Unveiling Extragalactic Star Formation Using Radio Recombination Lines: An Expanded Very Large Array Pilot Study With NGC 253

Kepley, Amanda A.; Chomiuk, Laura; Johnson, K. E.; Goss, W. M.; Balser, Dana S.; Pisano, D. J.

doi:10.1088/2041-8205/739/1/l24

Cited by 19 publications

(24 citation statements)

References 32 publications

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“…It is unlikely that an active galactic nucleus is present, as the H40α line would appear > ∼ 1000 km s −1 in width. We do not detect any asymmetry in the line emission from the central source as had been reported in some prior recombination line observations (Mohan et al 2002;Kepley et al 2011) but not others. The reason for this discrepancy is unclear, although one possibility is that the line shapes differ because the lower-frequency lines are probing less dense gas than the H40α line.…”

Section: Datasupporting

confidence: 74%

“…Puxley et al (1997) obtained a distance-adjusted Q of (7.0 ± 1.5) × 10 53 s −1 from H40α data that is significantly higher than our Q or other measurements of Q, but the line is detected at the ∼5σ level, which may indicate issues with the reliability of their data. Rodríguez-Rico et al (2006) and Kepley et al (2011) report Q based on lower-frequency recombination line data that are ∼3× lower than our measurement. his could be related to sensitivity issues since they had difficulty detecting line emission from all three sources that we detected.…”

Section: Discussioncontrasting

confidence: 52%

“…Seaquist & Bell 1977;Mebold et al 1980;Anantharamaiah & Goss 1996;Puxley et al 1997;Mohan et al 2002Mohan et al , 2005Rodríguez-Rico et al 2006;Kepley et al 2011). This includes the detection of H40α emission by Puxley et al (1997).…”

Section: Introductionmentioning

confidence: 99%

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ALMA observations of 99 GHz free–free and H40α line emission from star formation in the centre of NGC 253

Bendo

Beswick

D'Cruze

et al. 2015

Monthly Notices of the Royal Astronomical Society: Letters

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We present Atacama Large Millimeter/submillimeter Array observations of 99.02 GHz freefree and H40α emission from the centre of the nearby starburst galaxy NGC 253. We calculate electron temperatures of 3700-4500 K for the photoionized gas, which agrees with previous measurements. We measure a photoionizing photon production rate of(3.2 ± 0.2) × 10 53 s −1and a star formation rate of 1.73 ± 0.12 M ⊙ yr −1 within the central 20×10 arcsec, which fall within the broad range of measurements from previous millimetre and radio observations but which are better constrained. We also demonstrate that the dust opacities are ∼3 dex higher than inferred from previous near-infrared data, which illustrates the benefits of using millimetre star formation tracers in very dusty sources.

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Section: Datasupporting

confidence: 74%

Section: Discussioncontrasting

confidence: 52%

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ALMA observations of 99 GHz free–free and H40α line emission from star formation in the centre of NGC 253

Bendo

Beswick

D'Cruze

et al. 2015

Monthly Notices of the Royal Astronomical Society: Letters

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“…As we have shown, the SSA model is statistically ruled out (Section 4.2.2). Given the overwhelming evidence of a significant thermal component in the central starburst (e.g., Figure 2; Ulvestad & Antonucci 1997;Keto et al 1999;Kepley et al 2011) coexisting with synchrotron plasma, the synchrotron FFA model is more likely than the low-energy cutoff in the electron population. The plasma becomes optically thick around a frequency of 230 MHz.…”

Section: Broadband Spectrum Of Total Radio Emissionmentioning

confidence: 99%

Spectral Energy Distribution and Radio Halo of NGC 253 at Low Radio Frequencies

Kapińska

Staveley‐Smith

Crocker

et al. 2017

ApJ

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We present new radio continuum observations of NGC253 from the Murchison Widefield Array at frequencies between 76 and 227 MHz. We model the broadband radio spectral energy distribution for the total flux density of NGC253 between 76 MHz and 11 GHz. The spectrum is best described as a sum of a central starburst and extended emission. The central component, corresponding to the inner 500 pc of the starburst region of the galaxy, is best modeled as an internally free-free absorbed synchrotron plasma, with a turnover frequency around 230 MHz. The extended emission component of the spectrum of NGC253 is best described as a synchrotron emission flattening at low radio frequencies. We find that 34% of the extended emission (outside the central starburst region) at 1 GHz becomes partially absorbed at low radio frequencies. Most of this flattening occurs in the western region of the southeast halo, and may be indicative of synchrotron self-absorption of shock-reaccelerated electrons or an intrinsic low-energy cutoff of the electron distribution. Furthermore, we detect the large-scale synchrotron radio halo of NGC253 in our radio images. At 154-231 MHz the halo displays the well known X-shaped/horn-like structure, and extends out to ∼8 kpc in the z-direction (from the major axis).

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“…Often, multi-wavelength observations are used to accomplish this (e.g., Murphy et al 2011), and add an additional layer of complication to the use of SFR(RRL). Exploratory work is still ongoing to test how efficiently RRLs can be detected in external galaxies (e.g., Kepley et al 2011), and what advantage they can bring relative to more classical and efficient methods. If the high-density, and heavily dust-obscured, regime turns out to be the main niche for these tracers (Yun 2008), they will need to be carefully weighted against SFR(IR), in light of the potentially heavy impact of the Lyc absorption by dust.…”

Section: Indicators Based On Ionised Gas Emissionmentioning

confidence: 99%

Star formation rate indicators

Calzetti¹

2013

Secular Evolution of Galaxies

200

184

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If we are to develop a comprehensive and predictive theory of galaxy formation and evolution, it is essential that we obtain an accurate assessment of how and when galaxies assemble their stellar populations, and how this assembly varies with environment. There is strong observational support for the hierarchical assembly of galaxies, but by definition the dwarf galaxies we see today are not the same as the dwarf galaxies and proto-galaxies that were disrupted during the assembly. Our only insight into those disrupted building blocks comes from sifting through the resolved field populations of the surviving giant galaxies to reconstruct the star formation history, chemical evolution, and kinematics of their various structures. To obtain the detailed distribution of stellar ages and metallicities over the entire life of a galaxy, one needs multi-band photometry reaching solar-luminosity main sequence stars. The Hubble Space Telescope can obtain such data in the outskirts of Local Group galaxies. To perform these essential studies for a fair sample of the Local Universe will require observational capabilities that allow us to extend the study of resolved stellar populations to much larger galaxy samples that span the full range of galaxy morphologies, while also enabling the study of the more crowded regions of relatively nearby galaxies. With such capabilities in hand, we will reveal the detailed history of star formation and chemical evolution in the universe.

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Unveiling Extragalactic Star Formation Using Radio Recombination Lines: An Expanded Very Large Array Pilot Study With NGC 253

Cited by 19 publications

References 32 publications

ALMA observations of 99 GHz free–free and H40α line emission from star formation in the centre of NGC 253

ALMA observations of 99 GHz free–free and H40α line emission from star formation in the centre of NGC 253

Spectral Energy Distribution and Radio Halo of NGC 253 at Low Radio Frequencies

Star formation rate indicators

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