Sofia Rojas Ruiz

Sofia Rojas Ruiz   (Colombia)

rojas @

Quasars and Galaxies at the Epoch of Reionization

Quasars are highly energetic sources that provide important tools to understand the Epoch of Reionization, which is the time when the universe transitioned from being completely neutral to ionized. Observational searches demonstrate that quasars in the early universe are rare, however, it is not yet well-understood how these objects can form so early-on. I am investigating the quasar P352-15, the most radio-loud quasar already near the end of Reionization at redshift z~6, which corresponds to 960 million years after the Big Bang. This quasar is the most powerful radio emitter at these high redshifts and shows the first direct evidence of extended radio jets (~1.5 kpc) at z~6. I am analyzing NOEMA sub-mm data of this source that would help characterize the dust and gas properties of the host galaxy. Additionally, I have VLT X-shooter and Gemini GNIRS near-infrared spectral data that will be used to calculate the black hole mass of P352-15. Combining all these data sets we can study the coevolution of the galaxy and black hole of this source, and also set constraints on the lifetime of the quasar.

Another project I am working on is to probe whether the most distant quasars live in special environments. Quasars are believed to reside in the most massive dark matter halos and therefore they are expected to live in overdensities, which is still observationally controversial. I am looking for Lyman-break galaxies in the nearby proximity of the most distant quasar up to date, J1342+0928 at redshift z=7.54. We have data from the Hubble Space Telescope in three filters covering continuous wavelength from optical to NIR. I will use the photometric redshift technique to find galaxy candidates and this way confirm one of the first large-scale structures of the universe.

In my group, we continue to hunt for high-redshift quasars. We attempt this by selecting quasar candidates based on colors from big sky surveys, and performing follow up observations with the 2.2m Max-Planck-Gesellschaft telescope in La Silla, Chile. I go to this telescope to obtain further photometric data so that later we can determine the best quasar candidate for spectroscopic confirmation with 8 meter-class telescopes

Supervisor:    Eduardo Banados   (MPIA)

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