Atomic Diagnostics of X-ray Irradiated Protoplanetary Disks

We study atomic line diagnostics of the inner regions of protoplanetary disks with our model of X-ray irradiated disk atmospheres which was previously used to predict observable levels of the NeII and NeIII fine-structure transitions at 12.81 and 15.55mum. We extend the X-ray ionization theory to sulfur and calculate the fraction of sulfur in S, S+, S2+ and sulfur molecules. For the D'Alessio generic T Tauri star disk, we find that the SI fine-structure line at 25.55mum is below the detection level of the Spitzer Infrared Spectrometer (IRS), in large part due to X-ray ionization of atomic S at the top of the atmosphere and to its incorporation into molecules close to the mid-plane. We predict that observable fluxes of the SII 6718/6732AA forbidden transitions are produced in the upper atmosphere at somewhat shallower depths and smaller radii than the neon fine-structure lines. This and other forbidden line transitions, such as the OI 6300/6363AA and the CI 9826/9852AA lines, serve as complementary diagnostics of X-ray irradiated disk atmospheres. We have also analyzed the potential role of the low-excitation fine-structure lines of CI, CII, and OI, which should be observable by SOFIA and Herschel.Comment: Accepted by Ap

Black hole accretion and star formation as drivers of gas excitation and chemistry in Mrk231

We present a full high resolution SPIRE FTS spectrum of the nearby ultraluminous infrared galaxy Mrk231. In total 25 lines are detected, including CO J=5-4 through J=13-12, 7 rotational lines of H2O, 3 of OH+ and one line each of H2O+, CH+, and HF. We find that the excitation of the CO rotational levels up to J=8 can be accounted for by UV radiation from star formation. However, the approximately flat luminosity distribution of the CO lines over the rotational ladder above J=8 requires the presence of a separate source of excitation for the highest CO lines. We explore X-ray heating by the accreting supermassive black hole in Mrk231 as a source of excitation for these lines, and find that it can reproduce the observed luminosities. We also consider a model with dense gas in a strong UV radiation field to produce the highest CO lines, but find that this model strongly overpredicts the hot dust mass in Mrk231. Our favoured model consists of a star forming disk of radius 560 pc, containing clumps of dense gas exposed to strong UV radiation, dominating the emission of CO lines up to J=8. X-rays from the accreting supermassive black hole in Mrk231 dominate the excitation and chemistry of the inner disk out to a radius of 160 pc, consistent with the X-ray power of the AGN in Mrk231. The extraordinary luminosity of the OH+ and H2O+ lines reveals the signature of X-ray driven excitation and chemistry in this region.Comment: 5 pages, 2 figures, accepted for publication in Astronomy & Astrophysics Special Issue on Herschel first result

Household Water Supply Strategies in Urban Bandung, Indonesia: Findings and Implications for Future Water Access Reporting

Through structured interviews and statistical analyses, this study investigated access to water and strategies of 1227 vulnerable households in Bandung, Indonesia. The use of mixed water sources, household water treatment, and home storage suggest low trust in improved sources, and compromised safety and reliability of water. While official statistics suggest a high level of access to improved water sources, full-time access to such sources is overestimated. Integration of user behavior into the new monitoring approach for the water supply sector in the post-2015 development framework is proposed

ALMA Observations of Warm Molecular Gas and Cold Dust in NGC 34

We present ALMA Cycle-0 observations of the CO (6-5) line emission (rest-frame frequency = 691.473 GHz) and of the 435$\mu m$ dust continuum emission in the nuclear region of NGC 34, a local luminous infrared galaxy (LIRG) at a distance of 84 Mpc (1" = 407 pc) which contains a Seyfert 2 active galactic nucleus (AGN) and a nuclear starburst. The CO emission is well resolved by the ALMA beam ($\rm 0."26\times 0."23$), with an integrated flux of $\rm f_{CO~(6-5)} = 1004\; (\pm 151) \; Jy\; km\; s^{-1}$. Both the morphology and kinematics of the CO (6-5) emission are rather regular, consistent with a compact rotating disk with a size of 200 pc. A significant emission feature is detected on the red-shifted wing of the line profile at the frequency of the $\rm H^{13}CN\; (8-7)$ line, with an integrated flux of $\rm 17.7 \pm 2.1 (random) \pm 2.7 (sysmatic)\; Jy\;km\; s^{-1}$. However, it cannot be ruled out that the feature is due to an outflow of warm dense gas with a mean velocity of $\rm 400\; km\; s^{-1}$. The continuum is resolved into an elongated configuration, and the observed flux corresponds to a dust mass of $\rm M_{dust} = 10^{6.97\pm 0.13}\; M_{sun}$. An unresolved central core ($\rm radius \simeq 50\; pc$) contributes $28\%$ of the continuum flux and $19\%$ of the CO (6-5) flux, consistent with insignificant contributions of the AGN to both emissions. Both the CO (6-5) and continuum spatial distributions suggest a very high gas column density ($\rm >= 10^4\; M_{sun}\; pc^{-2}$) in the nuclear region at $\rm radius <= 100\; pc$.Comment: 10 pages, 13 figures, accepted for publication in Astrophysical Journa

