R. Neri

Institut de Radioastronomie Millimétrique, Grenoble, Rhône-Alpes, France

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Publications (300)1322.22 Total impact

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    ABSTRACT: We present the first observations of H$^{13}$CN$(1-0)$, H$^{13}$CO$^+(1-0)$ and SiO$(2-1)$ in NGC 6240, obtained with the IRAM PdBI. Combining a Markov Chain Monte Carlo (MCMC) code with Large Velocity Gradient (LVG) modelling we derive posterior probability density functions (pdfs) for the dense gas parameters, including mass$-$luminosity conversion factors, finding a large amount of dense molecular gas $(\sim10^{10}M_\odot)$ in cold, dense clouds ($T_k\sim10$ K, $n_{{\rm H}_2}\sim10^6$ cm$^{-3}$) with a small volume filling factor $(<0.002)$. Including literature CO data we present simultaneously fitted multi-species, two phase models which spontaneously separate into a hot, diffuse phase ($\log_{10}\left(T_k / [{\rm K}]\right) = 3.2^{3.3}_{3.1}$, $\log_{10}\left(n_{{\rm H}_2} / [{\rm cm}^{-3}]\right)=3.6^{3.8}_{3.5}$) and a cold, dense phase ($\log_{10}\left(T_k / [{\rm K}]\right) = 0.9^{0.9}_{0.8}$, $\log_{10}\left(n_{{\rm H}_2} / [{\rm cm}^{-3}]\right)=6.6^{6.8}_{6.3}$). A restricted three phase model is used to include the ubiquitous diffuse, CO bearing gas phase and we derive a global $\alpha_{\rm CO}=1.5^{7.1}_{1.1}$ with gas masses $\log_{10}\left(M / [M_\odot]\right)=10.1_{10.0}^{10.8}$, dominated by the dense gas. We find that the [$^{12}$C]/[$^{13}$C] ratio is only slightly elevated ($98^{230}_{65}$), contrary to the very high [CO]/[$^{13}$CO] ratio (300-500) reported in the literature. The high [HCN]/[H$^{13}$CN] and [HCO$^+$]/[H$^{13}$CO$^+$] abundance ratios $(300^{500}_{200})$ we find are due to isotope fractionation in the cold, dense clouds.
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    ABSTRACT: Galaxy evolution scenarios predict that the feedback of star formation and nuclear activity (AGN) can drive the transformation of gas-rich spiral mergers into ULIRGs, and, eventually, lead to the build-up of QSO/elliptical hosts. We study the role that star formation and AGN feedback have in launching and maintaining the molecular outflows in two starburst-dominated advanced mergers, NGC1614 and IRAS17208-0014, by analyzing the distribution and kinematics of their molecular gas reservoirs. We have used the PdBI array to image with high spatial resolution (0.5"-1.2") the CO(1-0) and CO(2-1) line emissions in NGC1614 and IRAS17208-0014, respectively. The velocity fields of the gas are analyzed and modeled to find the evidence of molecular outflows in these sources and characterize the mass, momentum and energy of these components. While most (>95%) of the CO emission stems from spatially-resolved (~2-3kpc-diameter) rotating disks, we also detect in both mergers the emission from high-velocity line wings that extend up to +-500-700km/s, well beyond the estimated virial range associated with rotation and turbulence. The kinematic major axis of the line wing emission is tilted by ~90deg in NGC1614 and by ~180deg in IRAS17208-0014 relative to their respective rotating disk major axes. These results can be explained by the existence of non-coplanar molecular outflows in both systems. In stark contrast with NGC1614, where star formation alone can drive its molecular outflow, the mass, energy and momentum budget requirements of the molecular outflow in IRAS17208-0014 can be best accounted for by the existence of a so far undetected (hidden) AGN of L_AGN~7x10^11 L_sun. The geometry of the molecular outflow in IRAS17208-0014 suggests that the outflow is launched by a non-coplanar disk that may be associated with a buried AGN in the western nucleus.
