Padeli P. Papadopoulos

CO (4-3) and Dust Emission in Two Powerful High-z Radio Galaxies, and CO Lines at High Redshifts

We report the detection of submillimeter emission from dust at 850 μm and of the 12CO J = 4-3 line in the two distant powerful radio galaxies 4C 60.07 (z = 3.79) and 6C 1909+722 (z = 3.53). In 4C 60.07, the dust emission is also detected at 1.25 mm. The estimated molecular gas masses are large, of the order of ~(0.5-1) × 1011 M☉. The large far-infrared (FIR) luminosities (LFIR ~ 1013 L☉) suggest that we are witnessing two major starburst phenomena, while the observed large velocity widths (ΔVFWHM 500 km s-1) are characteristic of mergers. In the case of 4C 60.07, the CO emission extends over ~30 kpc and spans a velocity range of 1000 km s-1. It consists of two distinct features with FWHM of 550 km s-1 and ~150 km s-1, and line centers separated by 700 km s-1. The least massive of these components is probably very gas rich, with potentially 60% of its dynamical mass in the form of molecular gas. The extraordinary morphology of the CO emission in this object suggests that it is not just a scaled-up version of a local ultraluminous infrared galaxy, and it may be a formative stage of the elliptical host of the residing radio-loud active galactic nucleus (AGN). Finally, we briefly explore the effects of the wide range of gas-excitation conditions expected for starburst environments on the luminosity of high-J CO lines and conclude that in unlensed objects, CO (J + 1 → J), J + 1 > 3 lines can be significantly weak with respect to CO J = 1-0, and this can hinder their detection even in the presence of substantial molecular gas masses.

Molecular Gas, Morphology, and Seyfert Galaxy Activity

We probe the cause of the elevated star formation in host galaxies of Seyfert 2 nuclei compared with Seyfert 1 hosts and with field galaxies.12CO (1-0) observations of a large sample of Seyfert galaxies indicate no significant difference in the total amount of molecular gas as a function of the Seyfert nuclear type, nor are Seyfert galaxies significantly different in this regard from a sample of field galaxies once selection effects are accounted for. Therefore, the total amount of molecular gas is not responsible for the enhanced star-forming activity in Seyfert 2 hosts. To probe how this gas is being converted more efficiently into stars in Seyfert 2 hosts than in the other galaxies, we investigate the occurrence of bars, interactions, and distorted morphologies among Seyfert galaxies. We find a significantly higher rate of asymmetric morphologies for Seyfert 2 galaxies with respect to Seyfert 1 galaxies and field galaxies. Relative to field galaxies, the effect is at a greater than 99.9% confidence level. The presence of asymmetric morphologies in individual Seyfert galaxies is correlated with their tendency to exhibit enhanced star-forming activity. These results suggest that asymmetric morphologies are an important cause for the link between Seyfert type and star-forming activity: bars and distortions in Seyfert 2 hosts are likely both to enhance star-forming activity and to funnel gas into the nuclear region, thus obscuring and possibly contributing to the feeding of the active nucleus.

