The Molecular Gas Component of Galaxy Disks

AbstractThe molecular gas in galaxy disks shows much more galaxy to galaxy variation than does the atomic gas. Detailed studies show that this variation can be attributed to differences in hydrostatic pressure in the disks due largely to variations in the stellar surface density and the total gas surface density. One prediction of pressure modulated H2 formation is that the location where HI and H2 have equal surface densities occurs at a constant value of the stellar surface density in the disk. Observations confirm this constancy to 40%.

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Evidence for supernova feedback sustaining gas turbulence in nearby star-forming galaxies

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038223 ◽

2020 ◽

Vol 641 ◽

pp. A70 ◽

Cited By ~ 2

Author(s):

Cecilia Bacchini ◽

Filippo Fraternali ◽

Giuliano Iorio ◽

Gabriele Pezzulli ◽

Antonino Marasco ◽

...

Keyword(s):

Star Formation ◽

Kinetic Energy ◽

Surface Density ◽

Neutral Medium ◽

Molecular Gas ◽

Driving Mechanism ◽

Nearby Star ◽

Star Forming ◽

Radial Profiles ◽

Atomic Gas

It is widely known that the gas in galaxy discs is highly turbulent, but there is much debate on which mechanism can energetically maintain this turbulence. Among the possible candidates, supernova (SN) explosions are likely the primary drivers but doubts remain on whether they can be sufficient in regions of moderate star formation activity, in particular in the outer parts of discs. Thus, a number of alternative mechanisms have been proposed. In this paper, we measure the SN efficiency η, namely the fraction of the total SN energy needed to sustain turbulence in galaxies, and verify that SNe can indeed be the sole driving mechanism. The key novelty of our approach is that we take into account the increased turbulence dissipation timescale associated with the flaring in outer regions of gaseous discs. We analyse the distribution and kinematics of HI and CO in ten nearby star-forming galaxies to obtain the radial profiles of the kinetic energy per unit area for both the atomic gas and the molecular gas. We use a theoretical model to reproduce the observed energy with the sum of turbulent energy from SNe, as inferred from the observed star formation rate (SFR) surface density, and the gas thermal energy. For the atomic gas, we explore two extreme cases in which the atomic gas is made either of cold neutral medium or warm neutral medium, and the more realistic scenario with a mixture of the two phases. We find that the observed kinetic energy is remarkably well reproduced by our model across the whole extent of the galactic discs, assuming η constant with the galactocentric radius. Taking into account the uncertainties on the SFR surface density and on the atomic gas phase, we obtain that the median SN efficiencies for our sample of galaxies are ⟨ηatom⟩ = 0.015−0.008+0.018 for the atomic gas and ⟨ηmol⟩ = 0.003−0.002+0.006 for the molecular gas. We conclude that SNe alone can sustain gas turbulence in nearby galaxies with only few percent of their energy and that there is essentially no need for any further source of energy.

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Perseus arm - a new perspective on star formation and spiral structure in our home galaxy

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab2704 ◽

2021 ◽

Author(s):

M Wienen ◽

C M Brunt ◽

C L Dobbs ◽

D Colombo

Keyword(s):

Star Formation ◽

Surface Density ◽

Milky Way ◽

Velocity Structure ◽

Data Cube ◽

High Angular Resolution ◽

Molecular Gas ◽

Linear Scale ◽

Perseus Arm ◽

Spiral Arm

Abstract Expansion of (sub)millimetre capabilities to high angular resolution offered with interferometers allows to resolve giant molecular clouds (GMCs) in nearby galaxies. This enables us to place the Milky Way in the context of other galaxies to advance our understanding of star formation in our own Galaxy. We thus remap 12CO (1 - 0) data along the Perseus spiral arm in the outer Milky Way to a fixed physical resolution and present the first spiral arm data cube at a common distance as it would be seen by an observer outside the Milky Way. To achieve this goal we calibrated the longitude-velocity structure of 12CO gas of the outer Perseus arm based on trigonometric distances and maser velocities provided by the BeSSeL survey. The molecular gas data were convolved to the same spatial resolution along the whole spiral arm and regridded on to a linear scale map with the coordinate system transformed to the spiral arm reference frame. We determined the width of the Perseus spiral arm to be 7.8 ± 0.2 km s−1 around the kinematic arm centre. To study the large scale structure we derived the 12CO gas mass surface density distribution of velocities shifted to the kinematic arm centre and arm length. This yields a variation of the gas mass surface density along the arm length and a compression of molecular gas mass at linear scale. We determined a thickness of ∼63 pc on average for the Perseus spiral arm and a centroid of the molecular layer of 8.7 pc.

