scholarly journals 5.11. Dense molecular gas in nearby galaxies

1998 ◽  
Vol 184 ◽  
pp. 231-233 ◽  
Author(s):  
Y. Gao ◽  
P.M. Solomon
Keyword(s):  
Dipole Moment ◽  
Surface Brightness ◽  
Galactic Nuclei ◽  
Molecular Gas ◽  
Galactic Disks ◽  
Central Regions ◽  
Nearby Galaxies ◽  
Gas Properties

HCN, one of the most abundant high dipole-moment molecules (traces molecular gas at densities ≳ 3 × 104 cm−3 whereas CO traces at ∼ 500 cm−3), has only been detected in ∼ 25 galaxies, primarily towards the galactic nuclei (Solomon et al. 1992; Nguyen-Q-Rieu et al. 1992; Helfer & Blitz 1993; Aalto et al. 1995). Dense molecular gas properties in “normal” galactic disks, as compared to the centers of “normal” spirals, starbursts, and luminous IR galaxies are not clear. As part of a large HCN survey in 60 galaxies (Gao 1996; Gao & Solomon 1997), we present here HCN observations in central regions of a few nearby galaxies. HCN was mapped at least along the major axes in the inner disks to determine the total HCN luminosity, the distribution with radius of HCN emission, and of the surface brightness ratio of SBR ≡ IHCN/ICO.

scholarly journals Physical properties and kinematics of the molecular gas near galaxy nuclei

1997 ◽  
Vol 178 ◽  
pp. 489-500
Author(s):  
L.J. Tacconi
Keyword(s):  
Physical Properties ◽  
Spatial Resolution ◽  
Chemical Processes ◽  
Molecular Gas ◽  
Submillimeter Wavelength ◽  
Nearby Galaxies ◽  
Physical And Chemical ◽  
Size Scales ◽  
Made In ◽  
Gas Properties

During the last decade there have been enormous steps forward in our understanding of the molecular gas properties of other galaxies, due to the huge increase in sensitivity and spatial resolution of instruments in the millimeter and submillimeter wavelength ranges. In particular, the emphasis has shifted from trying to detect CO in a variety of objects to studying the gas distributions and kinematics in a variety of species and transitions. For nearby galaxies, we are now able to study the physical and chemical processes occurring in the molecular gas over GMC size scales. Here I discuss a few examples of progress made in the study of galaxy nuclei.

scholarly journals The ALMaQUEST Survey – II. What drives central starbursts at z ∼ 0?

2020 ◽  
Vol 492 (4) ◽  
pp. 6027-6041 ◽  
Author(s):  
Sara L Ellison ◽  
Mallory D Thorp ◽  
Hsi-An Pan ◽  
Lihwai Lin ◽  
Jillian M Scudder ◽  
...  
Keyword(s):  
Star Formation ◽  
Surface Density ◽  
Stellar Mass ◽  
Starburst Galaxies ◽  
Molecular Gas ◽  
Central Regions ◽  
Primary Driver ◽  
Nearby Galaxies ◽  
Field Unit ◽  
Formation Efficiency

ABSTRACT Starburst galaxies have elevated star formation rates (SFRs) for their stellar mass. In Ellison et al., we used integral field unit maps of SFR surface density (ΣSFR) and stellar mass surface density (Σ⋆) to show that starburst galaxies in the local universe are driven by SFRs that are preferentially boosted in their central regions. Here, we present molecular gas maps obtained with the Atacama Large Millimeter Array (ALMA) observatory for 12 central starburst galaxies at z ∼ 0 drawn from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. The ALMA and MaNGA data are well matched in spatial resolution, such that the ALMA maps of molecular gas surface density ($\Sigma _{\rm H_2}$) can be directly compared with MaNGA maps at kpc-scale resolution. The combination of $\Sigma _{\rm H_2}$, Σ⋆ and ΣSFR at the same resolution allow us to investigate whether central starbursts are driven primarily by enhancements in star formation efficiency (SFE) or by increased gas fractions. By computing offsets from the resolved Kennicutt-Schmidt relation ($\Sigma _{\rm H_2}$ versus ΣSFR) and the molecular gas main sequence (Σ⋆ versus $\Sigma _{\rm H_2}$), we conclude that the primary driver of the central starburst is an elevated SFE. We also show that the enhancement in ΣSFR is accompanied by a dilution in O/H, consistent with a triggering that is induced by metal poor gas inflow. These observational signatures are found in both undisturbed (9/12 galaxies in our sample) and recently merged galaxies, indicating that both interactions and secular mechanisms contribute to central starbursts.

scholarly journals Active galactic nuclei winds as the origin of the H2 emission excess in nearby galaxies

2019 ◽  
Vol 491 (1) ◽  
pp. 1518-1529 ◽  
Author(s):  
Rogemar A Riffel ◽  
Nadia L Zakamska ◽  
Rogério Riffel
Keyword(s):  
Star Formation ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Indirect Detection ◽  
Molecular Gas ◽  
Host Galaxies ◽  
Spatially Resolved ◽  
Tightly Coupled ◽  
Nearby Galaxies ◽  
A Minor

