We present high angular resolution observations of the HCN(1-0) emission (at ~1" or ~34 pc), together with CO J = 1-0, 2-1, and 3-2 observations, toward the Seyfert 2 nucleus of M51 (NGC 5194). The overall HCN(1-0) distribution and kinematics are very similar to that of the CO lines, which have been indicated as the jet-entrained molecular gas in our past observations. In addition, high HCN(1-0)/CO(1-0) brightness temperature ratio of about unity is observed along the jets, similar to that observed at the shocked molecular gas in our Galaxy. These results strongly indicate that both diffuse and dense gases are entrained by the jets and outflowing from the AGN. The channel map of HCN(1-0) at the systemic velocity shows a strong emission right at the nucleus, where no obvious emission has been detected in the CO lines. The HCN(1-0)/CO(1-0) brightness temperature ratio at this region reaches >2, a value that cannot be explained considering standard physical/chemical conditions. Based on our calculations, we suggest infrared pumping and possibly weak HCN masing, but still requiring an enhanced HCN abundance for the cause of this high ratio. This suggests the presence of a compact dense obscuring molecular gas in front of the nucleus of M51, which remains unresolved at our ~1" (~34 pc) resolution, and consistent with the Seyfert 2 classification picture.
We present the results of our ALMA observations of three AGN-dominated nuclei in optical Seyfert 1 galaxies (NGC 7469, I Zw 1, and IC 4329 A) and eleven luminous infrared galaxies (LIRGs) with various levels of infrared estimated energetic contributions by AGNs at the HCN and HCO+ J=3-2 emission lines. The HCN and HCO+ J=3-2 emission lines are clearly detected at the main nuclei of all sources, except for IC 4329 A. The vibrationally excited (v2=1f) HCN J=3-2 and HCO+ J=3-2 emission lines are simultaneously covered, and HCN v2=1f J=3-2 emission line signatures are seen in the main nuclei of tw…
A systematic study is performed on radio properties of H$_{2}$O megamaser host Seyfert 2 galaxies, through multi-band radio continuum observations (at 11cm, 6.0 cm, 3.6 cm, 2.0 cm and 1.3 cm) with the Effelsberg 100-m radio telescope within a total time duration of four days. For comparison, a control Seyfert 2 galaxy sample without detected maser emission was also observed. Spectral indices were determined for those sources for which measurements exist at two adjacent bands assuming a power-law dependence S$_ν\propto ν^{-α}$, where S is the flux density and $ν$ is the frequency. Comparisons o…
The nearby Sy 1 galaxy NGC 1097 represents an ideal laboratory to explore the molecular chemistry in the presence and surroundings of an active galactic nucleus. Exploring the distribution of different molecular species allows us to understand the physical processes affecting the ISM both in the AGN vicinity as well as in the outer star forming molecular ring. We carried out 3 mm ALMA observations of HCN, HCO+, CCH, CS, HNCO, SiO, HC3N, and SO as well as the 13C isotopologues. All species were imaged over the central 2 kpc (~30") of the galaxy at a resolution of ~2.2"x1.5 (150 pc x 100 pc). HC…
Analyzing archival data from different telescopes, H2O megamaser Seyfert 2s appeared to exhibit higher nuclear radio luminosities than non-masing Seyfert 2s (Zhang et al. 2012). This has been confirmed by our follow-up study on multi-band (11, 6, 3.6, 2, 1.3 cm) radio properties of maser host Seyfert 2s, through systematic Effelsberg observations (Liu et al. 2017). The nuclear radio luminosity was supposed to be a suitable indicator to guide future AGN maser searches. Thus we performed a pilot survey with the Effelsberg telescope on H2O maser emission toward a small sample of radio-bright Seyf…
We discuss the dense molecular gas in central regions of nearby Seyfert galaxies, and report new arcsec resolution observations of HCN(1-0) and HCO$^+$(1-0) for 3 objects. In NGC 3079 the lines show complex profiles as a result of self-absorption and saturated continuum absorption. H$^{13}$CN reveals the continuum absorption profile, with a peak close to the galaxy's systemic velocity that traces disk rotation, and a second feature with a blue wing extending to $-350$km s$^{-1}$ that most likely traces a nuclear outflow. The morphological and spectral properties of the emission lines allow us …
