Verónica Firpo

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

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 H?, [N?II]???6548, 6584, and [S?II]???6717, 6731, 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 H? blob lacking stellar continuum is detected at the same recessional velocity ~7?kpc away from the galaxy. The individual narrower H? components show high intrinsic velocity dispersion (? ~ 30-80?km?s?1), 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?1. The broad underlying H? components indicate in all cases large expansion velocities (full width zero intensity ?1000?km?s?1) and very high luminosities (up to ~1042 erg s?1), 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.

Abundance determination of multiple star-forming regions in the H II galaxy SDSS J165712.75+321141.4

We analyze high signal-to-noise spectrophotometric observations acquired simul- taneously with TWIN, a double-arm spectrograph, from 3400 to 10400u of three star-forming regions in the Hii galaxy SDSS J165712.75+321141.4. We have measured four line temperatures: Te((Oiii)), Te((Siii)), Te((Oii)), and Te((Sii)), with high preci- sion, rms errors of order 2%, 5%, 6% and 6%, respectively, for the brightest region, and slightly worse for the other two. The temperature measurements allowed the direct derivation of ionic abundances of oxygen, sulphur, nitrogen, neon and argon. We have computed CLOUDY tailor-made models which reproduce the O 2+ mea- sured thermal and ionic structures within the errors in the three knots, with deviations of only 0.1 dex in the case of O + and S 2+ ionic abundances. In the case of the electron temperature and the ionic abundances of S + /H + , we find major discrepancies which could be consequence of the presence of colder diffuse gas. The star formation history derived using STARLIGHT shows a similar age distribution of the ionizing popula- tion among the three star-forming regions. This fact suggests a similar evolutionary history which is probably related to a process of interaction with a companion galaxy that triggered the star formation in the different regions almost at the same time. The hardness of the radiation field mapped through the use of the softness parame- teris the same within the observational errors for all three regions, implying that the equivalent effective temperature of the radiation fields are very similar for all the studied regions of the galaxy, in spite of some small differences in the ionization state of different elements. Regarding the kinematics of the galaxy, the gas rotation curve shows a deviation from the circular motion probably due either to an interaction process or related to an expanding bubble or shell of ionized gas approaching us. A dynamical mass of 2.5×10 10 Mis derived from the rotation curve.

High resolution spectroscopy of the BCD galaxy Haro 15: I. Internal kinematics

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.

High-resolution spectroscopy of the blue compact dwarf galaxy Haro 15 - II. Chemodynamics: Haro 15: physical properties

We present a detailed study of the physical properties of the nebular material in four starforming knots of the blue compact dwarf galaxy Haro 15. Using long-slit and echelle spectroscopy obtained at Las Campanas Observatory, we study the physical conditions (electron density and temperatures), ionic and total chemical abundances of several atoms, reddening and ionization structure, for the global flux and for the different kinematical components. The latter was derived by comparing the oxygen and sulphur ionic ratios to their corresponding observed emission-line ratios (the η and η � plots) in different regions of the galaxy. Applying the direct method or empirical relationships for abundance determination, we perform a comparative analysis between these regions. The similarities found in the ionization structure of the different kinematical components imply that the effective temperatures of the ionizing radiation fields are very similar in spite of some small differences in the ionization state of the different elements. Therefore, the different gaseous kinematical components identified in each star-forming knot are probably ionized by the same star cluster. However, the difference in the ionizing structure of the two knots with knot A showing a lower effective temperature than knot B suggests a different evolutionary stage for them consistent with the presence of an older and more evolved stellar population in the first.

High-resolution spectroscopy of the blue compact dwarf galaxy Haro 15 - I. Internal kinematics: Haro 15: internal kinematic

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.

High-resolution spectroscopy of the blue compact dwarf galaxy Haro 15 – I. Internal kinematics

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.