Detection of H92 alpha Recombination Line from the Galaxies NGC 3628, IC 694, and NGC 1365

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

doi:10.1086/173510

Cited by 40 publications

(68 citation statements)

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“…As in NGC 660, formaldehyde is seen in absorption against the extended central radio continuum source suggesting the presence of large masses of high-density molecular gas (Mangum et al 2008, and references therein). Indeed, the center of NGC 3628 resembles that of NGC 660 also by its complement of compact radio continuum sources (none coinciding with the nucleus) representing active regions in the circumnuclear star-burst contributing about 10% to the total radio continuum emission (Carral et al 1990), and by its H92α radio recombination line emission from high-density HII regions (n HII ≈ 10 4 cm −3 -Anantharamaiah et al 1993;Zhao et al 1997). The central core of NGC 3628 is also bright in X-rays, and the galaxy has an extended halo of soft X-ray emission surrounding a central outflow, apparently a galactic (star-burstdriven) super-wind bubble (Dahlem et al 1996(Dahlem et al , 1998Strickland et al 2004a,b;Grimes et al 2005;Flohic et al 2006).…”

Section: Ngc 3628mentioning

confidence: 99%

CI and CO in nearby galaxy centers

Israel¹

2009

A&A

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Aims. We study the physical properties and mass 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 278, NGC 660, NGC 3628, NGC 4631, and NGC 4666, as well as 492 GHz [CI] maps in three of these are used to model the molecular gas. Results. All five objects contain bright CO emission in the central regions. Clear central concentrations were found in NGC 660, NGC 3628, and NGC 4666, but not in the weakest CO emitters NGC 278 and NGC 4631. In all cases, the observed lines could be modeled only with at least two distinct gas components. The physical condition of the molecular gas is found to differ from galaxy to galaxy. Relatively tenuous (density 100-1000 cm −3 ) and high kinetic temperature (100-150 K) gas occur in all galaxies, except perhaps NGC 3628, mixed with cooler (10-30 K) and denser (0.3−1.0 × 10 4 cm −3 ) gas. The CO-to-H 2 conversion factor X is typically an order of magnitude less than the "standard" value in the Solar Neighborhood in all galaxy centers. The molecular gas is constrained within radii between 0.6 and 1.5 kpc from the nuclei. Within these radii, H 2 masses are typically 0.6−1.5 × 10 8 M , which corresponds to no more than a few per cent of the dynamical mass in the same region.

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Section: Ngc 3628mentioning

confidence: 99%

CI and CO in nearby galaxy centers

Israel¹

2009

A&A

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“…We used the collection of H II regions model from Anantharamaiah et al (1993). We considered a grid of models with electron temperature, T e , in the range 1000 K to 12 500 K, electron density, n e , in the range 10 cm −3 to 10 6 cm −3 , and effective diameter of the line-emitting gas (∼volume 1/3 ), l, in the range 0.01 pc to 100 pc.…”

Section: Modelling the Ionized Gasmentioning

confidence: 99%

Detection of the H92αrecombination line from the starbursts in the Circinus galaxy and NGC 1808

Roy

Goss²,

Anantharamaiah

2008

A&A

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Context. Gas ionized by starburst activity radiates radio recombination lines (RRLs), from which one can derive the plasma conditions and the number of massive stars formed in the burst, free of dust obscuration effects. Aims. We aimed to find detectable RRL emission from additional extragalactic starburst systems and to use the line properties to estimate the properties of the ionized gas. Methods. We conducted a search for RRLs in the nearby extragalactic starburst or Seyfert galaxies NGC 1808, the Circinus galaxy, NGC 4038/9, II Zw 40, NGC 6221, NGC 7552, IRAS 18325-5926, IC 5063, and VV 114. We used the Very Large Array with resolution of 3 to 32 and the Australia Telescope Compact Array with resolution of 10 to search for the RRLs H91α and H92α with rest frequencies of 8.6 GHz and 8.3 GHz. From the new detections we derive conditions in the starburst regions. Results. We detected for the first time RRLs from the starburst nuclei in the Circinus galaxy and NGC 1808. The Circinus galaxy was detected in RRL emission with a line strength integrated over the source of 3.2 mJy, making it the fourth-strongest extragalactic RRL emitter known at this frequency (after NGC 4945, M 82, and NGC 253) and so is suitable for detailed study. The line and continuum emission from the Circinus galaxy can be matched by a model consisting of a collection of 50 to 10 000 H II regions with temperatures of 5000 K, densities of 500 cm −3 to 50 000 cm −3 , and a total effective diameter of 3 pc to 50 pc. The Lyman continuum production rate required to maintain the ionization is 1 × 10 52 s −1 to 3 × 10 53 s −1 , which requires 300 to 9000 O5 stars to be produced in the starburst, inferring a star formation rate of 0.2 M yr −1 to 6 M yr −1 . NGC 1808 was detected in RRL emission at 3.9σ with a line strength of 0.47 mJy at the expected velocity. No radio recombination lines were detected from the other galaxies surveyed to a 3σ limit of 0.3 mJy to 1.4 mJy. Conclusions. We have detected RRLs from two galaxies, adding to the small but growing number of known extragalactic RRL emitters. The Circinus galaxy is strong and especially suited to high-quality follow-up spectroscopic study. We derived conditions and star formation rates in the starbursting regions. Uncertainties can be reduced by future multi-transition studies.

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“…We considered a simple model consisting of a collection of spherical H II regions, all with the same diameter, electron temperature, T e , electron density, n e , in a volume of uniform synchrotron emission, following [9]. Models with 10 to 300 H II regions, all with T e ∼ 5000 K, n e ∼ (10 3 to 10 4 ) cm −3 and size of (5 to 600) pc produced good matches to the line and continuum emission.…”

Section: Detection Of Ngc 3256mentioning

confidence: 99%

Radio Recombination Lines from Starbursts: NGC 3256, NGC 4945 and the Circinus Galaxy

Roy¹,

Goss²,

Mohan³

et al. 2005

AIP Conference Proceedings

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Abstract.A renewed attempt to detect radio recombination lines from external galaxies has resulted in the measurement of lines from several bright starburst galaxies. The lines are produced by hydrogen ionized by young, high-mass stars and are diagnostic of the conditions and gas dynamics in the starburst regions without problems of dust obscuration. We present here detections of the lines H91α and H92α near 8.6 GHz from the starburst nuclei in NGC 3256, NGC 4945, and the Circinus galaxy using the ATCA and VLA. Modelling the line emitting region as a collection of H II regions, we derive the required number of H II regions, their temperature, density, and distribution.

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Detection of H92 alpha Recombination Line from the Galaxies NGC 3628, IC 694, and NGC 1365

Cited by 40 publications

References 0 publications

CI and CO in nearby galaxy centers

CI and CO in nearby galaxy centers

Detection of the H92αrecombination line from the starbursts in the Circinus galaxy and NGC 1808

Radio Recombination Lines from Starbursts: NGC 3256, NGC 4945 and the Circinus Galaxy

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