Galaxy Evolution

(12.3.19) Understanding the formation and evolution of galaxies, and in particular the establishment of the Hubble sequence, is one of the most pressing question in modern astronomy. Interestingly, it is also one of the most challenging because it requires to constrain a variety of complex physical mechanisms acting over a vast range of spatiall scales: from mega-parsec scales tracing the gravitational collapse of the large-scale structures of the Universe, through kilo-parsec scales at which the assembly of galaxies and AGN-driven feedback happens, to parsec scales where the formation of stars and SNe-driven feedback take place. To add to this complexity, these mechanisms dramatically change over cosmic time, from the earliest epochs when the first galaxies hierarchically formed from pristine gas and re-ionize the Universe, through the cosmic peak of star formation activity when stars and bulges formed in gas-rich galaxies, to the present when most of the gas in galaxies is exhausted.

Our research focuses on the evolution of the star formation activity of galaxies across cosmic time and to understand the physical conditions of the interstellar medium driving this evolution. We employ a multi-wavelength approach using state-of-the-art observations with ground-based (e.g., ALMA, NOEMA, VLA, APEX, IRAM-30m, VLT) and space (e.g., HST, Spitzer, Herschel, Chandra) observatories.

From the present to the peak epoch of cosmic star formation (i.e., redshift 0 to 3), we take advantage of deep and large multi-wavelength extragalactic surveys, like COSMOS, to isolate the main mechanisms controlling star formation in galaxies. In particular, we study in detail their thermal dust emission  via new deep (sub)millimetre galaxy surveys (e.g., GISMO-2mm, right) and their molecular line emission via dedicated follow-up. With these observations, we obtain critical constraints on their star formation activity, dust and gas content, as well as gas surface density, revealing thereby their principal modes of star formation.

Beyond the peak of cosmic star formation activity (redshift z>3), where cosmological dimming makes it difficult to observe large samples of typical galaxies, we study the detailed structure, dynamics and conditions of the interstellar medium of the brightest star-forming galaxies, such as quasars, lensed (sub)millimetre-selected galaxies, and galaxies selected through C+ line searches in  ALMA archive 

The GISMO-2 mm survey in the COSMOS field observed using the IRAM 30m-telescope, constitutes the widest deep 2 mm survey obtained to-date, reaching a uniform 0.23 mJy/beam sensitivity over an area of 276 square arcmin (Magnelli et al., 2019).

AzTEC/C159, a star-forming galaxy at z~4.5 (Jiménez-Andrade et al., 2018) observed in the 158 micron fine structure line of ionised carbon. (a) ALMA moment maps that show a gas-dominated, rotation-supported disk. This is one of the best examples of a flat rotation curve at large radius (at least 4 kpc) of an object in the early Universe. (b) C+ line spectrum (blue), together with CO J=2-1 and CO J=5-4 from JVLA and NOEMA, respectively.

Epoch of reionization: To shed light on this widely unexplored early cosmic epoch, we participate in the construction of the CCAT-prime telescope and the development of its Epoch of Recombination Spectrometer (EoR-Spec). through three dimensional intensity maps of the C+ 158 micron line, with EoR-Spec we will perform the first high signal-to-noise large-scale measurement of the clustering signal from star-forming galaxies in the epoch of reionization. These intensity maps will not only trace the cosmic star formation activity at this epoch, but also illuminate the underlying and evolving Cosmic Web, and thus constrains the growth of structures in the early Universe.

We closely collaborate with international colleagues and within the Cologne-Bonn collaborative research center CRC-956. This collaborative center aims at studying the impact and condition of star formation over all galactic and extragalactic scales, using observational and laboratory astrophysics, instrumentation and modeling. Our research benefits from the technical expertise in the German ALMA ARC node hosted by our group and that of Prof. Schilke in Cologne.

We offer exciting PhD, Master, and Bachelor thesis opportunities. If you are interested in any of these topics, please talk to us!