[en] IRAM operates two observatories - the 30-meter Telescope on Pico Veleta in Spain and NOEMA, an interferometer of ten 15-meter antennas on Plateau de Bure in France. Both observatories allow to observe at millimeter wavelengths. Here, we aim at discussing the complementary between continuum observations with NOEMA and NIKA2 at the 30m and their role at the cutting edge of research in astronomy. In particular, we will review possible synergies of continuum studies from nearby star forming regions to high red-shift galaxies at cosmological distances.

[en] The high abundances of Complex Organic Molecules (COMs) with respect to methanol, the most abundant COM, detected toward low-mass protostars, tend to be underpredicted by astrochemical models. This discrepancy might come from the large beam of the single-dish telescopes, encompassing several components of the studied protostar, commonly used to detect COMs. To address this issue, we have carried out multi-line observations of methanol and several COMs toward the two low-mass protostars NGC 1333-IRAS 2A and -IRAS 4A with the Plateau de Bure interferometer at an angular resolution of 2″, resulting in the first multi-line detection of the O-bearing species glycolaldehyde and ethanol and of the N-bearing species ethyl cyanide toward low-mass protostars other than IRAS 16293. The high number of detected transitions from COMs (more than 40 methanol transitions for instance) allowed us to accurately derive the source size of their emission and the COM column densities. The COM abundances with respect to methanol derived toward IRAS 2A and IRAS 4A are slightly, but not substantitally, lower than those derived from previous single-dish observations. The COM abundance ratios do not vary significantly with the protostellar luminosity, over five orders of magnitude, implying that low-mass hot corinos are quite chemically rich as high-mass hot cores. Astrochemical models still underpredict the abundances of key COMs, such as methyl formate or di-methyl ether, suggesting that our understanding of their formation remains incomplete

[en] We report the detection of 23 OH⁺ 1 → 0 absorption, emission, or P-Cygni-shaped lines and CO(J = 9→8) emission lines in 18 Herschel-selected z = 2–6 starburst galaxies with the Atacama Large Millimeter/submillimeter Array and the NOrthern Extended Millimeter Array, taken as part of the Gas And Dust Over cosmic Time Galaxy Survey. We find that the CO(J = 9→8) luminosity is higher than expected based on the far-infrared luminosity when compared to nearby star-forming galaxies. Together with the strength of the OH⁺ emission components, this may suggest that shock excitation of warm, dense molecular gas is more prevalent in distant massive dusty starbursts than in nearby star-forming galaxies on average, perhaps due to an impact of galactic winds on the gas. OH⁺ absorption is found to be ubiquitous in massive high-redshift starbursts, and is detected toward 89% of the sample. The majority of the sample shows evidence for outflows or inflows based on the velocity shifts of the OH⁺ absorption/emission, with a comparable occurrence rate of both at the resolution of our observations. A small subsample appears to show outflow velocities in excess of their escape velocities. Thus, starburst-driven feedback appears to be important in the evolution of massive galaxies in their most active phases. We find a correlation between the OH⁺ absorption optical depth and the dust temperature, which may suggest that warmer starbursts are more compact and have higher cosmic-ray energy densities, leading to more efficient OH⁺ ion production. This is in agreement with a picture in which these high-redshift galaxies are “scaled-up” versions of the most intense nearby starbursts.

[en] One serious challenge for planet formation is the rapid inward drift of pebble-sized dust particles in protoplanetary disks. Dust trapping at local maxima in the disk gas pressure has received much theoretical attention but still lacks observational support. The cold dust emission in the AB Aur disk forms an asymmetric ring at a radius of about 120 au, which is suggestive of dust trapping in a gas vortex. We present high spatial resolution (0.″58 × 0.″78 ≈ 80 × 110 au) NOEMA observations of the 1.12 mm and 2.22 mm dust continuum emission from the AB Aur disk. Significant azimuthal variations of the flux ratio at both wavelengths indicate a size segregation of the large dust particles along the ring. Our continuum images also show that the intensity variations along the ring are smaller at 2.22 mm than at 1.12 mm, contrary to what dust trapping models with a gas vortex have predicted. Our two-fluid (gas+dust) hydrodynamical simulations demonstrate that this feature is well explained if the gas vortex has started to decay due to turbulent diffusion, and dust particles are thus losing the azimuthal trapping on different timescales depending on their size. The comparison between our observations and simulations allows us to constrain the size distribution and the total mass of solid particles in the ring, which we find to be of the order of 30 Earth masses, enough to form future rocky planets.

