit for the distance of the bulk γ-ray production region from the supermassive black hole (SMBH) of ~0.8-1.6 pc, i.e. at the outer edge of the broad-line region (BLR) or beyond. A 3mm τ = 1 surface at ~2-3 pc from the jet base (i.e. well outside the 'canonical BLR') finally suggests that BLR material extends to several parsec distances from the SMBH. © 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.
Mahieu S.,Institute Of Radio Astronomie Millimetrique |
Maier D.,Institute Of Radio Astronomie Millimetrique |
Lazareff B.,Institute Of Planeotologie Et Dastrophysique Of Grenoble Ipag |
Navarrini A.,Institute Of Radio Astronomie Millimetrique |
And 5 more authors.
IEEE Transactions on Terahertz Science and Technology | Year: 2012
The Atacama Large Millimeter/Sub-millimeter Array (ALMA) will be composed of at least 65 high-precision antennas. In this framework, IRAM is responsible for the design and production (component manufacturing and procurement, assembly and test) of 65 production and 8 spare state-of-the-art receivers, covering the 275-373 GHz frequency range, called the ALMA Band-7 cartridges. The core part of the receiver consists of dual polarization sideband separating (2SB) superconducting (SIS) mixers designed and fabricated at IRAM, and cascaded with 4-8 GHz cryogenic isolators and low noise amplifiers. © 2011 IEEE.
Dasyra K.M.,Paris Observatory |
Combes F.,Paris Observatory |
Novak G.S.,Paris Observatory |
Bremer M.,Institute Of Radio Astronomie Millimetrique |
And 4 more authors.
Astronomy and Astrophysics | Year: 2014
We present a comparison of the molecular gas properties in the outflow vs. in the ambient medium of the local prototype radio-loud and ultraluminous- infrared galaxy 4C12.50 (IRAS 13451+1232), using new data from the IRAM Plateau de Bure Interferometer and 30m telescope and from the Herschel space telescope. Previous H2 (0-0) S(1) and S(2) observations with the Spitzer space telescope had indicated that the warm (~400 K) molecular gas in 4C12.50 is made up of a 1.4(± 0.2) × 108M⊙ ambient reservoir and a 5.2(±1.7) × 107M⊙ outflow. The new CO(1-0) data cube indicates that the corresponding cold (25 K) H2 gas mass is 1.0(±0.1) × 1010M ⊙ for the ambient medium and < 1.3 × 108 M⊙ for the outflow, when using a CO-intensity-to-H 2-mass conversion factor α of 0.8 M⊙/(K kms-1 pc2). The combined mass outflow rate is high, 230-800 M⊙/yr, but the amount of gas that could escape the galaxy is low. A potential inflow of gas from a 3.3(±0.3) × 10 8M⊙ tidal tail could moderate any mass loss. The mass ratio of warm-to-cold molecular gas is ≳30 times higher in the outflow than in the ambient medium, indicating that a non-negligible fraction of the accelerated gas is heated to temperatures at which star formation is inefficient. This conclusion is robust against the use of different α factor values and/or different warm gas tracers (H2 vs. H2 plus CO). With the CO-probed gas mass at least 40 times lower at 400 K than at 25 K, the total warm-to-cold mass ratio is always lower in the ambient gas than in the entrained gas. Heating of the molecular gas could facilitate the detection of new outflows in distant galaxies by enhancing their emission in intermediate rotational number CO lines. © 2014 ESO.
Matsushita S.,Academia Sinica, Taiwan |
Dinh-V-Trung,Vietnam Academy of Science and Technology |
Boone F.,Toulouse 1 University Capitole |
Boone F.,Roche Holding AG |
And 3 more authors.
Astrophysical Journal | Year: 2015
We present high angular resolution observations of the HCN(1-0) emission (at ∼1″ or ∼34 pc), together with CO J = 1-0, 2-1, and 3-2 observations, toward the Seyfert 2 nucleus of M51 (NGC 5194). The overall HCN(1-0) distribution and kinematics are very similar to that of the CO lines, which have been indicated as the jet-entrained molecular gas in our past observations. In addition, high HCN(1-0)/CO(1-0) brightness temperature ratio of about unity is observed along the jets, similar to that observed at the shocked molecular gas in our Galaxy. These results strongly indicate that both diffuse and dense gases are entrained by the jets and outflowing from the active galactic nucleus. The channel map of HCN(1-0) at the systemic velocity shows a strong emission right at the nucleus, where no obvious emission has been detected in the CO lines. The HCN(1-0)/CO(1-0) brightness temperature ratio at this region reaches >2, a value that cannot be explained considering standard physical/chemical conditions. Based on our calculations, we suggest infrared pumping and possibly weak HCN masing, but still requiring an enhanced HCN abundance for the cause of this high ratio. This suggests the presence of a compact dense obscuring molecular gas in front of the nucleus of M51, which remains unresolved at our ∼1″ (∼34 pc) resolution, and consistent with the Seyfert 2 classification picture. © 2015. The American Astronomical Society. All rights reserved.
Agudo I.,Institute Astrofisica Of Andalucia |
Agudo I.,Boston University |
Thum C.,Institute Of Radio Astronomie Millimetrique |
Wiesemeyer H.,Max Planck Institute for Radio Astronomy |
And 5 more authors.
Astronomy and Astrophysics | Year: 2012
Context. Several millimeter and submillimeter facilities with linear polarization observing capabilities have started operating during the last years. These facilities, as well as other previous millimeter telescopes and interferometers, require bright and stable linear polarization calibrators to calibrate new instruments and to monitor their instrumental polarization. The current limited number of adequate calibrators implies difficulties in the acquisition of these calibration observations. Aims. Looking for additional linear polarization calibrators in the millimeter spectral range, we started monitoring 3C 286 in mid-2006. This source is a standard and highly stable polarization calibrator for radio observations. Methods. Here we present the 3 mm and 1 mm monitoring observations obtained between September 2006 and January 2012 with the XPOL polarimeter on the IRAM 30 m Millimeter Telescope. Results. Our observations show that 3C 286 is a bright source of constant total flux with 3 mm flux density S 3 mm = (0.91 ± 0.02) Jy. The 3 mm linear polarization degree (p 3 mm = [13.5 ± 0.3] %) and polarization angle (χ 3 mm = [37.3 ± 0.8] °, expressed in the equatorial coordinate system) were also constant during the time span of our observations. Although with poorer time sampling and signal-to-noise ratio, our 1 mm observations of 3C 286 are also reproduced by a constant source of 1 mm flux density (S 1 mm = [0.30 ± 0.03] Jy), polarization fraction (p 1 mm = [14.4 ± 1.8] %), and polarization angle (χ 1 mm = [33.1 ± 5.7]°). Conclusions. This, together with the previously known compact structure of 3C 286-extended by ∼3.5′′ in the sky-allow us to propose 3C 286 as a new calibrator for both single-dish and interferometric polarization observations at 3 mm, and possibly at shorter wavelengths. © 2012 ESO.
Benedettini M.,National institute for astrophysics |
Viti S.,University College London |
Codella C.,National institute for astrophysics |
Gueth F.,Institute Of Radio Astronomie Millimetrique |
And 6 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013
We present high spatial resolution (750 au at 250 pc) maps of the B1 shock in the blue lobe of the L1157 outflow in four lines: CS (3-2), CH3OH (3K-2K), HC3N (16-15) and p-H2CO (202-301). The combined analysis of the morphology and spectral profiles has shown that the highest velocity gas is confined in a few compact (≈5 arcsec) bullets, while the lowest velocity gas traces the wall of the gas cavity excavated by the shock expansion. A large velocity gradient model applied to the CS (3-2) and (2-1) lines provides an upper limit of 106 cm-3 to the averaged gas density in B1 and a range of 5 × 103 = nH2 = 5 × 105 cm-3 for the density of the high-velocity bullets. The origin of the bullets is still uncertain: they could be the result of local instabilities produced by the interaction of the jet with the ambient medium or could be clumps already present in the ambient medium that are excited and accelerated by the expanding outflows. The column densities of the observed species can be reproduced qualitatively by the presence in B1 of a C-type shock and only models where the gas reaches temperatures of at least 4000K can reproduce the observed HC3N column density. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.