Extended [CII] Emission in Local Luminous Infrared Galaxies

We present Herschel/PACS observations of extended [CII]157.7{\mu}m line emission detected on ~ 1 - 10 kpc scales in 60 local luminous infrared galaxies (LIRGs) from the Great Observatories All-sky LIRG Survey (GOALS). We find that most of the extra-nuclear emission show [CII]/FIR ratios >~ 4 x 10^-3, larger than the mean ratio seen in the nuclei, and similar to those found in the extended disks of normal star-forming galaxies and the diffuse inter-stellar medium (ISM) of our Galaxy. The [CII] "deficits" found in the most luminous local LIRGs are therefore restricted to their nuclei. There is a trend for LIRGs with warmer nuclei to show larger differences between their nuclear and extra-nuclear [CII]/FIR ratios. We find an anti-correlation between [CII]/FIR and the luminosity surface density, {\Sigma}_IR, for the extended emission in the spatially-resolved galaxies. However, there is an offset between this trend and that found for the LIRG nuclei. We use this offset to derive a beam filling-factor for the star-forming regions within the LIRG disks of ~ 6 % relative to their nuclei. We confront the observed trend to photo-dissociation region (PDR) models and find that the slope of the correlation is much shallower than the model predictions. Finally, we compare the correlation found between [CII]/FIR and {\Sigma}_IR with measurements of high-redshift starbursting IR-luminous galaxies.Comment: Accepted for publication in ApJ Letters. 5 pages, 2 figure

CI observations in the CQ Tau proto-planetary disk: evidence for a very low gas-to-dust ratio ?

Gas and dust dissipation processes of proto-planetary disks are hardly known. Transition disks between Class II (proto-planetary disks) and Class III (debris disks) remain difficult to detect. We investigate the carbon chemistry of the peculiar CQ Tau gas disk. It is likely a transition disk because it exhibits weak CO emission with a relatively strong millimeter continuum, indicating that the disk might be currently dissipating its gas content. We used APEX to observe the two CI lines at 492GHz and 809 GHz in the disk orbiting CQ Tau. We compare the observations to several chemical model predictions. We focus our study on the influence of the stellar UV radiation shape and gas-to-dust ratio. We did not detect the CI lines. However, our upper limits are deep enough to exclude high-CI models. The only available models compatible with our limits imply very low gas-to-dust ratio, of the order of a few, only. These observations strengthen the hypothesis that CQ Tau is likely a transition disk and suggest that gas disappears before dust.Comment: 5 pages, 5 figures, accepted for publication in A&

ALMA Observations of Warm Dense Gas in NGC 1614 --- Breaking of Star Formation Law in the Central kpc

We present ALMA Cycle-0 observations of the CO (6-5) line emission and of the 435um dust continuum emission in the central kpc of NGC 1614, a local luminous infrared galaxy (LIRG) at a distance of 67.8 Mpc (1 arcsec = 329 pc). The CO emission is well resolved by the ALMA beam (0".26 x 0".20) into a circum-nuclear ring, with an integrated flux of f_{CO(6-5)} = 898 (+-153) Jy km/s, which is 63(+-12)% of the total CO(6-5) flux measured by Herschel. The molecular ring, located between 100pc < r < 350pc from the nucleus, looks clumpy and includes seven unresolved (or marginally resolved) knots with median velocity dispersion of 40 km/s. These knots are associated with strong star formation regions with \Sigma_{SFR} 100 M_\sun/yr/kpc^{2} and \Sigma_{Gas} 1.0E4 M_\sun/pc^{2}. The non-detections of the nucleus in both the CO (6-5) line emission and the 435um continuum rule out, with relatively high confidence, a Compton-thick AGN in NGC 1614. Comparisons with radio continuum emission show a strong deviation from an expected local correlation between \Sigma_{Gas} and \Sigma_{SFR}, indicating a breakdown of the Kennicutt-Schmidt law on the linear scale of 100 pc.Comment: 13 pages, 10 figures; accepted by Ap

High-resolution mapping of the physical conditions in two nearby active galaxies based on 12CO(1-0), (2-1) and (3-2) lines

