| 1. |
- Cicone, C., et al.
(författare)
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Massive molecular outflows and evidence for AGN feedback from CO observations
- 2014
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 562, s. 25-
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Tidskriftsartikel (refereegranskat)abstract
- We study the properties of massive, galactic-scale outflows of molecular gas and investigate their impact on galaxy evolution. We present new IRAMPdBI CO(1-0) observations of local ultra-luminous infrared galaxies (ULIRGs) and quasar-hosts: a clear signature of massive and energetic molecular outflows, extending on kpc scales, is found in the CO(1-0) kinematics of four out of seven sources, with measured outflow rates of several 100M(circle dot)yr(-1). We combine these new observations with data from the literature, and explore the nature and origin of massive molecular outflows within an extended sample of 19 local galaxies. We find that starburst-dominated galaxies have an outflow rate comparable to their star formation rate (SFR), or even higher by a factor of similar to 2-4, implying that starbursts can indeed be effective in removing cold gas from galaxies. Nevertheless, our results suggest that the presence of an active galactic nucleus (AGN) can boost the outflow rate by a large factor, which is found to increase with the L-AGN/L-bol ratio. The gas depletion time scales due to molecular outflows are anti-correlated with the presence and luminosity of an AGN in these galaxies, and range from a few hundred million years in starburst galaxies down to just a few million years in galaxies hosting powerful AGNs. In quasar hosts, the depletion time scales due to the outflow are much shorter than the depletion time scales due to star formation. We estimate the outflow kinetic power and find that, for galaxies hosting powerful AGNs, it corresponds to about 5% of the AGN luminosity, as expected by models of AGN feedback. Moreover, we find that momentum rates of about 20 L-AGN/c are common among the AGN-dominated sources in our sample. For "pure" starburst galaxies, our data tentatively support models in which outflows are mostly momentum-driven by the radiation pressure from young stars onto dusty clouds. Overall, our results indicate that, although starbursts are effective in powering massive molecular outflows, the presence of an AGN may strongly enhance such outflows, and therefore have a profound feedback effect on the evolution of galaxies by efficiently removing fuel for star formation, hence quenching star formation.
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| 2. |
- Castro-Carrizo, A., et al.
(författare)
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Mapping the 12CO J = 1-0 and J = 2-1 emission in AGB and early post-AGB circumstellar envelopes. I. The COSAS program, first sample
- 2010
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 523:4, s. A59-
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Tidskriftsartikel (refereegranskat)abstract
- We present COSAS (CO Survey of late AGB Stars), a project to map and analyze the 12CO J = 1−0 and J = 2−1 line emission in a representative sample of circumstellar envelopes around AGB and post-AGB stars. The survey was undertaken with the aim of investigating small- and large-scale morphological and kinematical properties of the molecular environment surrounding stars in the late AGB and early post-AGB phases. For this, COSAS combines the high sensitivity and spatial resolving power of the IRAM Plateau de Bure interferometer with the better capability of the IRAM 30 m telescope to map extended emission. The global sample encompasses 45 stars selected to span a range in chemical type, variability type, evolutionary state, and initial mass. COSAS provides means to quantify variations in the mass-loss rates, assess morphological and kinematical features, and to investigate the appearance of fast aspherical winds in the early post-AGB phase. This paper, which is the first of a series of COSAS papers, presents the results from the analyses of a first sample of 16 selected sources. The envelopes around late AGB stars are found to be mostly spherical, often mingled with features such as concentric arcs (R Cas and TX Cam), a broken spiral density pattern (TX Cam), molecular patches testifying to aspherical mass-loss (WX Psc, IK Tau, V Cyg, and S Cep), and also with well-defined axisymmetric morphologies and kinematical patterns (X Her and RX Boo). The sources span a wide range of angular sizes, from relatively compact (CRL 2362, OH 104.9+2.4 and CRL 2477) to very large (χ Cyg and TX Cam) envelopes, sometimes partially obscured by self-absorption features, which particularly for IK Tau and χ Cyg testifies to the emergence of aspherical winds in the innermost circumstellar regions. Strong axial structures with more or less complex morphologies are detected in four early post-AGB stars (IRAS 20028+3910, IRAS 23321+6545, IRAS 19475+3119 and IRAS 21282+5050) of the sub-sample.
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| 3. |
- Wang, R., et al.
