Preprint typeset using LATEX style emulateapj v. 12/16/11 Herschel/SPIRE SUB-MILLIMETER SPECTRA OF LOCAL ACTIVE GALAXIES⋆,⋆⋆ (original) (raw)
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Herschel /Spire Submillimeter Spectra of Local Active Galaxies
The Astrophysical Journal, 2013
We present the submillimeter spectra from 450 to 1550 GHz of 11 nearby active galaxies observed with the SPIRE Fourier Transform Spectrometer (SPIRE/FTS) on board Herschel. We detect CO transitions from J up = 4 to 12, as well as the two [C i] fine structure lines at 492 and 809 GHz and the [N ii]1461 GHz line. We used radiative transfer models to analyze the observed CO spectral line energy distributions. The FTS CO data were complemented with ground-based observations of the low-J CO lines. We found that the warm molecular gas traced by the mid-J CO transitions has similar physical conditions (n H 2 ∼ 10 3.2-10 3.9 cm −3 and T kin ∼ 300-800 K) in most of our galaxies. Furthermore, we found that this warm gas is likely producing the mid-IR rotational H 2 emission. We could not determine the specific heating mechanism of the warm gas, however, it is possibly related to the star formation activity in these galaxies. Our modeling of the [C i] emission suggests that it is produced in cold (T kin < 30 K) and dense (n H 2 > 10 3 cm −3) molecular gas. Transitions of other molecules are often detected in our SPIRE/FTS spectra. The HF J = 1-0 transition at 1232 GHz is detected in absorption in UGC 05101 and in emission in NGC 7130. In the latter, near-infrared pumping, chemical pumping, or collisional excitation with electrons are plausible excitation mechanisms likely related to the active galactic nucleus of this galaxy. In some galaxies, few H 2 O emission lines are present. Additionally, three OH + lines at 909, 971, and 1033 GHz are identified in NGC 7130.
2010
We present a detailed analysis of the gas conditions in the H 2 luminous radio galaxy 3C 326 N at z∼0.1, which has a low star-formation rate (SFR∼0.07 M yr −1 ) in spite of a gas surface density similar to those in starburst galaxies. Its star-formation efficiency is likely a factor ∼10-50 lower than those of ordinary star-forming galaxies. Combining new IRAM CO emission-line interferometry with existing Spitzer mid-infrared spectroscopy, we find that the luminosity ratio of CO and pure rotational H 2 line emission is factors 10-100 lower than what is usually found. This may suggest that most of the molecular gas is warm. The Na D absorption-line profile of 3C 326 N in the optical suggests an outflow with a terminal velocity of ∼ −1800 km s −1 and a mass outflow rate of 30-40 M yr −1 , which cannot be explained by star formation. The mechanical power implied by the wind, of order 10 43 erg s −1 , is comparable to the bolometric luminosity of the emission lines of ionized and molecular gas. To explain these observations, we propose a scenario where a small fraction of the mechanical energy of the radio jet is deposited in the interstellar medium of 3C 326 N, which powers the outflow, and the line emission through a mass, momentum and energy exchange between the different gas phases of the ISM. Dissipation times are of order 10 7−8 yrs, similar or greater than the typical jet lifetime. Small ratios of CO and PAH surface brightnesses in another 7 H 2 luminous radio galaxies suggest that a similar form of AGN feedback could be lowering star-formation efficiencies in these galaxies in a similar way. The local demographics of radio-loud AGN suggests that secular gas cooling in massive early-type galaxies of ≥ 10 11 M could generally be regulated through a fundamentally similar form of 'maintenance-phase' AGN feedback.
The Astrophysical Journal, 2012
We report the detection of far-IR CO rotational emission from the prototypical Seyfert 2 galaxy NGC 1068. Using Herschel-PACS, we have detected 11 transitions in the J upper = 14-30 (E upper /k B = 580-2565 K) range, all of which are consistent with arising from within the central 10 (700 pc). The detected transitions are modeled as arising from two different components: a moderate-excitation (ME) component close to the galaxy systemic velocity and a high-excitation (HE) component that is blueshifted by ∼80 km s −1. We employ a large velocity gradient model and derive n H2 ∼ 10 5.6 cm −3 , T kin ∼ 170 K, and M H2 ∼ 10 6.7 M for the ME component and n H2 ∼ 10 6.4 cm −3 , T kin ∼ 570 K, and M H2 ∼ 10 5.6 M for the HE component, although for both components the uncertainties in the density and mass are ±(0.6-0.9) dex. Both components arise from denser and possibly warmer gas than traced by low-J CO transitions, and the ME component likely makes a significant contribution to the mass budget in the nuclear region. We compare the CO line profiles with those of other molecular tracers observed at higher spatial and spectral resolution and find that the ME transitions are consistent with these lines arising in the ∼200 pc diameter ring of material traced by H 2 1-0 S(1) observations. The blueshift of the HE lines may also be consistent with the bluest regions of this H 2 ring, but a better kinematic match is found with a clump of infalling gas ∼40 pc north of the active galactic nucleus (AGN). We consider potential heating mechanisms and conclude that X-ray-or shock heating of both components is viable, while far-UV heating is unlikely. We discuss the prospects of placing the HE component near the AGN and conclude that while the moderate thermal pressure precludes an association with the ∼1 pc radius H 2 O maser disk, the HE component could potentially be located only a few parsecs more distant from the AGN and might then provide the N H ∼ 10 25 cm −2 column obscuring the nuclear hard X-rays. Finally, we also report sensitive upper limits extending up to J upper = 50, which place constraints on a previous model prediction for the CO emission from the X-ray obscuring torus.
A Spectral Line Survey of NGC 7027 at Millimeter Wavelengths
The Astrophysical Journal, 2008
We report on a recent spectral line survey of the planetary nebula (PN) NGC 7027 using the Arizona Radio Observatory (ARO) 12 m telescope and the Heinrich Hertz Submillimeter Telescope (SMT) at millimeter wavelengths. The spectra covering the frequency ranges 71-111 GHz, 157-161 GHz, and 218-267 GHz were obtained with a typical sensitivity of rms < 8 mK. A total of 67 spectral lines are detected, 21 of which are identified with 8 molecular species, 32 with recombination lines from hydrogen and helium, and 14 remains unidentified. As the widths of emission lines from CO, other neutral molecules, molecular ions, as well as recombination of H + and He + are found to be different with each other, the line strengths and profiles are used to investigate the physical conditions and chemical processes of the neutral envelope of NGC 7027. The column densities and fractional abundances relative to H 2 of the observed molecular species are calculated and compared with predictions from chemical models. We found evidence for overabundance of N 2 H + and underabundance of CS and HNC in NGC 7027, suggesting that X-ray emission and shock wave may play an important role in the chemistry of the hot molecular envelope of the young PN. Subject headings: ISM: molecules -radio lines: ISM -ISM: abundanceplanetary nebulae: individual (NGC 7027) 1 The 12 m telescope and the Heinrich Hertz Submillimeter Telescope (SMT) is operated by the Arizona Radio Observatory (ARO), Steward Observatory, University of Arizona.
Discovery of Far-Infrared Pure Rotational Transitions of CH[TSUP]+[/TSUP] in NGC 7027
The Astrophysical Journal, 1997
We report the discovery of the rotational spectrum of CH ϩ in the Infrared Space Observatory Long Wavelength Spectrometer (LWS) spectrum of the planetary nebula NGC 7027. The identification relies on a 1996 reanalysis of the LWS spectrum by Liu et al. and on new LWS data. The strong line at 179.62 m (coinciding with the 2 12 -1 01 transition of water vapor) and the lines at 119.90 and 90.03 m (reported as unidentified by Liu et al.), whose frequencies are in the harmonic relation 2Ϻ3:4, are shown to arise from the J ϭ 2-1, 3-2, and 4 -3 rotational transitions of CH ϩ . This identification is strengthened by the new LWS spectra of NGC 7027, which clearly show the next two rotational lines of CH ϩ at 72.140 and 60.247 m. This is the first time that the pure rotational spectrum of CH ϩ has been observed. This discovery opens the possibility of probing the densest and warmest zones of photodissociation regions. We derive a rotational temperature for the CH ϩ lines of 150 H 20 K and a CH ϩ ͞CO abundance ratio of 2-6 ϫ 10 Ϫ4 . Subject headings: planetary nebulae: individual (NGC 7027) -infrared: ISM: lines and bands FIG. 1.-CH ϩ lines observed in NGC 7027 (the continuum has been subtracted from the data). The solid lines are Gaussian line profile fits to the observed features (for blends, contributions from individual components are shown as dashed lines). The J ϭ 2-1 line at 179.62 m was previously assigned to H 2 O. For the J ϭ 4 -3 line, spectra from two different detectors-LW1 (bottom panel; the sharp rise at short wavelengths is due to the strong [O III] 88.36 m line) and SW5 (upper panel)-are shown. The J ϭ 4 -3 line is blended with the J ϭ 29 -28 line of CO at 90.16 m, which could contribute with an intensity less than 10 Ϫ19 W cm Ϫ2 -the J ϭ 27-26 and J ϭ 26 -25 lines of CO can be seen in the bottom left-hand panel of Fig. 2 with intensities of 110 Ϫ19 W cm Ϫ2 . The lines at 59.5 and 60.7 m in the top left-hand panel are unknown. L66 CERNICHARO ET AL. Vol. 483 L68 CERNICHARO ET AL.
