scholarly journals The massive stellar population in the diffuse ionized gas of M33

1997 ◽  
Author(s):  
Charles G. Hoopes ◽  
René A. M. Walterbos
Keyword(s):  
Stellar Population ◽  
Ionized Gas ◽  
Diffuse Ionized Gas

scholarly journals Numerical models for the diffuse ionized gas in galaxies

2019 ◽  
Vol 622 ◽  
pp. A115 ◽  
Author(s):  
J. A. Weber ◽  
A. W. A. Pauldrach ◽  
T. L. Hoffmann
Keyword(s):  
Ionizing Radiation ◽  
Stellar Population ◽  
Galactic Plane ◽  
Ionized Gas ◽  
Hot Stars ◽  
Ionization Structure ◽  
Diffuse Ionized Gas ◽  
Solar Metallicity ◽  
Effective Temperatures ◽  
Spiral Arm

Context. The diffuse ionized gas (DIG) constitutes the largest fraction of the total ionized interstellar matter in star-forming galaxies, but it is still unclear whether the ionization is driven predominantly by the ionizing radiation of hot massive stars, as in H II regions, or whether additional sources of ionization have to be considered. Key to understanding the ionization mechanisms in the DIG is the line emission by the ionized gas. Aims. We systematically explore a plausible subset of the parameter space involving effective temperatures and metallicities of the ionizing sources, the effects of the hardening of their radiation by surrounding “leaky” H II regions with different escape fractions, as well as different scenarios for the clumpiness of the DIG, and compute the resulting line strength ratios for a number of diagnostic optical emission lines. Methods. For the ionizing fluxes we computed a grid of stellar spectral energy distributions (SEDs) from detailed, fully non-LTE model atmospheres that include the effects of stellar winds and line blocking and blanketing. To calculate the ionization and temperature structure in the interstellar gas we used spherically symmetric photoionization models and state-of-the-art three-dimensional (3D) non-LTE radiative transfer simulations, considering hydrogen, helium, and the most abundant metals. We first applied these methods to classical H II regions around hot stars, using the model SEDs at different metallicities and effective temperatures as ionizing fluxes, and compute the SEDs of the escaping radiation for different escape fractions of hydrogen-ionizing photons. In a second step, we studied the effects of the escaping radiation on the more dilute and extended DIG. Using 3D models simulating a section of a galactic spiral arm, we computed the ionization structure in the DIG for different scenarios for the inhomogeneity of the gas, assuming ionization by a stellar population SED based on plausible parameters. Results. We provide quantitative predictions of how the line ratios from H II regions and the DIG vary as a function of metallicity Z, stellar effective temperature Teff, and escape fraction fesc from the H II region. The range of predicted line ratios reinforces the hypothesis that the DIG is ionized by (filtered) radiation from hot stars. At one-tenth solar metallicity, radiation hardening is mostly due to hydrogen and helium, whereas at solar metallicity absorption by metals plays a significant role. The effects of hardening are seen primarily in the increase in the emission line ratios of the most important cooling lines of the gas, [N II]∕Hβ and [O II]∕Hβ at lower Teff, and [O III]∕Hβ at higher Teff. For low Teff nearly the entire He I-ionizing radiation is absorbed in the H II regions, thereby preventing the formation of high ionization stages such as O III in the DIG. The ionization structure of the DIG depends strongly on both the clumping factor fcl = 〈nH2〉/〈nH2〉 and the large-scale distribution of the gas. In our simulations about 10% of the ionizing radiation produced by hot massive stars in a spiral arm is sufficient to ionize the DIG up to a height of approximately 1 kpc above the galactic plane for a clumping factor close to the observed value of fcl ~ 5. Even small changes in simulation parameters such as the clumping factor can lead to considerable variation in the ionized volume. Both for a more homogeneous gas and a very inhomogeneous gas containing both dense clumps and channels with low gas density, the ionized region in the dilute gas above the galactic plane can cease to be radiation-bounded, allowing the ionizing radiation to leak into the intergalactic medium. Comparison of observed and predicted line ratios indicates that the DIG is typically ionized with a softer SED than predicted by the chosen stellar population synthesis model.

Far‐Ultraviolet and Hα Imaging of Nearby Spiral Galaxies: The OB Stellar Population in the Diffuse Ionized Gas

2001 ◽  
Vol 559 (2) ◽  
pp. 878-891 ◽  
Author(s):  
Charles G. Hoopes ◽  
Rene A. M. Walterbos ◽  
Gregory D. Bothun
Keyword(s):  
Stellar Population ◽  
Spiral Galaxies ◽  
Ionized Gas ◽  
Diffuse Ionized Gas ◽  
Far Ultraviolet

scholarly journals 3D optical spectroscopic study of NGC 3344 with SITELLE: I. Identification and confirmation of supernova remnants

2019 ◽  
Vol 488 (1) ◽  
pp. 803-829 ◽  
Author(s):  
I Moumen ◽  
C Robert ◽  
D Devost ◽  
R P Martin ◽  
L Rousseau-Nepton ◽  
...  
Keyword(s):  
Supernova Remnants ◽  
Flux Ratio ◽  
Large Magellanic Cloud ◽  
Emission Lines ◽  
Ionization Mechanism ◽  
H Ii Regions ◽  
Nearby Galaxy ◽  
Galactocentric Distance ◽  
Ionized Gas ◽  
Diffuse Ionized Gas

