The late-type spiral galaxy NGC 6946 is a prime example of molecular gas dynamics driven by "bars within bars". Here we use data from the BIMA SONG and HERACLES surveys to analyse the structure and stability of its molecular disc. Our radial profiles exhibit a clear transition at distance R ~ 1 kpc from the galaxy centre. In particular, the surface density profile breaks at R ~ 0.8 kpc and is well fitted by a double exponential distribution with scale lengths R_1 ~ 200 pc and R_2 ~ 3 kpc, while the 1D velocity dispersion sigma decreases steeply in the central kpc and is approximately constant at larger radii. The fact that we derive and use the full radial profile of sigma rather than a constant value is perhaps the most novel feature of our stability analysis. We show that the profile of the Q stability parameter traced by CO emission is remarkably flat and well above unity, while the characteristic instability wavelength exhibits clear signatures of the nuclear starburst and inner bar within bar. We also show that CO-dark molecular gas, stars and other factors can play a significant role in the stability scenario of NGC 6946. Our results provide strong evidence that gravitational instability, radial inflow and disc heating have driven the formation of the inner structures and the dynamics of molecular gas in the central kpc.
Hydrodynamical Simulations of the Barred Spiral Galaxy NGC 1097
NGC 1097是附近的一个棒旋星系，据信正在与位于其西北部的椭圆星系NGC 1097 A相互作用。它拥有一个塞弗特1核，周围环绕着一个星暴环。两条笔直的尘埃带连接到环上，几乎连续不断地延伸到酒吧。尘埃带的另一端连接到两个主旋臂上。为了对其结构和运动学特性提供物理理解，进行了二维流体动力学模拟。数值计算表明，气体的形态和运动学的许多功能可以重现提供的气体流量是由一个缓慢旋转的强酒吧相关的重力势。在计算中考虑了气体盘的自引力，我们发现星暴环是引力不稳定的，这与\citet{hsieh11}的观测结果是一致的。我们的模拟表明，气体流入率为0.17 M $_\sun$年$^{-1}$到该地区内的星暴环，即使在其形成后，导致核环和环核盘的共存。
We performed a series of 29 gasdynamical simulations of disc galaxies, barred and unbarred, with various stellar masses, to study the impact of the bar on star formation history. Unbarred galaxies evolve very smoothly, with a star formation rate (SFR) that varies by at most a factor of three over a period of 2 Gyr. The evolution of barred galaxies is much more irregular, especially at high stellar masses. In these galaxies, the bar drives a substantial amount of gas toward the centre, resulting in a high SFR, and producing a starburst in the most massive galaxies. Most of the gas is converted …
NGC 1808 is a nearby barred starburst galaxy with an outflow from the nuclear region. To study the inflow and outflow processes related to star formation and dynamical evolution of the galaxy, we have carried out \(^{12}\)CO (\(J=1-0\)) mapping observations of the central \(r\sim4\) kpc of NGC 1808 using the Atacama Large Millimeter/submillimeter Array (ALMA). Four distinct components of molecular gas are revealed at high spatial resolution of 2\arcsec (\(\sim100\) pc): (1) a compact (\(r<200\) pc) circumnuclear disk (CND), (2) \(r\sim500\) pc ring, (3) gas-rich galactic bar, and (4) spiral ar…
Suppression of star formation at the centre of barred AGN galaxies
Waseda University（早稻田大学）；University of Tsukuba（筑波大学）；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）；Purple Mountain Observatory, Chinese Academy of Sciences（中国科学院紫金山天文台）
To investigate the role of bars in the chemical evolution of isolated disc galaxies, we performed a series of 39 gas dynamical simulations of isolated barred and unbarred galaxies with various masses, initial gas fractions, and AGN feedback models. The presence of a bar drives a substantial amount of gas toward the central region of the galaxy. In the most massive galaxies, this results in a violent starburst, followed by a drop in star formation resulting from gas exhaustion. The time delay between Type Ia and Type II supernovae explosions means that barred galaxies experience a rapid increas…
We study the star formation activity of nearby galaxies with bars using a sample of late-type galaxies at 0.02$\leq z \leq$ 0.05489 and $M_r <-19.5$ from the Sloan Digital Sky Survey. We compare the physical properties of strongly and weakly barred galaxies with those of non-barred galaxies that have stellar mass and redshift distributions similar to barred galaxies. We find that the star formation activity of strongly barred galaxies probed by starburstiness, $\it{g-r}$, NUV$-r$, and mid-infrared [3.4]$-$[12] colors is, on average, lower than that of non-barred galaxies. However, weakly barre…
Vaulting the barrier: An intrinsic mechanism to fuel the gas beyond the nuclear ring into the central region of barred galaxies
Kagoshima University（鹿儿岛大学）；Kobe University（神户大学）；National Astronomical Observatory of Japan（日本国立天文台）；Ehime University, Research Center for Space and Cosmic Evolution（爱媛大学宇宙进化研究中心）；Hokkaido University, Faculty of Science（北海道大学理学部）
