Spectroscopic confirmation of a substantial population of luminous red galaxies at redshifts z ≳ 2

We confirm spectroscopically the existence of a population of galaxies at z greater than or similar to 2 with rest-frame optical colors similar to normal nearby galaxies. The galaxies were identified by their red near-infrared colors in deep images obtained with the Infrared Spectrometer and Array Camera on the Very Large Telescope of the field around the foreground cluster MS 1054-03. Redshifts of six galaxies with J(s)-K-s > 2.3 were measured from optical spectra obtained with the W. M. Keck telescope. Five out of six are in the range, demonstrating that the 2.43 = z = 3.52 J(s)-K-s color selection is quite efficient. The rest-frame ultraviolet spectra of confirmed z > 2 galaxies display a range of properties, with two galaxies showing emission lines characteristic of active galactic nuclei, two having Lyalpha in emission, and one showing interstellar absorption lines only. Their full spectral energy distributions are well described by constant star formation models with ages 1.4-2.6 Gyr, except for one galaxy whose colors indicate a dusty starburst. The confirmed z > 2 galaxies are very luminous: their K-s magnitudes are in the range 19.2-19.9, corresponding to rest-frame absolute V magnitudes from -24.8 to -23.2. Assuming that our bright spectroscopic sample is representative for the general population of J(s)-K-s selected objects, we find that the surface density of red z greater than or similar to 2 galaxies is approximate to0.9 arcmin(-2) to K-s = 21. The surface density is comparable to that of Lyman break-selected galaxies with K-s < 21, when corrections are made for the different redshift distributions of the two samples. Although there will be some overlap between the two populations, most "optical-break" galaxies are too faint in the rest-frame ultraviolet to be selected as Lyman break galaxies. The most straightforward interpretation is that star formation in typical optical-break galaxies started earlier than in typical Lyman break galaxies. Optical-break galaxies may be the oldest and most massive galaxies yet identified at, and they z 1 2 could evolve into early-type galaxies and bulges

Cross-calibration of CO- versus dust-based gas masses and assessment of the dynamical mass budget in Herschel-SDSS Stripe82 galaxies

We present a cross-calibration of CO- and dust-based molecular gas masses at z ≤ 0.2. Our results are based on a survey with the IRAM 30-m telescope collecting CO(1–0) measurements of 78 massive (logM⋆/M⊙> 10) galaxies with known gas-phase metallicities and with IR photometric coverage from Wide-field Infrared Survey Explorer(WISE; 22 μm) and Herschel Spectral and Photometric Imaging Receiver (SPIRE; 250, 350, 500μm). We find a tight relation (∼0.17 dex scatter) between the gas masses inferred from CO and dust continuum emission, with a minor systematic offset of 0.05 dex. The two methods can be brought into agreement by applying a metallicity-dependent adjustment factor (∼0.13 dex scatter). We illustrate that the observed offset is consistent with a scenario in which dust traces not only molecular gas but also part of the HI reservoir, residing in the H2-dominated region of the galaxy. Observations of the CO(2–1) to CO(1–0) line ratio for two-thirds of the sample indicate a narrow range in excitation properties, with a median ratio of luminosities ⟨R21⟩ ∼ 0.64. Finally, we find dynamical mass constraints from spectral line profile fitting to agree well with the anticipated mass budget enclosed within an effective radius, once all mass components (stars, gas, and dark matter) are accounted for

PHIBSS2: survey design and z=0.5-0.8 results Molecular gas reservoirs during the winding-down of star formation

