Radio Recombination Lines from the Nuclear Regions of Starburst Galaxies

Zhao, Jun‐Hui; Anantharamaiah, K. R.; Goss, W. M.; Viallefond, F.

doi:10.1086/178041

Cited by 46 publications

(71 citation statements)

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“…The bright core is the site of a powerful starburst. Radio observations reveal numerous supernova remnants, HII regions and water masers throughout (Kronberg & Biermann 1981;Zhao et al 1996;Lisenfeld et al 1996;Tarchi et al 2000Tarchi et al , 2002; a lowluminosity AGN may be present (Inui et al 2005). X-ray observations also reveal a starburst-driven superwind carrying material away from the galaxy's plane (Armus et al 1995;Della Ceca et al 1999).…”

Section: Ngc 2146mentioning

confidence: 97%

CI and CO in nearby galaxy centers

Israel¹

2008

A&A

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Aims. We study the physical properties and amount of molecular gas in the central regions of galaxies with active nuclei. Methods. Maps and measurements of the J = 1−0, J = 2−1, J = 3−2, J = 4−3 12 CO, the J = 1−0, J = 2−1, and J = 3−2 13 CO lines in the central arcminute squared of NGC 1068, NGC 2146, NGC 3079, NGC 4826, and NGC 7469, as well as 492 GHz CI maps in three of these are used to model the molecular gas clouds in these galaxies. Results. Bright CO concentrations were detected and mapped in all five objects. In all cases, the observed lines could be fitted with two distinct gas components. The physical condition of the molecular gas is found to differ from galaxy to galaxy. Rather high kinetic temperatures of 125−150 K occur in NGC 2146 and NGC 3079. Very high densities of 0.3−1.0 × 10 5 cm −3 occur in NGC 2146, NGC 3079, and NGC 7469. The CO to H 2 conversion factor X is typically an order of magnitude less than the "standard" value in the solar neighborhood. The molecular gas is constrained within radii between 0.9 and 1.5 kpc from the nuclei. Within these radii, H 2 masses are typically 1.2−2.5 × 10 8 M . The exception is the (relatively nearby) merger NGC 4826 with R = 0.3 kpc, and M = 3 × 10 7 M . The H 2 mass is typically about one per cent of the dynamical mass in the same region.

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Section: Ngc 2146mentioning

confidence: 97%

CI and CO in nearby galaxy centers

Israel¹

2008

A&A

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“…See Prouton et al (2004 Table 3 for details; (d) NVSS, Condon et al (1998); (e) Condon et al (1991a); (f) Sopp & Alexander (1991); (g) Sopp & Alexander (1992); (h) Gregory & Condon (1991); (i) Griffith et al (1994); (j) Griffith et al (1995); (k) Condon et al (1983); (l) Dressel & Condon (1978); (m) Condon et al (1991b); (n) Rush et al (1996); (o) Baan & Klöckner (2006); (p) Crawford et al (1996); (q) Sramek & Tovmassian (1976); (r) Imanishi et al (2006); (s) Zhao et al (1996); (t) Rodriguez-Rico et al (2005); (u) Anantharamaiah et al (2000); (v) Douglas et al (1996); (w) Ficarra et al (1985). 22.3 ± 1 a 22.5 10.0 ± 0.3 b…”