We present a numerical study of the impact of AGN accretion and feedback on the star formation history of barred disc galaxies. Our goal is to determine whether the effect of feedback is positive (enhanced star formation) or negative (quenched star formation), and to what extent. We performed a series of 12 hydrodynamical simulations of disc galaxies, 10 barred and 2 unbarred, with various initial gas fractions and AGN feedback prescriptions. In barred galaxies, gas is driven toward the centre of the galaxy and causes a starburst, followed by a slow decay, while in unbarred galaxies the SFR in…
The lenticular galaxy IC 676 is a barred galaxy with double nuclei and active star formation in the central region. In this work we present the long-slit spectroscopy and archival multi-wavelength images to investigate the nature and origin of the double nuclei in IC 676. Through photometric 1D brightness profiles and 2D image decomposition, we show that this galaxy consists of a stellar bar with the length of $\sim$ 2.5 kpc and two Sérsic disks both of which with Sérsic index $\it n \sim$ 1.3. There is probably little or no bulge component assembled in IC 676. The luminosities of the double n…
Observations and simulations of barred spiral galaxies have shown that, in general, the spiral arms rotate at a different pattern speed to that of the bar. The main conclusion from the bibliography is that the bar rotates faster than the spiral arms with a double or even a triple value of angular velocity. The theory that prevails in explaining the formation of the spiral arms in the case of a barred spiral galaxy with two pattern speeds is the manifold theory, where the orbits that support the spiral density wave are chaotic, and are related to the manifolds emanating from the Lagrangian poin…
Galactic bars are frequent in disk galaxies and they may support the transfer of matter towards the central engine of active nuclei. The barred galaxy NGC 1097 has magnetic forces controlling the gas flow at several kpc scales, which suggest that magnetic fields (B-fields) are dynamically important along the bar and nuclear ring. However, the effect of the B-field on the gas flows in the central kpc scale has not been characterized. Using thermal polarized emission at $89$ $μ$m with HAWC+/SOFIA, here, we measure that the polarized flux is spatially located at the contact regions of the outer-b…
Revealing the properties of molecular gas in starburst galaxies is key to understand the process of star formation across cosmic history. In this paper, we present our recent high-resolution ($\sim1''$ or 50 pc) ALMA observations of the nearby, barred starburst galaxy NGC 1808, and highlight some of the main findings: (1) the discovery of a double peak revealed in the distributions of CO (3-2) and CS (2-1) in the circumnuclear disk indicating the presence of a molecular gas torus with a radius of $r\sim30$ pc; inside the torus, we found a compact source of dust continuum at 0.87 mm and CO, coi…
Exploring the Relationship Between Bars, Star Formation Activity, and Host Galaxy Properties from $\mathbf{z \sim 0}$ to $\mathbf{z \sim 2}$
The University of Texas at Austin（德克萨斯大学奥斯汀分校）；NASA Goddard Space Flight Center（美国宇航局戈达德太空飞行中心）；Instituto de Astrofísica de Canarias（加那利天体物理研究所）；Universidad de La Laguna（拉古纳大学）
ALMA Imaging of Gas and Dust in a Galaxy Protocluster at Redshift 5.3: [CII] Emission in "Typical" Galaxies and Dusty Starbursts ~1 Billion Years after the Big Bang
The center of the nearby galaxy NGC\,253 hosts a population of more than a dozen super star clusters (SSCs) which are still in the process of forming. The majority of the star formation of the burst is concentrated in these SSCs, and the starburst is powering a multiphase outflow from the galaxy. In this work, we measure the 350~GHz dust continuum emission towards the center of NGC\,253 at 47~milliarcsecond (0.8 pc) resolution using data from the Atacama Large Millimeter/submillimeter Array (ALMA). We report the detection of 350~GHz (dust) continuum emission in the outflow for the first time, …
Galaxy Zoo Bar Lengths: A Catalogue of Measurements from Hubble Space Telescope Images and the Evolution of Galactic Bar Structure at z < 1
University of California, Santa Cruz（加州大学圣克鲁兹分校）；Lancaster University（兰卡斯特大学）；Haverford College（哈弗福德学院）；University of California, San Diego（加州大学圣迭戈分校）；Masaryk University（马萨里克大学）
