ESO PhD student
European Southern Observatory
asantama@eso.org
About me
I am a professional astronomer studying substellar formation. I use multi-wavelengh observations to cover the very first stages to the circumsubstellar disks.
Born and raised in Madrid where I obtained a Physics degree from Universidad Complutense de Madrid in 2014 and a Master in Astrophysics under the supervision of Prof. P. Sánchez-Blázquez. At the same
time I was a trainee student in the European Space Astronomy Center (ESA). I am a PhD student at Universidad de Valparaíso since August 2015. In February 2017 I obtained a studentship
at the European Southern Observatory. By the way, check out my recent here.
We combine observations at several wavelengths to study brown dwarf as they evolve. The prestellar cores and the Class 0 stage can only be seen using
radio wavelengths where the gas and dust envelopes at very low temperature are emitting the bulk of energy. Meanwhile, we can study Class I/II/III sources
using: (1) optical wavelengths to obtain information about the central source, (2) infrared wavelengths that give us information about dust at higher temperature
in the circumsubstellar disk, and (3) radio wavelengths that trace the gas and dust at 10-20K.
to study Brown Dwarf formation
We identified a set of prestellar cores in the substellar regime without optical/IR counterparts using AzTEC/ASTE maps at 1.1 mm
in the Lupus 1 and 3 star forming region. Then, we complemented the sample with spectroscopically confirmed Class II from the literature. A total
number of 64 sources were pointed with ALMA. Using all the available archives we built the SED for each of the detections as well as we inferred the mass
from the cold dust. We classified our sample in 9 prestellar cores without optical/IR counterpart candidates, 1 Class 0/I candidate, 2 Class I candidates and
7 Class II (6 of them previously known and 1 candidate). Six of the prestellar cores seems to be formed by gravitational contraction. The Class 0/I candidate
showed a very completed SED and the bolometric luminosity confirmed the substellar origin of the source. Finally, we measured the dust disk masses for the
Class II objects and I compared it against the mass of the central object. We also found all the Class II BD observed with ALMA in other SFR and measured the
dust disk masses when Gaia parallaxes were available. Lupus disk have similar masses to the ones in Taurus. Unfortunately,
the masses that we are obtaining (below 10 earth masses) showing us that according to the current planet formation theories seems to be not possible to form planetary mass companions in these BDs.
or
We studied a substellar companion orbiting at a distance of ∼1100 AU from a central binary system. We used X-Shooter spectroscopy from near ultraviolet to near
infrared to measure accretion with the same techniques that are used in T-Tauri stars. This work is the most comprehensive study of substellar accretion in
wide SSC to date. When we compared the accretion rate in low mass stars and other the one obtained in substellar companions we see that are very similar. Accretion rate
can help us to differentiate among the formation scenario, unfortunately, the uncertainties regarding the mass of the object and the age are not allowing us
to infer the origin of the object. So, future work should focussed in statistical a point of view of accretion in isolated BD.
Additionally, we determined the spectral type, gravity, and effective temperature via comparison with models and observational templates of young brown dwarfs.
Mass accretion rates vs stellar mass. Triangles shows upper limits. Black squares are the wide substellar companions.
Data shown in blue are accretion rates given in Natta et al. (2006) which are measured using Pa β while those in red are measured with Brγ.
Purple symbols represent measurements from Herczeg et al. (2009) and green pentagons have been obtained from Muzerolle et al. (2005). It seem that SSCs roughly follow the correlation between
mass and accretion rate of young stellar objects.
CV
Education
Ph.D in Astrophysics, 2015 - present
Universidad de Valparaíso & European Southern Observatory
PH.D thesis: The origin of Brown dwarfs
Supervisor: Itziar de Gregorio-Monsalvo and Matthias R. Schreiber
Santamaría-Miranda, A.S, De Gregorio-Monsalvo, I., et al. in prep: The early stages at substellar formation in Lupus 1 and 3 clouds with ALMA
Santamaría-Miranda, A., Cáceres, C., Schreiber, M.R.,: Accretion signatures in the X-shooter spectrum of the substellar companion to SR12. MNRAS, 475, 2994s.
Accepted Observing Proposals
(as Principle Investigator, years correspond to dates of acceptance)
ALMA,"From cores to protobrown dwarfs: Unraveling the substellar formation mechanism in Lupus 4" 2018
HAWK-I/VLT,"Confirming the nature of Lupus pre-and proto-brown dwarf candidates" 2018
APEX,"A search of submillimeter water masers at 321 GHz in young stellar objects." 2018
ALMA,"Unvealing the true nature of the subluminous young stellar object Par-Lup3-4." 2017
MagE/Las Campanas Observatory,"Debris or not Debris? Determining the Nature of Low-mass Disks around Young Stars." 2016
Scientific Talks in conferences
“The wonders of star formation”, Edinburgh, United Kingdom. Poster.
"Formation of substellar objects: Theory and observations". Madrid, Spain. May 2018
"Diversis mundi: The Solar System in an Exoplanetary context". Santiago, Chile. March 2018
"Star Formation from Cores to Clusters". Santiago, Chile. March 2017
Outreach
Contributor and member of Editorial Board of Astrobitos (Astrobites en español)
European Southern Observatory
Alonso de Córdova 3107
Vitacura, Casilla 19001
Santiago, Chile
email: asantama@eso.org
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i = 0;
while (!deck.isInOrder()) {
print 'Iteration ' + i;
deck.shuffle();
i++;
}
print 'It took ' + i + ' iterations to sort the deck.';