Fontani F.,ESO |
Fontani F.,Institute Of Radio Astronomie Millimetrique |
Palau A.,Institute Of Ciencies Of Lespai Csic Ieec |
Caselli P.,University of Leeds |
And 8 more authors.
Astronomy and Astrophysics | Year: 2011
Context. Theory predicts, and observations confirm, that the column density ratio of a molecule containing D to its counterpart containing H can be used as an evolutionary tracer in the low-mass star formation process. Aims. Since it remains unclear if the high-mass star formation process is a scaled-up version of the low-mass one, we investigated whether the relation between deuteration and evolution can be applied to the high-mass regime. Methods. With the IRAM-30 m telescope, we observed rotational transitions of N2D+ and N2H+ and derived the deuterated fraction in 27 cores within massive star-forming regions understood to represent different evolutionary stages of the massive-star formation process. Results. The abundance of N2D+ is higher at the pre-stellar/cluster stage, then drops during the formation of the protostellar object(s) as in the low-mass regime, remaining relatively constant during the ultra-compact HII region phase. The objects with the highest fractional abundance of N 2D+ are starless cores with properties very similar to typical pre-stellar cores of lower mass. The abundance of N2D + is lower in objects with higher gas temperatures as in the low-mass case but does not seem to depend on gas turbulence. Conclusions. Our results indicate that the N2D+-to-N2H+ column density ratio can be used as an evolutionary indicator in both low- and high-mass star formation, and that the physical conditions influencing the abundance of deuterated species likely evolve similarly during the processes that lead to the formation of both low- and high-mass stars. © 2011 ESO.
Jimenez-Serra I.,Harvard - Smithsonian Center for Astrophysics |
Martin-Pintado J.,CSIC - National Institute of Aerospace Technology |
Baez-Rubio A.,CSIC - National Institute of Aerospace Technology |
Patel N.,Harvard - Smithsonian Center for Astrophysics |
Thum C.,Institute Of Radio Astronomie Millimetrique
Astrophysical Journal Letters | Year: 2011
We present the first detection of the H40α, H34α, and H31α radio recombination lines (RRLs) at millimeter wavelengths toward the high-velocity ionized jet in the Cepheus A HW2 star-forming region. From our single-dish and interferometric observations, we find that the measured RRLs show extremely broad asymmetric line profiles with zero-intensity line widths of ∼1100 kms-1. From the line widths, we estimate a terminal velocity for the ionized gas in the jet of ≥500 km s-1, consistent with that obtained from the proper motions of the HW2 radio jet. The total integrated line-to-continuum flux ratios of the H40α, H34α, and H31α lines are 43, 229, and 280 km s-1, clearly deviating from LTE predictions. These ratios are very similar to those observed for the RRL masers toward MWC349A, suggesting that the intensities of the RRLs toward HW2 are affected by maser emission. Our radiative transfer modeling of the RRLs shows that their asymmetric profiles could be explained by maser emission arising from a bi-conical radio jet with a semi-opening angle of 18°, electron density distribution varying as r-2.11, and turbulent and expanding wind velocities of 60 and 500 km s-1. © 2011. The American Astronomical Society. All rights reserved.
