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PhD in Astrophysics: Details
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Foundations
The UDP Astronomy Nucleus was created in 2013 to form a high-level international research group that could leverage Chile’s enormous comparative advantages to develop observational astronomy. Currently, Chile hosts the largest collection of telescopes in the world. Considering the new generation of telescopes under construction that will be installed in the country (E-ELT, GMT, and Vera Rubin/LSST), the Atacama desert in the north of Chile will concentrate approximately 70% of the world’s terrestrial astronomical infrastructure. This cutting-edge astronomical instrumentation represents a unique opportunity for Chilean universities to successfully compete for 10% of the observation time reserved for the host country on each telescope.
In 2023, the Astronomy Nucleus was renamed the Institute of Astrophysical Studies (IEA for Instituto de Estudios Astrofísicos). In the last decade, the IEA has established itself as a highly productive group, measured in publications by its members, awards, success in obtaining grants and observing time, and leadership in collaborations. In this context, creating a doctoral program in 2019, was an important step for consolidating the IEA as an internationally renowned group.
All the faculty members have embraced the challenge to create a new PhD program in Astrophysics in Chile that would be adapted to the current reality of astronomy and capture the good practices learned in all our previous institutions across the globe. The IEA became thus a fertile territory to plant new seeds in how we see modern astronomical research.
In addition to having access to a huge variety of observational data, which differentiates Chilean astrophysics from the rest, the main characteristics of our specific program are:
- Once a candidate meets the admission criteria to be considered for a PhD position (see below), diversity in research subjects, cultural background, gender, and availability of potential PhD advisors are taken into account. We are indeed proud of having achieved gender balance at all academic levels and have about 80% of international researchers in our institute.
- Our program is designed to allow students to develop their thesis project from the beginning of their PhD through research projects that help to learn skills and explore topics of interest.
- The initial cycle of 3 semesters offers courses adapted to the student’s interests, intending to deepen their knowledge of their research topics and explore various methods, in particular regarding observing techniques and data analysis.
- Our students design their PhD thesis project. This enables them to work on the subject they are most curious about and to quickly develop the soft skills of independence, proactivity, and planning. In this sense, PhD advisors help students in brainstorming and in evaluating if the thesis projects are ambitious but realistic enough to be successful.
- Currently, IEA members are PIs of several research grants that offer the students to be involved in various international projects, allowing them to travel to conferences and research visits in various countries.
Students can work in one or more of the research areas of the program:
- Astrophysics of Planetary Systems: planetary formation, protoplanetary disks, extrasolar planets, cosmic dust laboratory, solar system.
- Stellar and Galactic Astrophysics: stellar evolution, stellar populations and abundances, galactic dynamics, galactic archaeology, galactic transients, compact objects.
- Extragalactic Astrophysics: galactic evolution over cosmic time, extragalactic transients, active galactic nuclei, supermassive black holes.
Admission profile.
The program is intended for applicants holding a Bachelor’s or Master’s degree in astronomy or related sciences (physics, planetary sciences, mathematics, etc.). Applicants are expected to have excellent academic records in their previous studies, some experience in research projects, and a very high level of motivation for independent research in astronomy. Applicants should also be proficient in the English language (reading comprehension is essential, and oral and written expression are highly desirable) and be able to commit to full-time participation in the doctoral program and move to Chile.
Calls for applications are made once a year during the beginning of the second semester, and selected students starting either in March or in August of the following year. The number of admissions will depend on the availability of potential advisors and funding.
Below, we present examples of the work conducted by recent PhD graduates.
Thallis Pessi (Brazil)
PhD defended on 10 June 2024.
Thesis Title:
Characterizing the Environments of Core-Collapse Supernovae with MUSE
Supervisors:
Jose Prieto (UDP); Co-Supervisor: Joseph Anderson (ESO)
Areas: stars, galaxies stellar and galactic astronomy, extragalactic astronomy
Summary:
In this project, we studied the local environments of a minimally biased sample of 112 core-collapse supernovae detected by the ASAS-SN transient survey between 2014-2018 and observed with the MUSE integral field spectrograph at the VLT. We found that stripped-envelope SNe occurs in environments with higher metallicities than Type II SNe, while Type II and IIn SNe have very similar metallicities, ages, and star-formation rates, indicating that these events explode in similar environments. We also found a strong dependence in the occurrence of core-collapse SNe per unit star-formation as a function of metallicity and show that there is a strong decrease as metallicity increases. Finally, we discussed different possible explanations for these results and the implications of these results for different fields of astrophysics.