In a pilot project to study the relationship between star formation and molecular gas properties in nearby normal early-type galaxies, we used the IRAM 30m telescope to observe the 13CO(J=1-0), 13CO(J=2-1), HCN(J=1-0) and HCO+(J=1-0) line emission in the four galaxies of the SAURON sample with the strongest 12CO emission. We report the detection of 13CO emission in all four SAURON sources and HCN emission in three sources, while no HCO+ emission was found to our detection limits in any of the four galaxies. We find that the 13CO/12CO ratios of three SAURON galaxies are somewhat higher than tho…
We report ALMA observations of CO(3-2) emission in the Seyfert 1 galaxy NGC 1566, at a spatial resolution of 25 pc. Our aim is to investigate the morphology and dynamics of the gas inside the central kpc, and to probe nuclear fueling and feedback phenomena. NGC 1566 has a nuclear bar of 1.7 kpc radius and a conspicuous grand design spiral starting from this radius. The ALMA field of view, of diameter 0.9 kpc, lies well inside the nuclear bar and reveals a molecular trailing spiral structure from 50 to 300~pc in size, which is contributing to fuel the nucleus, according to its negative gravity …
We present ALMA Cycle 1 observations of the central kpc region of the luminous type-1 Seyfert galaxy NGC 7469 with unprecedented high resolution (0.5$"$ $\times$ 0.4$"$ = 165 pc $\times$ 132 pc) at submillimeter wavelengths. Utilizing the wide-bandwidth of ALMA, we simultaneously obtained HCN(4-3), HCO$^+$(4-3), CS(7-6), and partially CO(3-2) line maps, as well as the 860 $μ$m continuum. The region consists of the central $\sim$ 1$"$ component and the surrounding starburst ring with a radius of $\sim$ 1.5$"$-2.5$"$. Several structures connect these components. Except for CO(3-2), these dense g…
We present observational results of water vapor maser emission with our high-sensitivity 22 GHz VLBI imaging of the Seyfert galaxy NGC 1068. In this galaxy, there are the following four nuclear radio sources; NE, C, S1, and S2. Among them, the S1 component has been identified as the nucleus while the C component has been considered as attributed to the radio jet. In our VLBI observation, we find the following two types of the water maser emission at the S1 component. One is the linearly aligned component that is considered as an edge-on disk with the inner radius of 0.62 pc. The dynamical mass…
The distribution of warm molecular gas (1000--3000 K), traced by the near-IR H$_2$ 2.12 $μ$m line, has been imaged with a resolution $<0.5$ arcsec in the central 1 kpc of seven nearby Seyfert galaxies. We find that this gas is highly concentrated towards the central 100 pc and that its morphology is often symmetrical. Lanes of warm H$_2$ gas are observed only in three cases (NGC\,1068, NGC\,1386 and Circinus) for which the morphology is much wider and extended than the dust filaments. We conclude that there is no one-to-one correlation between dust and warm gas. This indicates that, if the dus…
Multiple molecular lines are useful for studying the physical properties of multiphase star-forming gas in different types of galaxies. We probe the molecular gas throughout the disc of the spiral galaxy NGC~5033, hosting an active galactic nucleus (AGN), using multiple low-$J$ CO lines [$^{12}$CO(1-0, 2-1, 3-2 and $^{13}$CO(1-0, 2-1)] and dense gas tracers [HCN(1-0) and HCO$^{+}$(1-0)]. Firstly, we determine the ratios of the integrated intensity maps and the ratio of intensities in position velocity diagrams. Secondly, we obtain the ratios of CO lines and high-density tracers at the centre; …
We present the first 100 pc scale view of the dense molecular gas in the central ~ 1.3 kpc region of the type-1 Seyfert NGC 1097 traced by HCN (J=4-3) and HCO+ (J=4-3) lines afforded with ALMA band 7. This galaxy shows significant HCN enhancement with respect to HCO+ and CO in the low-J transitions, which seems to be a common characteristic in AGN environments. Using the ALMA data, we study the characteristics of the dense gas around this AGN and search for the mechanism of HCN enhancement. We find a high HCN (J=4-3) to HCO+ (J=4-3) line ratio in the nucleus. The upper limit of the brightness …
We analyse the influence of the dynamical environment on the star formation (SF) relations of the dense molecular gas in the starburst (SB) ring of the Seyfert 2 galaxy NGC 1068. We used ALMA to image the emission of the 1-0 transitions of HCN and HCO+ with a resolution of 56 pc. We also used ancillary data of CO(1-0) at a resolution of ~100 pc, and CO(3-2) and its underlying continuum emission at ~40 pc. These observations allow us to probe a range of molecular gas densities (n(H2)~10$^{3-5}cm^{-3}$). The SF rate (SFR) is derived from Pa$α$ line emission imaged by HST/NICMOS. We analysed how …
We report ALMA observations of molecular gas and continuum emission in the 90 and 350 GHz bands toward a nearby Seyfert galaxy NGC 613. Radio continuum emissions were detected at 95 and 350 GHz from both the circum-nuclear disk (CND) ($r\leq90$ pc) and a star-forming ring (250 pc $\leq r\leq 340$ pc), and the 95 GHz continuum was observed to extend from the center at a position angle of $20^{\circ} \pm 8^{\circ}$. The archival 4.9 GHz data and our 95 GHz data show spectral indices of $α\leq -0.6$ and $-0.2$ along the jets and in the star-forming ring; these can be produced by synchrotron emiss…
With the incorporation of high-J molecular lines, we aim to constrain the physical conditions of the dense gas in the central region of the Seyfert 2 galaxy NGC 1068 and to determine signatures of the AGN or the starburst contribution. We used the James Clerk Maxwell Telescope to observe the J=4-3 transition of HCN, HNC, and HCO+, as well as the CN N_J=2_{5/2}-1_{3/2} and N_J=3_{5/2}-2_{5/2}, in NGC 1068. We estimate the excitation conditions of HCN, HNC, and CN, based on the line intensity ratios and radiative transfer models. We find that the bulk emission of HCN, HNC, CN, and the high-J HCO…
We report on Atacama Large Millimeter Array (ALMA) observations of CO(3-2) emission in the Seyfert2/starburst galaxy NGC1808, at a spatial resolution of 4pc. Our aim is to investigate the morphology and dynamics of the gas inside the central 0.5kpc and to probe the nuclear feeding and feedback phenomena. We discovered a nuclear spiral of radius 1"=45pc. Within it, we found a decoupled circumnuclear disk or molecular torus of a radius of 0.13"=6pc. The HCN(4-3) and HCO$\rm^+$(4-3) and CS(7-6) dense gas line tracers were simultaneously mapped and detected in the nuclear spiral and they present t…
We present new ~1" resolution data of the dense molecular gas in the central 50-100 pc of four nearby Seyfert galaxies. PdBI observations of HCN and, in 2 of the 4 sources, simultaneously HCO+ allow us to carefully constrain the dynamical state of the dense gas surrounding the AGN. Analysis of the kinematics shows large line widths of 100-200 km/s FWHM that can only partially arise from beam smearing of the velocity gradient. The observed morphological and kinematic parameters (dimensions, major axis position angle, red and blue channel separation, and integrated line width) are well reproduce…
Surveying the Whirlpool at Arcseconds with NOEMA (SWAN). IV. Extent of active galactic nucleus feedback on the interstellar medium
Universität Bonn（波恩大学）；Observatorio Astronómico Nacional (IGN)（国家天文台（西班牙地理与测绘研究所））；The Ohio State University（俄亥俄州立大学）；Center for Cosmology and Astro-Particle Physics, Ohio State University（俄亥俄州立大学宇宙学与天体粒子物理中心）；National Astronomical Observatory of Japan（日本国立天文台）；Max Planck Institute for Radio Astronomy（马克斯·普朗克射电天文研究所）；University of Arkansas（阿肯色大学）
We report ALMA observations of NGC 1052 to quest mass accretion in a gas-poor active galactic nucleus (AGN). We detected CO emission representing a rotating ring-like circumnuclear disk (CND) seen edge-on with the gas mass of $5.3 \times 10^{5}$ M$_{\odot}$. The CND has smaller gas mass than that in typical Seyfert galaxies with circumnuclear star formation and is too gas-poor to drive mass accretion onto the central engine. The continuum emission casts molecular absorption features of CO, HCN, HCO$^+$, SO, SO$_2$, CS, CN, and H$_2$O, with H$^{13}$CN and HC$^{15}$N and vibrationally-excited (v…
