Gaia-ESO Survey: Gas dynamics in the Carina nebula through optical emission lines^⋆,⋆⋆

¹ INAF–Osservatorio Astronomico di Palermo G.S.Vaiana, Piazza del Parlamento 1, 90134 Palermo, Italy
e-mail: damiani@astropa.inaf.it
² Dipartimento di Fisica e Chimica, Università di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
³ INAF–Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
⁴ INAF–Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
⁵ Armagh Observatory, College Hill, Armagh BT61 9DG, UK
⁶ School of Mathematics & Physics, Queen’s University Belfast, Belfast BT61 7NN, UK
⁷ Centro de Astrobiología (CSIC-INTA), ESAC campus, Camino bajo del castillo s/n, 28 692 Villanueva de la Cañada, Madrid, Spain
⁸ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
⁹ Instituto de Astrofísica de Andalucía-CSIC, Apdo. 3004, 18080 Granada, Spain
¹⁰ Moscow MV Lomonosov State University, Sternberg Astronomical Institute, 119992 Moscow, Russia
¹¹ INAF–Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy
¹² Dipartimento di Fisica e Astronomia, Sezione Astrofisica, Università di Catania, via S. Sofia 78, 95123 Catania, Italy
¹³ INAF–Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
¹⁴ ASI Science Data Center, via del Politecnico SNC, 00133 Roma, Italy
¹⁵ Instituto de Física y Astronomiía, Universidad de Valparaiíso, Chile
¹⁶ European Southern Observatory, Alonso de Cordova 3107 Vitacura, Santiago de Chile, Chile
¹⁷ Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK
¹⁸ Departamento de Ciencias Fisicas, Universidad Andres Bello, Republica 220, Santiago, Chile
¹⁹ INAF–Padova Observatory, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
²⁰ Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia
²¹ Departamento de Física, Ingeniería de Sistemas y Teoría de la Señal, Universidad de Alicante, Apdo. 99, 03080 Alicante, Spain

Received: 21 January 2016
Accepted: 1 April 2016

Abstract

Aims. We present observations from the Gaia-ESO Survey in the lines of Hα, [N II], [S II], and He I of nebular emission in the central part of the Carina nebula.

Methods. We investigate the properties of the two already known kinematic components (approaching and receding), which account for the bulk of emission. Moreover, we investigate the features of the much less known low-intensity high-velocity (absolute RV >50 km s^-1) gas emission.

Results. We show that gas giving rise to Hα and He I emission is dynamically well correlated with but not identical to gas seen through forbidden-line emission. Gas temperatures are derived from line-width ratios, and densities from [S II] doublet ratios. The spatial variation of N ionization is also studied, and found to differ between the approaching and receding components. The main result is that the bulk of the emission lines in the central part of Carina arise from several distinct shell-like expanding regions, the most evident found around η Car, the Trumpler 14 core, and the star WR25. These “shells” are non-spherical and show distortions probably caused by collisions with other shells or colder, higher-density gas. Some of them are also partially obscured by foreground dust lanes, while very little dust is found in their interior. Preferential directions, parallel to the dark dust lanes, are found in the shell geometries and physical properties, probably related to strong density gradients in the studied region. We also find evidence that the ionizing flux emerging from η Car and the surrounding Homunculus nebula varies with polar angle. The high-velocity components in the wings of Hα are found to arise from expanding dust reflecting the η Car spectrum.