scholarly journals CO Multi-line Imaging of Nearby Galaxies (COMING). VII. Fourier decomposition of molecular gas velocity fields and bar pattern speed

2019 ◽  
Author(s):  
Dragan Salak ◽  
Yuto Noma ◽  
Kazuo Sorai ◽  
Yusuke Miyamoto ◽  
Nario Kuno ◽  
...  
Keyword(s):  
Velocity Fields ◽  
Molecular Gas ◽  
Gas Velocity ◽  
Fourier Decomposition ◽  
Pattern Speed ◽  
Nearby Galaxies ◽  
Line Imaging

scholarly journals Gone with the heat: a fundamental constraint on the imaging of dust and molecular gas in the early Universe

2016 ◽  
Vol 3 (6) ◽  
pp. 160025 ◽  
Author(s):  
Zhi-Yu Zhang ◽  
Padelis P. Papadopoulos ◽  
R. J. Ivison ◽  
Maud Galametz ◽  
M. W. L. Smith ◽  
...  
Keyword(s):  
Structural Characteristics ◽  
High Redshift ◽  
Line Emission ◽  
Velocity Fields ◽  
Molecular Gas ◽  
Gas Velocity ◽  
High Redshift Galaxies ◽  
Mass Distributions ◽  
Line Imaging ◽  
Cold Dust

Images of dust continuum and carbon monoxide (CO) line emission are powerful tools for deducing structural characteristics of galaxies, such as disc sizes, H 2 gas velocity fields and enclosed H 2 and dynamical masses. We report on a fundamental constraint set by the cosmic microwave background (CMB) on the observed structural and dynamical characteristics of galaxies, as deduced from dust continuum and CO-line imaging at high redshifts. As the CMB temperature rises in the distant Universe, the ensuing thermal equilibrium between the CMB and the cold dust and H 2 gas progressively erases all spatial and spectral contrasts between their brightness distributions and the CMB. For high-redshift galaxies, this strongly biases the recoverable H 2 gas and dust mass distributions, scale lengths, gas velocity fields and dynamical mass estimates. This limitation is unique to millimetre/submillimetre wavelengths and unlike its known effect on the global dust continuum and molecular line emission of galaxies, it cannot be addressed simply. We nevertheless identify a unique signature of CMB-affected continuum brightness distributions, namely an increasing rather than diminishing contrast between such brightness distributions and the CMB when the cold dust in distant galaxies is imaged at frequencies beyond the Raleigh–Jeans limit. For the molecular gas tracers, the same effect makes the atomic carbon lines maintain a larger contrast than the CO lines against the CMB.

scholarly journals CO Multi-line Imaging of Nearby Galaxies (COMING). I. Physical properties of molecular gas in the barred spiral galaxy NGC 2903

2016 ◽  
Vol 68 (5) ◽  
pp. 89 ◽  
Author(s):  
Kazuyuki Muraoka ◽  
Kazuo Sorai ◽  
Nario Kuno ◽  
Naomasa Nakai ◽  
Hiroyuki Nakanishi ◽  
...  
Keyword(s):  
Physical Properties ◽  
Spiral Galaxy ◽  
Molecular Gas ◽  
Nearby Galaxies ◽  
Barred Spiral Galaxy ◽  
Line Imaging

scholarly journals CO multi-line imaging of nearby galaxies (COMING). IV. Overview of the project

2019 ◽  
Author(s):  
Kazuo Sorai ◽  
Nario Kuno ◽  
Kazuyuki Muraoka ◽  
Yusuke Miyamoto ◽  
Hiroyuki Kaneko ◽  
...  
Keyword(s):  
Sample Selection ◽  
Far Infrared ◽  
Stellar Mass ◽  
High Angular Resolution ◽  
Molecular Gas ◽  
Radio Observatory ◽  
Star Forming ◽  
Barred Galaxies ◽  
Nearby Galaxies ◽  
Line Imaging