Molecular Gas Disk Structures Around Active Galactic Nuclei

We present new high resolution numerical simulations of the interstellar medium (ISM) in a central R ≤ 32 parsecs region around a supermassive black hole (1.3 × 10M⊙) at a galactic center. Threedimensional hydrodynamic modeling of the ISM (Wada & Norman 2002) with the nuclear starburst now includes tracking of the formation of molecular hydrogen (H2 ) out of the neutral hydrogen phase as a function of the evolving ambient ISM conditions with a finer spatial resolution (0.125 pc). In a quasi equilibrium state, mass fraction of H2 is about 0.4 (total H2 mass is ≃ 1.5 × 10 M⊙) of the total gas mass for the uniform far UV (FUV) with G0 = 10 in Habing unit. As shown in the previous model, the gas forms an inhomogeneous disk, whose scale-height becomes larger in the outer region. H2 forms a thin nuclear disk in the inner ≃ 5 pc, which is surrounded by molecular clouds swelled up toward h . 10 pc. The velocity field of the disk is highly turbulent in the torus region, whose velocity dispersion is ≃ 20 km s on average. Average supernova rate (SNR) of ≃ 5 × 10yr is large enough to energize these structures. Gas column densities toward the nucleus larger than 10 cm are observed if the viewing angle is smaller than θv ≃ 50 ◦ from the edge-on. However, the column densities are distributed over almost two orders of magnitude around the average for any given viewing angle due to the clumpy nature of the torus. For a stronger FUV (G0 = 100), the total H2 mass in an equillibrium is only slightly smaller (≃ 0.35), a testimony to the strong self-shielding nature of H2, and the molecular gas is somewhat more concentrated in a mid-plane. Other properties of the ISM are not very sensitive either to the FUV intensity and the supernova rate. Finally the morphology and kinematics of the circumnuclear molecular gas disks emerging from our models is similar to that revealed by recent near infrared observations using VLTI/Keck. Subject headings: galaxies: Seyfert – galaxies: starburst – ISM: structure – ISM: molecules – method: numerical

CO SPECTRAL LINE ENERGY DISTRIBUTIONS OF INFRARED-LUMINOUS GALAXIES AND ACTIVE GALACTIC NUCLEI

We report on new sensitive CO J = 6-5 line observations of several luminous infrared galaxies (LIRGs; L IR(8-1000 ?m) 1011?L ?), 36% (8/22) of them ultraluminous infrared galaxies (ULIRGs) (L IR>1012?L ?), and two powerful local active galactic nuclei (AGNs)?the optically luminous QSO PG?1119+120 and the powerful radio galaxy 3C?293?using the James Clerk Maxwell Telescope on Mauna Kea in Hawaii. We combine these observations with existing low-J CO data and dust emission spectral energy distributions in the far-infrared-submillimeter from the literature to constrain the properties of the star-forming interstellar medium (ISM) in these systems. We then build the first local CO spectral line energy distributions (SLEDs) for the global molecular gas reservoirs that reach up to high J-levels. These CO SLEDs are neither biased by strong lensing (which affects many of those constructed for high-redshift galaxies), nor suffer from undersampling of CO-bright regions (as most current high-J CO observations of nearby extended systems do). We find: (1) a significant influence of dust optical depths on the high-J CO lines, suppressing the J = 6-5 line emission in some of the most IR-luminous LIRGs, (2) low global CO line excitation possible even in vigorously star-forming systems, (3) the first case of a shock-powered high-excitation CO SLED in the radio galaxy 3C?293 where a powerful jet-ISM interaction occurs, and (4) unusually highly excitated gas in the optically powerful QSO PG?1119+120. In Arp?220 and possibly other (U)LIRGs very faint CO J = 6-5 lines can be attributed to significant dust optical depths at short submillimeter wavelengths immersing those lines in a strong dust continuum, and also causing the C+ line luminosity deficit often observed in such extreme starbursts. Re-analysis of the CO line ratios available for submillimeter galaxies suggests that similar dust opacities also may be present in these high-redshift starbursts, with genuinely low excitation of large amounts of SF-quiescent gas being the only other possibility for their often low CO (high-J)/(low-J) line ratios. We then present a statistical method of separating these two almost degenerate possibilities, and show that high dust optical depths at submillimeter wavelengths can impede the diagnostic potential of submillimeter/IR lines (e.g., starbursts versus AGNs as gas excitation agents), which is of particular importance for the upcoming observations of the Herschel Space Observatory and the era of ALMA.

