@article {2014A\&A...564A.121C, title = {{The molecular gas reservoir of 6 low-metallicity galaxies from the Herschel Dwarf Galaxy Survey. A ground-based follow-up survey of CO(1-0), CO(2-1), and CO(3-2)}}, journal = {Astronomy and Astrophysics}, volume = {564}, year = {2014}, month = {apr}, pages = {A121}, abstract = {Context. Observations of nearby starburst and spiral galaxies have revealed that molecular gas is the driver of star formation. However, some nearby low-metallicity dwarf galaxies are actively forming stars, but CO, the most common tracer of this reservoir, is faint, leaving us with a puzzle about how star formation proceeds in these environments.
Aims: We aim to quantify the molecular gas reservoir in a subset of 6 galaxies from the Herschel Dwarf Galaxy Survey with newly acquired CO data and to link this reservoir to the observed star formation activity.
Methods: We present CO(1-0), CO(2-1), and CO(3-2) observations obtained at the ATNF Mopra 22-m, APEX, and IRAM 30-m telescopes, as well as [C ii] 157{$μ$}m and [O i] 63{$μ$}m observations obtained with the Herschel/PACS spectrometer in the 6 low-metallicity dwarf galaxies: Haro 11, Mrk 1089, Mrk 930, NGC 4861, NGC 625, and UM 311. We derived their molecular gas masses from several methods, including using the CO-to-H$_{2}$ conversion factor X$_{CO}$ (both Galactic and metallicity-scaled values) and dust measurements. The molecular and atomic gas reservoirs were compared to the star formation activity. We also constrained the physical conditions of the molecular clouds using the non-LTE code RADEX and the spectral synthesis code Cloudy.
Results: We detect CO in 5 of the 6 galaxies, including first detections in Haro 11 (Z \~{} 0.4 Z$_{\&sun;}$), Mrk 930 (0.2 Z$_{\&sun;}$), and UM 311 (0.5 Z$_{\&sun;}$), but CO remains undetected in NGC 4861 (0.2 Z$_{\&sun;}$). The CO luminosities are low, while [C ii] is bright in these galaxies, resulting in [C ii]/CO(1-0) {\ge} 10 000. Our dwarf galaxies are in relatively good agreement with the Schmidt-Kennicutt relation for total gas. They show short molecular depletion timescales, even when considering metallicity-scaled X$_{CO}$ factors. Those galaxies are dominated by their H i gas, except Haro 11, which has high star formation efficiency and is dominated by ionized and molecular gas. We determine the mass of each ISM phase in Haro 11 using Cloudy and estimate an equivalent X$_{CO}$ factor that is 10 times higher than the Galactic value. Overall, our results confirm the emerging picture that CO suffers from significant selective photodissociation in low-metallicity dwarf galaxies.}, keywords = {galaxies: dwarf, galaxies: ISM, infrared: galaxies, ISM: molecules, radio lines: galaxies}, doi = {10.1051/0004-6361/201322096}, url = {http://adsabs.harvard.edu/abs/2014A\%26A...564A.121C}, author = {Cormier, D. and Madden, S.~C. and Lebouteiller, V. and Hony, S. and Aalto, S. and F. Costagliola and Hughes, A. and R{\'e}my-Ruyer, A. and Abel, N. and Bayet, E. and Bigiel, F. and Cannon, J.~M. and Cumming, R.~J. and Galametz, M. and Galliano, F. and Viti, S. and Wu, R.} } @article {220, title = {{The molecular gas reservoir of 6 low-metallicity galaxies from the Herschel Dwarf Galaxy Survey. A ground-based follow-up survey of CO(1-0), CO(2-1), and CO(3-2)}}, journal = {\aap}, volume = {564}, year = {2014}, pages = {A121}, keywords = {galaxies: dwarf, galaxies: ISM, infrared: galaxies, ISM: molecules, radio lines: galaxies}, doi = {10.1051/0004-6361/201322096}, author = {Cormier, D. and Madden, S.~C. and Lebouteiller, V. and Hony, S. and Aalto, S. and Costagliola, F. and Hughes, A. and R{\'e}my-Ruyer, A. and Abel, N. and Bayet, E. and Bigiel, F. and Cannon, J.~M. and Cumming, R.~J. and Galametz, M. and Galliano, F. and Viti, S. and Wu, R.} } @article {218, title = {{Molecular line emission in NGC 1068 imaged with ALMA. I. An AGN-driven outflow in the dense molecular gas}}, journal = {\aap}, volume = {567}, year = {2014}, pages = {A125}, keywords = {galaxies: individual: NGC 1068, galaxies: ISM, galaxies: kinematics and dynamics, galaxies: nuclei, galaxies: Seyfert, radio lines: galaxies}, doi = {10.1051/0004-6361/201423843}, author = {Garcia-Burillo, S. and Combes, F. and Usero, A. and Aalto, S. and Krips, M. and Viti, S. and Alonso-Herrero, A. and Hunt, L.~K. and Schinnerer, E. and Baker, A.~J. and Boone, F. and Casasola, V. and Colina, L. and Costagliola, F. and Eckart, A. and Fuente, A. and Henkel, C. and Labiano, A. and Mart{\'\i}n, S. and Marquez, I. and Muller, S. and Planesas, P. and Ramos Almeida, C. and Spaans, M. and Tacconi, L.~J. and van der Werf, P.~P.} } @article {2014A\&A...567A.125G, title = {{Molecular line emission in NGC 1068 imaged with ALMA. I. An AGN-driven outflow in the dense molecular gas}}, journal = {Astronomy and Astrophysics}, volume = {567}, year = {2014}, month = {jul}, pages = {A125}, abstract = {
Aims: We investigate the fueling and the feedback of star formation and nuclear activity in NGC 1068, a nearby (D = 14 Mpc) Seyfert 2 barred galaxy, by analyzing the distribution and kinematics of the molecular gas in the disk. We aim to understand if and how gas accretion can self-regulate.