[en] We have imaged CO(J = 7 → 6) and C I(³ P ₂ → ³ P ₁) emission in the host galaxy of the z = 6.42 quasar SDSS J114816.64+525150.3 (hereafter J1148+5251) through observations with the Plateau de Bure Interferometer. The region showing CO(J = 7 → 6) emission is spatially resolved, and its size of 5 kpc is in good agreement with earlier CO(J = 3 → 2) observations. In combination with a revised model of the collisional line excitation in this source, this indicates that the highly excited molecular gas traced by the CO J = 7 → 6 line is subthermally excited (showing only 58% ± 8% of the CO J = 3 → 2 luminosity), but not more centrally concentrated. We also detect C I(³ P ₂ → ³ P ₁) emission in the host galaxy of J1148+5251, but the line is too faint to enable a reliable size measurement. From the C I(³ P ₂ → ³ P ₁) line flux, we derive a total atomic carbon mass of M_CI = 1.1 x10⁷ M _sun, which corresponds to ∼5 x 10^-4 times the total molecular gas mass. We also searched for H₂O(J_KaKc = 2₁₂ → 1₀₁) emission, and obtained a sensitive line luminosity limit of L^'_H2O< 4.4 x 10⁹ K km s^-1 pc², i.e., <15% of the CO(J = 3 → 2) luminosity. The warm, highly excited molecular gas, atomic gas and dust in this quasar host at the end of cosmic reionization maintain an intense starburst that reaches surface densities as high as predicted by (dust opacity) Eddington limited star formation over kiloparsec scales.

[en] We report the detection of CO J = 2→1, 5→4, and 6→5 emission in the highest-redshift submillimeter galaxy (SMG) AzTEC-3 at z = 5.298, using the Expanded Very Large Array and the Plateau de Bure Interferometer. These observations ultimately confirm the redshift, making AzTEC-3 the most submillimeter-luminous galaxy in a massive z ≅ 5.3 protocluster structure in the COSMOS field. The strength of the CO line emission reveals a large molecular gas reservoir with a mass of 5.3 x 10¹⁰(α_CO/0.8) M _sun, which can maintain the intense 1800 M _sun yr^-1 starburst in this system for at least 30 Myr, increasing the stellar mass by up to a factor of six in the process. This gas mass is comparable to 'typical' z ∼ 2 SMGs and constitutes ∼>80% of the baryonic mass (gas+stars) and 30%-80% of the total (dynamical) mass in this galaxy. The molecular gas reservoir has a radius of <4 kpc and likely consists of a 'diffuse', low-excitation component, containing (at least) 1/3 of the gas mass (depending on the relative conversion factor α_CO), and a 'dense', high-excitation component, containing ∼2/3 of the mass. The likely presence of a substantial diffuse component besides highly excited gas suggests different properties between the star-forming environments in z > 4 SMGs and z > 4 quasar host galaxies, which perhaps trace different evolutionary stages. The discovery of a massive, metal-enriched gas reservoir in an SMG at the heart of a large z = 5.3 protocluster considerably enhances our understanding of early massive galaxy formation, pushing back to a cosmic epoch where the universe was less than 1/12 of its present age.

[en] We present a detailed study of the molecular gas content and stellar population properties of three massive galaxies at 1 < z < 1.3 that are in different stages of quenching. The galaxies were selected to have quiescent optical/near-infrared spectral energy distribution and relatively bright emission at 24 μm, and show remarkably diverse properties. CO emission from each of the three galaxies is detected in deep NOEMA observations, allowing us to derive molecular gas fractions M _gas/M _* of 13%–23%. We also reconstruct the star formation histories by fitting models to the observed photometry and optical spectroscopy, finding evidence for recent rejuvenation in one object, slow quenching in another, and rapid quenching in the third system. To better constrain the quenching mechanism we explore the depletion times for our sample and other similar samples at z ∼ 0.7 from the literature. We find that the depletion times are highly dependent on the method adopted to measure the star formation rate: using the UV+IR luminosity we obtain depletion times about 6 times shorter than those derived using dust-corrected [O ii] emission. When adopting the star formation rates from spectral fitting, which are arguably more robust, we find that recently quenched galaxies and star-forming galaxies have similar depletion times, while older quiescent systems have longer depletion times. These results offer new, important constraints for physical models of galaxy quenching.

