Recent Talks

The initial mass function describes the distribution of masses for a population of stars and substellar objects when they are born. It defines the evolution of a population of stars and provides constrains on the star formation theory. The determination of the initial mass function in the substellar regime is still an open question in Astrophysics. Brown dwarfs do not have enough mass to sustain hydrogen fusion. As a consequence, mass and age are degenerate for these objects. An older high mass object may be indistinguishable from a younger low mass object. In my PhD thesis, through the characterization of brown dwarfs using several observational methods, I work towards solving the general problem of constraining the substellar initial mass function.

In my first project, I calculated trigonometric parallaxes of a sample of six cool brown dwarfs. I determined the luminosity for our objects and I found that one of them might be a brown dwarf binary. In my second project, I confirmed the youth of seven brown dwarfs (ages between 1 and 150 Myr) using spectroscopic data.In the last project of this PhD thesis, I aimed to refine the brown dwarf binary fraction using spectroscopic data in the optical and in the near infrared for 22 brown dwarfs. I found six new brown dwarf binary candidates, two of them were previously known.

The determination of distances, ages and the refinement of the brown dwarf binary fraction in this PhD thesis contribute to the determination of the initial mass function. In the next years, the Gaia satellite, the James Webb Space Telescope and the E-ELT will provide new data, allowing the discovery of new brown dwarf binaries, the constraining of atmospheric and evolutionary models, and the refinement of the initial mass function.

CARMENES may find the first uncontrovertible exoearth in the habitable zone of a star in the solar neighbourhood. Its acronym, 'Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Échelle Spectrographs', is long but self-explanatory. After six years of hard design and construction, CARMENES is currently being commissioned at the German-Spanish 3.5 m Calar Alto telescope in Almería. Well in advance of its American, Japanese and Canadian-French competitors, it will be in January 2016 the first and only ultra-stable high-resolution spectrograph covering the red optical and near-infrared. As its co-project manager, I will give a summary of the homonymous CARMENES instrument, the international consortium that has built it, the on-going on-sky commissioning, and the science project that will be carried with it during guaranteed time observations.

Models of galaxy formation predict that gas accretion from the cosmic web is a primary driver of star formation over cosmic history. Except in very dense environments where galaxy mergers are also important, model galaxies feed from cold streams of gas from the web that penetrate their dark matter haloes. Although these predictions are unambiguous, the observational support has been indirect so far. I will report spectroscopic evidence for this process in extremely metal-poor galaxies (XMPs) of the local Universe, taking the form of localized starbursts associated with gas having low metallicity. Because gas mixes azimuthally in a rotation timescale (a few hundred Myr),  the observed metallicity inhomogeneities are only possible if the metal-poor gas producing stars fell onto the disk recently. I will analyze several possibilities for the origin of the metal-poor gas, favoring the metal-poor gas infall predicted by numerical models. In addition, I will show model galaxies in cosmological numerical simulations with starbursts of low metallicity like to the star-forming regions in XMPs.

For over 20 years, the Southeastern Association for Research in Astronomy (SARA) has operated a remotely-accessible 1-m-class telescope at the Kitt Peak National Observatory near Tucson, Arizona that has served as a focus for faculty and student research.  From its four charter institutional members, the SARA consortium has grown to include a dozen universities spanning Indiana to Florida.  In 2007, SARA assumed operations of a similar remotely-operated telescope at Cerro Tololo Interamerican Observatory in Chile.  SARA has most recently partnered with the Instituto de Astrofisica de Canarias (IAC) to automate and assume operations of the Jacobus Kapteyn Telescope (JKT) at the Roque des los Muchachos on La Palma.  This talk will provide a brief historical perspective on the SARA consortium as well as a summary of our facilities, research interests and prospects for the future.