Dr. Francisco Pozo Nuñez
Overview of My Research
I am an Astrophysicist living in Heidelberg, Germany. I began my career as a professional researcher in 2014, focusing on understanding the physical nature of regions around supermassive black holes in active galactic nuclei. My specific areas of interest include their accretion disks, broad-line regions, and dust distributions. I utilize observations obtained from X-ray to UV/optical, and up to infrared energies. I invite you to learn more about my work below.
A Little About Me
I’m originally from the "whole year" beach and sunny city of Antofagasta located in the North of Chile. My passion for Astronomy took me to Germany for my PhD in Astrophysics at the Ruhr-Universität Bochum. In 2014, I started my first postdoctoral research at the Bochum Astronomical Institute. Two years later, a second postdoc in collaboration between Haifa and Tel-Aviv universities. A third postdoctoral work in 2018, back in Germany, due to the collaboration between Tel-Aviv, Haifa, and Bochum universities. Later in 2019 I started a collaboration between the Heidelberg Institute for Theoretical studies, the Max-Planck Institute for Astronomy, and the Nicolaus Copernicus Institute in Warsaw, Poland.
I am currently working at the Institute for Theoretical Studies (HITS) in Heidelberg, Germany.
Below you can learn more about my professional work and publications.
My Research
My research primarily centers on the environments of black holes in active galactic nuclei and star formation, aiming to unravel the processes driving the formation and evolution of galaxies. Additionally, a significant portion of my scientific work is devoted to designing, implementing, and optimizing algorithms for processing, managing, and analyzing large astronomical datasets. I have also integrated these algorithms with the development of automated and robotic operations for astronomical instruments. For more detailed insights into these projects, please read further below
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Star Formation and High-Mass stars
(coming soon)
Automation and astronomical instrumentation
(coming soon)
Publications
Only the past 3 years. A full list of publications can be found here.
November, 2023
González-Buitrago, D., García-Díaz, Ma T., Pozo Nunez, F., and Guo, Hengxiao. Published in MNRAS.
We present the results of a continuum reverberation mapping study of the radio-quiet type 1 Seyfert galaxy IRAS 09149-6206. To our surprise, the strong increase in soft X-ray fluxes is delayed by about 15 d compared to the optical UV fluctuations, which challenges the prediction of the lamp-post model. Our analysis of the X-ray variability reveals the presence of a non-variable spectral component at 0.3-6.0 keV along with variable excess emission at 2.0-3.0 keV, which could be partly related to relativistic reflection in the inner region of the accretion disc.
July, 2023
Czerny, Bozena., Panda, Swayamtrupta., et al. incl. Pozo Nunez, F. Published in Astronomy and Astrophysics.
We show that time delays for emission lines can be well measured from the main survey for the bright tail of the quasar distribution (about 15% of all sources) with an accuracy within 1σ error. For the DDF, the results for fainter quasars are also reliable when the entire ten years of data are used. There are also some prospects to measure the time delays for the faintest quasars at the lowest redshifts from the first two years of data, and possibly even from the first season.
June, 2023
Pozo Nunez, F. et al. Published in MNRAS.
Photometric reverberation mapping can detect the radial extent of the accretion disc (AD) in Active Galactic Nuclei by measuring the time delays between light curves observed in different continuum bands. Quantifying the constraints on the efficiency and accuracy of the delay measurements is important for recovering the AD size-luminosity relation, and potentially using quasars as standard candles.
June, 2023
Pozo Nunez, F. et al. Published in Astronomy and Astrophysics.
We present a probabilistic cross-correlation approach to estimate time delays in the context of reverberation mapping (RM) of active galactic nuclei (AGN). We reformulate the traditional interpolated cross-correlation method as a statistically principled model that delivers a posterior distribution for the delay.
February, 2023
Czerny, Bozena et al. incl. Pozo Nunez, F. Published in Astrophysics and Space Science.
Most ways to employ quasars for cosmology now require an advanced understanding of their structure, step by step. We briefly review this progress, with unavoidable personal biases, and concentrate on bright unobscured sources. We will mention the problem of the gas flow character close to the innermost stable circular orbit near the black hole, as discussed five decades ago.
February, 2023
Vaduvescu, Ovidiu et al. incl. Pozo Nunez, F. Published in Earth, Moon, and Planets.
This is the fourth data paper publishing lightcurve survey work of 52 Near Earth Asteroids (NEAs) using 10 telescopes available to the EURONEAR network between 2017 and 2020.
March, 2022
Wielgórski, Piotr et al. incl. Pozo Nunez, F. Published in The Astrophysical Journal.
We present time-series photometry of 21 nearby type II Cepheids in the near-infrared J, H, and K s passbands. We use this photometry, together with the Third Gaia Early Data Release parallaxes, to determine for the first time period-luminosity relations (PLRs) for type II Cepheids from field representatives of these old pulsating stars in the near-infrared regime.
October 28, 2021
Gianniotis, N., Pozo Nunez, F., and Polsterer, K.L. Published in Astronomy and Astrophysics.
We present a novel probabilistic flux variation gradient (PFVG) approach to separate the contributions of active galactic nuclei (AGN) and host galaxies in the context of photometric reverberation mapping (PRM) of AGN.
September 09, 2020
Lunnan, R. et al. incl. Pozo Nunez, F. Published in ApJ.