Methods: We have used the Atacama Large Millimeter Array (ALMA) to map the emission of a set of dense molecular gas (n(H$_{2}$) {\sime} 10$^{5 - 6}$ cm$^{-3}$) tracers (CO(3-2), CO(6-5), HCN(4-3), HCO$^{+}$(4-3), and CS(7-6)) and their underlying continuum emission in the central r \~{} 2 kpc of NGC 1068 with spatial resolutions \~{}0.3{\Prime} - 0.5{\Prime} (\~{}20-35 pc for the assumed distance of D = 14 Mpc).
Results: The sensitivity and spatial resolution of ALMA give an unprecedented detailed view of the distribution and kinematics of the dense molecular gas (n(H$_{2}$) {\ge} 10$^{5 - 6}$cm$^{-3}$) in NGC 1068. Molecular line and dust continuum emissions are detected from a r \~{} 200 pc off-centered circumnuclear disk (CND), from the 2.6 kpc-diameter bar region, and from the r \~{} 1.3 kpc starburst (SB) ring. Most of the emission in HCO$^{+}$, HCN, and CS stems from the CND. Molecular line ratios show dramatic order-of-magnitude changes inside the CND that are correlated with the UV/X-ray illumination by the active galactic nucleus (AGN), betraying ongoing feedback. We used the dust continuum fluxes measured by ALMA together with NIR/MIR data to constrain the properties of the putative torus using CLUMPY models and found a torus radius of 20$^{+6}$$_{-10}$pc. The Fourier decomposition of the gas velocity field indicates that rotation is perturbed by an inward radial flow in the SB ring and the bar region. However, the gas kinematics from r \~{} 50 pc out to r \~{} 400 pc reveal a massive (M$_{mol}$\~{} 2.7$^{+0.9}$$_{-1.2}$ {\times} 10$^{7}$ M$_{\&sun;}$) outflow in all molecular tracers. The tight correlation between the ionized gas outflow, the radio jet, and the occurrence of outward motions in the disk suggests that the outflow is AGN driven.
Conclusions: The molecular outflow is likely launched when the ionization cone of the narrow line region sweeps the nuclear disk. The outflow rate estimated in the CND, dM/dt\~{} 63$^{+21}$$_{-37}$ M$_{\&sun;}$ yr$^{-1}$, is an order of magnitude higher than the star formation rate at these radii, confirming that the outflow is AGN driven. The power of the AGN is able to account for the estimated momentum and kinetic luminosity of the outflow. The CND mass load rate of the CND outflow implies a very short gas depletion timescale of {\l}e}1 Myr. The CND gas reservoir is likely replenished on longer timescales by efficient gas inflow from the outer disk. Based on observations carried out with ALMA in Cycle 0.}, keywords = {galaxies: individual: NGC 1068, galaxies: ISM, galaxies: kinematics and dynamics, galaxies: nuclei, galaxies: Seyfert, radio lines: galaxies}, doi = {10.1051/0004-6361/201423843}, url = {http://adsabs.harvard.edu/abs/2014A\%26A...567A.125G}, author = {S. Garc{\'\i}a-Burillo and Combes, F. and Usero, A. and Aalto, S. and Krips, M. and Viti, S. and Alonso-Herrero, A. and Hunt, L.~K. and Schinnerer, E. and Baker, A.~J. and Boone, F. and Casasola, V. and Colina, L. and F. Costagliola and Eckart, A. and Fuente, A. and Henkel, C. and Labiano, A. and Mart{\'\i}n, S. and Marquez, I. and Muller, S. and Planesas, P. and Ramos Almeida, C. and Spaans, M. and Tacconi, L.~J. and van der Werf, P.~P.} } @article {2014A\&A...570A..28V, title = {{Molecular line emission in NGC 1068 imaged with ALMA. II. The chemistry of the dense molecular gas}}, journal = {Astronomy and Astrophysics}, volume = {570}, year = {2014}, month = {oct}, pages = {A28}, abstract = {
Aims: We present a detailed analysis of Atacama Large Millimeter/submillimeter Array (ALMA) Bands 7 and 9 data of CO, HCO$^{+}$, HCN, and CS, augmented with Plateau de Bure Interferometer (PdBI) data of the \~{}200 pc circumnuclear disc (CND) and the \~{}1.3 kpc starburst ring (SB ring) of NGC 1068, a nearby (D = 14 Mpc) Seyfert 2 barred galaxy. We aim to determine the physical characteristics of the dense gas present in the CND, and to establish whether the different line intensity ratios we find within the CND, as well as between the CND and the SB ring, are due to excitation effects (gas density and temperature differences) or to a different chemistry.