ABSTRACT In most galaxies, the fluxes of rotational H2 lines strongly correlate with star formation diagnostics [such as polycyclic aromatic hydrocarbons (PAHs)], suggesting that H2 emission from warm molecular gas is a minor by-product of star formation. We analyse the optical properties of a sample of 309 nearby galaxies derived from a parent sample of 2015 objects observed with the Spitzer Space Telescope. We find a correlation between the [O i]λ6300 emission-line flux and kinematics and the H2 S(3) 9.665 $\mu\mathrm{ m}$/PAH 11.3  $\mu\mathrm{ m}$. The [O i]λ6300 kinematics in active galactic nuclei (AGNs) cannot be explained only by gas motions due to the gravitational potential of their host galaxies, suggesting that AGN-driven outflows are important to the observed kinematics. While H2 excess also correlates with the fluxes and kinematics of ionized gas (probed by [O iii]), the correlation with [O i] is much stronger, suggesting that H2 and [O i] emissions probe the same phase or tightly coupled phases of the wind. We conclude that the excess of H2 emission seen in AGNs is produced by shocks due to AGN-driven outflows and in the same clouds that produce the [O i] emission. Our results provide an indirect detection of neutral and molecular winds and suggest a new way to select galaxies that likely host molecular outflows. Further ground- and space-based spatially resolved observations of different phases of the molecular gas (cold, warm, and hot) are necessary to test our new selection method.

scholarly journals CO Multi-line Imaging of Nearby Galaxies (COMING). X. Physical conditions of molecular gas and the local SFR–mass relation

2020 ◽  
Vol 72 (5) ◽  
Author(s):  
Kana Morokuma-Matsui ◽  
Kazuo Sorai ◽  
Yuya Sato ◽  
Nario Kuno ◽  
Tsutomu T Takeuchi ◽  
...  
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Formation Rate ◽  
Flux Ratio ◽  
Line Center ◽  
Molecular Gas ◽  
Mass Relation ◽  
Signal To Noise ◽  
Nearby Galaxies ◽  
Gas Properties

Abstract We investigate the molecular gas properties of galaxies across the main sequence of star-forming (SF) galaxies in the local Universe using 12CO(J = 1–0), hereafter 12CO, and 13CO(J = 1–0), hereafter 13CO, mapping data of 147 nearby galaxies obtained in the COMING project, a legacy project of the Nobeyama Radio Observatory. In order to improve the signal-to-noise ratios of both lines, we stack all the pixels where 12CO emission is detected after aligning the line center expected from the first-moment map of 12CO. As a result, 13CO emission is successfully detected in 80 galaxies with a signal-to-noise ratio larger than three. The error-weighted mean of the integrated-intensity ratio of 12CO to 13CO lines (R1213) of the 80 galaxies is 10.9, with a standard deviation of 7.0. We find that (1) R1213 positively correlates to specific star-formation rate (sSFR) with a correlation coefficient of 0.46, and (2) both the flux ratio of IRAS 60 μm to 100 μm (f60/f100) and the inclination-corrected linewidth of 12CO stacked spectra ($\sigma _{{\rm ^{12}CO},i}$) also correlate with sSFR for galaxies with the R1213 measurement. Our results support the scenario where R1213 variation is mainly caused by changes in molecular gas properties such as temperature and turbulence. The consequent variation of the CO-to-H2 conversion factor across the SF main sequence is not large enough to completely extinguish the known correlations between sSFR and Mmol/Mstar (μmol) or star-formation efficiency (SFE) reported in previous studies, while this variation would strengthen (weaken) the sSFR–SFE (sSFR–μmol) correlation.

scholarly journals Cloud-scale Molecular Gas Properties in 15 Nearby Galaxies

2018 ◽  
Vol 860 (2) ◽  
pp. 172 ◽  
Author(s):  
Jiayi Sun ◽  
Adam K. Leroy ◽  
Andreas Schruba ◽  
Erik Rosolowsky ◽  
Annie Hughes ◽  
...  
Keyword(s):  
Molecular Gas ◽  
Nearby Galaxies ◽  
Gas Properties

scholarly journals Giant Molecular Cloud Populations in Nearby Galaxies

2015 ◽  
Vol 11 (S315) ◽  
pp. 30-37 ◽  
Author(s):  
Annie Hughes ◽  
Sharon Meidt ◽  
Dario Colombo ◽  
Andreas Schruba ◽  
Eva Schinnerer ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Surface Brightness ◽  
Large Magellanic Cloud ◽  
Molecular Gas ◽  
Number Density ◽  
Global Pattern ◽  
Outer Disk ◽  
Giant Molecular Cloud ◽  
Nearby Galaxies ◽  
Low Mass

