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Complex gas kinematics in compact, rapidly assembling star-forming galaxies

R. O. Amorín Barbieri, J. M. Vílchez, G. F. Hägele, V. Firpo, E. Pérez-Montero, P. Papaderos

Deep, high resolution spectroscopic observations have been obtained for six compact, strongly star-forming galaxies at redshift z ∼ 0.1 - 0.3, most of them also known as green peas. Remarkably, these galaxies show complex emission-line profiles in the spectral region including Hα, [N II]λλ6548, 6584Å and [S II]λλ6717, 6731Å, consisting of the superposition of different kinematical components on a spatial extent of few kpc: a very broad line emission underlying more than one narrower component. For at least two of the observed galaxies some of these multiple components are resolved spatially in their 2D-spectra, whereas for another one a faint detached Hα blob lacking stellar continuum is detected at the same recessional velocity ∼7 kpc away from the galaxy. The individual narrower Hα components show high intrinsic velocity dispersion (σ ∼30–80 kms-1), suggesting together with unsharped masking HST images that star formation proceeds in an ensemble of several compact and turbulent clumps, with relative velocities of up to ∼500 kms-1. The broad underlying Hα components indicate in all cases large expansion velocities (full width zero intensity FWZI≥1000 km s-1) and very high luminosities (up to ∼1042erg s-1), probably showing the imprint of energetic outflows from SNe. These intriguing results underline the importance of green peas for studying the assembly of low-mass galaxies near and far.

galaxies: dwarf – galaxies: evolution – galaxies: kinematics and dynamics – galaxies: starburst

Based on observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

The Astrophysical Journal Letters
Volume 754, Number 2, Page L22_1
2012 August

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Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia