ALMA high spatial resolution observations of the dense molecular region of NGC 6302

Autor: Valentin Bujarrabal, R. Neri, M. Santander-García, A. Castro-Carrizo, C. Sanchez-Contreras, Romano L. M. Corradi, Javier Alcolea, G. Quintana-Lacaci
Přispěvatelé: Ministerio de Economía y Competitividad (España), European Research Council
Jazyk: angličtina
Rok vydání: 2016
Předmět:
Astrophysics::High Energy Astrophysical Phenomena
Equator
FOS: Physical sciences
02 engineering and technology
Astrophysics
Astrophysics::Cosmology and Extragalactic Astrophysics
01 natural sciences
Article
Base (group theory)
0103 physical sciences
Planetary nebulae: general
0202 electrical engineering
electronic engineering
information engineering
Radiative transfer
Astrophysics::Solar and Stellar Astrophysics
Ejecta
010303 astronomy & astrophysics
Astrophysics::Galaxy Astrophysics
Solar and Stellar Astrophysics (astro-ph.SR)
ISM: kinematics and dynamics
Physics
Nebula
020207 software engineering
Astronomy and Astrophysics
Radius
Planetary nebula
Astrophysics - Astrophysics of Galaxies
Stars
kinematics and dynamics [ISM]
Astrophysics - Solar and Stellar Astrophysics
Space and Planetary Science
Astrophysics of Galaxies (astro-ph.GA)
Astrophysics::Earth and Planetary Astrophysics
individual: NGC 6302 [Planetary nebulae]
Planetary nebulae: individual: NGC 6302
general [Planetary nebulae]
Zdroj: Digital.CSIC. Repositorio Institucional del CSIC
instname
Popis: [Context] The mechanism behind the shaping of bipolar planetary nebulae is still poorly understood. It is becoming increasingly clear that the main agents must operate at their innermost regions, where a significant equatorial density enhancement should be present and related to the collimation of light and jet launching from the central star preferentially towards the polar directions. Most of the material in this equatorial condensation must be lost during the asymptotic giant branch as stellar wind and later released from the surface of dust grains to the gas phase in molecular form. Accurately tracing the molecule-rich regions of these objects can give valuable insight into the ejection mechanisms themselves.
[Aims] We investigate the physical conditions, structure and velocity field of the dense molecular region of the planetary nebula NGC 6302 by means of ALMA band 7 interferometric maps.
[Methods] The high spatial resolution of the CO and CO J = 3-2 ALMA data allows for an analysis of the geometry of the ejecta in unprecedented detail. We built a spatio-kinematical model of the molecular region with the software SHAPE and performed detailed non-LTE calculations of excitation and radiative transfer with the shapemol plug-in.
[Results] We find that the molecular region consists of a massive ring out of which a system of fragments of lobe walls emerge and enclose the base of the lobes visible in the optical. The general properties of this region are in agreement with previous works, although the much greater spatial resolution of the data allows for a very detailed description. We confirm that the mass of the molecular region is 0.1 M. Additionally, we report a previously undetected component at the nebular equator, an inner, younger ring inclined ~60° with respect to the main ring, showing a characteristic radius of 7.5 × 10 cm, a mass of 2.7 × 10M, and a counterpart in optical images of the nebula. This inner ring has the same kinematical age as the northwest optical lobes, implying it was ejected approximately at the same time, hundreds of years after the ejection of the bulk of the molecular ring-like region. We discuss a sequence of events leading to the formation of the molecular and optical nebulae, and briefly speculate on the origin of this intriguing inner ring.
This work was partially supported by the Spanish MINECO within the programme “Físico-química del medio interestelar y circunestelar en la era de ALMA” (AYA2012-32032), and by the European Research Council (ERC Grant 610256: NANOCOSMOS).
Databáze: OpenAIRE
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