Abstract Observations of the molecular gas in galaxies are vital to understand the evolution and star-forming histories of galaxies. However, galaxies with molecular gas maps of their whole discs at sufficient resolution to distinguish galactic structures are severely lacking. Millimeter-wavelength studies at a high angular resolution across multiple lines and transitions are particularly needed, severely limiting our ability to infer the universal properties of molecular gas in galaxies. Hence, we conducted a legacy project with the 45 m telescope of the Nobeyama Radio Observatory, called the CO Multi-line Imaging of Nearby Galaxies (COMING), which simultaneously observed 147 galaxies with high far-infrared (FIR) flux in 12CO, 13CO, and C18O J = 1–0 lines. The total molecular gas mass was derived using the standard CO–to–H2 conversion factor and found to be positively correlated with the total stellar mass derived from the WISE 3.4 μm band data. The fraction of the total molecular gas mass to the total stellar mass in galaxies does not depend on their Hubble types nor the existence of a galactic bar, although when galaxies in individual morphological types are investigated separately, the fraction seems to decrease with the total stellar mass in early-type galaxies and vice versa in late-type galaxies. No differences in the distribution of the total molecular gas mass, stellar mass, or the total molecular gas to stellar mass ratio was observed between barred and non-barred galaxies, which is likely the result of our sample selection criteria, in that we prioritized observing FIR bright (and thus molecular gas-rich) galaxies.

scholarly journals CO Multi-line Imaging of Nearby Galaxies (COMING). III. Dynamical effect on molecular gas density and star formation in the barred spiral galaxy NGC 4303

2019 ◽  
Vol 71 (Supplement_1) ◽  
Author(s):  
Yoshiyuki Yajima ◽  
Kazuo Sorai ◽  
Nario Kuno ◽  
Kazuyuki Muraoka ◽  
Yusuke Miyamoto ◽  
...  
Keyword(s):  
Star Formation ◽  
Spiral Galaxy ◽  
Galactic Disk ◽  
Molecular Gas ◽  
Kinetic Temperature ◽  
Spiral Arms ◽  
Nearby Galaxies ◽  
Barred Spiral Galaxy ◽  
Barred Spiral Galaxies ◽  
Line Imaging

AbstractWe present the results of $^{12}\textrm{C}$$\textrm{O}$(J = 1–0) and $^{13}\textrm{C}$$\textrm{O}$(J = 1–0) simultaneous mappings toward the nearby barred spiral galaxy NGC 4303 as part of the CO Multi-line Imaging of Nearby Galaxies (COMING) project. Barred spiral galaxies often show lower star-formation efficiency (SFE) in their bar region compared to the spiral arms. In this paper, we examine the relation between the SFEs and the volume densities of molecular gas n(H2) in the eight different regions within the galactic disk with $\textrm{C}$$\textrm{O}$ data combined with archival far-ultraviolet and 24 μm data. We confirmed that SFE in the bar region is lower by 39% than that in the spiral arms. Moreover, velocity-alignment stacking analysis was performed for the spectra in the individual regions. Integrated intensity ratios of $^{12}\textrm{C}$$\textrm{O}$ to $^{13}\textrm{C}$$\textrm{O}$ (R12/13) ranging from 10 to 17 were the results of this stacking. Fixing a kinetic temperature of molecular gas, $n(\rm {H_2})$ was derived from R12/13 via non-local thermodynamic equilibrium (non-LTE) analysis. The density n(H2) in the bar is lower by 31%–37% than that in the arms and there is a rather tight positive correlation between SFEs and n(H2), with a correlation coefficient of ∼0.8. Furthermore, we found a dependence of $n(\rm {H}_2)$ on the velocity dispersion of inter-molecular clouds (ΔV/sin i). Specifically, n(H2) increases as ΔV/sin i increases when ΔV/sin i < 100 km s−1. On the other hand, n(H2) decreases as ΔV/sin i increases when ΔV/sin i > 100 km s−1. These relations indicate that the variations of SFE could be caused by the volume densities of molecular gas, and the volume densities could be governed by the dynamical influence such as cloud–cloud collisions, shear, and enhanced inner-cloud turbulence.

