scholarly journals Dust emission from the atomic and molecular gas in M 33: a changing β

2012 ◽  
Vol 10 (H16) ◽  
pp. 617-617
Author(s):  
Jonathan Braine ◽  
Fatemeh Tabatabaei ◽  
Manolis Xilouris
Keyword(s):  
High Resolution ◽  
Emission Spectrum ◽  
Dust Emission ◽  
Molecular Gas ◽  
Galactocentric Distance ◽  
Gas Phases ◽  
Atomic Medium ◽  
Young Object ◽  
Low Metallicity ◽  
Grey Body

AbstractWe use the very recently completed high-resolution IRAM CO survey of M33 with the high-resolution HI observations (published by Gratier et al. 2010, A&A, 522, 3) and Herschel Far-IR and submillimeter mapping observations to study how the dust behaves in the molecular and atomic gas phases of the interstellar medium (ISM). M33 is a “young" object in that it is gas-rich with a young stellar population and low metallicity as compared to large spirals like the Milky Way or Andromeda. Nonetheless, it is very clearly a spiral galaxy with a thin and reasonably axisymmetric disk. As such, it can be viewed as a stepping stone towards less evolved objects like magellanic irregulars (including the LMC and SMC) and perhaps distant objects in the early universe. More specifically, we look for radial variations in the dust emission spectrum (β parameter) as well as comparing regions dominated by either H2 or HI. The grey-body emission spectrum flattens (lower β) with galactocentric distance and generally is flatter in the atomic medium as compared to the molecular gas.

scholarly journals The molecular gas mass of M 33

2017 ◽  
Vol 600 ◽  
pp. A27 ◽  
Author(s):  
P. Gratier ◽  
J. Braine ◽  
K. Schuster ◽  
E. Rosolowsky ◽  
M. Boquien ◽  
...  
Keyword(s):  
Large Population ◽  
Density Ratio ◽  
Dust Emission ◽  
Molecular Gas ◽  
Galactocentric Distance ◽  
Large Program ◽  
Low Metallicity ◽  
Dust Surface ◽  
Co Emission ◽  
Co Observations

Do some environments favor efficient conversion of molecular gas into stars? To answer this, we need to be able to estimate the H2 mass. Traditionally, this is done using CO observations and a few assumptions but the Herschel observations which cover the far-IR dust spectrum make it possible to estimate the molecular gas mass independently of CO and thus to investigate whether and how the CO traces H2. Previous attempts to derive gas masses from dust emission suffered from biases. Generally, dust surface densities, H i column densities, and CO intensities are used to derive a gas-to-dust ratio (GDR) and the local CO intensity to H2 column density ratio (XCO), sometimes allowing for an additional CO-dark gas component (Kdark). We tested earlier methods, revealing degeneracies among the parameters, and then used a sophisticated Bayesian formalism to derive the most likely values for each of the parameters mentioned above as a function of position in the nearby prototypical low metallicity (12 + log (O/H) ~ 8.4) spiral galaxy M 33. The data are from the IRAM Large Program mapping in the CO(2–1) line along with high-resolution H i and Herschel dust continuum observations. Solving for GDR, XCO, and Kdark in macropixels 500 pc in size, each containing many individual measurements of the CO, H i, and dust emission, we find that (i) allowing for CO dark gas (Kdark) significantly improves fits; (ii) Kdark decreases with galactocentric distance; (iii) GDR is slightly higher than initially expected and increases with galactocentric distance; (iv) the total amount of dark gas closely follows the radially decreasing CO emission, as might be expected if the dark gas is H2 where CO is photodissociated. The total amount of H2, including dark gas, yields an average XCO of twice the galactic value of 2 × 1020 cm-2/ K km s-1, with about 55% of this traced directly through CO. The rather constant fraction of dark gas suggests that there is no large population of diffuse H2 clouds (unrelated to GMCs) without CO emission. Unlike in large spirals, we detect no systematic radial trend in XCO, possibly linked to the absence of a radial decrease in CO line ratios.

scholarly journals Dwarf Galaxies: Their Low Metallicity Interstellar Medium

2018 ◽  
Vol 14 (S344) ◽  
pp. 240-254 ◽  
Author(s):  
Suzanne C. Madden ◽  
Diane Cormier
Keyword(s):  
Dust Emission ◽  
Space Telescopes ◽  
Gas Reservoir ◽  
Gas Phases ◽  
Reservoir Models ◽  
Wide Range ◽  
Low Metallicity ◽  
Space Observatories ◽  
The Rich ◽  
Multi Phase

AbstractThis review describes where we are today in light of the dust and gas properties and their relation to star formation, in low metallicity galaxies of the local universe following recent surveys from sensitive infrared space telescopes, mainly Spitzer and Herschel space observatories as well as ground-based observations of the molecular gas reservoir. Models to interpret the ISM properties are gaining sophistication in order to account for the wide range of valuable observational diagnostics that we have today to trace the different gas phases, the broad range of photometry we have, from mid-infrared to submillimetre dust emission and the various galactic size scales that we can sample today. This review summarizes the rich multi-phase observations we can exploit today, and the multi-phase modeling approach to interpret the observations.

scholarly journals Chemical evolution of galaxies: emerging dust and the different gas phases in a new multiphase code

2020 ◽  
Vol 494 (1) ◽  
pp. 146-160
Author(s):  
I Millán-Irigoyen ◽  
M Mollá ◽  
Y Ascasibar
Keyword(s):  
Chemical Evolution ◽  
Milky Way ◽  
Molecular Gas ◽  
Multiphase Model ◽  
Milky Way Galaxy ◽  
Gas Phases ◽  
Conversion Rates ◽  
Low Metallicity ◽  
Consistent Treatment ◽  
Physical Principles