Agudo I.,Institute Astrofisica Of Andalucia Csic |
Agudo I.,Boston University |
Thum C.,Institute Of Radio Astronomie Millimetrique |
Wiesemeyer H.,Institute Radio Astronomia Milimetrica |
Krichbaum T.P.,Max Planck Institute for Radio Astronomy
Astrophysical Journal, Supplement Series | Year: 2010
We present the results from the first large (>100 sources) 3.5mm polarimetric survey of radio-loud active galactic nuclei (AGNs). This wavelength is favorable within the radio-millimeter range for measuring the intrinsic linearly polarized emission from AGNs, since in general it is only marginally affected by Faraday rotation of the electric vector position angle and depolarization. The I, Q, U, and V Stokes parameter observations were performed with the XPOL polarimeter at the IRAM 30m Telescope on different observing epochs from 2005 July (when most of the measurements were made) to 2009 October. Our sample consists of 145 flat-radio-spectrum AGNs with declination >-30°(J2000.0) and flux density ≳1Jy at ∼ 86GHz, as measured at the IRAM 30m Telescope from 1978 to 1994. This constraint on the radio spectrum causes our sample to be dominated by blazars, which allows us to conduct new statistical studies on this class of high-luminosity, relativistically beamed emitters. We detect linear and circular polarization (above minimum 3σ levels of ∼ 1.5% and ∼ 0.3%) for 76% and 6% of the sample, respectively. We find a clear excess in degree of linear polarization detected at 86GHz with regard to that at 15GHz by a factor of 2. Over our entire source sample, the luminosity of the jets is anticorrelated with the degree of linear polarization. Consistent with previous findings claiming larger Doppler factors for brighter γ-ray blazars, quasars listed in our sample, and in the Fermi Large Area Telescope Bright Source Catalog (LBAS), show larger luminosities than non-LBAS ones, but our data do not allow us to confirm the same for BL Lac objects. We do not find a clear relation between the linear polarization angle and the jet structural position angle for any source class in our sample. We interpret this as the consequence of a markedly non-axisymmetric character of the 3mm emitting region in the jets. We find that intrinsic circular polarization is the most likely mechanism for generation of the circular polarization detected in our observations. Our new data can be used to estimate the 3.5mm AGN contribution to measurements of the linear polarization of the cosmic microwave background, such as those performed by the Planck satellite. © 2010 The American Astronomical Society.
Zhao J.-H.,Harvard - Smithsonian Center for Astrophysics |
Blundell R.,Harvard - Smithsonian Center for Astrophysics |
Moran J.M.,Harvard - Smithsonian Center for Astrophysics |
Downes D.,Institute Of Radio Astronomie Millimetrique |
And 2 more authors.
Astrophysical Journal | Year: 2010
We report a study of the H30α line emission at 1.3 mm from the region around Sgr A* made with the Submillimeter Array at a resolution of 2″ over a field of 60″ (2 pc) and a velocity range of -360 to +345 km s-1. This field encompasses most of the Galactic center's "minispiral." With an isothermal homogeneous H II model, we determined the physical conditions of the ionized gas at specific locations in the Northern and Eastern Arms from the H30α line data along with Very Large Array data from the H92α line at 3.6 cm and from the radio continuum emission at 1.3 cm. The typical electron density and kinetic temperature in the minispiral arms are 3-21 × 104 cm-3 and 5000-13,000 K, respectively. The H30α and H92α line profiles are broadened due to the large velocity shear within and along the beam produced by dynamical motions in the strong gravitational field near Sgr A*. We constructed a threedimensional model of the minispiral using the orbital parameters derived under the assumptions that the gas flows are in Keplerian motion. The gas in the Eastern Arm appears to collide with the Northern Arm flow in the "Bar" region, which is located 0.1-0.2 pc south of and behind Sgr A*. Finally, a total Lyman continuum flux of 3 × 1050 photons s-1 is inferred from the assumption that the gas is photoionized and the ionizing photons for the high-density gas in the minispiral arms are from external sources, which is equivalent to ∼250 O9-type zero-age-main-sequence stars. © 2010. The American Astronomical Society.