| 1. |
- Gallerani, S., et al.
(author)
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ALMA suggests outflows in z ~ 5.5 galaxies
- 2018
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 473:2, s. 1909-1917
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Journal article (peer-reviewed)abstract
- We present the first attempt to detect outflows from galaxies approaching the Epoch of Reionization (EoR) using a sample of nine star-forming (SFR = 31 ± 20Mo˙ yr-1) z ~ 5.5 galaxies for which the [C II]158 μm line has been previously obtained with Atacama Large Millimeter Array (ALMA). We first fit each line with a Gaussian function and compute the residuals by subtracting the best-fitting model from the data. We combine the residuals of all sample galaxies and find that the total signal is characterized by a flux excess of ~0.5mJy extended over ~1000 km s-1. Although we cannot exclude that part of this signal is due to emission from faint satellite galaxies, we show that the most probable explanation for the detected flux excess is the presence of broad wings in the [CII] lines, signatures of starburst-driven outflows. We infer an average outflow rate of M˙ = 54 ± 23Mo˙ yr-1, providing a loading factor η = M˙/SFR = 1.7 ± 1.3 in agreement with observed local starbursts. Our interpretation is consistent with outcomes from zoomed hydrosimulations of Dahlia, a z ~ 6 galaxy (SFR ~ 100Mo˙ yr-1), whose feedback-regulated star formation results into an outflow rate M ~ 30Mo˙ yr-1. The quality of the ALMA data is not sufficient for a detailed analysis of the [C II] line profile in individual galaxies. Nevertheless, our results suggest that starburst-driven outflows are in place in the EoR and provide useful indications for future ALMA campaigns. Deeper observations of the [CII] line in this sample are required to better characterize feedback at high-z and to understand the role of outflows in shaping early galaxy formation.
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| 2. |
- Gallerani, S., et al.
(author)
-
ALMA suggests outflows in z similar to 5.5 galaxies
- 2018
-
In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 473:2, s. 1909-1917
-
Journal article (peer-reviewed)abstract
- We present the first attempt to detect outflows from galaxies approaching the Epoch of Reionization (EoR) using a sample of nine star-forming (SFR = 31 +/- 20M(circle dot) yr(-1)) z similar to 5.5 galaxies for which the [C II] 158 mu m line has been previously obtained with Atacama Large Millimeter Array (ALMA). We first fit each line with a Gaussian function and compute the residuals by subtracting the best-fitting model from the data. We combine the residuals of all sample galaxies and find that the total signal is characterized by a flux excess of similar to 0.5 mJy extended over similar to 1000 km s(-1). Although we cannot exclude that part of this signal is due to emission from faint satellite galaxies, we show that the most probable explanation for the detected flux excess is the presence of broad wings in the [C II] lines, signatures of starburst-driven outflows. We infer an average outflow rate of. M(over dot) = 54 +/- 23M(circle dot) yr(-1), providing a loading factor eta = M(over dot)/SFR = 1.7 +/- 1.3 in agreement with observed local starbursts. Our interpretation is consistent with outcomes from zoomed hydrosimulations of Dahlia, a z similar to 6 galaxy (SFR similar to 100M(circle dot) yr(-1)), whose feedback-regulated star formation results into an outflow rate. M(over dot) similar to 30M(circle dot) yr(-1). The quality of the ALMA data is not sufficient for a detailed analysis of the [C II] line profile in individual galaxies. Nevertheless, our results suggest that starburst-driven outflows are in place in the EoR and provide useful indications for future ALMA campaigns. Deeper observations of the [C II] line in this sample are required to better characterize feedback at high-z and to understand the role of outflows in shaping early galaxy formation.
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| 3. |
- Behrens, C., et al.
(author)
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Dusty galaxies in the Epoch of Reionization : simulations
- 2018
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 477:1, s. 552-565
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Journal article (peer-reviewed)abstract
- The recent discovery of dusty galaxies well into the Epoch of Reionization (redshift z > 6) poses challenging questions about the properties of the interstellar medium in these pristine systems. By combining state-of-the-art hydrodynamic and dust radiative transfer simulations, we address these questions focusing on the recently discovered dusty galaxy A2744_YD4 (z = 8.38, Laporte et al.). We show that we can reproduce the observed spectral energy distribution (SED) only using different physical values with respect to the inferred ones by Laporte et al., i.e. a star formation rate of SFR = 78 M(circle dot)yr(-1), a factor approximate to 4 higher than deduced from simple SED fitting. In this case, we find: (i) dust attenuation (corresponding to tau(v) = 1.4) is consistent with a Milky Way (MW) extinction curve; (ii) the dust-to-metal ratio is low, f(d) similar to 0.08, implying that early dust formation is rather inefficient;(iii) the luminosity-weighted dust temperature is high, T-d = 91 23 K, as a result of the intense (approximate to 100 x MW) interstellar radiation field; and (iv) due to the high T-d, the Atacama Large Millimeter/submillimeter Array Band 7 detection can be explained by a limited dust mass, M-d = 1.6 x 10(6) M-circle dot. Finally, the high dust temperatures might solve the puzzling low infrared excess (IRX) recently deduced for high-z galaxies from the IRX-beta relation.
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| 4. |
- Vallini, Livia, et al.
(author)
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CO line emission from galaxies in the Epoch of Reionization
- 2018
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 473:1, s. 271-285
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Journal article (peer-reviewed)abstract
- We study the CO line luminosity (L-CO), the shape of the CO spectral line energy distribution (SLED), and the value of the CO-to-H-2 conversion factor in galaxies in the Epoch of Reionization (EoR). For this aim, we construct a model that simultaneously takes into account the radiative transfer and the clumpy structure of giant molecular clouds (GMCs) where the CO lines are excited. We then use it to post-process state-of-the-art zoomed, high resolution (30 pc), cosmological simulation of a main-sequence (M-* approximate to 10(10) M-circle dot, SFR approximate to 100M(circle dot) yr(-1)) galaxy, 'Althaea', at z approximate to 6. We find that the CO emission traces the inner molecular disc (r approximate to 0.5 kpc) of Althaea with the peak of the CO surface brightness co-located with that of the [C-II] 158 mu m emission. Its LCO(1-0) = 10(4.85) L-circle dot is comparable to that observed in local galaxies with similar stellar mass. The high (Sigma(gas) approximate to 220M(circle dot) pc(-2)) gas surface density in Althaea, its large Mach number (M approximate to 30) and the warm kinetic temperature (T-k approximate to 45 K) of GMCs yield a CO SLED peaked at the CO(7-6) transition, i.e. at relatively high-J and a CO-to-H-2 conversion factor alpha(CO) approximate to 1.5M(circle dot) (K km s(-1) pc(2))(-1) lower than that of the Milky Way. The Atacama Large Millimeter/submillimeter Array observing time required to detect (resolve) at 5 sigma the CO(7-6) line from galaxies similar to Althaea is approximate to 13 h (approximate to 38 h).
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