Fraction Of Diffuse Emission Research Articles

PMAS optical integral field spectroscopy of luminous infrared galaxies

The general properties of luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) in the local universe are well known since large samples of these objects have been the subject of numerous spectroscopic works. There are, however, relatively few studies of large samples of LIRGs and ULIRGs using integral field spectroscopy (IFS). We analyze optical (3800-7200A) IFS data taken with the Potsdam Multi-Aperture Spectrophotometer (PMAS) of the central few kiloparsecs of 11 LIRGs. To study the stellar populations we fit the optical stellar continuum and the hydrogen recombination lines of selected regions. We analyze the excitation conditions of the gas using the spatially resolved properties of the brightest optical emission lines. The optical continua of the selected regions are well fitted with a combination of evolved (~0.7-10Gyr) and ionizing (1-20Myr) stellar populations. The latter is more obscured than the evolved population, and has visual extinctions in good agreement with those obtained from the Balmer decrement. Except for NGC 7771, there is no clear evidence for an important contribution to the optical light from an intermediate-aged population (~100-500Myr). Even after correcting for the presence of stellar absorption, a large fraction of spaxels with low observed equivalent widths of Halpha in emission still show enhanced [NII]/Halpha and [SII]/Halpha ratios. These ratios are likely to be produced by a combination of photoionization in HII regions and diffuse emission. These regions of enhanced ratios are generally coincident with low surface brightness HII regions and diffuse emission detected in the Halpha and Pa-alpha images. Using the PMAS line ratios and the NICMOS Pa-alpha photometry of HII regions we find that the fraction of diffuse emission in LIRGs varies from galaxy to galaxy, and it is generally less than 60% as found in other starburst galaxies. (Abridged)

Large scale structure of the ionized gas in the magellanic clouds

view Abstract Citations (123) References (61) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Large Scale Structure of the Ionized Gas in the Magellanic Clouds Kennicutt, Robert C., Jr. ; Bresolin, Fabio ; Bomans, Dominik J. ; Bothun, Gregory D. ; Thompson, Ian B. Abstract Calibrated Hα CCD images taken With the "Parking Lot Camera" are used to investigate the large scale properties of the ionized gas in the Magellanic Clouds. The integrated Hα luminosity, star formation, and the large-scale diffuse emission are studied and compared with other galaxies. The diffuse gas component accounts for 30%-40% of the total Hα emission in both galaxies. The integrated star formation rates and the fraction of diffuse emission are typical for Magellanic irregular galaxies. The Hα maps are used to derive a set of physical parameters for the known supergiant shells in the LMC and SMC. The Hα emission distribution have also been compared to the distribution of HI column density. Evidence for a star formation threshold is discussed. Publication: The Astronomical Journal Pub Date: February 1995 DOI: 10.1086/117304 Bibcode: 1995AJ....109..594K Keywords: Diffuse Radiation; Galactic Structure; H Alpha Line; Ionized Gases; Luminosity; Magellanic Clouds; Star Formation; Astronomical Maps; Charge Coupled Devices; Density Distribution; Hydrogen; Irregular Galaxies; Star Formation Rate; Astronomy; MAGELLANIC CLOUDS; ISM: STRUCTURE full text sources ADS | data products SIMBAD (25) NED (2)