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Vibrationally excited HC3N emission in NGC 1068: tracing the recent star formation in the starburst ring
- Source :
- DIGITAL.INTA Repositorio Digital del Instituto Nacional de Técnica Aeroespacial, Universitat Pompeu Fabra
- Publication Year :
- 2021
- Publisher :
- Oxford Academics: Oxford University Press, 2021.
-
Abstract
- Using ALMA data, we have studied the HC$_3$N and continuum emission in the starburst ring (SB ring) and the circumnuclear disc (CND) of the SB/AGN composite galaxy NGC 1068. We have detected emission from vibrationally excited HC$_3$N (HC$_3$N*) only towards one star-forming region of the SB ring. Remarkably, HC$_3$N* was not detected towards the CND despite its large HC$_3$N $v=0$ column density. From LTE and non-LTE modelling of HC$_3$N*, we obtained a dust temperature of $ T_\text{dust} \sim 250$ K and a density of $n_{\text{H}_2}=6\times10^5$ cm$^{-3}$ for this star-forming region. The estimated IR luminosity of $5.8\times10^8$ L$_\odot$ is typical of proto-Super Star Clusters (proto-SSC) observed in the SB galaxy NGC 253. We use the continuum emissions at $147$ GHz and $350$ GHz, along with CO and Pa $\alpha$, to estimate the ages of other $14$ SSCs in the SB ring. We find the youngest SSCs to be associated with the region connecting the nuclear bar with the SB ring, supporting the scenario of sequential star formation. For the CND, our analysis yields $T_\text{dust} \leqslant 100$ K and $n_{\text{H}_2}\sim(3-6)\times10^5$cm$^{-3}$. The very different dust temperatures found for the CND and the proto-SSC indicates that, while the dust in the proto-SSC is being efficiently heated from the inside by the radiation from massive proto-stars, the CND is being heated externally by the AGN, which in the IR optically thin case can only heat the dust to $56$ K. We discuss the implications of the non-detection of HC$_3$N* near the luminous AGN in NGC 1068 on the interpretation of the HC$_3$N* emission observed in the SB/AGN composite galaxies NGC 4418 and Arp 220.<br />Comment: submitted to MNRAS on 08/08/2020
- Subjects :
- Physics
010308 nuclear & particles physics
Star formation
FOS: Physical sciences
Astronomy and Astrophysics
Star Formation [Galaxies]
Astrophysics
01 natural sciences
Astrophysics - Astrophysics of Galaxies
Galaxy
Star cluster
Space and Planetary Science
Seyfert [galaxies]
Excited state
Astrophysics of Galaxies (astro-ph.GA)
0103 physical sciences
ISM [Galaxies]
Star Clusters [galaxies]
Individual: NGC1068 [Galaxies]
010303 astronomy & astrophysics
Subjects
Details
- Language :
- English
- Database :
- OpenAIRE
- Journal :
- DIGITAL.INTA Repositorio Digital del Instituto Nacional de Técnica Aeroespacial, Universitat Pompeu Fabra
- Accession number :
- edsair.doi.dedup.....6ff0651cf523e40c809ba545f7b37c34