FRANCISCO POZO NUNEZ
Astrophysicist


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           About my research:

My research focuses on active galactic nuclei and star formation, with the goal of understanding the processes behind the formation and evolution of galaxies. During my Phd in astrophysics, I worked  with Rolf Chini and Martin Haas in a Photometric reverberation mapping (PRM) method to study the geometry of the broad emission-line region (BLR), black hole masses and host-subtracted luminosities in active galactic nuclei (AGNs). I have planned and carried out optical and near-infrared multi-month observations with multiple telescopes in Chile in order to explore the prospects of inferring the structure of the BLR from photometric monitoring data. Through the use of broad and narrow-band filters I have measured the time delay between variations in the continuum and H-beta/H-alpha emission lines. The time delay was used to infer the size of the broad-line region. These results were placed in the context of the known BLR-size luminosity relationship and discussed its potential application to constrain cosmological parameters.

Results published in:

- Haas et al. 2011: Photometric AGN reverberation mapping - an efficient tool for BLR sizes, black hole masses, and host-subtracted AGN luminosities.



From spectroscopic observations I have calculated the velocity dispersion of the emission lines, and in combination with the BLR size I determined the masses of supermassive black holes. I have developed a new method for modeling the geometry of the BLR directly from photometric data which allow the determination of the geometry scaling factor used to constrain the real black hole mass in AGNs. I have found strong evidence for a disk-like BLR geometry, and discussed the deviations of Seyfert-1 galaxies from the SMBH-bulge velocity dispersion relation for quiescent galaxies.

Results published in:

- Pozo Nunez, F., Ramolla, M., Westhues, C., et al. 2012: Photometric reverberation mapping of 3C 120

- Pozo Nunez, F., Westhues, C., Ramolla, M., et al. 2013: Size and disk-like shape of the broad-line region of ESO 399-IG20

- Pozo Nunez, F., Haas, M., Ramolla, M., et al. 2014a: Modelling photometric reverberation data: a disk-like broad-line region and a potentially larger black hole mass for 3C120.





I have performed dust-reverberation studies in order to determine the dust-torus size of Seyfert galaxies. Through the modeling of the optical and near-infrared light curves, I have proposed a new scenario to explain the actual discrepancy between the observed time delay and the dust sublimation radius inferred from the optical-UV luminosity. In this scenario the dust torus is geometrically and optically thick, so that the observer only sees the facing rim of the torus wall, which lies closer to the observer than the torus equatorial plane and therefore leads to an observed foreshortened lag.

Results published in:

- Pozo Nunez et al. 2014b: Dust reverberation-mapping of the Seyfert 1 galaxy WPVS48.





After my Phd in July 2014, I worked as a Postdoc at the Astronomical Institute in Bochum. My research focussed mainly on AGNs. I study simultaneous observations for the broad-line region and dust thermal emission in order to test the unified scheme in Seyfert galaxies. I have obtained data with the Spitzer Space telescope/IRAC at 3.6 and 4.5 microns in order to study the echo of cooler dust and of deeply embedded hot dust expected in the optically thick case.

Results published in:

- Pozo Nunez, F., Ramolla, M., Westhues, C., et al. 2015a: The broad-line region and dust torus size of the Seyfert 1 galaxy PGC 50427.







Motivated by the need to understand the process behind the formation and evolution of galaxies, I have started also the research in the star formation field. In a pilot study I have introduced a new method to analyse near-infrared variability data of young stellar objects . A flux variation gradient (FVG) analysis on JHK band light curves allows measuring the mean temperature of the varying components. It appears to be a powerful tool not only to infer the presence of a circumstellar disk, but also to disentangle stellar and disk parameters. This offers the prospects to better constrain the variability amplitude --a crucial ingredient to infer the correct avalanche-like nature of the stellar mass growth. The FVG method also carries the potential to uncover unresolved binaries, the components of which may have largely different Near-infrared colors and which are therefore largely inaccessible to other observing techniques. This may add crucial support to the widely accepted hypothesis that all stars are born as multiples.

Results published in:

- Pozo Nunez, F., Haas., Chini, R., et al. 2015b: Circumstellar disks revealed by H/K flux variation gradients.





Currently we have started an automatized photometric monitoring of selected AGNs with the 46 cm and the 1meter telescope of the WISE observatory. The telescopes are equipped with Sloan r,i,z and five narrow band filters at 4300,5200,5700,6200 and 7000 A in order to perform variability studies of the central engine of AGNs. The program aims to observe a sample of 27 AGNs (V < 17 mag) for which some of them are selected according to tentative continuum time delay measurements obtained in previous works or having previous line RM measurements from the literature indicating good variability.

First results published in Publications of the Astronomical Society of the Pacific (PASP):

- Pozo Nunez, F., Chelouche, D., Kaspi, S., et al. (2017)Automatized photometric monitoring of active galactic nuclei with the
46 cm telescope of the WISE observatory.  Click to Figure 8 of paper.

Second results published in Nature Astronomy:

- Chelouche, D., Pozo Nunez, F. and Kaspi, S., (2018)Direct Evidence of non-disk optical continuum emission around an active black hole


Astronomy codes IDL:

Astronomy codes Python: