Fine-structure infrared lines from the Cassiopeia A knots

Docenko, Dmitrijs; Sunyaev, R.

doi:10.1051/0004-6361/200810366

Cited by 50 publications

(82 citation statements)

References 58 publications

(158 reference statements)

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“…Because the gas in Cas A can be ionised due to shocks and/or the radiation field, we assume that most of the [Si ii] emission comes from the ionised gas phase. The latter assumption is supported by the absence of any detected [O i] 63 µm or 145 µm line emission from Cas A (Docenko & Sunyaev 2010;. With a critical density of 10 3 cm −3…”

Section: Appendix B: Line Emissionmentioning

confidence: 84%

“…With unrealistically high dust masses needed to reproduce the IR-submm dust SED, we can exclude Mg0.7SiO2.7, CaAl12O19 and Al2O3 grains as the dominant dust species in Cas A. Also amorphous carbon grains might not be a plausible major dust component in Cas A due to the overwhelmingly oxygen-rich composition of the remnant (Chevalier & Kirshner 1979;Docenko & Sunyaev 2010). Due to the presence of a variety of metals in different parts of the SN ejecta (e.g., Rho et al 2008;Arendt et al 2014), the condensation of SN dust with a range of different dust compositions throughout the remnant might be more realistic 22 .…”

Section: Dust Sed Modelling and Resultsmentioning

confidence: 99%

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The dust mass in Cassiopeia A from a spatially resolvedHerschelanalysis

Looze¹,

Barlow²,

Swinyard³

et al. 2016

Mon. Not. R. Astron. Soc.

154

152

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Theoretical models predict that core-collapse supernovae (CCSNe) can be efficient dust producers (0.1-1.0 M ), potentially accounting for most of the dust production in the early Universe. Observational evidence for this dust production efficiency is however currently limited to only a few CCSN remnants (e.g., SN 1987A, Crab Nebula). In this paper, we revisit the dust mass produced in Cassiopeia A (Cas A), a ∼330-year old Orich Galactic supernova remnant (SNR) embedded in a dense interstellar foreground and background. We present the first spatially resolved analysis of Cas A based on Spitzer and Herschel infrared and submillimetre data at a common resolution of ∼0.6 for this 5 diameter remnant following a careful removal of contaminating line emission and synchrotron radiation. We fit the dust continuum from 17 to 500 µm with a fourcomponent interstellar medium (ISM) and supernova (SN) dust model. We find a concentration of cold dust in the unshocked ejecta of Cas A and derive a mass of 0.3-0.5 M of silicate grains freshly produced in the SNR, with a lower limit of ≥0.1-0.2 M . For a mixture of 50% of silicate-type grains and 50% of carbonaceous grains, we derive a total SN dust mass between 0.4 M and 0.6 M . These dust mass estimates are higher than from most previous studies of Cas A and support the scenario of supernova dominated dust production at high redshifts. We furthermore derive an interstellar extinction map for the field around Cas A which towards Cas A gives average values of A V = 6-8 mag, up to a maximum of A V = 15 mag.

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Section: Appendix B: Line Emissionmentioning

confidence: 84%

Section: Dust Sed Modelling and Resultsmentioning

confidence: 99%

The dust mass in Cassiopeia A from a spatially resolvedHerschelanalysis

Looze¹,

Barlow²,

Swinyard³

et al. 2016

Mon. Not. R. Astron. Soc.

154

152

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“…In a dense knot, the reverse shock is attenuated due to energy conservation. Following Docenko & Sunyaev (2010), a 2000 km s −1 reverse shock will be slowed to 200 km s −1 when crossing a knot 100 times denser than the interclump medium. For a 200 km s −1 shock, the gas temperature at the shock front reaches some 10 7 K, and pre-existing molecules, including CO, will be destroyed.…”

Section: Discussionmentioning

confidence: 99%

CO rotational line emission from a dense knot in Cassiopeia A

Wallström

Biscaro

Salgado

et al. 2013

A&A

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We report a Herschel detection of high-J rotational CO lines from a dense knot in the supernova remnant Cas A. Based on a combined analysis of these rotational lines and previously observed ro-vibrational CO lines, we find the gas to be warm (two components at ∼400 and 2000 K) and dense (10 6−7 cm −3 ), with a CO column density of ∼5 × 10 17 cm −2 . This, along with the broad line widths (∼400 km s −1 ), suggests that the CO emission originates in the post-shock region of the reverse shock. As the passage of the reverse shock dissociates any existing molecules, the CO has most likely reformed in the past several years in the post-shock gas. The CO cooling time is similar to the CO formation time, therefore we discuss possible heating sources (UV photons from the shock front, X-rays, electron conduction) that may maintain the high column density of warm CO.