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    ABSTRACT: We present high resolution (0."4) IRAM PdBI and ALMA mm and submm observations of the (Ultra) Luminous Infrared Galaxies ((U)LIRGs) IRAS17208-0014, Arp220, IC860 and Zw049.057 that reveal intense line emission from vibrationally excited (v2=1) J=3-2 and 4-3 HCN. The emission is emerging from buried, compact (r<17-70 pc) nuclei that have very high implied mid-infrared surface brightness >5e13 Lsun/kpc2. These nuclei are likely powered by accreting supermassive black holes (SMBHs) and/or hot (>200 K) extreme starbursts. Vibrational, v2=1, lines of HCN are excited by intense 14 micron mid-infrared emission and are excellent probes of the dynamics, masses and physical conditions of (U)LIRG nuclei when H2 column densities exceed 1e24 cm-2. It is clear that these lines open up a new interesting avenue to gain access to the most obscured AGNs and starbursts. Vibrationally excited HCN acts as a proxy for the absorbed mid-infrared emission from the embedded nuclei, which allows for reconstruction of the intrinsic, hotter dust SED. In contrast, the ground vibrational state (v=0), J=3-2 and 4-3 rotational lines of HCN and HCO+ fail to probe the highly enshrouded, compact nuclear regions due to strong self- and continuum absorption. The HCN and HCO+ line profiles are double-peaked because of the absorption and show evidence of non-circular motions - possibly in the form of in- or outflows. Detections of vibrationally excited HCN in external galaxies are so far limited to ULIRGs and early type spiral LIRGs and we discuss possible causes for this. We tentatively suggest that the peak of vibrationally excited HCN emission is connected to a rapid stage of nuclear growth, before the phase of strong feedback.
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    ABSTRACT: Aims. Our goal is to determine the molecular composition of the circumstellar disk around AB Aurigae (hereafter, AB Aur). AB Aur is a prototypical Herbig Ae star and the understanding of its disk chemistry is of paramount importance to understand the chemical evolution of the gas in warm disks. Methods. We used the IRAM 30-m telescope to perform a sensitive search for molecular lines in AB Aur as part of the IRAM Large program ASAI (A Chemical Survey of Sun-like Star-forming Regions). These data were complemented with interferometric observations of the HCO+ 1-0 and C17O 1-0 lines using the IRAM Plateau de Bure Interferometer (PdBI). Single-dish and interferometric data were used to constrain chemical models. Results. Throughout the survey, several lines of CO and its isotopologues, HCO+, H2CO, HCN, CN and CS, were detected. In addition, we detected the SO 54-33 and 56-45 lines, confirming the previous tentative detection. Comparing to other T Tauri's and Herbig Ae disks, AB Aur presents low HCN 3-2/HCO+ 3-2 and CN 2-1/HCN 3-2 line intensity ratios, similar to other transition disks. AB Aur is the only protoplanetary disk detected in SO thus far. Conclusions. We modeled the line profiles using a chemical model and a radiative transfer 3D code. Our model assumes a flared disk in hydrostatic equilibrium. The best agreement with observations was obtained for a disk with a mass of 0.01 Msun , Rin=110 AU, Rout=550 AU, a surface density radial index of 1.5 and an inclination of 27 deg. The intensities and line profiles were reproduced within a factor of 2 for most lines. This agreement is reasonable taking into account the simplicity of our model that neglects any structure within the disk. However, the HCN 3-2 and CN 2-1 line intensities were predicted more intense by a factor of >10. We discuss several scenarios to explain this discrepancy.
    Astronomy and Astrophysics 03/2015; 578. DOI:10.1051/0004-6361/201425347 · 4.48 Impact Factor
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    ABSTRACT: The high abundances of Complex Organic Molecules (COMs) with respect to methanol, the most abundant COM, detected towards 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 towards the two low-mass protostars NGC1333-IRAS2A and -IRAS4A with the Plateau de Bure interferometer at an angular resolution of 2 arcsec, resulting in the first multi-line detection of the O-bearing species glycolaldehyde and ethanol and of the N-bearing species ethyl cyanide towards 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 COMs column densities. The COMs abundances with respect to methanol derived towards IRAS2A and IRAS4A are slightly, but not substantitally, lower than those derived from previous single-dish observations. The COMs 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.