scholarly journals CO Multi-line Imaging of Nearby Galaxies (COMING). VI. Radial variations in star formation efficiency

2019 ◽  
Vol 71 (Supplement_1) ◽  
Author(s):  
Kazuyuki Muraoka ◽  
Kazuo Sorai ◽  
Yusuke Miyamoto ◽  
Moe Yoda ◽  
Kana Morokuma-Matsui ◽  
...  
Keyword(s):  
Star Formation ◽  
Formation Rate ◽  
Mass Function ◽  
Initial Mass Function ◽  
Molecular Gas ◽  
Spiral Arms ◽  
Nearby Galaxies ◽  
The Difference ◽  
Line Imaging ◽  
Formation Efficiency

Abstract We examined radial variations in molecular-gas based star formation efficiency (SFE), which is defined as star formation rate per unit molecular gas mass, for 80 galaxies selected from the CO Multi-line Imaging of Nearby Galaxies project (Sorai et al. 2019, PASJ, 71, S14). The radial variations in SFE for individual galaxies are typically a factor of 2–3, which suggests that SFE is nearly constant along the galactocentric radius. We found an averaged SFE in 80 galaxies of (1.69 ± 1.1) × 10−9 yr−1, which is consistent with Leroy et al. (2008, AJ, 136, 2782) if we consider the contribution of helium to the molecular gas mass evaluation and the difference in the assumed initial mass function between the two studies. We compared SFE among different morphological (i.e., SA, SAB, and SB) types, and found that SFE within the inner radii (r/r25 < 0.3, where r25 is the B-band isophotal radius at 25 mag arcsec−2) of SB galaxies is slightly higher than that of SA and SAB galaxies. This trend can be partly explained by the dependence of SFE on global stellar mass, which probably relates to the CO-to-H2 conversion factor through the metallicity. For two representative SB galaxies in our sample, NGC 3367 and NGC 7479, the ellipse of r/r25 = 0.3 seems to cover not only the central region but also the inner part of the disk, mainly the bar. These two galaxies show higher SFE in the bar than in the spiral arms. However, we found an opposite trend in NGC 4303; SFE is lower in the bar than in the spiral arms, which is consistent with earlier studies (e.g., Momose et al. 2010, ApJ, 721, 383). These results suggest a diversity of star formation activities in the bar.

Central kiloparsec of NGC 1326 observed with SINFONI

2020 ◽  
Vol 638 ◽  
pp. A53
Author(s):  
Nastaran Fazeli ◽  
Gerold Busch ◽  
Andreas Eckart ◽  
Françoise Combes ◽  
Persis Misquitta ◽  
...  
Keyword(s):  
Black Hole ◽  
Galaxy Evolution ◽  
Near Infrared ◽  
Velocity Fields ◽  
Molecular Gas ◽  
Nearby Galaxy ◽  
Stellar Content ◽  
Stellar Rotation ◽  
Supermassive Black Hole ◽  
Integral Field Spectrograph