Main thesis publications of PhD thesis:
https://ui.adsabs.harvard.edu/abs/2023A%26A…677A..28P/abstract
https://ui.adsabs.harvard.edu/abs/2023ApJ…955L..29P/abstract
Other publications during PhD:
https://ui.adsabs.harvard.edu/abs/2022ApJ…928..138P/abstract
https://ui.adsabs.harvard.edu/abs/2023A%26A…677L…1P/abstract
https://ui.adsabs.harvard.edu/abs/2024arXiv240502274P/abstract
Other information:
Video: https://www.youtube.com/watch?v=SeWqDMuqSW8
Press release: https://www.eso.org/public/videos/potw2345a/?lang
Personal website: https://thallispessi.wixsite.com/thallispessi
Camilo Gonzalez (Chile), PhD defended on 15 May 2024
Thesis title:
A Multiscale ALMA Study of Protoplanetary Disks in Ophiuchus: From Outflows to Substructures
Supervisor:
Lucas Cieza (UDP)
Areas: planetary systems, protoplanetary disks, low-mass stars and brown dwarfs.
Summary:
In this work, part of the Ophiuchus Disk Survey Employing ALMA (ODISEA) project, we present the largest sample of proto-brown dwarf candidates observed to date at millimeter wavelengths in a single molecular cloud. Within the sample of 21 objects, 16 are detected in Band-6 (1.3 mm / 230 GHz) dust continuum, and 10 display extended molecular gas structures in 12CO, 13CO, and C18O (2-1) lines. These observations suggest that proto-brown dwarfs are scaled-down versions of their higher mass counterparts (with disks, outflows, and envelopes) and that they form in a very similar way. We also present high-resolution ALMA observations of the remarkable binary system ISO-Oph 2. We conclude that the system contains the largest and smallest cavities, the smallest measured disk size, and the resolved cavity around the lowest-mass object (M⋆ ∼ 0.08 M⊙) in Ophiuchus. From the 12CO data, we find a bridge of gas connecting both disks. While the morphology of the rings around the primary might be due to an unseen disturber within the cavity, we speculate that the bridge might indicate an alternative scenario in which the secondary has recently flown by the primary star causing the azimuthal asymmetries in its disk. The ISO-Oph 2 system is therefore a great laboratory to study disk evolution, planet formation, and companion-disk interactions.
Main thesis publications of PhD thesis:
https://ui.adsabs.harvard.edu/abs/2020ApJ…902L..33G/abstract
Other publications during PhD as co-author.
https://ui.adsabs.harvard.edu/abs/2020ApJ…900….7H/abstract
https://ui.adsabs.harvard.edu/abs/2021MNRAS.501.2305Z/abstract
https://ui.adsabs.harvard.edu/abs/2021MNRAS.501.2934C/abstract
https://ui.adsabs.harvard.edu/abs/2022ApJ…938…54R/abstract
https://ui.adsabs.harvard.edu/abs/2023MNRAS.518.5620W/abstract
https://ui.adsabs.harvard.edu/abs/2023MNRAS.522.2611A/abstract
https://ui.adsabs.harvard.edu/abs/2023MNRAS.523.4970N/abstract
https://ui.adsabs.harvard.edu/abs/2023MNRAS.526.1545C/abstract
https://ui.adsabs.harvard.edu/abs/2024ApJ…966…96H/abstract
Other information:
Video: https://www.youtube.com/watch?v=Gom8Z2S1fUk
Video: https://www.youtube.com/watch?v=Tx-B7o_FFfk
Video: https://www.youtube.com/watch?v=VfAI8IxhXks
Pedro Nogueira (Brazil)
PhD defended on 11 April 2024
Thesis title:
A Millimeter and Near-Infrared Study of YSOs: From outbursting protostars to satellites
Supervisor:
Alice Zurlo (UDP); Co-Supervisor: Lucas Cieza (UDP)
Areas: planetary systems, protoplanetary disks, stars and brown dwarfs.
