Guillermo L. Bosch

Narrow-band CCD photometry of giant Hii regions

We have obtained accurate CCD narrow band Hβ and Hα photometry of Giant HII Regions in M 33, NGC 6822 and M 101. Comparison with previous determinations of emission line fluxes show large discrepancies; their probable origins are discussed. Combining our new photometric data with global velocity dispersion (σ) derived from emission line widths we have reviewed the L(Hβ)) σ relation. A reanalysis of the properties of the GEHRs included in our sample shows that age spread and the superposition of components in multiple regions introduce a considerable spread in the regression. Combining the information available in the literature regarding ages of the associated clusters, evolutionary footprints on the interstellar medium, and kinematical properties of the knots that build up the multiple GEHRs, we have found that a subsample - which we refer to as young and single GEHRs - do follow a tight relation in the L σ plane.

The Onfp Class in the Magellanic Clouds

The Onfp class of rotationally broadened, hot spectra was defined some time ago in the Galaxy, where its membership to date numbers only eight. The principal defining characteristic is a broad, centrally reversed He II λ 4686 emission profile; other emission and absorption lines are also rotationally broadened. Recent surveys in the Magellanic Clouds (MCs) have brought the class membership there, including some related spectra, to 28. We present a survey of the spectral morphology and rotational velocities, as a first step toward elucidating the nature of this class. Evolved, rapidly rotating hot stars are not expected theoretically, because the stellar winds should brake the rotation. Luminosity classification of these spectra is not possible, because the principal criterion (He II λ4686) is peculiar; however, the MCs provide reliable absolute magnitudes, which show that they span the entire range from dwarfs to supergiants. The Onfp line-broadening distribution is distinct and shifted toward larger values from those of normal O dwarfs and supergiants with >99.99% confidence. All cases with multiple observations show line-profile variations, which even remove some objects from the class temporarily. Some of them are spectroscopic binaries; it is possible that the peculiar profiles may have multiple causes among different objects. The origin and future of these stars are intriguing; for instance, they could be stellar mergers and/or gamma-ray-burst progenitors.

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.

G287.84—0.82: an infrared star cluster in the Carina nebula

We have studied the properties of an infrared cluster embedded in the gas and dust of the southern part of the Carina Nebula (NGC3372), where the probable existence of current star formation has already been predicted. We used mid-infrared (A & C bands) and near-infrared (JHKs) images from the MSX and the 2MASS surveys respectively, combined with an optical Hnarrow-band filter image obtained at the CTIO. The infrared star cluster has at least 17 members, and its parameters, radius and stellar density are in very good agreement with high- to intermediate-mass star formation scenarios. The detected IR sources have roughly the same intrinsic infrared excess determined from their position in colour-colour and colour-magnitude diagrams, suggesting that these objects could be related to pre-main sequence stars of high to intermediate mass. Furthermore, we present a low-dispersion spectrum of LS1883 (O9.5V) star located near the centre of the IR cluster. The position of this object in the colour-colour and colour-magnitude IR diagrams lies close to the reddening vector of an ZAMS O9V spectral type star, and it seems to be the first star of this cluster to emerge. All these facts are consistent with the current star-forming scenarios associated with highly embedded star clusters.

A kinematic analysis of the Giant star-forming Region of N11

In this work we present high resolution spectroscopic data of the giant star-forming region of N11, obtained with the GIRAFFE instrument at the Very Large Telescope. By using this data set, we find that most of the H

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

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

emission lines profiles in this complex can be fitted by a single Gaussian, however, multiple emission line profiles can be observed in the central region of N11. By adding all the spectra, we derive the integrated H

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

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Observed and Intrinsic Properties of Binary Stars Orbits

profile of this complex, which displays a width (

A search for OB stars in the field of the galactic OB association Bochum 7

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