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From massive spirals to dwarf irregulars: a new set of tight scaling relations for cold gas and stars driven by disc gravitational instability

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3367 ◽

2019 ◽

Vol 491 (4) ◽

pp. 4843-4851 ◽

Cited By ~ 8

Author(s):

Alessandro B Romeo

Keyword(s):

Angular Momentum ◽

Galaxy Evolution ◽

Simple Formula ◽

Gravitational Instability ◽

Stability Parameter ◽

Relative Mass ◽

Scaling Relations ◽

Molecular Gas ◽

Mass Content ◽

Atomic Gas

ABSTRACT We present a new set of galaxy scaling relations for the relative mass content of atomic gas, molecular gas, and stars. Such relations are driven by disc gravitational instability, and originate from the low galaxy-to-galaxy variance of Toomre’s Q stability parameter. We test such relations using more than 100 galaxies, from massive spirals to dwarf irregulars, thus spanning several orders of magnitude in stellar mass ($M_{\star }\approx 10^{6\rm {-}11}\, \mbox{M}_{\odot }$) and atomic gas mass ($M_{\rm{H\, \small {I}}}\approx 10^{7\rm {-}10.5}\, \mbox{M}_{\odot }$). Such tests demonstrate (i) that our scaling relations are physically motivated and tightly constrained, (ii) that the mass-averaged gravitational instability properties of galaxy discs are remarkably uniform across the sequence Sa–dIrr, and (iii) that specific angular momentum plays an important role in such a scenario. Besides providing new insights into a very important topic in galaxy evolution, this work provides a simple formula (equation 5) that one can use for generating other galaxy relations driven by disc instability. We explain how to do that, mention a few possible applications, and stress the importance of testing our approach further.

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The maximum stellar surface density due to the failure of stellar feedback

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/sty3386 ◽

2018 ◽

Vol 483 (4) ◽

pp. 5548-5553 ◽

Cited By ~ 3

Author(s):

Michael Y Grudić ◽

Philip F Hopkins ◽

Eliot Quataert ◽

Norman Murray

Keyword(s):

Surface Density ◽

Stellar Surface ◽

Stellar Feedback

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Molecular gas associated with Wolf-Rayet ring nebulae

Symposium - International Astronomical Union ◽

10.1017/s0074180900205780 ◽

1999 ◽

Vol 193 ◽

pp. 370-371 ◽

Cited By ~ 2

Author(s):

Anthony P. Marston ◽

Jaydene T. Welzmiller ◽

Mark A. Bransford ◽

John H. Black ◽

P. Bergman

Keyword(s):

Emission Line ◽

Massive Stars ◽

Molecular Gas ◽

Molecular Materials ◽

Ionized Gas ◽

Ring Nebulae ◽

Gas Component

We present the first 12CO 1→0 emission-line maps of the vicinities of two Wolf-Rayet stars (WR 16 and WR 75) and their associated ring nebulae. We illustrate that sizeable amounts of molecular gas appear associated with these ring nebulae and therefore that the mass of gas in ring nebulae is significantly higher than inferred from observations of the ionized gas component alone. We discuss the possible stellar and interstellar origins of these molecular materials and the implications for the evolution of massive stars up to the WR phase.

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Molecular outflow and feedback in the obscured quasar XID2028 revealed by ALMA

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731641 ◽

2018 ◽

Vol 612 ◽

pp. A29 ◽

Cited By ~ 30

Author(s):

M. Brusa ◽

G. Cresci ◽

E. Daddi ◽

R. Paladino ◽

M. Perna ◽

...

Keyword(s):

Host Galaxy ◽

Molecular Gas ◽

Test Case ◽

Feedback Effects ◽

Molecular Outflow ◽

The Galaxy ◽

Gas Consumption ◽

Massive Outflow ◽

Gas Component ◽

Fast Rotating

We imaged, with ALMA and ARGOS/LUCI, the molecular gas and dust and stellar continuum in XID2028, which is an obscured quasi-stellar object (QSO) at z = 1.593, where the presence of a massive outflow in the ionised gas component traced by the [OIII]5007 emission has been resolved up to 10 kpc. This target represents a unique test case to study QSO feedback in action at the peak epoch of AGN-galaxy co-evolution. The QSO was detected in the CO(5 − 4) transition and in the 1.3 mm continuum at ~30 and ~20σ significance, respectively; both emissions are confined in the central (<2 kpc) radius area. Our analysis suggests the presence of a fast rotating molecular disc (v ~ 400 km s−1) on very compact scales well inside the galaxy extent seen in the rest-frame optical light (~10 kpc, as inferred from the LUCI data). Adding available measurements in additional two CO transitions, CO(2 − 1) and CO(3 − 2), we could derive a total gas mass of ~1010 M⊙, thanks to a critical assessment of CO excitation and the comparison with the Rayleigh–Jeans continuum estimate. This translates into a very low gas fraction (<5%) and depletion timescales of 40–75 Myr, reinforcing the result of atypical gas consumption conditions in XID2028, possibly because of feedback effects on the host galaxy. Finally, we also detect the presence of high velocity CO gas at ~5σ, which we interpret as a signature of galaxy-scale molecular outflow that is spatially coincident with the ionised gas outflow. XID2028 therefore represents a unique case in which the measurement of total outflowing mass, of ~500–800 M⊙ yr−1 including the molecular and atomic components in both the ionised and neutral phases, was attempted for a high-z QSO.