Following the success of the Plateau de Bure high-z Blue Sequence Survey (PHIBSS), we present the PHIBSS2 legacy program, a survey of the molecular gas properties of star-forming galaxies on and around the star-formation main sequence (MS) at different redshifts using IRAM’s NOrthern Extended Millimeter Array (NOEMA). This survey significantly extends the existing sample of star-forming galaxies with CO molecular gas measurements, probing the peak epoch of star formation (z = 1 − 1.6) as well as its building-up (z = 2 − 3) and winding-down (z = 0.5 − 0.8) phases. The targets are drawn from the well-studied GOODS, COSMOS, and AEGIS cosmological deep fields and uniformly sample the MS in the stellar mass (M⋆) – star formation rate (SFR) plane with log(M⋆/M⊙) = 10 − 11.8 and SFR = 3.5 − 500 M⊙ yr−1 without morphological selection, thus providing a statistically meaningful census of star-forming galaxies at different epochs. We describe the survey strategy and sample selection before focusing on the results obtained at redshift z = 0.5 − 0.8, where we report 60 CO(2-1) detections out of 61 targets. We determine molecular gas masses between 2 × 109 and 5 × 1010 M⊙ and separately obtain disc sizes and bulge-to-total (B/T) luminosity ratios from HST I-band images. The median molecular gas-to-stellar mass ratio μgas∼ = 0.28 ± 0.04, gas fraction fgas∼ = 0.22 ± 0.02, and depletion time as well as their dependence with stellar mass and offset from the MS follow published scaling relations for a much larger sample of galaxies spanning a significantly wider range of redshifts, the cosmic evolution of the SFR being mainly driven by that of the molecular gas fraction. The galaxy-averaged molecular Kennicutt–Schmidt (KS) relation between molecular gas and SFR surface densities is strikingly linear, pointing towards similar star formation timescales within galaxies at any given epoch. In terms of morphology, the molecular gas content, the SFR, the disc stellar mass, and the disc molecular gas fraction do not seem to correlate with B/T and the stellar surface density, which suggests an ongoing supply of fresh molecular gas to compensate for the build-up of the bulge. Our measurements do not yield any significant variation of the depletion time with B/T and hence no strong evidence for morphological quenching within the scatter of the MS

Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole

This is the author accepted manuscript. the final version is available from EDP Sciences via the DOI in this recordThe highly elliptical, 16-year-period orbit of the star S2 around the massive black hole candidate Sgr A∗ is a sensitive probe of the gravitational field in the Galactic centre. Near pericentre at 120 AU ≈ 1400 Schwarzschild radii, the star has an orbital speed of ≈ 7650 km s-1, such that the first-order effects of Special and General Relativity have now become detectable with current capabilities. Over the past 26 years, we have monitored the radial velocity and motion on the sky of S2, mainly with the SINFONI and NACO adaptive optics instruments on the ESO Very Large Telescope, and since 2016 and leading up to the pericentre approach in May 2018, with the four-telescope interferometric beam-combiner instrument GRAVITY. From data up to and including pericentre, we robustly detect the combined gravitational redshift and relativistic transverse Doppler effect for S2 of z = Δλ / λ ≈ 200 km s-1/c with different statistical analysis methods. When parameterising the post-Newtonian contribution from these effects by a factor f, with f = 0 and f = 1 corresponding to the Newtonian and general relativistic limits, respectively, we find from posterior fitting with different weighting schemes f = 0.90 ± 0.09|stat ± 0.15|sys. The S2 data are inconsistent with pure Newtonian dynamics

Stimuli risibles et fonctions du rire en classe de français langue étrangère

Cette thèse traite du rôle et des fonctions du rire en classe de français langue étrangère. Le rire va bien au-delà d'une simple manifestation sonore : il remplit de multiples fonctions communicationnelles, émotionnelles et relationnelles. Le point central de cette recherche est la communication risible/rire, observée dans des séquences interactives. L'étude est basée sur l'analyse de deux corpus principaux constitués d'enregistrements vidéo de classes. Les publics concernés sont d'une part : des adolescents italiens apprenants de français à Rome ; d'autre part des apprenants " asiatiques " de niveau intermédiaire au Centre de Linguistique Appliquée de Besançon. La méthodologie de recherche est basée sur le croisement de données quantitatives et qualitatives. Les résultats montrent qu'au-delà des différences inhérentes aux deux groupes d'apprenants, on peut considérer que les stimuli et fonctions du rire présentent toutefois de nombreux caractères communsThis study is about the importance and the function of laughter in teaching/learning of French as a foreign language. Laughter is more than a simple sound : it has many roles and functions in communication, emotion and relationships in conversation. The main object of this research is about laughter and laughing based on the analysis of two principal groups. The concerned public are divided in two groups : teenagers studying French in Rome and Asian intermediate level students of French at the Centre de Linguistique Appliquée in Besançon. This research is based on the analysis of quantitative and qualitative data. The results showed that besides the differences inherent in each group of students, the causes and functions of laughter have many common characteristicsBESANCON-BU Lettres (250562101) / SudocSudocFranceF

