Dr. Antonio J. Porras-Valverde

About me

I am from San Jose, Costa Rica. I moved to the U.S. in 2010 to pursue my dream of becoming an astronomer. Currently, I am a Heising-Simons postdoctoral scholar at Yale University working primarily with Prof. Priya Natarajan. In 2023, I obtained my Ph.D. in astrophysics from Vanderbilt University working under the supervision of Prof. Kelly Holley-Bockelmann and Andreas Berlind. As a Fisk-Vanderbilt Master's-to-PhD Bridge fellow, I obtained my master's in physics from Fisk University. In 2015, I graduated from the University of North Carolina at Chapel Hill with a bachelor's degree in mathematics.

I had the opportunity to travel across the country and worldwide to present my research. Top left: At the AAS235 in Honolulu, Hawaii. Top right: standing on the single-dish Green Bank Telescope in West Virginia. Bottom left: With Dr. Jim Peebles 2019 Nobel Prize Awardee for Physics at the 2018 International Astronomical Union General Assembly in Vienna, Austria. Bottom right: At my first AAS227 meeting in Kissimmee, Florida, my first AAS meeting.

I traveled to talk about research done at several research experience for undergraduate programs. Left hand side, first and second panels show part of the NAC community, who helped me grow and get to where I am today. The last panel shows a picture of my first astronomy internship at the University of Toledo in 2012. Right hand side is just part of a photoshoot I had at the National Air and Space Museum, where I volunteered at the welcome desk when I first arrived in the US. There is where I consider to be the start of my astronomy journey.

Research

I am a theorist in the field of galaxy formation and evolution. I work on various problems within this field, in particular, understanding how black holes are formed and evolve in cosmological simulations, and how their existence play a role in the evolution of galaxies. To explore these problems, I use semi-analytic model Dark Sage and hydrodynamical simulation IllustrisTNG.

SMHMR for all, centrals, and satellite galaxies. The dotted lines show the median of the distribution of TNG300-1 (blue) and Dark Sage (brown) galaxies. The shaded regions show the 68th and 95th percentiles. We see both models predict different stellar-to-halo mass relations slopes. Additionally, both models predict such different scatter in stellar mass (Porras-Valverde et al. In prep).

Another challenge I work on is to understand what causes galaxies to stop forming stars. Throughout a galaxy's history, there are several physical mechanisms that contribute to galaxy quenching (star formation quenching is defined as a process or multiple processes which cease star formation). Here, we look at the SMHMR colored by the quenched fraction (logsSFR less than -11) for Dark Sage (top panels) and TNG (bottom panels) galaxies. We see that TNG predicts a stellar mass driven quenching, where at fixed halo mass, as we increase stellar mass, galaxies become quenched. This is not the case for Dark Sage galaxies, where both stellar mass and halo mass play a role in galaxy quenching (Porras-Valverde et al. In prep).

My most recent publication shows the stellar disk specific angular momentum to stellar mass function for different morphologies. Here, we compare Dark Sage predictions with that of several observations. Because Dark Sage does not calculate the angular momentum of the bulge, we do an approximation of it. On the left hand side, we approximate that the stellar disk specific angular momentum is equal to the stellar bulge specific angular momentum (an upper limit). On the right hand side, we assume a lower limit by setting the stellar bulge specific angular momentum equal to zero. We find that the left hand side case traces best the observations.

This result suggests a new interpretation different from the Fall and Romanowsky explanation. Fall and Romanowsky state that at fixed stellar mass, disk-dominated galaxies have high disk specific angular momentum (and low bulge specific angular momentum), whereas bulge-dominated galaxies have low disk specific angular momentum (and the angular momentum of the bulge is much lower). In our interpretation, both disks and bulges have the same angular momentum. Therefore, at fixed stellar mass, disk-dominated galaxies have high disk and bulge specific angular momentum, whereas bulge-dominated galaxies have low disk and bulge specific angular momentum. This difference in the interpretation of the results is showing that both explanations yield the same predictions.

Ratio of HI mass to stellar mass as a function of stellar mass for bulge-dominated (red) and disk-dominated (blue) galaxies. The solid grey and black lines show the ALFALFA and GASS detection limits, respectively. About 19 percent of bulge-dominated galaxies within our sample should theoretically be detected by both ALFALFA and GASS. Observationally, bulge-dominated galaxies with extended HI disks that are up to 2 to 5 times larger in size than the Milky Way have neither been widely detected nor ruled out.

Publications and CV

Peer-Reviewed
1. Antonio J. Porras-Valverde, Rachel Somerville, John Forbes, Kelly Holley-Bockelmann, Andreas Berlind, and Shy Genel. Why do semi-analytic models predict higher scatter in the stellar mass-halo mass relation than cosmological hydrodynamic simulations? Submitted to ApJ.
2. Antonio J. Porras-Valverde, Kelly Holley-Bockelmann, Andreas A. Berlind, and Adam R. H. Stevens. Angular momentum and Morphological Sequence of Massive Galaxies through Dark Sage. 2021. ApJ, 923, 2. doi:10.3847/1538-4357/ac31a5
3. Alexander P. Hoover, Antonio J. Porras, and Laura A. Miller. Pump or coast: The role of resonance and passive energy recapture in medusan swimming performance. 2019. Journal of Fluid Mechanics, 863, 1031-1061. doi:10.1017/jfm.2018.1007
4. A. J. Porras, S. R. Federman, D. E. Welty, and A. M. Ritchey. OH+ in Diffuse Molecular Clouds. 2014. ApJ, 781, L8. doi:10.1088/2041-8205/781/1/l8

ADS

Download long version CV

Cenca Bridge

In 2016, I started the Central American - Caribbean Bridge in Astrophysics organization (Cenca Bridge) to develop astronomy research opportunities in the region. Currently, I am a co-founder and co-leader of Cenca Bridge Inc., a U.S. nonprofit organization with over 100 undergraduate students from Central America and the Caribbean. As a co-leader, I have personally mentored 14 students: 8 are in masters and PhD programs in astrophysics and 4 that have started their own science mentoring programs in their own countries. I contribute to program management and development of computational and professional development workshops as well as the Cenca Bridge Remote Internship. I have also done work on the accounting and financial aspect of the organization.

Cenca Bridge is co-led by Dr. Gloria Fonseca Alvarez (Nicaragua), Valeria Urrutia Hurtado (Nicaragua), Yahira Mendoza (Honduras) and myself (Costa Rica). We make decisions of the program based on a consensus. We have students from Honduras, El Salvador, Guatemala, Nicaragua, Costa Rica, Panama, Dominican Republic, Trinidad and Togago, and Haiti. Some of my shared responsibilities in the group involve:

• Organize monthly social events and webinar series
• Organize computational and professional development workshops
• Seek research advisors for the remote internship
• Launch and review application for the remote internship. Make selections
• Peer-mentor remote internship students
• Manage the Cenca Bridge website
• Establish partnerships
• Participate in weekly co-leadership meetings
• Grant writting

Opening access to resources in mentorship, astrophysics research, and computation to marginalized communities is part of my values. This goes alongside my scientific research and without it, I cannot call myself a scientist.

Vanderbilt Article

Vanderbilt graduate student creates academic bridge for Central American and Caribbean students in astrophysics: article highlighting our team's contribution towards improving astrophysics research opporutnities in Central America and the Caribbean

Rostros Fisicos

Featured in Rostros Fisicos, a project lead by the University of Maryland College Park to highlight Latinx physicists across all stages of their career path.

This is a summary video of my interview. In later episodes, I discuss what motivated me to study astronomy, what is the field I am interested in, and what were the challenges I had to overcome to get where I am today.

Meet the Astronomer

Dyer Observatory features Vanderbilt experts to discuss topics in astronomy. These talks are geared towards the general audience.

In 2019, I presented a summary of methods that astronomers use to detect planets outside of our solar sistem. We discuss the radial velocity and transiting methods. Topics talked about: doppler effect, habitable zone, planets atmosphere.

In 2018, I provided an overview of how astronomers study galaxies, observationally and theoretically. Topics talked about: defining a galaxy, galaxy morphology, telescopes, electromagnetic spectrum, James Webb Space Telescope, cosmological simulations, the Milky Way.

Press

Interview conducted by Futurum Inspiring the next generation

Presentation given in Spanish to the National Academy of Sciences in Costa Rica. La Busqueda de vida en planetas extrasolares.

Interview conducted by Ticotal, an umbrella organization of the National Academy of Sciences in Costa Rica that highlights Costa Rican scientists abroad. Here I was higlighted in the Talento destacado Ticotal

NRAO-NAC program

The National Radio Astronomy Observatory (NRAO) National Astronomy Consortium (NAC) program provides a research internship in radio astronomy for undergraduate students in the US. The NAC program aims to increase the number of underrepresented minorities in STEM and is unique in its long-term mentorship. I am a true advocate for this program and actively contribute in supporting NAC Alums. From August 2015-May 2023, I have been involved in:

• Mentor NAC alums
• Organize professional development workshops
• Organize social events
• Co-organized the 2020 NACtober virtual conference and the 2021 NACtober virtual conference.

Alpha-Cen

Alpha-Cen is an organization for the development and strengthening of research in astronomy. From May 2017-December 2021, I have done the following:

• Co-founded Alpha-Cen
• Contributed to the bylaws
• Elected executive committee member
• Developed Alpha-Cen and NRAO partership yielding to NINE program accepting students in their intenrship
• Served as applicant reviewer for the NINE internship program
• Co-organized the 2020 Alpha-Cen General Assembly conference

Astrobitos

Astrobitos is a scientific blog in Spanish that summarizes scientific articles and digest them in a way that it is easier to understand and read. These articles are geared towards the general public, but in particular, for undergraduate students whose primary language is Spanish. Astrobitos is supported by the American Astronomical Society. I am an author for Astrobitos (December 2018-present). Our goal is to bridge undergraduate students and recent scientific discoveries in our field.

Vanderbilt Astro Web Admin

I am the web administrator and Astronomy Journal Club (AJC) co-host at Vanderbilt Unversity Department of Physics and Astronomy, Astronomy Group (August 2019-present). My responsibilities here include:

• Add new faculty, staff, and student information into the webpage
• Co-organize AJC weekly talks, contact speakers
• Host AJC talks, weekly

Request

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