Physical Conditions of the Molecular Gas in Seyfert Galaxies

We examine the physical conditions of the global molecular gas reservoir in the host galaxies of Seyfert 1 and Seyfert 2 nuclei. To do so, we acquired sensitive 12CO,13CO, J = 1-0, and J = 2-1 observations and collected available data from the literature for a sample of 27 Seyfert galaxies. We find that Seyfert galaxies have an average value for the 12CO/13CO J = 1-0 and J = 2-1 line ratios of R10 = 12 and R21 = 13, respectively, with no discernible dependence on the Seyfert type. The r12 = (2-1)/(1-0) line ratio for 12CO does not reveal any significant difference between the two types, but Seyfert galaxies as a class seem to have systematically lower values of r12 (~0.5-0.7) than do average spirals and starbursts. Moreover, for all the galaxies examined, but especially for Seyfert and starburst galaxies, we find that r12 is likely to be smaller as the area of the galaxy sampled by the telescope beam becomes larger. This may be the consequence of a global gas excitation gradient in galaxies where warm (Tkin 20 K) gas lies confined, preferably in their central regions (1 kpc), while a colder (Tkin 10 K), and possibly subthermally excited, gas phase dominates the more extended CO emission in the disk. For Seyfert and starburst galaxies, there are indications that their gas excitation gradients may be quite similar. Examination of the properties of the molecular gas by using the r12, R10, and R21 line ratios reveals that, unless r12 0.6, a single warm gas phase can account for the observed values of these ratios toward the central regions of an average Seyfert and/or starburst galaxy.

TRACING MOLECULAR GAS MASS IN EXTREME EXTRAGALACTIC ENVIRONMENTS: AN OBSERVATIONAL STUDY

U.L. acknowledges financial support from the research project AYA2007-67625-C02-02 from the Spanish Ministerio de Ciencia y Educacion and from the Junta de Anaducia.

Gas and Dust in NGC 7469: Submillimeter Imaging and CO J = 3-2

We present sensitive submillimeter imaging of the Seyfert 1 galaxy NGC 7469 at 850 and 450 μm with the Submillimeter Common User Bolometer Array on the James Clerk Maxwell Telescope and 12CO J = 3-2 line observations of its central starbursting region. The global dust spectrum, as constrained by the new set of submillimeter data and available 1.30 mm and IRAS 100 and 60 μm data, reveals a dominant warm dust component with a temperature of Td ~ 35 K and a global molecular gas-to-dust ratio M(H2)/Md ~ 600. Including the atomic gas component yields a total gas-to-dust ratio of ~830. Such high values are typical for IR-bright spiral galaxies, and in order to reconcile them with the significantly lower ratio of ~100 obtained for the Milky Way, a cold dust reservoir, inconspicuous at far-infrared wavelengths, is usually postulated. However, while there is good evidence for the presence of cold gas/dust in NGC 7469 beyond its central region, our 450 μm map and available interferometric 12CO J = 1-0 maps show the bright submillimeter/CO emission confined in the inner ~2.5 kpc, where a high 12CO (J = 3-2)/(J = 1-0) ratio (~0.85-1.0) is measured. This is consistent with molecular gas at Tkin 30 K, suggesting that the bulk of the interstellar medium in the starburst center of NGC 7469 is warm. Nevertheless, the corresponding total gas-to-dust ratio there remains high, of the order of ~500. We argue that, rather than unaccounted cold dust mass, this high ratio suggests an overestimate of M(H2) from its associated 12CO J = 1-0 line luminosity by a factor of ~5 when a Milky Way value for this conversion is used. Finally, the diffuse cold gas and dust that is the likely source of the observed faint extended 450 μm and 12CO J = 1-0 emission has an estimated total gas-to-dust ratio of ~50-160, closer to the Galactic value.

Extended Dust Emission and Atomic Hydrogen: A Reservoir of Diffuse H2 in NGC 1068

We report on sensitive sub-mm imaging observations of the prototype Seyfert~2/starburst galaxy NGC 1068 at 850

A New Twist to an Old Story: HE 0450–2958 and the ULIRG → Optically Bright QSO Transition Hypothesis

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The State of the molecular gas in a luminous starburst/Seyfert 2 galaxy: NGC 1068 revisited

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