ABSTRACT Dust plays an important role in the evolution of a galaxy, as it is one of the main ingredients for efficient star formation. Dust grains are also a sink/source of metals when they are created/destroyed, and, therefore, a self-consistent treatment is key in order to correctly model chemical evolution. In this work, we discuss the implementation of dust physics in our current multiphase model, which also follows the evolution of atomic, ionized and molecular gas. Our goal is to model the conversion rates among the different phases of the interstellar medium, including the creation, growth and destruction of dust, based, as far as possible, on physical principles rather than on phenomenological recipes. We first present the updated set of differential equations and then discuss the results. We calibrate our model against observations of the Milky Way Galaxy and compare its predictions with extant data. Our results are broadly consistent with the observed data for intermediate and high metallicities, but the models tend to produce more dust than is observed in the low-metallicity regime.

scholarly journals The molecular gas properties in external galaxies

2012 ◽  
Vol 8 (S292) ◽  
pp. 219-222
Author(s):  
E. Bayet ◽  
S. Viti ◽  
M. Bureau ◽  
R. Aladro ◽  
D. Williams ◽  
...  
Keyword(s):  
Computational Models ◽  
Chemical Properties ◽  
Cosmic Ray ◽  
Molecular Gas ◽  
Gas Phases ◽  
External Galaxies ◽  
Low Metallicity ◽  
Physical And Chemical ◽  
Theoretical Developments ◽  
And Chemical Properties

AbstractWe present a summary of the physical and chemical properties we have obtained for the molecular gas found in galaxies, an essential triggering ingredient to any star formation (SF) process. In particular, we focus our studies on the molecular gas phases as traced by CO, HCO+ and CS line emissions, in a sample of galaxies including starbursts -SBs-, irregulars galaxies, low-metallicity sources, normal spirals, mergers, Early Type Galaxies (ETGs), galaxies with an Active Galactic Nucleus (AGN), with Cosmic Ray Dominated Regions (CRDRs) and with Photo-Dominated Regions (PDRs). Our studies mix theoretical developments (i.e. computational models) with the acquisition of large observational datatsets (at both low and high spatial resolution) that we then compare in order to better determine the conditions under which some SF activity is starting and/or is maintained.

scholarly journals Predicting the stellar and non-equilibrium dust emission spectra of high-resolution simulated galaxies with dart-ray

2015 ◽  
Vol 449 (1) ◽  
pp. 243-267 ◽  
Author(s):  
Giovanni Natale ◽  
Cristina C. Popescu ◽  
Richard. J. Tuffs ◽  
Victor P. Debattista ◽  
Jörg Fischera ◽  
...  
Keyword(s):  
High Resolution ◽  
Dust Emission ◽  
Emission Spectra ◽  
Non Equilibrium

High resolution Fourier spectroscopy of P2 infrared emission spectrum

1978 ◽  
Vol 72 (2) ◽  
pp. 189-199 ◽  
Author(s):  
C Amiot ◽  
C Effantin ◽  
J d'Incan ◽  
J Verges
Keyword(s):  
High Resolution ◽  
Emission Spectrum ◽  
Infrared Emission ◽  
Fourier Spectroscopy

scholarly journals Molecules as tracers of galaxy evolution

2012 ◽  
Vol 8 (S292) ◽  
pp. 199-208 ◽  
Author(s):  
Susanne Aalto
Keyword(s):  
Black Holes ◽  
Star Formation ◽  
High Resolution ◽  
Galaxy Evolution ◽  
Large Scale ◽  
Short Review ◽  
Stimulated Emission ◽  
Molecular Gas ◽  
Infrared Galaxies ◽  
Luminous Infrared Galaxies

AbstractStudying the molecular phase of the interstellar medium in galaxies is fundamental for the understanding of the onset and evolution of star formation and the growth of supermassive black holes. We can use molecules as observational tools exploiting them as tracers of chemical, physical and dynamical conditions. In this short review, key molecules (e.g. HCN, HCO+, HNC, HC3N, CN, H3O+) in identifying the nature of buried activity and its evolution are discussed including some standard astrochemical scenarios. Furthermore, we can use IR excited molecular emission to probe the very inner regions of luminous infrared galaxies (LIRGs) allowing us to get past the optically thick dust barrier of the compact obscured nuclei, e.g. in the dusty LIRG NGC4418. High resolution studies are often necessary to separate effects of excitation and radiative transport from those of chemistry - one example is absorption and effects of stimulated emission in the ULIRG Arp220. Finally, molecular gas in large scale galactic outflows is briefly discussed.

High resolution spectrum of GdO

1976 ◽  
Vol 54 (24) ◽  
pp. 2429-2434 ◽  
Author(s):  
B. R. Yadav ◽  
S. B. Rai ◽  
D. K. Rai
Keyword(s):  
High Resolution ◽  
Emission Spectrum ◽  
Visible Emission ◽  
High Resolution Spectrum ◽  
First Order ◽  
Isotopic Shifts ◽  
Vibrational Constants ◽  
Dc Arc

The visible emission spectrum of the GdO molecule has been produced in a DC arc source and has been photographed in the first order of a 10.6 m grating spectrograph. Bands are shown to have a six-headed structure and improved vibrational constants have been obtained in this study. Isotopic shifts have been calculated for the various isotopic molecules. Tentative suggestions regarding the nature of the transition have been made.

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