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“…The physical structure of shocked SN ejecta has been discussed in several previous studies (41)(42)(43)(44)(45)(46). A noticeable characteristic of the shocks propagating into SN ejecta composed of calculation is done by using a shock code developed for SN ejecta (45,47,48) with updated atomic constants for phosphorus.…”

Section: [P Ii] and [Fe Ii] Emission From Shocked Sn Ejectamentioning

confidence: 99%

“…In principle, there could be some emission from the preshock region photoionized by the shock radiation (43,44,46), but in the Cas A knots the observed high electron densities (3 × 10 3 -2 × 10 In SN ejecta swept-up by a reverse shock, it is likely that a wide range of preshock densities and also a wide range of shock speeds are present (44,45). We ran a grid of models and have found that, in order to match the observed [Fe II] line ratios, the shock speed should be < ∼ 50 km s −1 and the preshock densities should be > ∼ 100 cm −3 .…”

Section: [P Ii] and [Fe Ii] Emission From Shocked Sn Ejectamentioning

confidence: 99%

Phosphorus in the Young Supernova Remnant Cassiopeia A

Koo

Lee

Moon

et al. 2013

Science

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Phosphorus (31 P), which is essential for life, is thought to be synthesized in massive stars and dispersed into interstellar space when these stars explode as supernovae (SNe). Here we report on near-infrared spectroscopic observations of the young SN remnant Cassiopeia A, which show that the abundance ratio of phosphorus to the major nucleosynthetic product iron ( 56 Fe) in SN material is up to 100 times the average ratio of the Milky Way, confirming that phosphorus is produced in SNe. The observed range is compatible with predictions from SN nucleosynthetic models but not with the scenario in which the chemical elements in the inner SN layers are completely mixed by hydrodynamic instabilities during the explosion.1 Phosphorus (P) is an indispensable ingredient for life together with carbon, hydrogen, nitrogen, oxygen, and sulfur (S). In our solar system, its abundance relative to hydrogen is 2.8×10 −7by number, which is 50 to 1900 times less than those of the other life-keeping α elements (1).The abundance of P in the diffuse interstellar medium and stars in our galaxy's disk is comparable with that of the solar system or the cosmic abundance, with some dependence on metallicity (2, 3). P is believed to be mainly formed in massive [ > ∼ 8 M ⊙ ] stars by neutron capture on silicon (Si) in hydrostatic neon-burning shells in the pre-SN stage and also in explosive carbon and neon burning layers during SN explosion (4, 5).Freshly synthesized P should thus be found in young core-collapse SN remnants (SNRs)resulting from the explosion of massive stars. Cassiopeia A (Cas A) is the youngest confirmed core-collapse SNR in our galaxy; it has been extensively studied in all wavebands (Fig. 1).It is located at a distance of 3.4 kpc (6) and thought to be the remnant of a SN event in C.E.1681 ± 19 (7). The spectrum of the light echo from the SN event indicated a SN of Type IIb that had a small hydrogen envelope at the time of explosion (8). The total estimated mass of the SN ejecta is 2 to 4 M ⊙ , and the inferred initial mass of the progenitor star ranges from 15 to 25 M ⊙ (9, 10). Emission from P II was previously detected from Cas A (11), but no analysis of the emission line has been done.We conducted near-infrared (NIR) spectroscopic observations of the main SN ejecta shell using the TripleSpec spectrograph mounted on the Palomar 5-m Hale telescope in 2008 ( The knots show distinct spectroscopic and kinematic properties depending on their origins (Fig. 2) Their properties match those of "quasi-stationary flocculi", the material lost from the hydrogen envelope of the progenitor during its red-supergiant phase as slow wind (13,14). 3) imply that the P-to-Fe abundance ratio by number, X(P/Fe), of the SN ejecta knots is up to 100 times higher than the cosmic abundance X ⊙ (P/Fe) = 8.1 × 10 −3 (1), whereas the knots of the circumstellar medium have ratios close to the cosmic abundance. The enhanced P abundance over Fe in these SN ejecta knots is direct evidence for the in situ production of P in Cas A.The observed range of X...

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Fine-structure infrared lines from the Cassiopeia A knots

Cited by 50 publications

References 58 publications

The dust mass in Cassiopeia A from a spatially resolvedHerschelanalysis

The dust mass in Cassiopeia A from a spatially resolvedHerschelanalysis

CO rotational line emission from a dense knot in Cassiopeia A

Phosphorus in the Young Supernova Remnant Cassiopeia A

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