Section: Appendix A: Individual Objectsmentioning

confidence: 99%

Modeling the spectral energy distribution of ULIRGs

Clemens¹,

Vega

Bressan

et al. 2007

A&A

109

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Aims. We aim to constrain new starburst/AGN models of IRAS bright galaxies via their spectral energy distribution from the nearinfrared to the radio. To this end, we determine the radio spectra for a sample of 31 luminous and ultraluminous IRAS galaxies (LIRGs/ULIRGs). Methods. We present here new high frequency VLA observations at 22.5 GHz and 8.4 GHz and also derive fluxes at other radio frequencies from archival data. Together with radio data from the literature, we construct the radio spectrum for each source. In the selection of data we have made every effort to ensure that these fluxes neither include contributions from nearby objects, nor underestimate the flux due to high interferometer resolution.Results. From our sample of well-determined radio spectra we find that very few have a straight power-law slope. Although some sources show a flattening of the radio spectral slope at high frequencies, the average spectrum shows a steepening of the radio spectrum from 1.4 to 22.5 GHz. This is unexpected, because in sources with high rates of star formation, we expect that flat spectrum, free-free emission will make a significant contribution to the radio flux at higher radio frequencies. Despite this trend, the radio spectral indices between 8.4 and 22.5 GHz are flatter for sources with higher values of the far-infrared (FIR)-radio flux density ratio, q, when this is calculated at 8.4 GHz. Therefore, sources that are deficient in radio emission relative to FIR emission (presumably younger sources) have a larger thermal component to their radio emission. However, we find no correlation between the radio spectral index between 1.4 and 4.8 GHz and q at 8.4 GHz. Because the low frequency spectral index is affected by free-free absorption, and this is a function of source size for a given mass of ionised gas, this is evidence that the ionised gas in ULIRGs shows a range of densities. Conclusions. The youngest LIRGs and ULIRGs are characterised by flatter average radio spectral indices from 1.4 to 22.5 GHz, and by a larger contribution to their high frequency, radio spectra from free-free emission. However, the youngest sources are not those that have the greatest free-free absorption at low radio frequencies. The sources in which the effects of free-free absorption are strongest are instead the most compact sources. Although these have the warmest FIR colours, they are not necessarily the youngest sources.

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“…A nebular diagnostic like radio recombination lines (RRLs) can probe thermal gas with large emission measures (EMs). In the centimeterwavelength range, RRLs have been shown to be detectable from nuclear starburst regions in a number of nearby galaxies (Shaver, Churchwell, & Rots 1977 ;Seaquist & Bell 1977 ;Puxley et al 1991 ;Anantharamaiah et al 1993 ;Zhao et al 1996 ;Phookun, Anantharamaiah, & Goss 1998). These lines have proven to be good probes of gas density and are reliable estimators of ionized gas mass and the ionizing photon Ñux in these starburst regions.…”

Section: Introductionmentioning

confidence: 99%

Very Large Array Observations of the H92α Line from NGC 5253 and Henize 2‐10: Ionized Gas around Super Star Clusters

Mohan

Anantharamaiah

Goss

2001

ApJ

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We have detected the H92a radio recombination line from two dwarf starburst galaxies, NGC 5253 and He 2-10, using the Very Large Array. Both the line data as well as the radio continuum data are used to model the properties of the ionized gas in the centers of these galaxies. We consider a multidensity model for radio recombination lines and show why previous models, which were based on the assumption of gas at a single density, are valid in many situations. The models show that the ionized gas has a density of D104 cm~3 in both galaxies, with an e †ective size of 2È10 pc and a total mass of D104The derived production rate of Lyman continuum photons is D2.5 ] 1052 s~1 in both the galaxies, M _ . and the corresponding mass of stars (assuming a Salpeter initial mass function) is D105 The M _ . implied stellar density shows that the observed radio recombination lines arise from ionized gas around super star clusters (SSCs) in both galaxies (these SSCs have been recently detected through their radio continuum emission). The existence of D104 of ionized gas within a few parsecs of an SSC places M _ strict constraints on dynamical models. Using simple arguments, the parameter space for a few possible models are derived. The well-known radioÈfar-infrared correlation also holds for NGC 5253, although the radio emission from this galaxy is almost completely thermal. It is shown that NGC 5253 is strong evidence that the component of far-infrared emission from warm dust is correlated separately with the component of radio emission from thermal bremsstrahlung.

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Radio Recombination Lines from the Nuclear Regions of Starburst Galaxies

Cited by 46 publications

References 4 publications

CI and CO in nearby galaxy centers

CI and CO in nearby galaxy centers

Modeling the spectral energy distribution of ULIRGs

Very Large Array Observations of the H92α Line from NGC 5253 and Henize 2‐10: Ionized Gas around Super Star Clusters

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