AbstractWe present new results from a comparative analysis of the resolved giant molecular cloud (GMC) populations in six nearby galaxies. We show that the GMCs in denser environments–M51, the centre of NGC6946–have greater CO surface brightness and higher velocity dispersions relative to their size than GMCs in less dense environments. We find systematic differences in the GMC mass distribution among galaxies, such that more of the molecular gas in the low-mass galaxies (M33, the Large Magellanic Cloud) and the outer disk of M31 is located in low mass clouds. Using the number density of GMCs in the interarm regions of M51, we argue that GMC destruction in this region is regulated by shear, and that cloud lifetimes there are finite and short, ~20 to 30 Myr. Our results indicate the importance of galactic environment on the evolution of GMCs, and on a galaxy's global pattern of star formation.

scholarly journals Induced Starburst and Nuclear Activity: Faith, Facts and Theory

1990 ◽  
Vol 124 ◽  
pp. 689-704 ◽  
Author(s):  
Isaac Shlosman
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Host Galaxies ◽  
Galactic Disks ◽  
Nuclear Activity ◽  
Gravitational Instabilities ◽  
Physical Understanding ◽  
Central Regions ◽  
Axisymmetric Perturbations

AbstractThe problem of the origin of starburst and nuclear (nonstellar) activity in galaxies is reviewed. A physical understanding of mechanism(s) that induce both types of activity requires one to address the following issues: 1) what is the source of fuel that powers starbursts and active galactic nuclei? and 2) how it is channeled towards the central regions of host galaxies? As a possible clue, we examine the role of non-axisymmetric perturbations of galactic disks and analyze their potential triggers. Global gravitational instabilities in the gas on scales ~ 100 pc appear to be crucial for fueling the active galactic nuclei.

scholarly journals Molecular Gas in Galactic Nuclei

1989 ◽  
Vol 8 ◽  
pp. 605-607
Author(s):  
Nick Scoville
Keyword(s):  
Galactic Nuclei ◽  
Central Star ◽  
Molecular Gas ◽  
Interstellar Matter ◽  
Star Forming ◽  
Ngc 6946 ◽  
Luminous Galaxies ◽  
Rapid Formation ◽  
Central Regions ◽  
Ngc 1068

Recent high resolution interferometric observations of the molecular gas in luminous IR galaxies reveal extraordinary concentrations of star forming material in the central few kpc. In several of the nearest IR bright galaxies, the molecular gas in the central regions is concentrated in a bar-like distribution (IC342, NGC 6946, and NGC 253) and in NGC 1068, approximately 40% of the molecular gas is confined to two arms or a ring at approximately 1.6 kpc radius. Interferometry on the most luminous galaxies (LIR ≥ 1011L⊙) reveals that approximately half of the total interstellar matter is contained in the central kpc with mean densities of several hundred H2 cm-3. Such gas concentrations should result in the very rapid formation of stars, i.e. a central star burst yielding a massive central star cluster.

High‐Resolution13CO and C18OJ= 1–0 Observations of NGC 1068: Molecular Gas Properties and a High C18O/13CO Intensity Ratio

1997 ◽  
Vol 477 (1) ◽  
pp. 518-518 ◽  
Author(s):  
Padeli P. Papadopoulos ◽  
E. R. Seaquist ◽  
N. Z. Scoville
Keyword(s):  
Intensity Ratio ◽  
Molecular Gas ◽  
Ngc 1068 ◽  
Gas Properties

scholarly journals Hot gaseous atmospheres of rotating galaxies observed with XMM–Newton

2020 ◽  
Vol 499 (4) ◽  
pp. 5163-5174
Author(s):  
A Juráňová ◽  
N Werner ◽  
P E J Nulsen ◽  
M Gaspari ◽  
K Lakhchaura ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Active Galactic Nuclei ◽  
Spiral Galaxy ◽  
Galactic Nuclei ◽  
X Ray ◽  
Hot Gas ◽  
Heating And Cooling ◽  
Theoretical Predictions ◽  
Central Regions ◽  
Gaseous Atmospheres

ABSTRACT X-ray emitting atmospheres of non-rotating early-type galaxies and their connection to central active galactic nuclei have been thoroughly studied over the years. However, in systems with significant angular momentum, processes of heating and cooling are likely to proceed differently. We present an analysis of the hot atmospheres of six lenticulars and a spiral galaxy to study the effects of angular momentum on the hot gas properties. We find an alignment between the hot gas and the stellar distribution, with the ellipticity of the X-ray emission generally lower than that of the optical stellar emission, consistent with theoretical predictions for rotationally supported hot atmospheres. The entropy profiles of NGC 4382 and the massive spiral galaxy NGC 1961 are significantly shallower than the entropy distribution in other galaxies, suggesting the presence of strong heating (via outflows or compressional) in the central regions of these systems. Finally, we investigate the thermal (in)stability of the hot atmospheres via criteria such as the TI- and C-ratio, and discuss the possibility that the discs of cold gas present in these objects have condensed out of the hot atmospheres.

Sign in / Sign up

Export Citation Format

Share Document