Methods: We estimate the column densities of each species in local thermodynamic equilibrium (LTE). We then compute large one-dimensional, non-LTE radiative transfer grids (using RADEX) by using only the CO transitions first, and then all the available molecules to constrain the densities, temperatures, and column densities within the CND. We finally present a preliminary set of chemical models to determine the origin of the gas.
Results: We find that, in general, the gas in the CND is very dense ({\gt}10$^{5}$ cm$^{-3}$) and hot (T{\gt} 150 K), with differences especially in the temperature across the CND. The AGN position has the lowest CO/HCO$^{+}$, CO/HCN, and CO/CS column density ratios. The RADEX analyses seem to indicate that there is chemical differentiation across the CND. We also find differences between the chemistry of the SB ring and some regions of the CND; the SB ring is also much colder and less dense than the CND. Chemical modelling does not succeed in reproducing all the molecular ratios with one model per region, suggesting the presence of multi-gas phase components.
Conclusions: The LTE, RADEX, and chemical analyses all indicate that more than one gas-phase component is necessary to uniquely fit all the available molecular ratios within the CND. A higher number of molecular transitions at the ALMA resolution is necessary to determine quantitatively the physical and chemical characteristics of these components. Tables 5-11 are available in electronic form at http://www.aanda.org}, keywords = {galaxies: active, galaxies: individual: NGC 1068, galaxies: ISM, galaxies: nuclei, molecular processes, radio lines: galaxies}, doi = {10.1051/0004-6361/201424116}, url = {http://adsabs.harvard.edu/abs/2014A\%26A...570A..28V}, author = {Viti, S. and S. Garc{\'\i}a-Burillo and Fuente, A. and Hunt, L.~K. and Usero, A. and Henkel, C. and Eckart, A. and Mart{\'\i}n, S. and Spaans, M. and Muller, S. and Combes, F. and Krips, M. and Schinnerer, E. and Casasola, V. and F. Costagliola and Marquez, I. and Planesas, P. and van der Werf, P.~P. and Aalto, S. and Baker, A.~J. and Boone, F. and Tacconi, L.~J.} } @article {217, title = {{Molecular line emission in NGC 1068 imaged with ALMA. II. The chemistry of the dense molecular gas}}, journal = {\aap}, volume = {570}, year = {2014}, pages = {A28}, keywords = {galaxies: active, galaxies: individual: NGC 1068, galaxies: ISM, galaxies: nuclei, molecular processes, radio lines: galaxies}, doi = {10.1051/0004-6361/201424116}, author = {Viti, S. and Garcia-Burillo, S. and Fuente, A. and Hunt, L.~K. and Usero, A. and Henkel, C. and Eckart, A. and Mart{\'\i}n, S. and Spaans, M. and Muller, S. and Combes, F. and Krips, M. and Schinnerer, E. and Casasola, V. and Costagliola, F. and Marquez, I. and Planesas, P. and van der Werf, P.~P. and Aalto, S. and Baker, A.~J. and Boone, F. and Tacconi, L.~J.} } @article {2011A\&A...527A..69A, title = {{H$_{3}$O$^{+}$ line emission from starbursts and AGNs}}, journal = {Astronomy and Astrophysics}, volume = {527}, year = {2011}, month = {mar}, pages = {A69}, abstract = {Context. The H$_{3}$O$^{+}$ molecule probes the chemistry and the ionization rate of dense circumnuclear gas in galaxies.
Aims: We use the H$_{3}$O$^{+}$ molecule to investigate the impact of starburst and AGN activity on the chemistry of the molecular interstellar medium.
Methods: Using the JCMT, we have observed the 3$_{2}$$^{+}$ - 2$_{2}$$^{+}$ 364 GHz line of p-H$_{3}$O$^{+}$ towards the centres of seven active galaxies.
