PROJECTS
DUST DEPLETION IN LOW METALLICITY ENVIRONMENTS: METAL-Z PROJECT
CIRCUM GALACTIC MEDIUM OF THE NARBY MILKY WAY ANALOGUES: COS-SAGA PROJECT
CIRCUM-GALACTIC MEDIUM - QUASAR ABSORBERS AND THEIR HOST GALAXIES
Galaxies are constantly fed by the diffuse material from the intergalactic medium through the Circum-Galactic Medium (CGM). We can probe these vast gaseous halos around galaxies by studying absorbers detected in the spectra of bright background quasars. To understand the dynamics of the system we combine the physical properties from the absorption features with the broader view of the absorber’s host and its environment by emission diagnostics, using IFU spectroscopy. We characterise the quasar absorbers and their host galaxies in our survey MUSE - ALMA Halos. The survey consists of 5 quasar fields with 14 large (log(N(HI)) > 18.0) N(HI) absorbers and 43 galaxies associated with these systems, found within an impact parameter of 200 kpc from the quasar sightline. The surprisingly large fraction of groups associated with absorbers introduces a challenging connecting CGM detected in absorption to a particular galaxy or multiple galaxies. Using a multi-wavelength dataset (UVES, HST, MUSE, ALMA) we study in detail the properties of the absorbing gas as well as the galaxies associated quasar absorbers. With ALMA observations we are able for the first time to analyze the molecular gas content of these galaxies and derive their star formation efficiencies. Such studies of the gas kinematics and metallicity and the general CGM properties of the absorber host galaxies allow constraining galaxy evolution models.
Galaxies are constantly fed by the diffuse material from the intergalactic medium through the Circum-Galactic Medium (CGM). We can probe these vast gaseous halos around galaxies by studying absorbers detected in the spectra of bright background quasars. To understand the dynamics of the system we combine the physical properties from the absorption features with the broader view of the absorber’s host and its environment by emission diagnostics, using IFU spectroscopy. We characterise the quasar absorbers and their host galaxies in our survey MUSE - ALMA Halos. The survey consists of 5 quasar fields with 14 large (log(N(HI)) > 18.0) N(HI) absorbers and 43 galaxies associated with these systems, found within an impact parameter of 200 kpc from the quasar sightline. The surprisingly large fraction of groups associated with absorbers introduces a challenging connecting CGM detected in absorption to a particular galaxy or multiple galaxies. Using a multi-wavelength dataset (UVES, HST, MUSE, ALMA) we study in detail the properties of the absorbing gas as well as the galaxies associated quasar absorbers. With ALMA observations we are able for the first time to analyze the molecular gas content of these galaxies and derive their star formation efficiencies. Such studies of the gas kinematics and metallicity and the general CGM properties of the absorber host galaxies allow constraining galaxy evolution models.
MOLECULAR GAS CONTENT OF GALAXIES - BLIND CO EMISSION LINE SURVEY IN ALMA CALIBRATION DATA (ALMACAL)
The Star Formation History of the Universe changes with time and has a clear maximum around redshift z ~ 2, but it is not clear what drives the subsequent decline. Recent studies have suggested a possible link between the cosmic density of H2 - the most abundant molecule in the Universe - and the Star Formation History of the Universe (Decarli et al. 2019, Keating et al. 2016, Riechers et al. 2018). The second most abundant molecule, still linked to star formation, is CO and its rotational transitions are bright and relatively easy to observe with ALMA. By studying the CO emission in galaxies we can quantify the molecular gas density in galaxies. We address this topic in a blind CO emission-line survey using ALMACAL - an extensive science project utilizing ALMA calibration data for scientific purposes. ALMA calibrators are usually bright sub-mm quasars (mostly blazars) and are relatively straightforward to subtract from the data, leaving an image or data cube of the calibrator field. Using the ALMACAL cubes with the longest integration time, we build a cosmologically significant volume over which we can blindly search for CO emission lines. Thanks to a uniqueness of the ALMACAL dataset we can study galaxies over a wide area and are not sensitive to the effects of cosmic variance.
The Star Formation History of the Universe changes with time and has a clear maximum around redshift z ~ 2, but it is not clear what drives the subsequent decline. Recent studies have suggested a possible link between the cosmic density of H2 - the most abundant molecule in the Universe - and the Star Formation History of the Universe (Decarli et al. 2019, Keating et al. 2016, Riechers et al. 2018). The second most abundant molecule, still linked to star formation, is CO and its rotational transitions are bright and relatively easy to observe with ALMA. By studying the CO emission in galaxies we can quantify the molecular gas density in galaxies. We address this topic in a blind CO emission-line survey using ALMACAL - an extensive science project utilizing ALMA calibration data for scientific purposes. ALMA calibrators are usually bright sub-mm quasars (mostly blazars) and are relatively straightforward to subtract from the data, leaving an image or data cube of the calibrator field. Using the ALMACAL cubes with the longest integration time, we build a cosmologically significant volume over which we can blindly search for CO emission lines. Thanks to a uniqueness of the ALMACAL dataset we can study galaxies over a wide area and are not sensitive to the effects of cosmic variance.
TIME - DOMAIN ASTRONOMY - TRANSIENTS IN THE CENTRES OF GALAXIES
Transients occurring in the galactic nuclei are challenging to find and to classify due to strong contamination from their host galaxy. However, they include a range of interesting events: Tidal Disruption Events (TDE), supernovae Type Ia, Type II or extreme behaviour of Active Galactic Nuclei. In my thesis, I describe the project in which we systematically searched for nuclear transients in OGLE and Gaia surveys in real-time and archival data. We investigated in detail about 20 transients, for which we obtained classification spectroscopy on the largest telescopes in the world (SALT, VLT, NTT, NOT). Among 27 discovered objects we found several supernovae of various types, especially type IIn and TDE candidates. In the archival 6–years long photometric data from OGLE we found supernovae, AGN variability and TDE candidates. We have identified long-lasting transients which light curve shapes, that do not match any of known types of transients. For these, we conducted the spectroscopic classification of their hosts to help verify the nature of these events. |
|