Gas inflow processes in the vicinity of galactic nuclei play a crucial role in galaxy evolution and supermassive black hole growth. Exploring the central kiloparsec of galaxies is essential to shed more light on this subject. We present near-infrared H- and K-band results of the nuclear region of the nearby galaxy NGC 1326, observed with the integral-field spectrograph SINFONI mounted on the Very Large Telescope. The field of view covers 9″ × 9″ (650 × 650 pc2). Our work is concentrated on excitation conditions, morphology, and stellar content. The nucleus of NGC 1326 was classified as a LINER, however in our data we observed an absence of ionised gas emission in the central r ∼ 3″. We studied the morphology by analysing the distribution of ionised and molecular gas, and thereby detected an elliptically shaped, circum-nuclear star-forming ring at a mean radius of 300 pc. We estimate the starburst regions in the ring to be young with dominating ages of < 10 Myr. The molecular gas distribution also reveals an elongated east to west central structure about 3″ in radius, where gas is excited by slow or mild shock mechanisms. We calculate the ionised gas mass of 8 × 105 M⊙ completely concentrated in the nuclear ring and the warm molecular gas mass of 187 M⊙, from which half is concentrated in the ring and the other half in the elongated central structure. The stellar velocity fields show pure rotation in the plane of the galaxy. The gas velocity fields show similar rotation in the ring, but in the central elongated H2 structure they show much higher amplitudes and indications of further deviation from the stellar rotation in the central 1″ aperture. We suggest that the central 6″ elongated H2 structure might be a fast-rotating central disc. The CO(3–2) emission observations with the Atacama Large Millimeter/submillimeter Array reveal a central 1″ torus. In the central 1″ of the H2 velocity field and residual maps, we find indications for a further decoupled structure closer to a nuclear disc, which could be identified with the torus surrounding the supermassive black hole.

scholarly journals Double X/Peanut Structures in Barred Galaxies – Insights from an N–body Simulation

2020 ◽  
Author(s):  
Bogdan C Ciambur ◽  
Francesca Fragkoudi ◽  
Sergey Khoperskov ◽  
Paola Di Matteo ◽  
Françoise Combes
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Large Fraction ◽  
Formation Time ◽  
Dark Matter Halo ◽  
Barred Galaxies ◽  
Pattern Speed ◽  
Nearby Galaxies ◽  
Dynamical Instabilities ◽  
Bow Tie

Abstract Boxy, peanut– or X–shaped “bulges” are observed in a large fraction of barred galaxies viewed in, or close to, edge-on projection, as well as in the Milky Way. They are the product of dynamical instabilities occurring in stellar bars, which cause the latter to buckle and thicken vertically. Recent studies have found nearby galaxies that harbour two such features arising at different radial scales, in a nested configuration. In this paper we explore the formation of such double peanuts, using a collisionless N–body simulation of a pure disc evolving in isolation within a live dark matter halo, which we analyse in a completely analogous way to observations of real galaxies. In the simulation we find a stable double configuration consisting of two X/peanut structures associated to the same galactic bar – rotating with the same pattern speed – but with different morphology, formation time, and evolution. The inner, conventional peanut-shaped structure forms early via the buckling of the bar, and experiences little evolution once it stabilises. This feature is consistent in terms of size, strength and morphology, with peanut structures observed in nearby galaxies. The outer structure, however, displays a strong X, or “bow-tie”, morphology. It forms just after the inner peanut, and gradually extends in time (within 1 to 1.5 Gyr) to almost the end of the bar, a radial scale where ansae occur. We conclude that, although both structures form, and are dynamically coupled to, the same bar, they are supported by inherently different mechanisms.

scholarly journals The JCMT Nearby Galaxies Legacy Survey – XI. Environmental variations in the atomic and molecular gas radial profiles of nearby spiral galaxies

2017 ◽  
Vol 467 (4) ◽  
pp. 4282-4292 ◽  
Author(s):  
Angus Mok ◽  
C. D. Wilson ◽  
J. H. Knapen ◽  
J. R. Sánchez-Gallego ◽  
E. Brinks ◽  
...  
Keyword(s):  
Spiral Galaxies ◽  
Molecular Gas ◽  
Radial Profiles ◽  
Environmental Variations ◽  
Nearby Galaxies

scholarly journals SKA studies of nearby galaxies: star-formation, accretion processes and molecular gas across all environments

2015 ◽  
Author(s):  
Rob J. Beswick ◽  
Elias Brinks ◽  
Miguel Perez-Torres ◽  
Anita Richards ◽  
Susanne Aalto ◽  
...  
Keyword(s):  
Star Formation ◽  
Molecular Gas ◽  
Nearby Galaxies
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