We present a detailed analysis of high resolution observations of the three lowest CO transitions in two nearby active galaxies, NGC4569 and NGC4826. The CO(1-0) and (2-1) lines were observed with the Plateau de Bure Interferometer and the CO(3-2) line with the Submillimeter Array. Combining these data allows us to compare the emission in the three lines and to map the line ratios, R21=I_{CO(2-1)}/I_{CO(1-0)} and R32=I_{CO(3-2)}/I_{CO(1-0)} at a resolution of ~2", i.e., a linear resolution of 160 pc for NGC4569 and 40 pc for NGC4826. In both galaxies the emission in the three lines is similarly distributed spatially and in velocity, and CO is less excited (R32<0.6) than in the Galactic Center or the centers of other active galaxies studied so far. According to a pseudo-LTE model the molecular gas in NGC4569 is cold and mainly optically thick in the CO(1-0) and (2-1) lines; less than 50% of the gas is optically thin in the CO(3-2) line. LVG modeling suggests the presence of an elongated ring of cold and dense gas coinciding with the ILR of the stellar bar. More excited gas is resolved in the circumnuclear disk of NGC4826. According to our pseudo-LTE model this corresponds to warmer gas with a ~50% of the CO(3-2) emission being optically thin. LVG modeling indicates the presence of a semicircular arc of dense and cold gas centered on the dynamical center and ~70 pc in radius. The gas temperature increases and its density decreases toward the center. A near side/far side asymmetry noticeable in the CO, R32 and Pa-alpha maps suggests that opacity effects play a role. Examining published CO maps of nearby active galaxies we find similar asymmetries suggesting that this could be a common phenomenon in active galaxies. These mainly qualitative results open new perspectives for the study of active galaxies with the future Atacama Large Millimeter/submillimeter Array.Comment: accepted for publication in A&

Herschel observations of water vapour in Markarian 231

The Ultra Luminous InfraRed Galaxy Mrk 231 reveals up to seven rotational lines of water (H2O) in emission, including a very high-lying (E_{upper}=640 K) line detected at a 4sigma level, within the Herschel/SPIRE wavelength range, whereas PACS observations show one H2O line at 78 microns in absorption, as found for other H2O lines previously detected by ISO. The absorption/emission dichotomy is caused by the pumping of the rotational levels by far-infrared radiation emitted by dust, and subsequent relaxation through lines at longer wavelengths, which allows us to estimate both the column density of H2O and the general characteristics of the underlying far-infrared continuum source. Radiative transfer models including excitation through both absorption of far-infrared radiation emitted by dust and collisions are used to calculate the equilibrium level populations of H2O and the corresponding line fluxes. The highest-lying H2O lines detected in emission, with levels at 300-640 K above the ground state, indicate that the source of far-infrared radiation responsible for the pumping is compact (radius=110-180 pc) and warm (T_{dust}=85-95 K), accounting for at least 45% of the bolometric luminosity. The high column density, N(H2O)~5x10^{17} cm^{-2}, found in this nuclear component, is most probably the consequence of shocks/cosmic rays, an XDR chemistry, and/or an "undepleted chemistry" where grain mantles are evaporated. A more extended region, presumably the inner region of the 1-kpc disk observed in other molecular species, could contribute to the flux observed in low-lying H2O lines through dense hot cores, and/or shocks. The H2O 78 micron line observed with PACS shows hints of a blue-shifted wing seen in absorption, possibly indicating the occurrence of H2O in the prominent outflow detected in OH (Fischer et al., this volume).Comment: 5 pages, 3 figure

Water formation on bare grains: When the chemistry on dust impacts interstellar gas

Context. Water together with O2 are important gas phase ingredients to cool dense gas in order to form stars. On dust grains, H2 O is an important constituent of the icy mantle in which a complex chemistry is taking place, as revealed by hot core observations. The formation of water can occur on dust grain surfaces, and can impact gas phase composition. Aims. The formation of molecules such as OH, H2 O, HO2, H2 O2, as well as their deuterated forms and O2 and O3 is studied in order to assess how the chemistry varies in different astrophysical environments, and how the gas phase is affected by grain surface chemistry. Methods. We use Monte Carlo simulations to follow the formation of molecules on bare grains as well as the fraction of molecules released into the gas phase. We consider a surface reaction network, based on gas phase reactions, as well as UV photo-dissociation of the chemical species. Results. We show that grain surface chemistry has a strong impact on gas phase chemistry, and that this chemistry is very different for different dust grain temperatures. Low temperatures favor hydrogenation, while higher temperatures favor oxygenation. Also, UV photons dissociate the molecules on the surface, that can reform subsequently. The formation-destruction cycle increases the amount of species released into the gas phase. We also determine the time scales to form ices in diffuse and dense clouds, and show that ices are formed only in shielded environments, as supported by observations.Comment: Accepted in A&