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|Title: ||Observational constrains on the chemical evolution of high redshift galaxies through 3D spectroscopy.|
|Authors: ||Troncoso Iribarren, Paulina Alejandra|
|Tutor: ||Maiolino, Roberto|
|Keywords: ||Galaxy evolution|
Star forming galaxies
|Issue Date: ||21-Jan-2013|
|Abstract: ||In this thesis I investigate the properties of 34 star forming galaxies at z ~3.4, by exploiting data
obtained with the VLT near-infrared integral field spectrometer SINFONI. By using the SINFONI
spectra, along with multi-band photometric images, I investigate the metal content, dynamics and
star formation in these galaxies.
One of the most important results is that z~ 3.4 galaxies deviate from the scaling relations between
mass, star formation rate and metallicity characterizing local and low redshift galaxies (z<2), in the
sense that galaxies at z>3 are characterized by metallicities significantly lower. This deviation
occurring only at z>3 must trace a different galaxy evolutionary mechanism in place at such early
epochs, with respect to galaxies at 0<z<2. However, I show that the deviation from the local scaling
relations is not associated with dynamics of the host galaxy (rotating disks and mergers/interacting
galaxies deviate by the same amount), hence an increased rate of merging cannot be responsible for
By using the integral field spectroscopic information I could map the metallicity in a subsample of
10 galaxies at z ~3.4. These are among the first metallicity gradients measured at such high redshift.
We find that a significant fraction of galaxies are characterized by inverted (positive) metallicity
gradients, i.e. the metallicity increases towards the outer regions, in contrast to what observed locally.
Also for what concerns the metallicity gradients, I found that the occurrence of inverted gradients
is not correlated with the galaxy dynamical properties. A more detailed investigation reveals that
the metallicity anticorrelates with the star formation rate, which peaks in the central region of
galaxies. This result supports the models of smooth gas inflows feeding galaxies at high redshift. In
this scenario the pristine infall both boosts star formation (through the Schmidt-Kennicutt law) and
dilutes the metallicity, generating the observed anti-correlation.
By mapping the distribution of the star formation, and by inverting the Schmidt-Kennicutt relation,
I could also infer the distribution and total content of molecular gas in these z~ 3 galaxies. I found evidence
that the average gas fraction in galaxies at z>3 does not follow the steep increasing evolution
from z=0 to z ~2. Between z~ 2 and z~ 3 the average gas fraction in galaxies remains constant or,
possibly, even decreases. Our findings are marginally consistent with the models expectations on the
evolution of the gas content in galaxies and further support the scenario that the evolution of cosmic
star formation in galaxies is primarily driven by the evolution of the amount of gas in galaxies, and
not by an evolution in the efficiency of star formation.
By combining the information on the gas content and on the metallicity I could infer the galaxy
properties can only be explained by a combination of massive inflows and massive outflows, both
of which a factor of few to several higher than in the host galaxy. Such massive flows in the early
universe are likely responsible for the different properties and deviations of galaxies at z 3 relative
to local and low redshift galaxies.
I further explore the physical mechanisms driving galaxy formation and evolution by comparingmy
observational results with detailed semi-analytical models and cosmological simulations specifically
developed, in collaboration with other teams, to trace the metallicity evolution and distribution in
|Research interests: ||Observational techniques-Galaxy evolution-ISM- Theoretical Astrophysics-Metallicity-Star forming galaxies|
|Skills short description: ||My research focuses on the field of galaxy formation and evolution.
In particular during my PhD I gained experience on the use of Integral Field Spectrographs and the preparations for the use of the NIRSpec hosted by the JWST. I used these observational results to constrain theoretical models of galaxy formation and evolution (semi-analytical and RAMSES, RAMSES-CH).
My first research topics were focused on solving the themodynamics of systems with long-range interactions, through numerical tests and Monte Carlo simulations.|
|Personal skills keywords: ||confidently speaks in public|
eloquent, concise, certain, inquiring
identifies and assess problems
solves problems, good management of software
programing, speak and write in four languages
|Appears in PhD:||ASTRONOMIA|
Files in This Item:
|thesis.pdf||Main thesis article||12.77 MB||Adobe PDF|
File del Curriculum Vitae:
|CurriculumVitae.pdf|| ||161.77 kB||Adobe PDF|
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