We present a 190-307 GHz broadband spectrum obtained with Z-Spec of NGC 1068 with new measurements of molecular rotational transitions. After combining our measurements with those previously published and considering the specific geometry of this Seyfert 2 galaxy, we conduct a multi-species Bayesian likelihood analysis of the density, temperature, and relative molecular abundances of HCN, HNC, CS, and HCO+. We find that these molecules trace warm (T > 100 K) gas of H2 number densities 10^4.2 - 10^4.9 cm^-3. Our models also place strong constraints on the column densities and relative abundance…
We investigate the fueling and the feedback of star formation and nuclear activity in NGC1068, a nearby (D=14Mpc) Seyfert 2 barred galaxy, by analyzing the distribution and kinematics of the molecular gas in the disk. We have used ALMA to map the emission of a set of dense molecular gas 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 ~ 2kpc of NGC1068 with spatial resolutions ~ 0.3"-0.5" (~ 20-35pc). Molecular line and dust continuum emissions are detected from a r ~ 200pc off-centered circumnuclear disk (CND), from the 2.6kp…
We present a detailed analysis of 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 disk (CND) and the ~ 1.3 kpc starburst ring (SB ring) of NGC~1068, a nearby (D = 14 Mpc) Seyfert 2 barred galaxy. We aim at determining the physical characteristics of the dense gas present in the CND and 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. We estimate t…
Recent developments in (sub-)millimeter facilities have drastically changed the amount of information obtained from extragalactic spectral scans. In this paper, we present a feature extraction technique using principal component analysis (PCA) applied to arcsecond-resolution (1.0-2.0 arcsec = 72-144 pc) spectral scan datasets for the nearby type-2 Seyfert galaxy, NGC 1068, using Band 3 of the Atacama Large Millimeter/submillimeter Array. We apply PCA to 16 well-detected molecular line intensity maps convolved to a common 150 pc resolution. In addition, we include the [SIII]/[SII] line ratio an…
We present \ci\,(2--1) and multi-transition $^{12}$CO observations of a dusty star-forming galaxy, ACT\,J2029+0120, which we spectroscopically confirm to lie at $z$\,=\,2.64. We detect CO(3--2), CO(5--4), CO(7--6), CO(8--7), and \ci\,(2--1) at high significance, tentatively detect HCO$^{+}$(4--3), and place strong upper limits on the integrated strength of dense gas tracers (HCN(4--3) and CS(7--6)). Multi-transition CO observations and dense gas tracers can provide valuable constraints on the molecular gas content and excitation conditions in high-redshift galaxies. We therefore use this uniqu…
Recent observational studies have shown that H2O emission at (rest) submillimeter wavelengths is ubiquitous in infrared galaxies, both in the local and in the early Universe, suggestive of far-infrared pumping of H2O by dust in warm regions. In this work, models are presented that show that (i) the highest-lying H2O lines (E_{upper}>400 K) are formed in very warm (T_{dust}>~90 K) regions and require high H2O columns (N_{H2O}>~3x10^{17} cm^{-2}), while lower lying lines can be efficiently excited with T_{dust}~45-75 K and N_{H2O}~(0.5-2)x10^{17} cm^{-2}; (ii) significant collisional excitation …
We report ALMA observations of CO(3-2) emission in the Seyfert galaxy NGC613, at a spatial resolution of 17pc, as part of our NUclei of GAlaxies sample. Our aim is to investigate the morphology and dynamics of the gas inside the central kpc, and to probe nuclear fueling and feedback phenomena. The morphology of CO(3-2) line emission reveals a 2-arm trailing nuclear spiral at $r\lesssim$100pc and a circumnuclear ring at ~350pc radius, that is coincident with the star-forming ring seen in the optical images. The molecular gas in the galaxy disk is in a remarkably regular rotation, however, the k…