The Astrophysical Journal, 2014
We present Herschel SPIRE-FTS observations of the Antennae (NGC 4038/39), a well studied, nearby (22 Mpc) ongoing merger between two gas rich spiral galaxies. The SPIRE-FTS is a low spatial (FWHM ∼ 19 − 43) and spectral (∼ 1.2 GHz) resolution mapping spectrometer covering a large spectral range (194 − 671 µm, 450 GHz − 1545 GHz). We detect 5 CO transitions (J = 4 − 3 to J = 8 − 7), both [CI] transitions and the [NII]205µm transition across the entire system, which we supplement with ground based observations of the CO J = 1 − 0, J = 2 − 1 and J = 3 − 2 transitions, and Herschel PACS observations of [CII] and [OI]63µm. Using the CO and [CI] transitions, we perform both a LTE analysis of [CI], and a non-LTE radiative transfer analysis of CO and [CI] using the radiative transfer code RADEX along with a Bayesian likelihood analysis. We find that there are two components to the molecular gas: a cold (T kin ∼ 10 − 30 K) and a warm (T kin 100 K) component. By comparing the
Discovery of far-IR pure rotational transitions of CH+ in NGC 70271
We report the discovery of the rotational spectrum of CH ϩ in the Infrared Space Observatory Long Wavelength Spectrometer (LWS) spectrum of the planetary nebula NGC 7027. The identification relies on a 1996 reanalysis of the LWS spectrum by Liu et al. and on new LWS data. The strong line at 179.62 m (coinciding with the 2 12 -1 01 transition of water vapor) and the lines at 119.90 and 90.03 m (reported as unidentified by Liu et al.), whose frequencies are in the harmonic relation 2Ϻ3:4, are shown to arise from the J ϭ 2-1, 3-2, and 4 -3 rotational transitions of CH ϩ . This identification is strengthened by the new LWS spectra of NGC 7027, which clearly show the next two rotational lines of CH ϩ at 72.140 and 60.247 m. This is the first time that the pure rotational spectrum of CH ϩ has been observed. This discovery opens the possibility of probing the densest and warmest zones of photodissociation regions. We derive a rotational temperature for the CH ϩ lines of 150 H 20 K and a CH ϩ ͞CO abundance ratio of 2-6 ϫ 10 Ϫ4 . Subject headings: planetary nebulae: individual (NGC 7027) -infrared: ISM: lines and bands FIG. 1.-CH ϩ lines observed in NGC 7027 (the continuum has been subtracted from the data). The solid lines are Gaussian line profile fits to the observed features (for blends, contributions from individual components are shown as dashed lines). The J ϭ 2-1 line at 179.62 m was previously assigned to H 2 O. For the J ϭ 4 -3 line, spectra from two different detectors-LW1 (bottom panel; the sharp rise at short wavelengths is due to the strong [O III] 88.36 m line) and SW5 (upper panel)-are shown. The J ϭ 4 -3 line is blended with the J ϭ 29 -28 line of CO at 90.16 m, which could contribute with an intensity less than 10 Ϫ19 W cm Ϫ2 -the J ϭ 27-26 and J ϭ 26 -25 lines of CO can be seen in the bottom left-hand panel of Fig. 2 with intensities of 110 Ϫ19 W cm Ϫ2 . The lines at 59.5 and 60.7 m in the top left-hand panel are unknown. L66 CERNICHARO ET AL. Vol. 483 L68 CERNICHARO ET AL.
