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

AMORÍN, R.; VÍLCHEZ, J. M; HÄGELE, G. F; FIRPO, V.; PÉREZ-MONTERO, E.

ASTROPHYSICAL JOURNAL

IOP PUBLISHING LTD

Lugar: Londres; Año: 2012 vol. 754 p. 1 - 6

0004-637X

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 Halpha, [N II] 6548, 6584A, and [S II] 6717, 6731A, consisting of the superposition of different kinematical components on a spatial extent of few kiloparsecs: 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 two-dimensional spectra, whereas for another one a faint detached Halpha blob lacking stellar continuum is detected at the same recessional velocity ~7 kpc away from the galaxy. The individual narrower Halpha components show high intrinsic velocity dispersion (sigma ~ 30-80 km/s), suggesting together with unsharped masking Hubble Space Telescope images that star formation proceeds in an ensemble of several compact and turbulent clumps, with relative velocities of up to ~500 km/s. The broad underlying Halpha components indicate in all cases large expansion velocities (full width zero intensity 1000 km/s) and very high luminosities (up to ~10^42 erg/s), probably showing the imprint of energetic outflows from supernovae. These intriguing results underline the importance of green peas for studying the assembly of low-mass galaxies near and far.