We present photometry and spectroscopy of four hydrogen-poor luminous supernovae discovered during the 2-month long science commissioning and early operations of the Zwicky Transient Facility (ZTF) survey.
April 04, 2020
Cho, Hojin. et al. incl. Pozo Nunez, F. Published in ApJ.
We present a variability study of the lowest-luminosity Seyfert 1 nucleus of the galaxy NGC 4395 based on photometric monitoring campaigns in 2017 and 2018. Using 22 ground-based and space telescopes, we monitored NGC 4395 with a ∼5-minute cadence during a period of 10 days and obtained light curves in the ultraviolet (UV), V, J, H, and K/Ks bands, as well as narrowband Hα.
March 03, 2020
Lobban, A. P. et al. incl. Pozo Nunez, F. Published in MNRAS.
We report on the results of a multiwavelength monitoring campaign of the bright, nearby Seyfert galaxy Ark 120, using a ∼50-d observing programme with Swift and a ∼4-month co-ordinated ground-based observing campaign, pre-dominantly using the Skynet Robotic Telescope Network. We find that the longer wavelength emission is delayed with respect to the shorter wavelength emission. Within our measurement uncertainties, the time delays are consistent with a disc reprocessing scenario.
December 12, 2019
Pozo Nunez, F. et al. Published in MNRAS.
We present the results of a 2 yr optical continuum photometric reverberation mapping campaign carried out on the nucleus of the Seyfert-1 galaxy Mrk509. The size of the disc is, however, a factor of 1.8 larger than predictions based on the standard thin-disc theory. We argue that, for the particular case of Mrk509, a larger black hole mass due to the unknown geometry scaling factor can reconcile the difference between the observations and theory.
December 12, 2019
Pozo Nunez, F. et al. Published in MNRAS.
We report results from a search for Galactic high-mass eclipsing binaries. We model the light curves of 26 systems within the framework of the Roche geometry and calculate fundamental parameters for each system component. The deduced mass ratios q = M2/M1 reach from 0.4 to 1.0 with an average value of 0.8. The similarity of masses suggests that these high-mass binaries were created during the star formation process rather than by tidal capture.
January 01, 2019
Chelouche, D. Pozo Nunez. et al. Published in Nature Astronomy.
Here, we report new reverberation data based on a unique narrowband-imaging design, and argue that time delays between adjacent optical bands are primarily associated with the reprocessing of light by a farther away under-appreciated non-disk component.
Science highlights & Press Releases
Article published in Nature Astronomy.
Direct evidence of non-disk optical continuum emission around an active black hole
January 15, 2019
In this work, we proved the existence of high-density material that has been thrown towards the outskirts of the accretion disk of a supermassive black hole (see figure below). The phenomenon occurs due to the force of radiation pressure exerted on the dust particles located around the accretion disk. This new component could represent the origin of the gas that orbits around the black hole. The velocity of this gas is widely used to estimate the masses of black holes in active galaxies.
The project was planned and carried out during my stay as a Post-doc at the University of Haifa in Israel in collaboration with the University of Tel-Aviv and the University of Bochum in Germany. Our goal was to study the interior of Active galaxies that host supermassive black holes in order to be able to answer questions about the origin of the enormous amount of energy observed.
The use of a new observation system together with the implementation of robotic observations has allowed us to reach an unprecedented photometric precision that has led to the discovery of this material around the black hole. Our study has a direct impact on the measurement of fundamental physical properties of black holes and their evolution in the universe.
The observations of this supermassive black hole were made by the 46cm telescope that belongs to the Wise observatory of Tel Aviv University located in the Negev desert in Israel. We have implemented an observation system that is unique in the world, and which consist of the use of filters specifically designed to capture the emission of the accretion disk and its surroundings. A first study was published in Publications of the Astronomical Society of the Pacific (http://iopscience.iop.org/article/10.1088/1538-3873/aa7a55/pdf)
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Press release in Germany: "Den Geheimnissen der Schwarzen Loecher auf der Spur"
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Rhein-Neckar-Zeitung: "Francisco Nunez ist den Geheimnissen des Alls auf der Spur"
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in Chile: "Investigacion sobre agujeros negros: Universidad Catolica del Norte"
Article published in Science.
A fast and long-lived outflow from the supermassive black hole in NGC5548
June 19, 2014
Supermassive black holes in the nuclei of active galaxies expel large amounts of matter through powerful winds of ionized gas. The archetypal active galaxy NGC 5548 has been studied for decades, and high-resolution X-ray and UV observations have previously shown a persistent ionized outflow. An observing campaign in 2013 with six space observatories shows the nucleus to be obscured by a long-lasting, clumpy stream of ionized gas never seen before. It blocks 90% of the soft X-ray emission and causes simultaneous deep, broad UV absorption troughs. The outflow velocities of this gas are up to five times faster than those in the persistent outflow, and at a distance of only a few light days from the nucleus, it may likely originate from the accretion disk.
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Press release in Germany: "Swiftly moving gas streamer eclipses supermassive black hole"
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National Geographic: "Best Space Pictures: A Black Hole Blows.."
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SciTechDaily: "Scientist Shed New Light on Black Hole Development"
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Explanatory video: https://www.youtube.com/watch?v=Cp5VBREndAs
Astronomy and Astrophysics highlight in 2014.
Dust reverberation-mapping of the Seyfert 1 galaxy WPVS48
January 01, 2014
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.