Molecular Hydrogen Excitation around Active Galactic Nuclei
The Astrophysical Journal, 2005
We report R ∼ 3000 Very Large Telescope ISAAC K-band spectroscopy of the nuclei (i.e. central 100-300 pc) of nine galaxies hosting an active galactic nucleus. For five of these we also present spectra of the circumnuclear region out to 1 kpc. We have measured a number of molecular hydrogen lines in the ν = 1 − 0, 2 − 1, and 3 − 2 vibrational transitions, as well as the Brγ and He i recombination lines, and the Na i stellar absorption feature. Although only three of the galaxies are classified as type 1 Seyferts in the literature, broad Brγ (FWHM 1000 km s −1) is seen in seven of the objects. The ν = 1 − 0 emission appears thermalised at temperatures T ∼ 1000 K. However, the ν = 2 − 1 and ν = 3 − 2 emission show evidence of being radiatively excited by far-ultraviolet photons. The photo-dissociation region models that fit the data best are, as for the ultraluminous infrared galaxies in Davies et al. (2003), those for which the H 2 emission arises in dense clouds illuminated by intense FUV radiation. The Na i stellar absorption line is clearly seen in six of the nuclear spectra of these AGN, indicating the presence of a significant population of late type stars. It is possible that these stars are a result of the same episode of star formation that gave rise to the stars heating the PDRs. It seems unlikely that the AGN is the dominant source of excitation for the near infrared H 2 emission: in two of the nuclear spectra H 2 was not detected at all, and in general we find no evidence of suppression of the 2-1 S(3) line, which may occur in X-ray irradiated gas. Our data do not reveal any significant difference between the nuclear and circumnuclear line ratios, suggesting that the physical conditions of the dominant excitation mechanism are similar both near the AGN and in the larger scale environment around it, and that star formation is an important process even in the central 100 pc acround AGN.
Astronomy and Astrophysics, 2003
We present results of a comprehensive multi-frequency study of the radio galaxy B3 J2330+3927. The 1. 9 wide radio source, consisting of 3 components, is bracketed by 2 objects in our Keck K-band image. Optical and near-IR Keck spectroscopy of these two objects yield z = 3.087 ± 0.004. The brightest (K = 18.8) object has a standard type II AGN spectrum, and is the most likely location of the AGN, which implies a one-sided jet radio morphology. Deep 113 GHz observations with the IRAM Plateau de Bure Interferometer reveal CO J = 4−3 emission, which peaks at the position of the AGN. The CO line is offset by 500 km s −1 from the systemic redshift of the AGN, but corresponds very closely to the velocity shift of an associated H I absorber seen in Lyα. This strongly suggests that both originate from the same gas reservoir surrounding the AGN host galaxy. Simultaneous 230 GHz interferometer observations find a ∼3× lower integrated flux density when compared to single dish 250 GHz observations with MAMBO at the IRAM 30 m telescope. This can be interpreted as spatially resolved thermal dust emission at scales of 0. 5 to 6 . Finally, we present a τ < 1.3% limit to the H I 21 cm absorption against the radio source, which represents the seventh nondetection out of 8 z > 2 radio galaxies observed to date with the WSRT. We present mass estimates for the atomic, neutral, and ionized hydrogen, and for the dust, ranging from M(H I) = 2 × 10 7 M derived from the associated H I absorber in Lyα up to M(H 2 ) = 7 × 10 10 M derived from the CO emission. This indicates that the host galaxy is surrounded by a massive reservoir of gas and dust. The K-band companion objects may be concentrations within this reservoir, which will eventually merge with the central galaxy hosting the AGN.
The Astrophysical Journal, in press. 28mar2000
We present m ulti-transition observations of the HCO + molecule toward the very young star forming region associated with the NGC 2264G molecular out ow. Anomalous emission is observed in the lowest rotational transition: the J=4!3 and J=3!2 transitions clearly trace the dense core encompassing the exciting source of the molecular out ow, whereas the HCO + J=1!0 is barely detected at a much l o wer intensity and has a much broader line shape. Analysis of the data strongly suggests that the HCO + J=1!0 emission arising from the core is being absorbed e ciently by a cold low density e n velope around the core or a foreground cloud. This result seems exceptional, yet the J=1!0 HCO + and HCN emission from other dense cores especially those in giant molecular clouds may be a ected. In these cases, the rare isotopes of these molecules and higher rotational transitions of the main isotopes should be used to study these regions. Two quiescent clumps, JMG99 G1 and G2, are detected in the blue lobe of the NGC 2264G molecular out ow, close to shock excited near-IR H 2 knots. These clumps belong to the class of radiatively excited clumps, i.e., the radiation from the shock e v aporates the dust mantles and initiates a photochemical process, enhancing the emission of the HCO + .