Mrk\,622 is a Compton Thick AGN and a double-peaked narrow emission line galaxy, thus a dual AGN candidate. In this work, new optical long-slit spectroscopic observations clearly show that this object is rather a triple peaked narrow emission line galaxy, with both blue and red shifted narrow emission lines, as well as a much narrower emission line centred at the host galaxy systemic velocity. The average velocity offset between the blue and red shifted components is $\sim$500 km\,s$^{-1}$, which is producing the apparent double-peaked emission lines. These two components are in the loci of AG…
We report the Atacama Large Millimeter/submillimeter Array (ALMA) observations of the metal rich host galaxy of superluminous supernova (SLSN) PTF10tpz, a barred spiral galaxy at z=0.03994. We find the CO(1-0) emission to be confined within the bar of the galaxy. The distribution and kinematics of molecular gas in the host galaxy resemble gas flows along two lanes running from the tips of the bar towards the galaxy center. These gas lanes end in a gaseous structure in the inner region of the galaxy, likely associated with an inner Lindblad resonance. The interaction between the large-scale gas…
We present interferometric observations of CO lines (12CO(1-0, 2-1) and 13CO(1-0, 2-1)) and dense gas tracers (HCN(1-0), HCO+(1-0), HNC(1-0) and HNCO(4-3)) in two nearby edge-on barred lenticular galaxies, NGC 4710 and NGC 5866, with most of the gas concentrated in a nuclear disc and an inner ring in each galaxy. We probe the physical conditions of a two-component molecular interstellar medium in each galaxy and each kinematic component by using molecular line ratio diagnostics in three complementary ways. First, we measure the ratios of the position-velocity diagrams of different lines, secon…
We report on Atacama Large Millimeter Array (ALMA) observations of CO(3-2) emission in the Seyfert2/starburst galaxy NGC1808, at a spatial resolution of 4pc. Our aim is to investigate the morphology and dynamics of the gas inside the central 0.5kpc and to probe the nuclear feeding and feedback phenomena. We discovered a nuclear spiral of radius 1"=45pc. Within it, we found a decoupled circumnuclear disk or molecular torus of a radius of 0.13"=6pc. The HCN(4-3) and HCO$\rm^+$(4-3) and CS(7-6) dense gas line tracers were simultaneously mapped and detected in the nuclear spiral and they present t…
We present results from Atacama Large Millimeter/submillimeter Array (ALMA) observations of CS from the nearby galaxy NGC 1068 ($\sim14$ Mpc). This Seyfert 2 barred galaxy possesses a circumnuclear disc (CND, $r\sim200$ pc) and a starburst ring (SB ring, $r\sim1.3$ kpc). These high-resolution maps ($\sim0.5$", $\sim35$ pc) allow us to analyse specific sub-regions in the galaxy and investigate differences in line intensity ratios and physical conditions, particularly those between the CND and SB ring. Local thermodynamic equilibrium (LTE) analysis of the gas is used to calculate CS densities in…
NGC 1808 is a nearby barred spiral galaxy which hosts young stellar clusters in a patchy circumnuclear ring with a radius of $\sim 240\,\mathrm{pc}$. In order to study the gaseous and stellar kinematics and the star formation properties of the clusters, we perform seeing-limited $H+K$-band near-infrared integral-field spectroscopy with SINFONI of the inner $\sim 600\,\mathrm{pc}$. From the $M_\mathrm{BH}-σ_*$ relation, we find a black hole mass of a few $10^7\,M_\odot$. We estimate the age of the young stellar clusters in the circumnuclear ring to be $\lesssim 10\,\mathrm{Myr}$. No age gradien…
Galaxy UV Legacy Project: Survey Description and First Insights Into NGC 4449 Recent History of Star Formation
Gemini Observatory/NSFs NOIRLab（双子座天文台/美国国家光学红外天文研究实验室）；Space Telescope Science Institute（太空望远镜科学研究所）；AURA for the European Space Agency (ESA), ESA Office, Space Telescope Science Institute（欧洲航天局（ESA）办公室，太空望远镜科学研究所）；Dept. of Astronomy, University of Massachusetts, Amherst（马萨诸塞大学阿默斯特分校天文学系）；Department of Physics, The University of Auckland（奥克兰大学物理系）；Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg（海德堡大学天文学计算研究所）；University of Arizona（亚利桑那大学）；Astrophysics Research Cluster, School of Mathematical and Physical Sciences, University of Sheffield（谢菲尔德大学数理科学学院天体物理学研究集群）；Department of Astronomy, O（天文学系）
We study the feedback of star formation and nuclear activity on the chemistry of molecular gas in NGC1068, a nearby (D=14Mpc) Seyfert 2 barred galaxy, by analyzing if the abundances of key molecular species like ethynyl (C2H), a classical tracer of PDR, change in the different environments of the disk of the galaxy. We have used ALMA to map the emission of the hyperfine multiplet of C2H(N=1-0) and its underlying continuum emission in the central r~35"(2.5kpc)-region of the disk of NGC1068 with a spatial resolution 1.0"x0.7"(50-70pc). We have developed a set of time-dependent chemical models to…