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The evolution of the spiral galaxy M51a

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315009916 ◽

2015 ◽

Vol 11 (S319) ◽

pp. 129-129

Author(s):

Xiaoyu Kang ◽

Fenghui Zhang ◽

Ruixiang Chang

Keyword(s):

Star Formation ◽

Surface Density ◽

Evolutionary History ◽

Surface Brightness ◽

Star Formation Rate ◽

Formation Rate ◽

Molecular Gas ◽

Peak Time ◽

Model Predictions ◽

Inside Out

AbstractA simple model for M51a is constructed to explore its evolutionary history by assuming its disk grows from continuous gas infall, which is shaped by a free parameter-the infall-peak time tp. By adopting a constant infall-peak time tp = 7.0Gyr, our model predictions can reproduce most of the observed constraints and still show that the disk of M51a forms inside-out. Our results also show that the current molecular gas surface density, the star-formation rate and the UV-band surface brightness are important quantities to trace the effect of recent interactions on galactic star-formation process.

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Dynamical measurement of the stellar surface density of face-on galaxies

Astronomy and Astrophysics ◽

10.1051/0004-6361/201527122 ◽

2015 ◽

Vol 585 ◽

pp. A17 ◽

Cited By ~ 6

Author(s):

G. W. Angus ◽

G. Gentile ◽

B. Famaey

Keyword(s):

Surface Density ◽

Stellar Surface ◽

Dynamical Measurement

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The ISM scaling relations in DustPedia late-type galaxies: A benchmark study for the Local Universe

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936665 ◽

2020 ◽

Vol 633 ◽

pp. A100 ◽

Cited By ~ 12

Author(s):

V. Casasola ◽

S. Bianchi ◽

P. De Vis ◽

L. Magrini ◽

E. Corbelli ◽

...

Keyword(s):

Gas Phase ◽

Stellar Mass ◽

Scaling Relations ◽

Molecular Gas ◽

Mass Ratio ◽

Late Type ◽

Local Universe ◽

Dust Mass ◽

Atomic Gas ◽

Galaxy Morphology

Aims. The purpose of this work is the characterization of the main scaling relations between all of the interstellar medium (ISM) components, namely dust, atomic, molecular, and total gas, and gas-phase metallicity, as well as other galaxy properties, such as stellar mass (Mstar) and galaxy morphology, for late-type galaxies in the Local Universe. Methods. This study was performed by extracting late-type galaxies from the entire DustPedia sample and by exploiting the large and homogeneous dataset available thanks to the DustPedia project. The sample consists of 436 galaxies with morphological stage spanning from T = 1−10, Mstar from 6 × 107 to 3 × 1011 M⊙, star formation rate from 6 × 10−4 to 60 M⊙ yr−1, and oxygen abundance from 12 + log(O/H) = 8−9.5. Molecular and atomic gas data were collected from the literature and properly homogenized. All the masses involved in our analysis refer to the values within the optical disks of galaxies. The scaling relations involving the molecular gas are studied by assuming both a constant and a metallicity-dependent CO-to-H2 conversion factor (XCO). The analysis was performed by means of the survival analysis technique, in order to properly take into account the presence of both detection and nondetection in the data. Results. We confirm that the dust mass correlates very well with the total gas mass, and find –for the first time– that the dust mass correlates better with the atomic gas mass than with the molecular one. We characterize important mass ratios such as the gas fraction, the molecular-to-atomic gas mass ratio, the dust-to-total gas mass ratio (DGR), and the dust-to-stellar mass ratio, and study how they relate to each other, to galaxy morphology, and to gas-phase metallicity. Only the assumption of a metallicity-dependent XCO reproduces the expected decrease of the DGR with increasing morphological stage and decreasing gas-phase metallicity, with a slope of about 1. The DGR, the gas-phase metallicity, and the dust-to-stellar mass ratio are, for our galaxy sample, directly linked to galaxy morphology. The molecular-to-atomic gas mass ratio and the DGR show a positive correlation for low molecular gas fractions, but for galaxies rich in molecular gas this trend breaks down. To our knowledge, this trend has never been found before, and provides new constraints for theoretical models of galaxy evolution and a reference for high-redshift studies. We discuss several scenarios related to this finding. Conclusions. The DustPedia database of late-type galaxies is an extraordinary tool for the study of the ISM scaling relations, thanks to its homogeneous collection of data for the different ISM components. The database is made publicly available to the whole community.

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