    The Astrophysical Journal 02/2015; 804(2). DOI:10.1088/0004-637X/804/2/81 · 6.28 Impact Factor
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    ABSTRACT: We present interferometric observations of the CN 1-0 (113.491 GHz), N2H+ 1-0 (93.173 GHz), H(41)a (92.034 GHz), CH3CN (91.987 GHz), CS 3-2 (146.969 GHz), c-C3H2 3-2 (145.089 GHz), H2CO 2-1 (145.603 GHz) and HC3N 16-15 (145.601 GHz) lines towards M82, carried out with the IRAM Plateau de Bure Interferometer (PdBI). PDR chemical modelling is used to interpret these observations. Our results show that the abundances of N2H+, CS and H13 CO+ remain quite constant across the galaxy confirming that these species are excellent tracers of the dense molecular gas. On the contrary, the abundance of CN increases by a factor of 3 in the inner x2 bar orbits. The [CN]/[N2 H+ ] ratio is well correlated with the H(41)a emission at all spatial scales down to 100 pc. Chemical modelling shows that the variations in the [CN]/[N2H+] ratio can be explained as the consequence of differences in the local intestellar UV field and in the average cloud sizes within the nucleus of the galaxy. Our high-spatial resolution imaging of the starburst galaxy M 82 shows that the star formation activity has a strong impact on the chemistry of the molecular gas. In particular, the entire nucleus behaves as a giant photon-dominated region (PDR) whose chemistry is determined by the local UV flux. The detection of N2H+ shows the existence of a population of clouds with Av >20 mag all across the galaxy plane. These clouds constitute the molecular gas reservoir for the formation of new stars and, although distributed all along the nucleus, the highest concentration occurs in the outer x1 bar orbits (R = 280 pc).
    Astronomy and Astrophysics 02/2015; 578. DOI:10.1051/0004-6361/201525653 · 4.48 Impact Factor
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    ABSTRACT: We present the results of interferometric spectral line observations of Arp 220 at 3.5mm and 1.2mm from the Plateau de Bure Interferometer (PdBI), imaging the two nuclear disks in H$^{13}$CN$(1 - 0)$ and $(3 - 2)$, H$^{13}$CO$^+(1 - 0)$ and $(3 - 2)$, and HN$^{13}$C$(3 - 2)$ as well as SiO$(2 - 1)$ and $(6 - 5)$, HC$^{15}$N$(3 - 2)$, and SO$(6_6 - 5_5)$. The gas traced by SiO$(6 - 5)$ has a complex and extended kinematic signature including a prominent P Cygni profile, almost identical to previous observations of HCO$^+(3 - 2)$. Spatial offsets $0.1''$ north and south of the continuum centre in the emission and absorption of the SiO$(6 - 5)$ P Cygni profile in the western nucleus (WN) imply a bipolar outflow, delineating the northern and southern edges of its disk and suggesting a disk radius of $\sim40$ pc, consistent with that found by ALMA observations of Arp 220. We address the blending of SiO$(6 - 5)$ and H$^{13}$CO$^+(3 - 2)$ by considering two limiting cases with regards to the H$^{13}$CO$^+$ emission throughout our analysis. Large velocity gradient (LVG) modelling is used to constrain the physical conditions of the gas and to infer abundance ratios in the two nuclei. Our most conservative lower limit on the [H$^{13}$CN]/[H$^{13}$CO$^+$] abundance ratio is 11 in the WN, cf. 0.10 in the eastern nucleus (EN). Comparing these ratios to the literature we argue on chemical grounds for an energetically significant AGN in the WN driving either X-ray or shock chemistry, and a dominant starburst in the EN.
    The Astrophysical Journal 12/2014; 800(1). DOI:10.1088/0004-637X/800/1/25 · 6.28 Impact Factor
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    ABSTRACT: We obtained high resolution (0."25 to 0."90) observations of HCN and HCO+ J=3-2 of the ultraluminous QSO galaxy Mrk231 with the IRAM Plateau de Bure Interferometer. We find luminous HCN and HCO+ 3-2 emission in the main disk and we detect compact (r<90 pc) vibrationally excited HCN 3-2, v2=1f emission centred on the nucleus. The velocity field of the vibrationally excited HCN is strongly inclined (PA=155 deg.) compared to the east-west rotation of the main disk. The nuclear molecular mass is estimated to 8e8 Msun with an average N(H2)of 1.2e24 cm-2. Prominent, spatially extended (>350 pc) line wings are found for HCN 3-2 with velocities +-750 km/s. Line ratios indicate that the emission is emerging in dense gas n=1e4 - 5e5 cm-3 of elevated HCN abundance X(HCN)=1e-8 to 1e-6. High X(HCN) also allows for the emission to originate in gas of more moderate density. We tentatively detect nuclear emission from the reactive ion HOC+ with HCO+/HOC+=10-20. The HCN v2=1f line emission is consistent with the notion of a hot, dusty, warped inner disk of Mrk231 where the v2=1f line is excited by bright mid-IR 14 micron continuum. We estimate the vibrational temperature T_vib to 200-400 K. We propose that 50% of the main HCN emission may have its excitation affected by the radiation field through IR pumping of the vibrational ground state. The HCN emission in the line wings, however, is more extended and thus likely not strongly affected by IR pumping. Our results reveal that dense clouds survive (and/or are formed) in the AGN outflow on scales of at least several hundred pc before evaporating or collapsing. The elevated HCN abundance in the outflow is consistent with warm chemistry possibly related to shocks and/or X-ray irradiated gas. An upper limit to the mass and momentum flux is 4e8 Msun and 12L_AGN/c, respectively, and we discuss possible driving mechanisms for the dense outflow.
