ORCID Profile
0000-0002-5777-1629
Current Organisations
CNRS Délégation Paris B
,
CNRS Délégation Paris Michel-Ange
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Publisher: Oxford University Press (OUP)
Date: 07-02-2017
DOI: 10.1093/MNRAS/STX331
Publisher: Oxford University Press (OUP)
Date: 16-03-2011
Publisher: EDP Sciences
Date: 2017
DOI: 10.1051/0004-6361/201629173
Abstract: We present the discovery of a molecular cloud at z abs ≈ 2.5255 along the line of sight to the quasar SDSS J 000015.17+004833.3. We use a high-resolution spectrum obtained with the Ultraviolet and Visual Echelle Spectrograph together with a deep multi-wavelength medium-resolution spectrum obtained with X-shooter (both on the Very Large Telescope) to perform a detailed analysis of the absorption lines from ionic, neutral atomic and molecular species in different excitation levels, as well as the broad-band dust extinction. We find that the absorber classifies as a D ed Lyman- α system (DLA) with log N (H i ) (cm -2 ) = 20.8 ± 0.1. The DLA has super-solar metallicity ( Z ~ 2.5 Z ⊙ , albeit to within a factor of two to three) with a depletion pattern typical of cold gas and an overall molecular fraction f = 2 N (H 2 )/(2 N (H 2 ) + N (H i )) ~ 50%. This is the highest f -value observed to date in a high- z intervening system. Most of the molecular hydrogen arises from a clearly identified narrow ( b ~ 0.7km s -1 ), cold component in which carbon monoxide molecules are also found, with log N (CO)≈ 15. With the help of the spectral synthesis code Cloudy, we study the chemical and physical conditions in the cold gas. We find that the line of sight probes the gas deep after the H i -to-H 2 transition in a ~4−5 pc-size cloud with volumic density n H ~ 80 cm -3 and temperature of only 50 K. Our model suggests that the presence of small dust grains (down to about 0.001 μ m) and high cosmic ray ionisation rate ( ζ H ~ a few times 10 -15 s -1 ) are needed to explain the observed atomic and molecular abundances. The presence of small grains is also in agreement with the observed steep extinction curve that also features a 2175 Å bump. Interestingly, the chemical and physical properties of this cloud are very similar to what is seen in diffuse molecular regions of the nearby Perseus complex, despite the former being observed when the Universe was only 2.5 Gyr old. The high excitation temperature of CO rotational levels towards J0000+0048 betrays however the higher temperature of the cosmic microwave background. Using the derived physical conditions, we correct for a small contribution (0.3 K) of collisional excitation and obtain T CMB ( z = 2.53) ≈ 9.6 K, in perfect agreement with the predicted adiabatic cooling of the Universe.
Publisher: Oxford University Press (OUP)
Date: 2012
Publisher: IOP Publishing
Date: 05-2014
DOI: 10.1088/1475-7516/2014/05/027
Abstract: We measure the large-scale cross-correlation of quasars with the Lyα forest absorption, using over 164,000 quasars from Data Release 11 of the SDSS-III Baryon Oscillation Spectroscopic Survey. We extend the previous study of roughly 60,000 quasars from Data Release 9 to larger separations, allowing a measurement of the Baryonic Acoustic Oscillation (BAO) scale along the line of sight c /( H ( z = 2.36) r s ) = 9.0±0.3 and across the line of sight D A ( z = 2.36)/ r s = 10.8±0.4, consistent with CMB and other BAO data. Using the best fit value of the sound horizon from Planck data ( r s = 147.49 Mpc), we can translate these results to a measurement of the Hubble parameter of H ( z = 2.36) = 226±8 km s −1 Mpc −1 and of the angular diameter distance of D A ( z = 2.36) = 1590±60 Mpc. The measured cross-correlation function and an update of the code to fit the BAO scale (baofit) are made publicly available.
Publisher: American Physical Society (APS)
Date: 14-12-2015
Publisher: EDP Sciences
Date: 06-2012
Publisher: EDP Sciences
Date: 11-2013
Publisher: Oxford University Press (OUP)
Date: 10-2008
Publisher: American Astronomical Society
Date: 06-2022
Abstract: We report the first direct measurement of the helium isotope ratio, 3 He/ 4 He, outside of the Local Interstellar Cloud, as part of science-verification observations with the upgraded CRyogenic InfraRed Echelle Spectrograph. Our determination of 3 He/ 4 He is based on metastable He i * absorption along the line of sight toward Θ 2 A Ori in the Orion Nebula. We measure a value 3 He/ 4 He = (1.77 ± 0.13) × 10 −4 , which is just ∼40% above the primordial relative abundance of these isotopes, assuming the Standard Model of particle physics and cosmology, ( 3 He/ 4 He) p = (1.257 ± 0.017) × 10 −4 . We calculate a suite of galactic chemical evolution simulations to study the Galactic build up of these isotopes, using the yields from Limongi & Chieffi for stars in the mass range M = 8–100 M ⊙ and Lagarde et al. for M = 0.8–8 M ⊙ . We find that these simulations simultaneously reproduce the Orion and protosolar 3 He/ 4 He values if the calculations are initialized with a primordial ratio 3 He / 4 He p = ( 1.043 ± 0.089 ) × 10 − 4 . Even though the quoted error does not include the model uncertainty, this determination agrees with the Standard Model value to within ∼2 σ . We also use the present-day Galactic abundance of deuterium (D/H), helium (He/H), and 3 He/ 4 He to infer an empirical limit on the primordial 3 He abundance, 3 He / H p ≤ ( 1.09 ± 0.18 ) × 10 − 5 , which also agrees with the Standard Model value. We point out that it is becoming increasingly difficult to explain the discrepant primordial 7 Li/H abundance with nonstandard physics, without breaking the remarkable simultaneous agreement of three primordial element ratios (D/H, 4 He/H, and 3 He/ 4 He) with the Standard Model values.
Publisher: American Astronomical Society
Date: 25-06-2020
Abstract: This paper documents the 16th data release (DR16) from the Sloan Digital Sky Surveys (SDSS), the fourth and penultimate from the fourth phase (SDSS-IV). This is the first release of data from the Southern Hemisphere survey of the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) new data from APOGEE-2 North are also included. DR16 is also notable as the final data release for the main cosmological program of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), and all raw and reduced spectra from that project are released here. DR16 also includes all the data from the Time Domain Spectroscopic Survey and new data from the SPectroscopic IDentification of ERosita Survey programs, both of which were co-observed on eBOSS plates. DR16 has no new data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey (or the MaNGA Stellar Library “MaStar”). We also preview future SDSS-V operations (due to start in 2020), and summarize plans for the final SDSS-IV data release (DR17).
Publisher: Oxford University Press (OUP)
Date: 22-08-2013
Publisher: American Astronomical Society
Date: 04-02-2016
Publisher: Oxford University Press (OUP)
Date: 27-08-2010
Publisher: Oxford University Press (OUP)
Date: 09-2009
No related grants have been discovered for Pasquier Noterdaeme.