(författare)
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STAR FORMATION AND GAS KINEMATICS OF QUASAR HOST GALAXIES AT z similar to 6: NEW INSIGHTS FROM ALMA
- 2013
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 773:1
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Tidskriftsartikel (refereegranskat)abstract
- We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of the [C Pi] 158 mu m fine structure line and dust continuum emission from the host galaxies of five redshift 6 quasars. We also report complementary observations of 250 GHz dust continuum and CO (6-5) line emission from the z = 6.00 quasar SDSS J231038.88+185519.7 using the IRAM facilities. The ALMA observations were carried out in the extended array at 0.'' 7 resolution. We have detected the line and dust continuum in all five objects. The derived [C Pi] line luminosities are 1.6 x 10(9) to 8.7 x 10(9) L-circle dot and the [C Pi]-to-FIR luminosity ratios are 2.9-5.1 x 10(-4), which is comparable to the values found in other high-redshift quasar-starburst systems and local ultra-luminous infrared galaxies. The sources are marginally resolved and the intrinsic source sizes (major axis FWHM) are constrained to be 0.'' 3-0.'' 6 (i.e., 1.7-3.5 kpc) for the [C Pi] line emission and 0.'' 2-0.'' 4 (i.e., 1.2-2.3 kpc) for the continuum. These measurements indicate that there is vigorous star formation over the central few kpc in the quasar host galaxies. The ALMA observations also constrain the dynamical properties of the star-forming gas in the nuclear region. The intensity-weighted velocity maps of three sources show clear velocity gradients. Such velocity gradients are consistent with a rotating, gravitationally bound gas component, although they are not uniquely interpreted as such. Under the simplifying assumption of rotation, the implied dynamical masses within the [C Pi]-emitting regions are of order 10(10)-10(11) M-circle dot. Given these estimates, the mass ratios between the supermassive black holes and the spheroidal bulge are an order of magnitude higher than the mean value found in local spheroidal galaxies, which is in agreement with results from previous CO observations of high redshift quasars.
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| 4. |
- Aalto, Susanne, 1964, et al.
(författare)
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Detection of HCN, HCO+, and HNC in the Mrk 231 molecular outflow. Dense molecular gas in the AGN wind
- 2012
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 537, s. 44-51
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Tidskriftsartikel (refereegranskat)abstract
- We obtained high-resolution (1.''55 × 1.''28) observations of HCN, HCO+, HNC 1-0 and HC3N 10-9 of the ultraluminous galaxy (ULIRG) Mrk 231 with the IRAM Plateau de Bure Interferometer.Results: We detect luminous emission from HCN, HCO+ and HNC 1-0 in the QSO ULIRG Mrk 231. All three lines show broad line wings - which are particularly prominent for HCN. Velocities are found to be similar ( ≈ ± 750 km s-1) to those found for CO 1-0. This is the first time bright HCN, HCO+ and HNC emission has been detected in a large-scale galactic outflow. We find that both the blue- and red-shifted line wings are spatially extended by at least 0.''75 (>700 pc) in a north-south direction. The line wings are brighter (relative to the line center intensity) in HCN than in CO 1-0 and line ratios suggest that the molecular outflow consists of dense (n > 104 cm-3) and clumpy gas with a high HCN abundance X(HCN) > 10-8. These properties are consistent with the molecular gas being compressed and fragmented by shocks in the outflow. Alternatively, HCN is instead pumped by mid-IR continuum, but we propose that this effect is not strong for the spatially extended outflowing gas. In addition, we find that the rotation of the main disk, in east-west direction, is also evident in the HCN, HCO+ and HNC line emission. An unexpectedly bright HC3N 10-9 line is detected inside the central 400 pc of Mrk 231. This HC3N emission may emerge from a shielded, dust-enshrouded region within the inner 40-50 pc where the gas is heated to high temperatures (200-300 K) by the AGN.
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| 5. |
- Burillo, S. G., et al.
(författare)
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Molecular gas chemistry in AGN. II. High-resolution imaging of SiO emission in NGC 1068: shocks or XDR?
- 2010
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 519:Article Number: A2
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Tidskriftsartikel (refereegranskat)abstract
- Context. This paper is part of a multi-species survey of line emission from the molecular gas in the circum-nuclear disk (CND) of the Seyfert 2 galaxy NGC 1068. Unlike in other active galaxies, the intensely star-forming regions in NGC 1068 and the CND can be resolved with current instrumentation. This makes this galaxy an optimal test-bed to probe the effects of AGN on the molecular medium at similar to 100 pc scales. Aims. Single-dish observations have provided evidence that the abundance of silicon monoxide (SiO) in the CND of NGC 1068 is enhanced by 3-4 orders of magnitude with respect to the values typically measured in quiescent molecular gas in the Galaxy. We aim at unveiling the mechanism(s) underlying the SiO enhancement. Methods. We have imaged the emission of the SiO(2-1) (86.8 GHz) and CN(2-1) (226.8 GHz) lines in NGC 1068 at similar to 150 pc and 60 pc spatial resolution with the IRAM Plateau de Bure interferometer (PdBI). We have also obtained complementary IRAM 30 m observations of HNCO and methanol (CH3OH) lines. These species are known as tracers of shocks in the Galaxy. Results. SiO is detected in a disk of similar to 400 pc size around the AGN. SiO abundances in the CND of similar to(1-5) x 10(-9) are about 1-2 orders of magnitude above those measured in the starburst ring. The overall abundance of CN in the CND is high: similar to(0.2-1) x 10(-7). The abundances of SiO and CN are enhanced at the extreme velocities of gas associated with non-circular motions close to the AGN (r
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