    Astronomy and Astrophysics 11/2014; DOI:10.1051/0004-6361/201423987 · 4.48 Impact Factor
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    ABSTRACT: Past observations of QSO host galaxies at z >6 have found cold gas and star formation on compact scales of a few kiloparsecs. We present new high sensitivity IRAM PdBI follow-up observations of the [CII] 158micron emission line and FIR continuum in the host galaxy of SDSS J1148+5152, a luminous QSO at redshift 6.4189. We find that a large fraction of the gas traced by [CII] is at high velocities, up to ~1400 km/s relative to the systemic velocity, confirming the presence of a major quasar-driven outflow indicated by previous observations. The outflow has a complex morphology and reaches a maximum projected radius of ~30 kpc. The extreme spatial extent of the outflow allows us, for the first time in an external galaxy, to estimate mass-loss rate, kinetic power and momentum rate of the outflow as a function of the projected distance from the nucleus and the dynamical time-scale. These trends reveal multiple outflow events during the past 100 Myr, although the bulk of the mass, energy and momentum appear to have been released more recently, within the past ~20 Myr. Surprisingly, we discover that also the quiescent gas at systemic velocity is extremely extended. More specifically, we find that, while 30% of the [CII] within v\in(-200, 200) km/s traces a compact component that is not resolved by our observations, 70% of the [CII] emission in this velocity range is extended, with a projected FWHM size of 17.4+-1.4 kpc. We detect FIR continuum emission associated with both the compact and the extended [CII] components, although the extended FIR emission has a FWHM of 11+-2 kpc, thus smaller than the extended [CII] source. Overall, our results indicate that the cold gas traced by [CII] is distributed up to r~30 kpc. A large fraction of extended [CII] is likely associated with star formation on large scales, but the [CII] source extends well beyond the FIR continuum.
    Astronomy and Astrophysics 09/2014; 574. DOI:10.1051/0004-6361/201424980 · 4.48 Impact Factor
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    ABSTRACT: We report the serendipitous detection of the CO(17-16) emission line toward the quasar SDSSJ114816.64+525150.3 (J1148) at redshift z = 6.4 obtained with the Plateau de Bure Interferometer. The CO(17-16) line is possibly contaminated by OH+ emission, that may account for ~ 35 - 60% of the total flux observed. Photo-Dissociation and X-ray Dominated Regions (PDRs and XDRs) models show that PDRs alone cannot reproduce the high luminosity of the CO(17-16) line relative to low-J CO transitions and that XDRs are required. By adopting a composite PDR+XDR model we derive molecular cloud and radiation field properties in the nuclear region of J1148. Our results show that highly excited CO lines represent a sensitive and possibly unique tool to infer the presence of X-ray faint or obscured supermassive black hole progenitors in high-z galaxies.
    Monthly Notices of the Royal Astronomical Society 09/2014; 445(3). DOI:10.1093/mnras/stu2031 · 5.23 Impact Factor
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    ABSTRACT: We combine molecular gas masses inferred from CO emission in 500 star forming galaxies (SFGs) between z=0 and 3, from the IRAM-COLDGASS, PHIBSS1/2 and other surveys, with gas masses derived from Herschel far-IR dust measurements in 512 galaxy stacks over the same stellar mass/redshift range. We constrain the scaling relations of molecular gas depletion time scale (tdepl) and gas fraction (Mmolgas/M*) with redshift, specific star formation rate (sSFR) and stellar mass (M*) in SFGs. The CO- and dust-based scaling relations agree remarkably well. This suggests that the CO-H2 mass conversion factor varies little within +-0.6 dex of the main sequence line, and less than a factor of 2 throughout this redshift range. We find that tdepl scales as (1+z)^-0.3 *(sSFR)^-0.5, with no M* dependence. The resulting steep redshift dependence of Mmolgas/M* ~ (1+z)^3 mirrors that of the sSFR and probably reflects the gas supply rate. The decreasing gas fractions at high M* are driven by the flattening of the SFR-M* relation. At constant M*, a larger sSFR is due to a combination of an increasing gas fraction and a decreasing depletion time scale. As a result galaxy integrated samples of the Mmolgas-SFR rate relation exhibit a super-linear slope, which increases with the range of sSFR. With these new relations it is now possible to determine Mmolgas with an accuracy of +-0.1 dex in relative terms, and +-0.2 dex including systematic uncertainties.
