A. Sievers
A5046331422- Astrophysics and Star Formation Studies
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Radio Astronomy Observations and Technology
- Astronomy and Astrophysical Research
- Superconducting and THz Device Technology
- Gamma-ray bursts and supernovae
- Atmospheric Ozone and Climate
- Astro and Planetary Science
- Neutrino Physics Research
- Molecular Spectroscopy and Structure
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Spectroscopy and Laser Applications
- Particle Accelerators and Free-Electron Lasers
- Adaptive optics and wavefront sensing
- Dark Matter and Cosmic Phenomena
- Calibration and Measurement Techniques
- Gyrotron and Vacuum Electronics Research
- Scientific Research and Discoveries
- Cosmology and Gravitation Theories
- Particle physics theoretical and experimental studies
- Advanced Chemical Physics Studies
- Advanced Combustion Engine Technologies
Institut de Radioastronomie Millimétrique
2004-2024
Instituto de Radioastronomía Milimétrica
2015-2024
Ausonius Institut de Recherche sur l'Antiquité et le Moyen age
1995-2024
Centre National de la Recherche Scientifique
2014-2022
Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique et Atmosphères
2022
Sorbonne Université
2022
Université Paris Sciences et Lettres
2022
Laboratoire de Physique Subatomique et de Cosmologie
2014
Max Planck Institute for Radio Astronomy
1991
University of Cape Town
1984
We are conducting COLD GASS, a legacy survey for molecular gas in nearby galaxies. Using the IRAM 30m telescope, we measure CO(1-0) line sample of ~350 (D=100-200 Mpc), massive galaxies (log(M*/Msun)>10.0). The is selected purely according to stellar mass, and therefore provides an unbiased view these systems. By combining data with SDSS photometry spectroscopy, GALEX imaging high-quality Arecibo HI data, investigate partition condensed baryons between stars, atomic 0.1-10L* In this paper,...
We study the relation between molecular gas and star formation in a volume-limited sample of 222 galaxies from COLD GASS survey, with measurements CO(1–0) line IRAM 30-m telescope. The are at redshifts 0.025 < z 0.05 have stellar masses range 10.0 log M★/M⊙ 11.5. complemented by deep Arecibo H i observations homogeneous Sloan Digital Sky Survey GALEX photometry. A reference that includes both ultraviolet (UV) far-infrared data is used to calibrate our estimates rates seven optical/UV bands....
We have conducted a multiwavelength survey of 42 radio loud narrow-1ine Seyfert 1 galaxies (RLNLS1s), selected by searching among all the known sources this type and omitting those with steep spectra. analyse data from frequencies to X-rays, supplement these information available online catalogues literature in order cover full electromagnetic spectrum. This is largest for source. detected 90% X-rays found 17% at γ rays. Extreme variability high energies was also found, down timescales as...
We present simultaneous Planck, Swift, Fermi, and ground-based data for 105 blazars belonging to three samples with flux limits in the soft X-ray, hard gamma-ray bands. Our unique set has allowed us demonstrate that selection method strongly influences results, producing biases cannot be ignored. Almost all BL Lac objects have been detected by Fermi-LAT, whereas ~40% of flat-spectrum radio quasars (FSRQs) radio, X-ray selected are still below detection limit even after integrating 27 months...
Millimeter-wave continuum astronomy is today an indispensable tool for both general Astrophysics studies and Cosmology. General purpose, large field-of-view instruments are needed to map the sky at intermediate angular scales not accessible by high-resolution interferometers coarse resolution space-borne or ground-based surveys. These have be installed focal plane of largest single-dish telescopes. In this context, we constructed deployed a multi-thousands pixels dual-band (150 260 GHz,...
The exact location of the gamma-ray emitting region in blazars is still controversial. In order to attack this problem we present first results a cross-correlation analysis between radio (11 cm 0.8 mm wavelength, F-GAMMA program) and (0.1-300 GeV) ~ 3.5 year light curves 54 Fermi-bright blazars. We perform source stacking estimate significances chance correlations using mixed correlations. Our reveal: (i) highly significant multi-band (radio lagging gamma rays) when averaging over whole...
We present the first detection of l-C3H+ hydrocarbon in interstellar medium. The Horsehead WHISPER project, a millimeter unbiased line survey at two positions, namely photo-dissociation region (PDR) and nearby shielded core, revealed consistent set eight unidentified lines toward PDR position. Six them are detected with signal-to-noise ratio from 6 to 19, while last ones tentatively detected. Mostly noise appears same frequency dense located less than 40" away. simultaneously fit 1)...
The prototype of the NIKA2 camera, NIKA, is an instrument operating at IRAM 30-m telescope, which can observe simultaneously 150 and 260GHz. One main goals to measure pressure distribution in galaxy clusters high resolution using thermal SZ (tSZ) effect. Such observations have already proved be excellent probe cluster distributions even redshifts. However, important fraction host submm and/or radio point sources, significantly affect reconstructed signal. Here we report on <20" 260GHz...
We aim to develop the Orion B Giant Molecular Cloud (GMC) as a local template for interpreting extra-galactic molecular line observations. use wide-band receiver at IRAM-30m spatially and spectrally resolve GMC. The observations cover almost 1 square degree 26" resolution with bandwidth of 32 GHz from 84 116 in only two tunings. Among mapped spectral lines are 12CO, 13CO, C18O, C17O, HCN, HNC, 12CN, CCH, HCO+, N2H+ (1-0), 12CS, 32SO, SiO, c-C3H2, CH3OH (2-1) transitions. introduce anatomy...
