Tutor: Søren Larsen
Students: Avet Harutyunyan, Saskia Hekker, Anatoliy Ivantsov, Loredana Vetere
M87, the central giant elliptical galaxy in the Virgo cluster, is surrounded by thousands of globular clusters of which the brightest can be seen even in ground-based images. In this project we use images from the ACS and WFPC2 cameras on board HST to characterise the properties of globular clusters in M87. In particular, we are interested in the relative numbers and spatial distributions of metal-rich and metal-poor globular clusters, and in comparing these with data for the Milky Way.
Tutor: Nicolas Cardiel
Students: Joana Ascenso, Lucia Ballo, Jose Luis Cervantes Rodriguez, Boriana Ivanova
The analysis of absorption features in early-type objects (elliptical and lenticular galaxies, spiral bulges, globular clusters,...) is a powerful tool to understand the mechanisms responsible for the formation and evolution of those systems. In this project multiobject spectroscopic observations of globular clusters in NGC3585, obtained with FORS2 at the UT2 VLT, have been employed to analyze their average age and metallicity. The data have been retreived from the ESO archive, and reduced following a special treatment of data and error frames. In this sense, error images have been created from the raw data using first principles (gain and readout noise), and reduced in parallel throughout the whole reduction procedure. This method guarantees a more reliable estimation of random errors in the measured line-strength indices.
Tutor: Marina Rejkuba
Students: Dimitrios Gouliermis, Nataliya Kovalenko, Maria Morales, Loredana Spezzi
Cetus dwarf spheroidal galaxy has been discovered in 1999 by Whiting et al. It is thus one of the least known Local Group galaxies and an interesting target for the stellar population studies. Archival broad band images taken in 1999 in the B and R-band with FORS1 at the UT1 VLT can be used to construct deep color-magnitude diagram of this galaxy and compare its morphology with the stellar evolution model isochrones. The goal of the project is to reduce the data, do psf photometry in the crowded field, construct the color-magnitude diagram and luminosity function and derive the mean ages and metallicities of the stars in this galaxy.
Tutor: Jochen Liske
Students: Alireza Aghaee, Begoña Ascaso Angles, Ryan Houghton,Yuri Bialetski
The nature of low redshift Lyman alpha absorption systems and their relation to galaxies are currently the topic of a lively debate in the literature. In this project we will investigate this relation by combining a large, homogeneous sample of Lyman alpha absorbers, derived from HST FOS spectra, with a sample of galaxies with known redshifts drawn from the Sloan Digital Sky Survey. This results in a sample of absorber-galaxy pairs and allows us to examine the arguments for and against a physical connection between the two classes of objects.
Tutor: Anna Pasquali
Students: Massimiliano Esposito, Maria Ángeles Martínez Carballo, Jouni Tapani Kainulainen, Szymon Kozlowski
Observations have shown that star formation is particularly enhanced in the nuclear region of galaxy mergers, since galaxy interactions are able to concentrate large amounts of gas (ionized to molecular) at the centre of a major merger. NGC 6240 is an example of this process which also induces
the formation of massive young clusters in the galaxy nucleus. ARP 299 is a well known interacting pair of galaxies, at an early phase of their merger. Its strong mid-infrared emission as measured by IRAS classifies it as an Ultra Luminous Infrared Galaxy very similar to NGC 6240, and it is explained in terms
of dust emission, this dust being a byproduct of star formation.
At optical wavelengths, the nuclei of ARP 299 are characterised
by a number of bright compact sources, the situ of on-going
We have made use of archived HST/WFPC2 U,B,V,I images and HST/NICMOS H imaging to derive the stellar age and mass of these compact sources. Specifically, we have fitted the observed colours with STARBURST99 models computed for solar metallicity and processed with STSDAS/CALCPHOT in order to translate the synthetic spectra into synthetic magnitudes in the filters system used for WFPC2 and NICMOS.
We have thus derived stellar ages between 7 and 18 Myrs and masses ranging from few 10^4 to few 10^6 Mo, which place the compact sources of ARP 299 well among the massive young clusters typically observed in galaxy mergers such as the Antennae and NGC 6240 and in starbust galaxies like NGC 7673.