    The Astrophysical Journal 09/2014; 800(1). DOI:10.1088/0004-637X/800/1/20 · 6.28 Impact Factor
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    ABSTRACT: The evolution of the cosmic star formation rate (SFR) is characterized by a peak around redshift z=2-3 and a subsequent drop by an order of magnitude. High levels of star formation are sustained by a continuous supply of fresh gas and high molecular gas fractions. But once galaxies exceed a certain mass or enter a harsh environment, star formation is quenched, and different phenomena could explain the resulting evolution of the cosmic SFR. Is it mostly driven by the available molecular gas, or because star formation processes are more efficient at high redshift? Here we present the results and the perspectives of the PHIBSS programs, which aim at understanding early galaxy evolution and the winding-down of star formation from the perspective of the galaxies' molecular gas reservoirs. These programs use statistically meaningful samples of galaxies belonging to the massive end of the star formation main-sequence at different redshifts. The previous IRAM PHIBSS program has already uncovered large molecular gas reservoirs at redshifts z∼1-2, with gas fractions 4 to 10 times higher than in the local Universe, and the ongoing IRAM and ALMA programs extend the sample to a wider range of redshifts and to a more complete sampling of the stellar mass-SFR plane. The IRAM PHIBSS2 legacy program is designed to make full use of the upcoming NOEMA capabilities.
    SF2A 2014; 06/2014
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    ABSTRACT: Context. The existence of disks around high-mass stars has yet to be established on a solid ground, as only few reliable candidates are known to date. The disk rotating about the similar to 10(4) L-circle dot protostar IRAS 20126+4104 is probably the most convincing of these. Aims. We would like to resolve the disk structure in IRAS 20126+4104 and, if possible, investigate the relationship between the disk and the associated jet emitted along the rotation axis. Methods. We performed observations at 1.4 mm with the IRAM Plateau de Bure interferometer attaining an angular resolution of similar to 0 ''.4 (similar to 660 AU). We imaged the methyl cyanide J = 12 -> 11 ground state and vibrationally excited transitions as well as the (CH3CN)-C-13 isotopologue, which had proved to be disk tracers. Results. Our findings confirm the existence of a disk rotating about a similar to 7-10 M-circle dot star in IRAS 20126+4104, with rotation velocity increasing at small radii. The dramatic improvement in sensitivity and spectral and angular resolution with respect to previous observations allows us to establish that higher excitation transitions are emitted closer to the protostar than the ground state lines, which demonstrates that the gas temperature is increasing towards the centre. We also find that the material is asymmetrically distributed in the disk and speculate on the possible origin of such a distribution. Finally, we demonstrate that the jet emitted along the disk axis is co-rotating with the disk. Conclusions. We present iron-clad evidence of the existence of a disk undergoing rotation around a B-type protostar, with rotation velocity increasing towards the centre. We also demonstrate that the disk is not axially symmetric. These results prove that B-type stars may form through disk-mediated accretion as their low-mass siblings do, but also show that the disk structure may be significantly perturbed by tidal interactions with (unseen) companions, even in a relatively poor cluster such as that associated with IRAS 20126+4104.
    Astronomy and Astrophysics 06/2014; 566. DOI:10.1051/0004-6361/201323065 · 4.48 Impact Factor
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    ABSTRACT: We present ALMA observations of the [CII] line and far-infrared (FIR) continuum of a normally star-forming galaxy in the reionization epoch, the z=6.96 Ly-alpha emitter (LAE) IOK-1. Probing to sensitivities of sigma_line = 240 micro-Jy/beam (40 km/s channel) and sigma_cont = 21 micro-Jy/beam, we found the galaxy undetected in both [CII] and continuum. Comparison of UV - FIR spectral energy distribution (SED) of IOK-1, including our ALMA limit, with those of several types of local galaxies (including the effects of the cosmic microwave background, CMB, on the FIR continuum) suggests that IOK-1 is similar to local dwarf/irregular galaxies in SED shape rather than highly dusty/obscured galaxies. Moreover, our 3 sigma FIR continuum limit, corrected for CMB effects, implies intrinsic dust mass M_dust < 6.4 x 10^7 M_sun, FIR luminosity L_FIR < 3.7 x 10^{10} L_sun (42.5 - 122.5 micron), total IR luminosity L_IR < 5.7 x 10^{10} L_sun (8 - 1000 micron) and dust-obscured star formation rate (SFR) < 10 M_sun/yr, if we assume that IOK-1 has a dust temperature and emissivity index typical of local dwarf galaxies. This SFR is 2.4 times lower than one estimated from the UV continuum, suggesting that < 29% of the star formation is obscured by dust. Meanwhile, our 3 sigma [CII] flux limit translates into [CII] luminosity, L_[CII] < 3.4 x 10^7 L_sun. Locations of IOK-1 and previously observed LAEs on the L_[CII] vs. SFR and L_[CII]/L_FIR vs. L_FIR diagrams imply that LAEs in the reionization epoch have significantly lower gas and dust enrichment than AGN-powered systems and starbursts at similar/lower redshifts, as well as local star-forming galaxies.
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    ABSTRACT: We present ALMA observations of the [CII] line and far-infrared (FIR) continuum of a normally star-forming galaxy in the reionization epoch, the z=6.96 Ly-alpha emitter (LAE) IOK-1. Probing to sensitivities of sigma_line = 240 micro-Jy/beam (40 km/s channel) and sigma_cont = 21 micro-Jy/beam, we found the galaxy undetected in both [CII] and continuum. Comparison of UV - FIR spectral energy distribution (SED) of IOK-1, including our ALMA limit, with those of several types of local galaxies (including the effects of the cosmic microwave background, CMB, on the FIR continuum) suggests that IOK-1 is similar to local dwarf/irregular galaxies in SED shape rather than highly dusty/obscured galaxies. Moreover, our 3 sigma FIR continuum limit, corrected for CMB effects, implies intrinsic dust mass M_dust < 6.4 x 10^7 M_sun, FIR luminosity L_FIR < 3.7 x 10^{10} L_sun (42.5 - 122.5 micron), total IR luminosity L_IR < 5.7 x 10^{10} L_sun (8 - 1000 micron) and dust-obscured star formation rate (SFR) < 10 M_sun/yr, if we assume that IOK-1 has a dust temperature and emissivity index typical of local dwarf galaxies. This SFR is 2.4 times lower than one estimated from the UV continuum, suggesting that < 29% of the star formation is obscured by dust. Meanwhile, our 3 sigma [CII] flux limit translates into [CII] luminosity, L_[CII] < 3.4 x 10^7 L_sun. Locations of IOK-1 and previously observed LAEs on the L_[CII] vs. SFR and L_[CII]/L_FIR vs. L_FIR diagrams imply that LAEs in the reionization epoch have significantly lower gas and dust enrichment than AGN-powered systems and starbursts at similar/lower redshifts, as well as local star-forming galaxies.
    The Astrophysical Journal 04/2014; 792(1). DOI:10.1088/0004-637X/792/1/34 · 6.28 Impact Factor
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    ABSTRACT: A class of post-AGB/protoplanetary objects are characterized by their low-mass nebula and NIR excess, probably indicative of dust kept close to the central star. We performed deep systematic observations of CO line emission in them. Almost all sources have been detected and show characteristic profiles that, both from theoretical and observational grounds, are known to be very good indicators of rotating disks. We conclude that, very probably, extended rotating disks are systematically present in this class of post-AGB objects. The main properties of the disks (mass, size, dynamics) are estimated, in particular they show a moderate mass of ~ 1e-3 - 1e-2 solar mass. Our observations also show that slow outflows (~ 10 km/s) coexist with the rotating disk in many of these objects, probably in all them. In general they represent a small fraction of the nebular mass, but can be dominant in some cases. Recent high-quality ALMA maps have shown the complex structure of the best studied source, the Red Rectangle. The equatorial disk and the outflow are accurately described. In particular we suggest that the expanding gas has been pulled away from the disk, probably by interaction with the collimated and fast post-AGB jets.
