Academic Interests:
  • Galaxy and structure formation/evolution
  • Large scale structure
  • Numerical simulation
  • Academic references:
  • Dr. Kelly Holley- Bockelmann
  • Dr. Andreas Berlind
  • Email:
    antonio[dot]j[dot]porras[at]vanderbilt[dot]edu

    Antonio J. Porras-Valverde.

    Welcome to my webpage. I am a PhD candidate in Astrophysics at Vanderbilt University. I obtained a master's degree in Physics from Fisk University and a bachelor's degree in Mathematics from the University of North Carolina at Chapel Hill.

      About me: Moved to the United States from San José, Costa Rica on February 18th 2010. I mentor Centroamerican-Caribbean students at https://cencabridgeastro.weebly.com/

      Current Work

      My research focuses galaxy formation using semi-analytic model Dark Sage.

      The stellar-to-halo mass relation colored by the quenched fraction for both Dark Sage (top panels) and TNG (bottom panels) for all (left), centrals (mid), and satellite (right) galaxies. Red colors show galaxies more quenched, while blue colors show star-forming galaxies.

      Controling for stellar mass and halo mass: galaxy quenching predictions using IllustrisTNG and Dark Sage

      We use the hydrodynamical simulation IllustrisTNG and semi-analytic model Dark Sage to understand the effects of stellar mass and halo mass in driving galaxy quenching. Dark Sage and IllustrisTNG predict that both halo mass and stellar mass play a role in driving quenching. Both models also predict that satellite galaxies behave similar to centrals. However, the two models are quite different in detail, with Dark sage producing a SHMR with much larger scatter than IllustrisTNG.

      Specific angular momentum of the stellar disk as a function of stellar mass for bulge-dominated (red), intermediate(green), and disk-dominated (blue) galaxies.

      Angular momentum and Morphological Sequence of Massive Galaxies through Dark Sage

      Using semi-analytic model Dark Sage, we examine the baryonic, stellar, and dark matter specific angular momentum (j) of a sequence of galaxy morphologies as a function of stellar mass. Our paper shows that Dark Sage is able to reproduce the observed relation (Porras-Valverde et al. 2019). Surprisingly, within our stellar mass range, bulge-dominated galaxies have higher jdark matter than disk-dominated galaxies. We find that the relationship between morphology and jdark matter disappears when controlling for halo mass. Thus, halo mass, rather than jdark matter is what drives the predicted galaxy morphologies.

      Past Research

      Undergraduate projects

      Fig 1. NGC 6240 VLA Ka band at 33GHz with resolution 0.77" x 0.61"

      High Resolution 33GHz Observations of Embedded Star Formation in NGC6240

      During the summer of 2016, I observed luminous infrared galaxy NGC6240 at 33GHz using the Very Large Array (C configuration) to understand its extreme star formation environment. This galaxy is particularly interesting given that it hosts two active supermassive black holes. After calculating its star formation rate (SFR) using the radio continuum, we found that NGC6240's SFR is more than that of the Milk Way. We also approximated the SFR surface density to be similar to the Orion core, but spread over at a larger scale. This research was done at the National Radio Astronomy Observatory in Charlottesville, Virginia.

      Collaborators: Dr. Aaron Evans, Sean Linden, Dr. Loreto Barcos-Muñoz

      Compact Steep Spectrum Object Found in Galaxy Merger 1015+364 at 2.3 and 8.5GHz

      In search for binary supermassive black holes, I investigated ongoing galaxy merger 1015+364 using the Very Long Baseline Array at 2.3 and 8.5 GHZ (S/X band respectively). After detecting two radio sources about 20 parsecs apart, I calculated their flux density and spectral index which led to the conclusion of both sources being young radio objects with steep synchrotron spectrum. This brought the questions of whether these type of objects may arrive from coalesce binary supermassive black hole, which in this case we could not detect. This research was done at the National Radio Astronomy Observatory in Socorro, New Mexico.

      Collaborators: Dr. Sarah Burke-Spolaor

      Fig 2. Contour plot of S and X band emissions laid on top of another.

      Fig 3. Absorption lines for OH+, OH, CH, CH+ toward BD-145037 star.

      OH+ in Diffuse Molecular Clouds

      My first research experience involved observing near ultraviolet observations of OH and OH+ of over 60 stars using VLT (UVES instrument). We looked at OH+ absorption lines which came from high CH+ to CH density ratio. Similarly, we traced OH absorption present close to CN lines. Our main result shows that OH+ detections may favor low-density gas, whereas OH absorption may appear at high density regions of gas. While OH+ leads to OH production, we argued that the environmental preference of OH and OH+ suggests that the observed OH in high density regions might come from a different formation mechanism. For more information, please refer to my paper publication on this matter. This research was done at the University of Toledo.