High-resolution imaging of phibss z ∼ 2 main-sequence galaxies in co j = 1 → 0

We present Karl Jansky Very Large Array observations of the CO J = 1 - 0 transition in a sample of four z ∼ 2 main-sequence galaxies. These galaxies are in the blue sequence of star-forming galaxies at their redshift, and are part of the IRAM Plateau de Bure HIgh-z Blue Sequence Survey which imaged them in CO J = 3 - 2. Two galaxies are imaged here at high signal-to-noise, allowing determinations of their disk sizes, line profiles, molecular surface densities, and excitation. Using these and published measurements, we show that the CO and optical disks have similar sizes in main-sequence galaxies, and in the galaxy where we can compare CO J = 1 - 0 and J = 3 - 2 sizes we find these are also very similar. Assuming a Galactic CO-to-H2 conversion, we measure surface densities of Smol ∼ 1200 M⊙ pc-2 in projection and estimate ∑mol ∼ 500-900 M⊙ pc-2 deprojected. Finally, our data yields velocity-integrated Rayleigh-Jeans brightness temperature line ratios r31 that are approximately at unity. In addition to the similar disk sizes, the very similar line profiles in J = 1 - 0 and J = 3 - 2 indicate that both transitions sample the same kinematics, implying that their emission is coextensive. We conclude that in these two main-sequence galaxies there is no evidence for significant excitation gradients or a large molecular reservoir that is diffuse or cold and not involved in active star formation. We suggest that r31 in very actively star-forming galaxies is likely an indicator of how well-mixed the star formation activity and the molecular reservoir are

An ∼600 pc View of the Strongly Lensed, Massive Main-sequence Galaxy J0901: A Baryon-dominated, Thick Turbulent Rotating Disk with a Clumpy Cold Gas Ring at z = 2.259

Abstract We present a high-resolution kinematic study of the massive main-sequence star-forming galaxy (SFG) SDSS J090122.37+181432.3 (J0901) at z = 2.259, using ∼0.″36 Atacama Large Millimeter/submillimeter Array CO(3–2) and ∼0.″1–0.″5 SINFONI/VLT Hα observations. J0901 is a rare, strongly lensed but otherwise normal massive ( log ( M ⋆ / M ⊙ ) ∼ 11 ) main-sequence SFG, offering a unique opportunity to study a typical massive SFG under the microscope of lensing. Through forward dynamical modeling incorporating lensing deflection, we fit the CO and Hα kinematics in the image plane out to about one disk effective radius (R e ∼ 4 kpc) at an ∼600 pc delensed physical resolution along the kinematic major axis. Our results show high intrinsic dispersions of the cold molecular and warm ionized gas (σ 0,mol. ∼ 40 km s−1 and σ 0,ion. ∼ 66 km s−1) that remain constant out to R e; a moderately low dark matter fraction (f DM ∼ 0.3–0.4) within R e; and a centrally peaked Toomre Q parameter—agreeing well with the previously established σ 0 versus z, f DM versus Σbaryon, and Q's radial trends using large-sample non-lensed main-sequence SFGs. Our data further reveal a high stellar mass concentration within ∼1–2 kpc with little molecular gas, and a clumpy molecular gas ring-like structure at R ∼ 2–4 kpc, in line with the inside-out quenching scenario. Our further analysis indicates that J0901 had assembled half of its stellar mass only ∼400 Myr before its observed cosmic time, and the cold gas ring and dense central stellar component are consistent with signposts of a recent wet compaction event of a highly turbulent disk found in recent simulations.</jats:p

