تقرير
The GLEAM 200 MHz Local Radio Luminosity Function for AGN and Star-forming Galaxies
| العنوان: | The GLEAM 200 MHz Local Radio Luminosity Function for AGN and Star-forming Galaxies |
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| المؤلفون: | Franzen, T. M. O., Seymour, N., Sadler, E. M., Mauch, T., White, S. V., Jackson, C. A., Chhetri, R., Quici, B., Bell, M. E., Callingham, J. R., Dwarakanath, K. S., For, B., Gaensler, B. M., Hancock, P. J., Hindson, L., Hurley-Walker, N., Johnston-Hollitt, M., Kapinska, A. D., Lenc, E., McKinley, B., Morgan, J., Offringa, A. R., Procopio, P., Staveley-Smith, L., Wayth, R. B., Wu, C., Zheng, Q. |
| سنة النشر: | 2021 |
| المجموعة: | Astrophysics |
| مصطلحات موضوعية: | Astrophysics - Astrophysics of Galaxies |
| الوصف: | The GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) is a radio continuum survey at 76-227 MHz of the entire southern sky (Declination $<+30\deg$) with an angular resolution of $\approx 2$ arcmin. In this paper, we combine GLEAM data with optical spectroscopy from the 6dF Galaxy Survey to construct a sample of 1,590 local (median $z \approx 0.064$) radio sources with $S_{200\,\mathrm{MHz}} > 55$ mJy across an area of $\approx 16,700~\mathrm{deg}^{2}$. From the optical spectra, we identify the dominant physical process responsible for the radio emission from each galaxy: 73 per cent are fuelled by an active galactic nucleus (AGN) and 27 per cent by star formation. We present the local radio luminosity function for AGN and star-forming galaxies at 200 MHz and characterise the typical radio spectra of these two populations between 76 MHz and $\sim 1$ GHz. For the AGN, the median spectral index between 200 MHz and $\sim 1$ GHz, $\alpha_{\mathrm{high}}$, is $-0.600 \pm 0.010$ (where $S \propto \nu^{\alpha}$) and the median spectral index within the GLEAM band, $\alpha_{\mathrm{low}}$, is $-0.704 \pm 0.011$. For the star-forming galaxies, the median value of $\alpha_{\mathrm{high}}$ is $-0.650 \pm 0.010$ and the median value of $\alpha_{\mathrm{low}}$ is $-0.596 \pm 0.015$. Among the AGN population, flat-spectrum sources are more common at lower radio luminosity, suggesting the existence of a significant population of weak radio AGN that remain core-dominated even at low frequencies. However, around 4 per cent of local radio AGN have ultra-steep radio spectra at low frequencies ($\alpha_{\mathrm{low}} < -1.2$). These ultra-steep-spectrum sources span a wide range in radio luminosity, and further work is needed to clarify their nature. Comment: 28 pages, 18 figures, accepted for publication in PASA |
| نوع الوثيقة: | Working Paper |
| DOI: | 10.1017/pasa.2021.36 |
| URL الوصول: | http://arxiv.org/abs/2107.09030 |
| رقم الأكسشن: | edsarx.2107.09030 |
| قاعدة البيانات: | arXiv |
| DOI: | 10.1017/pasa.2021.36 |
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