      Collaborators: Dr. Steven R. Federman, Dr. Dan E. Welty, Adam M. Ritchey

      Flexibility and Reynolds number Effect in Optimizing Jellyfish Propulsion

      As an undergraduate mathematician, I studied the role of flexibility and the reyonlds number effect in jellyfish propulsion using numerical models. From my 3D oblate jellyfish model, we found out that for high viscous environments, the resonant frequency of the bell increases. Our results suggests that jellyfish swim faster at their resonant frequency and they can maximize their swimming efficiency by expanding its bell and allowing vortex fluid rings from beneath transport fluid that would make the jellyfish coast. This research was done at the University of North Carolina at Chapel Hill funded by the Summer Undergraduate Research Fellowship (SURF) grant. Check out my latest paper on this work: Coast or Pump?

      Collaborators: Dr. Laura Miller, Dr. Alexander Hoover

      Fig 4. 2D Simulation of a swimming oblate jellyfish

      Curriculum Vitae

      Education

      Vanderbilt University
      Doctor of Philosophy in Astrophysics
      Completion: May 2023
      Fisk University
      Master of Arts in Physics
      August 2016 - May 2018
      University of North Carolina - Chapel Hill
      Bachelor of Mathematics
      August 2012 - May 2015
      Northern Virginia Community College
      English as a Second Language courses
      August 2010 - May 2012

      Awards

      American Physical Society Travel award for Excellence in Graduate Research August 2018
      Vanderbilt University McMinn Summer Research Award Summer 2018
      National Science Foundation Graduate Research Fellowship Honorable Mention April 2016
      Office for Undergraduate Research Travel Award April 2015
      Proposal for Very Long Baseline Interferometer (VLBI) Telescope time. Awarded two hours Summer 2015

      Fellowships

      Fisk-Vanderbilt Bridge Fellow August 2016 - May2018
      National Radio Astronomy Observatory REU Fellow Summer 2015 - 2016
      University of North Carolina - Chapel Hill REU Fellow Summer 2014
      University of Toledo REU Fellow Summer 2012

      Science outreach

      Giving back to our community

      Dyer Obervatory - Meet the Astronomer Lectures

      Every year, I volunteer to give a scientific talk to the general audience about an exciting topic in astronomy. In May 2018, I gave a lecture titled "Why is the Milky Way the Way it is?", which focused on understanding the shape of our Milky Way and how astronomers use telescopes to study galaxies. In April 2019, I gave a lecture titled "The Quest for Life on Extrasolar Planets", which discussed ways to find life in planets outside of our solar system. I summarized ways to detect planets and what astronomers look for in terms of finding life in exoplanets. Here is the abstract: To watch the lectures, visit https://dyer.vanderbilt.edu/lectures-dyer/.

      Astrobitos Collaboration. December 2018 - present

      I am an author for Astrobitos, a blog dedicated to summarize recent scientific articles in astronomy supported by the American Astronomical Society. The format is just like Astrobites. The only difference is that Astrobitos is in Spanish. Every month, I write an paper summary in Spanish, while editting someone else's paper summary article. Our goal is to bridge undergraduate students and recent scientific discoveries in our field. To learn more, visit astrobitos.org.

      Member of NAC Council of Representatives for Engagement (CORE). October 2018 - present

      As a National Astronomy Consortium (NAC) alumn and member of the CORE council, our job is to find ways to engage the NAC student community through professional development webinars, while providing a safe environment for guidance and questions about our journey through academia. To learn more, visit the NAC CORE webiste.

      Central American-Caribbean (Cenca) Bridge in Astrophysics. June 2016 - Present

      I founded the Cenca bridge with the goal of mentor undergraduate students from the region, while developing academic research opportunities in astronomy. Every month, we meet via zoom to host a guest who talks about their research and intersectional experiences as an astrophysicst. As part of Cenca, we offer the REU-internship program, where students with no research experience have the opportunity to work on a six month research project. We mentor these students, offering professional development workshops. To learn more, visit https://cencabridgeastro.weebly.com/. Cenca has a strong focus on mentoring women and nontraditional students from the region so that they can achieve their goals.

      Astrofisica Centroamericana y del Caribe (Alpha-Cen). May 2017 - Present

      I am part of the executive committee of Alpha-Cen, a nonprofit organization with the goal to highlight astrophysics works and connect academic resources in astronomy in the region. As part of Alpha-Cen, we recently organized the 2020 Alpha-Cen General Assembly virtual conference. To learn more about Alpha-Cen, visit https://ecfm.usac.edu.gt/jrsacahui/AstroCentro/Astro.html.

      Very Large Array. Socorro, NM. Summer 2015

      I gave group tours of about forty people on the VLA site.

      Math Help Center. Chapel Hill, NC. August 2014 - May 2015

      I volunteered as an undergraduate tutor helping students from algebra to Calculus III. I volunteer once a week for one hour technically, but sometimes I like staying longer depending on the availability of tutors.

      Orange County Council. Chapel Hill, NC. August 2013 - December 2014

      I volunteered as a tutor for English and Mathematics two-three hours per week. I help UNC Housing and Dinning staff accomplish their GED (equivalent to high school diploma) certificate.

      Smithsonian National Air and Space Museum. Washington, D.C. May 2011 - May 2012

      I volunteered in the Welcome Center, greeting visitors and providing information about the artifacts in the museum such that the Wright Brothers airplanes, the moon rock, Gemini, Sputnik, Spirit of Saint Louis, and many others.


      Find me on ...