Context. The nature of turbulence in molecular clouds is one the key parameters that control star formation efficiency: compressive motions, as opposed to solenoidal can trigger collapse cores, or mark expansion Hii regions.
Abstract The lower-energy peak of the spectral energy distribution blazars has commonly been ascribed to synchrotron radiation from relativistic particles in jets. Despite consensus regarding jet emission processes, particle acceleration mechanism is still debated. Here, we present first X-ray polarization observations PG 1553+113, a high-synchrotron-peak blazar observed by Imaging Polarimetry Explorer (IXPE). We detect an degree (10 ± 2)% along electric-vector position angle ψ X = 86° 8°....
Abstract We report the first >99% confidence detection of X-ray polarization in BL Lacertae. During a recent X-ray/ γ -ray outburst, 287 ks observation (2022 November 27–30) was taken using Imaging Polarimetry Explorer (IXPE), together with contemporaneous multiwavelength observations from Neil Gehrels Swift observatory and XMM-Newton soft X-rays (0.3–10 keV), NuSTAR hard (3–70 optical Calar Alto Perkins Telescope observatories. Our data suggest that IXPE energy band is at crossover...
We have mapped the 1300 μm dust emission of a 6' × 16' field in OMC-2 and -3 region detected an extended filamentary structure with at least 11 embedded condensations 10 OMC-3. Six been observed previously μm, two were also by IRAS. eight new sources six wave bands from 350 to 2000 derived upper limits for their far-infrared (FIR) IRAS raw data. The millimeter/submillimeter originates cold (Td ~ 20 K), individual components gas masses 5 M☉ < Mgas 36 M☉. ratio Lbol/Lsmm is below 70 associated...
Continuum radiometers based on bolometers have a long tradition at the Max-Planck-Institut fur Radioastronomie (MPIfR) in Bonn, Germany. Arrays of been under development since early 90s. A small 7-element system, operating 300 mK, saw first light 1992 IRAM 30 m- telescope and has used successfully by numerous observers that facility then. While this array had conventional 'composite' design, it was obvious larger arrays, especially for higher frequencies, could take advantage...
We present high resolution large scale observations of the molecular and atomic gas in Local Group Galaxy M33. The were carried out using HERA at 30m IRAM telescope CO(2-1) line achieving a 12"x2.6 km/s, enabling individual GMCs to be resolved. observed region mainly along major axis radius 8.5 kpc, covers strip with HIFI/PACS Spectrometers as part HERM33ES Herschel key program. achieved sensitivity main beam temperature is 20-50 mK 2.6 km/s velocity resolution. luminosity 1.7\pm0.1x10^7...
We present the results of a series radio, optical, X-ray and gamma-ray observations BL Lac object S50716+714 carried out between April 2007 January 2011. The multi-frequency were obtained using several ground space based facilities. intense optical monitoring source reveals faster repetitive variations superimposed on long-term variability trend at time scale ~350 days. Episodes fast recur scales ~ 60-70 simultaneous activity frequencies favors SSC mechanism for production high-energy...
Complex (iso-)nitrile molecules, such as CH3CN and HC3N, are relatively easily detected in our Galaxy other galaxies. We constrain their chemistry through observations of two positions the Horsehead edge: photo-dissociation region (PDR) dense, cold, UV-shielded core just behind it. systematically searched for lines CH3CN, C3N, some isomers sensitive unbiased line survey at 3, 2, 1mm. derived column densities abundances Bayesian analysis using a large velocity gradient radiative transfer...
We studied the radio emission from four radio-loud and gamma-ray-loud narrow-line Seyfert 1 galaxies. The goal was to investigate whether a relativistic jet is operating at source, quantify its characteristics. relied on most systematic monitoring of such system in cm mm bands which conducted with Effelsberg 100 m IRAM 30 telescopes covers longest time-baselines frequencies date. extract variability parameters compute brightness temperatures Doppler factors. powers were computed light curves...
Recent population studies have shown that the variability Doppler factors can adequately describe blazars as a population. We use flux density variations found within extensive radio multi-wavelength datasets of F-GAMMA program, total 10 frequencies from 2.64 up to 142.33 GHz, in order estimate for 58 $γ$-ray bright sources, 20 which no factor has been estimated before. employ specifically designed algorithms obtain model each flare at frequency. then identify event and track its evolution...
Context. The γ-ray BL Lac object OJ 287 is known to exhibit inner-parsec “jet-wobbling”, high degrees of variability at all wavelengths and quasi-stationary features, including an apparent (≈100°) position-angle change in projection on the sky plane.
Measurement of the gas velocity distribution in galaxy clusters provides insight into physics mergers, through which large scale structures form Universe. Velocity estimates within intracluster medium (ICM) can be obtained via Sunyaev-Zel'dovich (SZ) effect, but its observation is challenging both term sensitivity requirement and control systematic effects, including removal contaminants. In this paper we report resolved observations, at 150 260 GHz, SZ effect toward triple merger MACS...
Aims. We aim to probe the magnetic field geometry and particle acceleration mechanism in relativistic jets of supermassive black holes. Methods. conducted a polarimetry campaign from radio X-ray wavelengths high-synchrotron-peak (HSP) blazar Mrk 421, including Imaging Polarimetry Explorer (IXPE) measurements 2022 December 6–8. During IXPE observation, we also monitored 421 using Swift -XRT obtained single observation with XMM-Newton improve spectral analysis. The time-averaged polarization...