Results: We have detected p-H$_{3}$O$^{+}$ towards IC 342, NGC 253, NGC 1068, NGC 4418, and NGC 6240. Upper limits were obtained for IRAS 15250 and Arp 299. We find large H$_{3}$O$^{+}$ abundances (N(H$_{3}$O$^{+}$)/N(H$_{2}$) {\gsim} 10$^{-8}$) in all detected galaxies apart from in IC 342 where it is about one order of magnitude lower. We note, however, that uncertainties in N(H$_{3}$O$^{+}$) may be significant due to lack of definite information on source size and excitation. We furthermore compare the derived N(H$_{3}$O$^{+}$) with N(HCO$^{+}$) and find that the H$_{3}$O$^{+}$ to HCO$^{+}$ column density ratio is large in NGC 1068 (24), moderate in NGC 4418 and NGC 253 (4-5), slightly less than unity in NGC 6240 (0.7) and lowest in IC 342 (0.2-0.6). We compare our results with models of X-ray and photon dominated regions (XDRs and PDRs).
Conclusions: For IC 342 we find that a starburst PDR chemistry can explain the observed H$_{3}$O$^{+}$ abundance. For the other galaxies, the large H$_{3}$O$^{+}$ columns are generally consistent with XDR models. In particular for NGC 1068 the elevated N(H$_{3}$O$^{+}$)/N(HCO$^{+}$) ratio suggests a low column density XDR. For NGC 4418 however, large HC$_{3}$N abundances are inconsistent with the XDR interpretation. An alternative possibility is that H$_{3}$O$^{+}$ forms through H$_{2}$O evaporating off dust grains and reacting with HCO$^{+}$ in warm, dense gas. This scenario could also potentially fit the results for NGC 253. Further studies of the excitation and distribution of H$_{3}$O$^{+}$ - as well as Herschel observations of water abundances - will help to further constrain the models.}, keywords = {galaxies: active, galaxies: evolution, galaxies: starburst, ISM: molecules, radio lines: galaxies}, doi = {10.1051/0004-6361/201015878}, url = {http://adsabs.harvard.edu/abs/2011A\%26A...527A..69A}, author = {Aalto, S. and F. Costagliola and van der Tak, F. and Meijerink, R.} } @article {2011A\&A...527A.150L, title = {{A survey of HC$_{3}$N in extragalactic sources. Is HC$_{3}$N a tracer of activity in ULIRGs?}}, journal = {Astronomy and Astrophysics}, volume = {527}, year = {2011}, month = {mar}, pages = {A150}, abstract = {Context. HC$_{3}$N is a molecule that is mainly associated with Galactic star-forming regions, but it has also been detected in extragalactic environments.
Aims: To present the first extragalactic survey of HC$_{3}$N, when combining earlier data from the literature with six new single-dish detections, and to compare HC$_{3}$N with other molecular tracers (HCN, HNC), as well as other properties (silicate absorption strength, IR flux density ratios, C ii flux, and megamaser activity).
Methods: We present mm IRAM 30 m, OSO 20 m, and SEST observations of HC$_{3}$N rotational lines (mainly the J = 10-9 transition) and of the J = 1-0 transitions of HCN and HNC. Our combined HC$_{3}$N data account for 13 galaxies (excluding the upper limits reported for the non-detections), while we have HCN and HNC data for more than 20 galaxies.
Results: A preliminary definition {\textquoteright}{\textquoteright}HC$_{3}$N-luminous galaxy{\textquoteright}{\textquoteright} is made based upon the HC$_{3}$N/HCN ratio. Most (\~{}80\%) HC$_{3}$N-luminous galaxies seem to be deeply obscured galaxies and (U)LIRGs. A majority (\~{}60\% or more) of the HC$_{3}$N-luminous galaxies in the sample present OH mega- or strong kilomaser activity. A possible explanation is that both HC$_{3}$N and OH megamasers need warm dust for their excitation. Alternatively, the dust that excites the OH megamaser offers protection against UV destruction of HC$_{3}$N. A high silicate absorption strength is also found in several of the HC$_{3}$N-luminous objects, which may help the HC$_{3}$N to survive. Finally, we find that a high HC$_{3}$N/HCN ratio is related to a high dust temperature and a low C ii flux. Appendix is only available in electronic form at http://www.aanda.org}, keywords = {galaxies: active, galaxies: ISM, galaxies: starburst, ISM: molecules, radio lines: galaxies, radio lines: ISM}, doi = {10.1051/0004-6361/201015565}, url = {http://adsabs.harvard.edu/abs/2011A\%26A...527A.150L}, author = {Lindberg, J.~E. and Aalto, S. and F. Costagliola and P{\'e}rez-Beaupuits, J.-P. and Monje, R. and Muller, S.} }