[en] We report on the results of a search for serendipitous sources in CO emission in 110 cubes targeting CO(2 − 1), CO(3 − 2), and CO(6 − 5) at z ∼ 1–2 from the second Plateau de Bure High-z Blue Sequence Survey (PHIBSS2). The PHIBSS2 observations were part of a 4 yr legacy program at the IRAM Plateau de Bure Interferometer aimed at studying early galaxy evolution from the perspective of molecular gas reservoirs. We present a catalog of 67 candidate secondary sources from this search, with 45 of the 110 data cubes showing sources in addition to the primary target that appear to be field detections, unrelated to the central sources. This catalog includes redshifts, line widths, and fluxes, as well as an estimation of their reliability based on their false-positive probability. We perform a search in the 3D Hubble Space Telescope/CANDELS catalogs for the secondary CO detections and tentatively find that ∼64% of these have optical counterparts, which we use to constrain their redshifts. Finally, we use our catalog of candidate CO detections to derive the CO(2 − 1), CO(3 − 2), CO(4 − 3), CO(5 − 4), and CO(6 − 5) luminosity functions over a range of redshifts, as well as the molecular gas mass density evolution. Despite the different methodology, these results are in very good agreement with previous observational constraints derived from blind searches in deep fields. They provide an example of the type of “deep-field” science that can be carried out with targeted observations.

[en] We present new millimeter and radio observations of nine z ∼ 6 quasars discovered in deep optical and near-infrared surveys. We observed the 250 GHz continuum in eight of the nine objects and detected three of them. New 1.4 GHz radio continuum data have been obtained for four sources, and one has been detected. We searched for molecular CO (6-5) line emission in the three 250 GHz detections and detected two of them. Combined with previous millimeter and radio observations, we study the far-infrared (FIR) and radio emission and quasar-host galaxy evolution with a sample of 18 z ∼ 6 quasars that are faint at UV and optical wavelengths (rest-frame 1450 A magnitudes of m₁₄₅₀ ≥ 20.2). The average FIR-to-active galactic nucleus (AGN) UV luminosity ratio of this faint quasar sample is about two times higher than that of the bright quasars at z ∼ 6 (m₁₄₅₀ < 20.2). A fit to the average FIR and AGN bolometric luminosities of both the UV/optically faint and bright z ∼ 6 quasars, and the average luminosities of samples of submillimeter/millimeter-observed quasars at z ∼ 2-5, yields a relationship of L_FIR ∼ L_bol^0.62. Five of the 18 faint z ∼ 6 quasars have been detected at 250 GHz. These 250 GHz detections, as well as most of the millimeter-detected optically bright z ∼ 6 quasars, follow a shallower trend of L_FIR ∼ L_bol^0.45 defined by the starburst-AGN systems in local and high-z universe. The millimeter continuum detections in the five objects and molecular CO detections in three of them reveal a few x 10⁸ M_sun of FIR-emitting warm dust and 10¹⁰ M_sun of molecular gas in the quasar host galaxies. All these results argue for massive star formation in the quasar host galaxies, with estimated star formation rates of a few hundred M_sun yr^-1. Additionally, the higher FIR-to-AGN luminosity ratio found in these 250 GHz detected faint quasars also suggests a higher ratio between star formation rate and supermassive black hole accretion rate than the UV/optically most luminous quasars at z ∼ 6.

[en] We report new IRAM/PdBI, JCMT/SCUBA-2, and VLA observations of the ultraluminous quasar SDSS J010013.02+280225.8 (hereafter, J0100+2802) at z = 6.3, which hosts the most massive supermassive black hole (SMBH), $1.24\times <!--\; ??\; -->{10}^{10}{M}_{\odot <!--\; ???\; -->}$, that is known at z > 6. We detect the [C ii] 158 μm fine structure line and molecular CO(6-5) line and continuum emission at 353, 260, and 3 GHz from this quasar. The CO(2-1) line and the underlying continuum at 32 GHz are also marginally detected. The [C ii] and CO detections suggest active star formation and highly excited molecular gas in the quasar host galaxy. The redshift determined with the [C ii] and CO lines shows a velocity offset of $\sim <!--\; ???\; -->1000\mathrm{k}\mathrm{m}{\mathrm{s}}^{-<!--\; ???\; -->1}$ from that measured with the quasar Mg ii line. The CO (2-1) line luminosity provides a direct constraint on the molecular gas mass, which is about $(1.0\pm <!--\; ??\; -->0.3)\times <!--\; ??\; -->{10}^{10}{M}_{\odot <!--\; ???\; -->}$. We estimate the FIR luminosity to be $(3.5\pm <!--\; ??\; -->0.7)\times <!--\; ??\; -->{10}^{12}{L}_{\odot <!--\; ???\; -->}$, and the UV-to-FIR spectral energy distribution of J0100+2802 is consistent with the templates of the local optically luminous quasars. The derived [C ii]-to-FIR luminosity ratio of J0100+2802 is 0.0010 ± 0.0002, which is slightly higher than the values of the most FIR luminous quasars at z ∼ 6. We investigate the constraint on the host galaxy dynamical mass of J0100+2802 based on the [C ii] line spectrum. It is likely that this ultraluminous quasar lies above the local SMBH–galaxy mass relationship, unless we are viewing the system at a small inclination angle.