The star-formation rates of 1.5 &lt; z &lt; 2.5 massive galaxies

The star formation rate (SFR) is a key parameter in the study of galaxy evolution. The accuracy of SFR measurements at z ∼ 2 has been questioned following a disagreement between observations and theoretical models. The latter predict SFRs at this redshift that are typically a factor 4 or more lower than the measurements. We present star-formation rates based on calorimetric measurements of the far-infrared (FIR) luminosities for massive 1.5 &lt; z &lt; 2.5, normal star-forming galaxies (SFGs), which do not depend on extinction corrections and/or extrapolations of spectral energy distributions. The measurements are based on observations in GOODS-N with the Photodetector Array Camera and Spectrometer (PACS) onboard Herschel, as part of the PACS evolutionary probe (PEP) project, that resolve for the first time individual SFGs at these redshifts at FIR wavelengths. We compare FIR-based SFRs to the more commonly used 24 μm and UV SFRs. We find that SFRs from 24 μm alone are higher by a factor of ∼4-7.5 than the true SFRs. This overestimation depends on luminosity: gradually increasing for log L(24 μm) &gt; 12.2 L⊙. The SFGs and AGNs tend to exhibit the same 24 μm excess. The UV SFRs are in closer agreement with the FIR-based SFRs. Using a Calzetti UV extinction correction results in a mean excess of up to 0.3 dex and a scatter of 0.35 dex from the FIR SFRs. The previous UV SFRs are thus confirmed and the mean excess, while narrowing the gap, is insufficient to explain the discrepancy between the observed SFRs and simulation predictions. © 2010 ESO

The evolution of the dust temperatures of galaxies in the SFR-M-* plane up to z similar to 2

We study the evolution of the dust temperature of galaxies in the SFR-Mâ̂- plane up to z ~ 2 using far-infrared and submillimetre observations from the Herschel Space Observatory taken as part of the PACS Evolutionary Probe (PEP) and Herschel Multi-tiered Extragalactic Survey (HerMES) guaranteed time key programmes. Starting from a sample of galaxies with reliable star-formation rates (SFRs), stellar masses (M-) and redshift estimates, we grid the SFR-M-parameter space in several redshift ranges and estimate the mean dust temperature (Tdust) of each SFR-M--z bin. Dust temperatures are inferred using the stacked far-infrared flux densities (100-500 μm) of our SFR-M--z bins. At all redshifts, the dust temperature of galaxies smoothly increases with rest-frame infrared luminosities (LIR), specific SFRs (SSFR; i.e., SFR/M-), and distances with respect to the main sequence (MS) of the SFR-M- plane (i.e., Δlog (SSFR)MS = log [SSFR(galaxy)/SSFRMS(M-,z)]). The Tdust-SSFR and Tdust-Δlog (SSFR)MS correlations are statistically much more significant than the Tdust-LIR one. While the slopes of these three correlations are redshift-independent, their normalisations evolve smoothly from z = 0 and z ~ 2. We convert these results into a recipe to derive Tdust from SFR, M- and z, valid out to z ~ 2 and for the stellar mass and SFR range covered by our stacking analysis. The existence of a strong Tdust-Δlog (SSFR)MS correlation provides us with several pieces of information on the dust and gas content of galaxies. Firstly, the slope of the T dust-Δlog (SSFR)MS correlation can be explained by the increase in the star-formation efficiency (SFE; SFR/Mgas) with Δlog (SSFR)MS as found locally by molecular gas studies. Secondly, at fixed Δlog (SSFR)MS, the constant dust temperature observed in galaxies probing wide ranges in SFR and M- can be explained by an increase or decrease in the number of star-forming regions with comparable SFE enclosed in them. And thirdly, at high redshift, the normalisation towards hotter dust temperature of the Tdust-Δlog (SSFR)MS correlation can be explained by the decrease in the metallicities of galaxies or by the increase in the SFE of MS galaxies. All these results support the hypothesis that the conditions prevailing in the star-forming regions of MS and far-above-MS galaxies are different. MS galaxies have star-forming regions with low SFEs and thus cold dust, while galaxies situated far above the MS seem to be in a starbursting phase characterised by star-forming regions with high SFEs and thus hot dust. © 2014 ESO