Abstract
Using echelle spectroscopy, obtained at Las Campanas Observatory, we present a detailed study of the internal kinematics of the nebular material in multiple knots of the blue compact dwarf galaxy Haro 15. A detailed analysis of the complex emission line profiles show the presence of an underlying broad component in almost all knots, and the brightest star-forming region shows unmistakable signs for the presence of two distinct narrow kinematical components. We also study the information that our analysis provides regarding the motion of the individual knots in the Haro 15 galaxy potential, confirming that they follow galactic rotation. Finally, we examine the relation between their velocity dispersion and luminosity, finding that almost all knots follow the relation for virialised systems. This holds for the strong narrow components identified in complex fits and for single profile fits, although the latter show a flatter slope. In agreement with previous findings, in this paper we show that the existence of multiple kinematical components among massive starbursts cannot be overlooked, as it has a noticeable effect on any subsequent analysis that relies on basic parameters.
Highlights
Already in the original list of blue galaxies with emission lines by Haro (1956) who described this object as a ‘minute cometary nebula’, Haro 15 was later included in several compilations of blue compact galaxies (BCGs)
In this paper we present echelle spectroscopy obtained with the 100-inch du Pont telescope at Las Campanas Observatory (LCO) of five different positions across Haro 15 which provide a velocity
The fluxes were derived from the amplitude (A) and the full width at half-maximum (FWHM) of the Gaussian profile obtained in the component fitting (F = 1.0645 × A × FWHM), and the corresponding errors were estimated taking into account the errors in these two parameters
Summary
Already in the original list of blue galaxies with emission lines by Haro (1956) who described this object as a ‘minute cometary nebula’, Haro 15 was later included in several compilations of blue compact galaxies (BCGs). We have found that all Haro 15 regions show evidence of wing broadening evident mainly in the Hα line and confirmed in other emission lines Another common feature of giant H II regions is the supersonic width of their emissionline profiles, the origin of these velocities is not yet clear (Terlevich & Melnick 1981; Hippelein 1986; Roy, Arsenault & Joncas 1986). This study is part of a project to obtain high spectral resolution echelle data to determine the nature of giant H II regions visible from the southern hemisphere and analyse the physical conditions of the ionized gas of these regions and blue compact dwarf galaxies. The flux calibrations were performed as described in Firpo et al (2005)
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