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    ABSTRACT: Aims. We investigate the different manifestations of AGN feedback in the evolved, powerful radio source 3C293 and their impact on the molecular gas of its host galaxy, which harbors young star-forming regions and fast outflows of HI and ionized gas. Methods. We study the distribution and kinematics of the molecular gas of 3C293 using high spatial resolution observations of the CO(1-0) and CO(2-1) lines, and the 3 and 1mm continuum taken with the IRAM PdBI. We mapped the molecular gas of 3C293 and compared it with the dust and star-formation images of the host. We searched for signatures of outflow motions in the CO kinematics, and reexamined the evidence of outflowing gas in the HI spectra. We also derived the star formation rate (SFR) and efficiency (SFE) of the host with all available SFR tracers from the literature, and compared them with the SFE of young and evolved radio galaxies and normal star-forming galaxies. Results. The CO(1-0) emission line shows that the molecular gas in 3C293 is distributed along a massive (2.2E10 Msun) warped disk with diameter of 21 kpc that rotates around the AGN. Our data show that the dust and the star formation are clearly associated with the CO disk. The CO(2-1) emission is located in the inner 7 kpc (diameter) region around the AGN, coincident with the inner part of the CO(1-0) disk. Both the CO(1-0) and CO(2-1) spectra reveal the presence of an absorber against the central regions of 3C293 that is associated with the disk. We do not detect any fast (>500 km/s) outflow motions in the cold molecular gas. The host of 3C293 shows an SFE consistent with the Kennicutt-Schmidt law. The apparently low SFE of evolved radio galaxies may be caused by an underestimation of the SFR and/or an overestimation of the molecular gas densities in these sources. We find no signatures of AGN feedback in the molecular gas of 3C293.
    Astronomy and Astrophysics 02/2014; 564. DOI:10.1051/0004-6361/201323123 · 4.48 Impact Factor
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    ABSTRACT: We study the properties of the interstellar medium in the interacting system BR1202-0725 at z=4.7 via its [NII] and [CII] fine-structure line emission. This system consists of a QSO, a sub-mm galaxy (SMG), and two Ly-alpha emitters (LAEs). Such a diversity in galaxy properties makes BR1202-0725 a unique laboratory of star formation and galaxy evolution at high redshift. We present ionized nitrogen ([NII] 205 micron) observations of this system, obtained with the IRAM Plateau de Bure Interferometer. We find no [NII] emission at the quasar location, but tentative [NII] line detections associated with the SMG and one of the LAEs. Together with available ionized carbon ([CII] 158 micron) ALMA observations of this system, we find the following: The [CII]/[NII] luminosity ratio is >5.5 for the QSO and the SMG, but it is as low as ~2 in the LAE, suggesting that, in this source, most of the [CII] emission is associated with the ionized medium (HII regions) rather than the neutral one (PDRs). This study demonstrates the importance of combined studies of multiple fine--structure lines in order to pin down the physical properties of the interstellar medium in distant galaxies.
    The Astrophysical Journal Letters 01/2014; 782(2). DOI:10.1088/2041-8205/782/2/L17 · 5.60 Impact Factor
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    ABSTRACT: We report ALMA observations of CO(3-2) emission in the Seyfert 1 galaxy NGC 1566, at a spatial resolution of 25 pc. Our aim is to investigate the morphology and dynamics of the gas inside the central kpc, and to probe nuclear fueling and feedback phenomena. NGC 1566 has a nuclear bar of 1.7 kpc radius and a conspicuous grand design spiral starting from this radius. The ALMA field of view, of diameter 0.9 kpc, lies well inside the nuclear bar and reveals a molecular trailing spiral structure of \sim 100 pc in size, which is possibly fueling the nucleus. The spiral starts with a large pitch angle from the center and then winds up in a pseudo-ring at the inner Lindblad resonance (ILR) of the nuclear bar. This is the first time that a trailing spiral structure is clearly seen driving the gas inwards inside the ILR ring of the nuclear bar. This phenomenon shows that the massive central black hole has a significant dynamical influence on the gas, triggering its fueling. The gaseous spiral is well correlated with the dusty spiral seen through extinction in HST images, and also with a spiral feature emitting 0.87mm continuum. This continuum emission must come essentially from cold dust heated by the interstellar radiation field. The HCN(4-3) and HCO+(4-3) lines were simultaneously mapped and detected in the nuclear spiral. The HCO+(4-3) line is 3 times stronger than the HCN(4-3), as expected when star formation excitation dominates over active galactic nucleus (AGN) heating. The CO(3-2)/HCO+(4-3) integrated intensity ratio is \sim 100. The molecular gas is in remarkably regular rotation, with only slight non-circular motions at the periphery of the nuclear spiral arms. These perturbations are quite small, and no outflow nor AGN feedback is detected.
    Astronomy and Astrophysics 01/2014; 565. DOI:10.1051/0004-6361/201423433 · 4.48 Impact Factor
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    ABSTRACT: We present the search for the [CII] emission line in three $z>6.5$ Lyman-alpha emitters (LAEs) and one J-Dropout galaxy using the Combined Array for Research in Millimeter-wave Astronomy (CARMA) and the Plateau de Bure Interferometer (PdBI). We observed three bright $z\sim6.5-7$ LAEs discovered in the SUBARU deep field (SDF) and the Multiple Imaged lensed $z\sim 11$ galaxy candidate found behind the galaxy cluster MACSJ0647.7+7015. For the LAEs IOK-1 ($z=6.965$), SDF J132415.7+273058 ($z=6.541$) and SDF J132408.3+271543 ($z=6.554$) we find upper limits for the [CII] line luminosity of $<2.05$, $<4.52$ and $<10.56\times10^{8}{\rm L}_{\odot}$ respectively. We find upper limits to the FIR luminosity of the galaxies using a spectral energy distribution template of the local galaxy NGC 6946 and taking into account the effects of the Cosmic Microwave Background on the mm observations. For IOK-1, SDF J132415.7+273058 and SDF J132408.3+271543 we find upper limits for the FIR luminosity of $<2.33$, $3.79$ and $7.72\times10^{11}{\rm L}_{\odot}$ respectively. For the lensed galaxy MACS0647-JD, one of the highest redshift galaxy candidate to date with $z_{\rm ph}=10.7^{+0.6}_{-0.4}$ we put an upper limit in the [CII] emission of $<1.36\times10^{8}\times(\mu/15)^{-1}{\rm L}_{\odot}$ and an upper limit in the FIR luminosity of $<6.1\times10^{10}\times(\mu/15)^{-1}{\rm L}_{\odot}$ (where $\mu$ is the magnification factor). We explore the different conditions relevant for the search for [CII] emission in high redshift galaxies as well as the difficulties for future observations with ALMA and CCAT.
    The Astrophysical Journal 01/2014; 784(2). DOI:10.1088/0004-637X/784/2/99 · 6.28 Impact Factor

Publication Stats

6k Citations
1,322.22 Total Impact Points

Institutions

  • 1991–2015
    • Institut de Radioastronomie Millimétrique
      Grenoble, Rhône-Alpes, France
  • 2014
    • National Astronomical Observatory of Japan
      Edo, Tōkyō, Japan
    • Hospital Universitario Henares
      Madrid, Madrid, Spain
  • 2013
    • Max Planck Institute for Radio Astronomy
      Bonn, North Rhine-Westphalia, Germany
    • University of Maryland, College Park
      • Department of Astronomy
      Maryland, United States
    • Cornell University
      • Department of Astronomy
      Ithaca, New York, United States
  • 2012
    • Saint Martin's University
      Мариго, Saint Martin
    • Imperial College London
      • Department of Physics
      Londinium, England, United Kingdom
  • 2011
    • University of Portsmouth
      • Institute of Cosmology and Gravitation ICG
      Portsmouth, England, United Kingdom
    • University of Padova
      • Department of Physics and Astronomy "Galileo Galilei"
      Padua, Veneto, Italy
  • 2003–2009
    • National Radio Astronomy Observatory
      Charlottesville, Virginia, United States
  • 2007
    • University of Bonn
      Bonn, North Rhine-Westphalia, Germany
  • 2006
    • Harvard-Smithsonian Center for Astrophysics
      • Smithsonian Astrophysical Observatory
      Cambridge, Massachusetts, United States
  • 2004
    • University of Cologne
      Köln, North Rhine-Westphalia, Germany
  • 2002
    • Spanish National Research Council
      • Department of Molecular Physics
      Madrid, Madrid, Spain
  • 1999
    • University of Massachusetts Amherst
      Amherst Center, Massachusetts, United States
  • 1988–1990
    • University of Tuebingen
      Tübingen, Baden-Württemberg, Germany