Summary:
In this work, we investigated the eruptive YSO system HBC 494 with ALMA Band-6 (1.3 mm) observations at ∼0.03′′ (12 au) resolution, revealing its binarity and dust/gas properties. HBC 494 is a FUor object in the Orion Molecular Cloud and the ALMA high-resolution observations showed two compact, but well-resolved disks with similar inclinations. The binary system exhibits a projected separation of ∼0.18′′ (75 au) and the northern component is ∼5 times brighter and ∼2 times larger than the southern one. We found that HBC 494 North has a mass similar to that of other FUors, while the HBC 494 South resembles EXor sources. We also explored the young binary system η Tel (age ∼ 8 Myr) with high-contrast imaging using the instrument VLT/SPHERE in the H-band. We performed astrometric, photometric, and orbital analysis. η Tel comprises a 2.09 M⊙ A-type star and a M7/M8 brown dwarf companion, η Tel B, separated by ∼4.2′′ (208 au). New SPHERE/IRDIS coronagraphic observations with a contrast of 10−5 at the location of the companion are presented in this work. Alongside previous literature on astrometric measurements, an astrometric study with a 19-year baseline was provided. The orbital analysis revealed a low eccentric orbit (e ∼ 0.173) with an inclination of 82.4 degrees (nearly edge-on) and a semi-major axis of 214 au. The mass of η Tel B was determined to be 47 MJUP, consistent with previous literature work. No significant residual indicative of a satellite or disk surrounding the companion is detected, with limits ruling out objects around η Tel B with masses as low as 1.6 MJUP at separations down to 33 au.
Main publications of PhD thesis:
https://ui.adsabs.harvard.edu/abs/2023MNRAS.523.4970N/abstract
https://ui.adsabs.harvard.edu/abs/2024arXiv240504723N/abstract
Other publications during PhD as co-author:
https://ui.adsabs.harvard.edu/abs/2021MNRAS.501.2934C/abstract
https://ui.adsabs.harvard.edu/abs/2022ApJ…938…54R/abstract
https://ui.adsabs.harvard.edu/abs/2022A%26A…666A.133Z/abstract
https://ui.adsabs.harvard.edu/abs/2024A%26A…684A..69G/abstract
Trystan Lambert (South Africa)
PhD defended 19 December 2023
Thesis title:
Exploring [CII] Haloes and Quasar Environments in and near the Epoch of Reionization
Supervisors:
Roberto Assef (UDP); Co-supervisors: Manuel Aravena (UDP), Chiara Mazzucchelli (UDP)
Summary:
In this project, we explored the environments of high redshift objects. In Lambert et al. (2023) we used deep ALMA observations to study the extended [CII] emission of a “normal” galaxy (i.e., close to L* luminosity) at z=5.25. We found a clear detection of a halo, one of the first detected in a single system without stacking a large number of objects, and found it is most likely the result of recent merger activity. In the second part of this thesis (Lambert et al. 2024), we studied the large-scale environment of a z=6.9 QSO by identifying Lyman alpha emitting galaxies through a combination of deep broad- and narrow-band observations with DECam at the CTIO 4-m telescope. While we find that overall there are about ~10 times more companion galaxies than expected for a random place in the sky (highlighting a very large overdensity), there is a total dearth of Lyman alpha emitting galaxies within 5Mpc of the QSO. We believe that this shows the QSO is affecting star formation in nearby systems and that this may explain the breadth of often conflicting results in the literature about high-z QSO environments.
Main publications of PhD thesis:
Lambert et al. (2023, MNRAS, 518, 3183)
Lambert et al. (2024, A&A, in press, arXiv:2402.06870)
Other publications:
https://ui.adsabs.harvard.edu/abs/2023ApJ…943..139M/abstract
https://ui.adsabs.harvard.edu/abs/2023A%26A…669A..46P/abstract
https://ui.adsabs.harvard.edu/abs/2021MNRAS.506.1073H/abstract
https://ui.adsabs.harvard.edu/abs/2019ApJS..245….6M/abstract
Danielle de Brito Silva (Brazil)
PhD defended 11 December 2023
Thesis title:
Unveiling the Milky Way before redshift 1 through its stellar population content
Supervisor:
Paula Jofré (UDP)
Summary:
This project consisted in studying the evolution of the early Milky Way through two fronts. The first one was by the chemical characterization of high resolution spectra of halo stars, which were observed with the MIKE instrument in Las Campanas Observatory. The second was by analyzing phylogenetic trees of a simulated galaxy, in order to understand the features in trees that reflect different star formation histories.
First author publications:
- https://ui.adsabs.harvard.edu/abs/2024ApJ…962..154D/abstract
- https://ui.adsabs.harvard.edu/abs/2022MNRAS.509.4637D/abstract
Additional information:
This is the first PhD thesis of the Núcleo Milenio ERIS (https://nucleomilenioeris.cl/en/), marking a success story for interdisciplinary research. In September 2024 Danielle will join as a postdoc at Uppsala University, Sweden.