ABSTRACT We present the first optical identification and confirmation of a sample of supernova remnants (SNRs) in the nearby galaxy NGC 3344. Using high spectral and spatial resolution data, obtained with the CFHT imaging Fourier transform spectrograph SITELLE, we identified about 2200 emission line regions, many of which are H ii regions, diffuse ionized gas regions, and also SNRs. Considering the stellar population and diffuse ionized gas background, which are quite important in NGC 3344, we have selected 129 SNR candidates based on four criteria for regions where the emission lines flux ratio [S ii]/H α ≥ 0.4. Emission lines of [O ii] λ3727, H β, [O iii] λλ4959,5007, H α, [N ii] λλ6548,6583, and [S ii] λλ6716,6731 have been measured to study the ionized gas properties of the SNR candidates. We adopted a self-consistent spectroscopic analysis, based on Sabbadin plots and Baldwin, Phillips & Terlevich diagrams, to confirm the shock-heated nature of the ionization mechanism in the candidates sample. With this analysis, we end up with 42 Confirmed SNRs, 45 Probable SNRs, and 42 Less likely SNRs. Using shock models, the confirmed SNRs seem to have a metallicity ranging between Large Magellanic Cloud and 2×solar. We looked for correlations between the size of the confirmed SNRs and their emission lines ratios, their galaxy environment, and their galactocentric distance: We see a trend for a metallicity gradient among the SNR population, along with some evolutionary effects.

scholarly journals LINER-like emission in red galaxies: evolutionary phase or recurring phenomenon?

2007 ◽  
Vol 3 (S245) ◽  
pp. 181-184
Author(s):  
Genevieve J. Graves
Keyword(s):  
Stellar Population ◽  
Velocity Dispersion ◽  
Large Fraction ◽  
Optical Emission ◽  
Ionized Gas ◽  
Satellite Galaxy ◽  
The Galaxy ◽  
Evolutionary Phase ◽  
Interstellar Material ◽  
Red Galaxies

AbstractWe present recent results showing that a large fraction of red sequence galaxies contain ionized gas with LINER-like optical emission line ratios. This emission is more frequently found in galaxies with lower central velocity dispersion (σ) and these galaxies typically have younger mean ages than galaxies at the same σ which do not host emission. We suggest that the presence of LINER-like emission may be determined by the quantity of interstellar material in these galaxies and may be associated with the recent accretion of a gas-rich satellite galaxy or alternatively with stellar mass loss that declines as the galaxy stellar population ages.

scholarly journals H ii regions in the CALIFA survey: I. catalogue presentation

2020 ◽  
Vol 494 (2) ◽  
pp. 1622-1646 ◽  
Author(s):  
C Espinosa-Ponce ◽  
S F Sánchez ◽  
C Morisset ◽  
J K Barrera-Ballesteros ◽  
L Galbany ◽  
...  
Keyword(s):  
Stellar Populations ◽  
Spectroscopic Properties ◽  
Emission Lines ◽  
H Ii Regions ◽  
Ionized Gas ◽  
New Approach ◽  
Integral Field Spectroscopy ◽  
Diffuse Ionized Gas ◽  
Spectroscopic Information ◽  
Selection Of

ABSTRACT We present a new catalogue of H ii regions based on the integral field spectroscopy (IFS) data of the extended CALIFA and PISCO samples. The selection of H ii regions was based on two assumptions: a clumpy structure with high contrast of H α emission and an underlying stellar population comprising young stars. The catalogue provides the spectroscopic information of 26 408 individual regions corresponding to 924 galaxies, including the flux intensities and equivalent widths of 51 emission lines covering the wavelength range between 3745 and 7200 Å. To our knowledge, this is the largest catalogue of spectroscopic properties of H ii regions. We explore a new approach to decontaminate the emission lines from diffuse ionized gas contribution. This diffuse gas correction was estimated to correct every emission line within the considered spectral range. With the catalogue of H ii regions corrected, new demarcation lines are proposed for the classical diagnostic diagrams. Finally, we study the properties of the underlying stellar populations of the H ii regions. It was found that there is a direct relationship between the ionization conditions on the nebulae and the properties of stellar populations besides the physicals condition on the ionized regions.

Diffuse Ionized Gas in the β CMa Tunnel

1997 ◽  
Vol 166 ◽  
pp. 173-176
Author(s):  
Olivier Dupin ◽  
Cécile Gry
Keyword(s):  
Interstellar Medium ◽  
Low Density ◽  
Ionized Gas ◽  
Local Bubble ◽  
Diffuse Ionized Gas ◽  
Main Components ◽  
Collisional Ionization ◽  
Dust Grain

AbstractWe present HST observations of the interstellar medium toward the star β CMa known to be located in a low density extension of the Local Bubble. Most of the matter in the sight-line is ionized and clumped in two main components. One of them, as well as one of the components detected toward ϵ CMa, is mostly ionized and only slightly depleted. Their ionization ratios are compatible with collisional ionization at T~25 000 K. These clouds could have been ionized by shocks related to the Local Bubble creation and also responsible of some dust grain sputtering.

Diffuse Ionized Gas Halos Seen with HST

2009 ◽  
pp. 161-163 ◽  
Author(s):  
Ralf-Jürgen Dettmar ◽  
Jörn Rossa ◽  
Michael Dahlem ◽  
Roeland van der Marel
Keyword(s):  
Ionized Gas ◽  
Diffuse Ionized Gas
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