Video: https://www.youtube.com/watch?v=jzz_dYAvFC8
Ana Posses (Brazil)
PhD defended 1 of December 2023
Thesis title:
The Structure and Dynamics of the Interstellar Medium of Galaxies in the Early Universe
Supervisor:
Manuel Aravena (UDP); Co-Supervisor: Jorge González-López (PUC, Carnegie)
Summary:
My thesis explored the morphology and kinematics of cold gas, star-forming regions, and stellar components in two massive star-forming galaxies at z = 5–7 using high-resolution (0.3″) ALMA observations of the [CII] 158µm line emission. For COS2987 at z = 6.8, our findings reveal a central source with extensions and candidate companions, displaying a velocity gradient typical of rotating disk galaxies. For CRISTAL-05 at z = 5.54, a complex close encounter with disturbed gas is observed, indicating significant [CII] emission beyond the galactic disk, linked to the merger. These results suggest that early galaxy assembly involves frequent satellite accretion, highlighting the necessity of high-resolution surveys to understand the formation and evolution of the earliest galaxies.
First author publications as part of PhD thesis:
https://ui.adsabs.harvard.edu/abs/2023A%26A…669A..46P/abstract
https://ui.adsabs.harvard.edu/abs/2024arXiv240303379P/abstract
Publications as co-author, during PhD:
https://ui.adsabs.harvard.edu/abs/2021A%26A…647A.194F/abstract
https://ui.adsabs.harvard.edu/abs/2023MNRAS.518.3183L/abstract
https://ui.adsabs.harvard.edu/abs/2023arXiv231117671M/abstract
https://ui.adsabs.harvard.edu/abs/2024arXiv240104919S/abstract
Other information:
Personal website: https://anapossesastro.wixsite.com/colabwithme
Dejene Zewdie (Ethiopia)
PhD defended on 19 October 2023
Thesis title:
Hot Dust Obscured Galaxies Environments
Supervisor:
Roberto Assef; Co-Supervisor: Manuel Aravena
Summary:
The main goal of this thesis was to study the environments of Hot Dust Obscured Galaxies, or Hot DOGs, by statistically estimating the density of companion galaxies identified using the Lyman break technique through deep imaging obtained with Gemini-S/GMOS-S and Magellan/IMACS. Hot DOGs are some of the most luminous, yet heavily obscured quasars known, and as such are expected to trace some of the densest regions of the Universe. Our results confirm this is the case, and suggest that these regions will become massive clusters at z=0, and that Hot DOGs likely represent an early stage in the formation of the brightest cluster galaxy.
Main publications during PhD:
Zewdie et al. (2023, A&A, 677, 54)
Zewdie et al. (2020, MNRAS, 498, 4345)
Other publications as co-author:
https://ui.adsabs.harvard.edu/abs/2024A%26A…682A.166F/abstract
https://ui.adsabs.harvard.edu/abs/2024arXiv240520479L/abstract
Other information:
Video: https://www.youtube.com/watch?v=oxfjbqMqeQs
Kriti Kamal Gupta (India):
PhD defended on 31 May 2023
Thesis title:
A large multiwavelength study of the local active galactic nuclei
Supervisor:
Claudio Ricci
Summary:
During her PhD, Kriti focused on studying the multi-wavelength emission properties of Active Galactic Nuclei (AGN) in the local Universe to enhance understanding of AGN accretion physics. She investigated the X-ray properties of obscured AGN using a sample of 386 hard-X-ray-selected Swift/BAT AGN. Her analysis revealed a negative correlation between the fraction of scattered X-ray radiation and the X-ray column density, suggesting possible explanations involving inclination angles or torus covering factors. In the second part of her thesis, Kriti conducted a broadband spectral energy distribution (SED) study of unobscured AGN, analyzing optical/UV and X-ray emission from 236 nearby AGN. Her work included fitting multi-temperature disk models and X-ray models, leading to the estimation of key quantities such as optical-to-X-ray spectral index, bolometric corrections, and Eddington ratios. She discovered a positive correlation between the 2-10 keV X-ray bolometric correction and bolometric luminosity, with the correlation disappearing at low Eddington ratios, suggesting changes in AGN accretion at these values. Her findings highlighted the Eddington ratio as a primary regulator of AGN accretion physics and emission properties.
First author publications:
https://ui.adsabs.harvard.edu/abs/2021MNRAS.504..428G/abstract
Gupta et al. 2024 (submitted to A&A)
Other publications:
https://ui.adsabs.harvard.edu/abs/2023ApJ…952L..28R/abstract
https://ui.adsabs.harvard.edu/abs/2023ApJ…959…27R/abstract
https://ui.adsabs.harvard.edu/abs/2023MNRAS.526.5072M/abstract
Other information:
Video: https://www.youtube.com/watch?v=leh49qw2Xo8
For information in Spanish from the UDP Doctorados website click here