THE SPATIAL DISTRIBUTION OF LARGE AND SMALL DUST GRAINS IN TRANSITIONAL DISKS ELIZABETH GUTIERREZ VILLANOVA UNIVERSITY 2015 SOCORRO COHORT STUDENT ADVISOR: LAURA PEREZ

WHAT ARE TRANSITIONAL DISKS? Circumstellar disk Disk goes from being optically thick to thin within a few Myr, lasting <10Myr within creation since gravitational collapse Key Features: Prominent Dust cavity Disk’s material is Keplerian in motion Fast lifetime Small percentage of entire population of nearest star-forming region Emit strong radiation at micron-millimeter wavelengths by disk Credit: jila.colorado.edu

WHY ARE TRANSITIONAL DISKS IMPORTANT? Understanding formation of solar systems like ours! Understanding diversity of exoplanets and planetary systems. Understanding how small and large grains make planetesimals. Ongoing planet formation thought to happen in this stage of disk evolution.

WAIT…THERE’S A PROBLEM! Being able to distinguish between different clearing mechanisms Photo-evaporation Grain growthForming Planet System Williams et Cieza grain sizes > our observed frequency = “invisible” in our data Our data

TARGETS OBSERVED LkCa15 SR21 RXJ SAO Distance: ~ 140 pc Region: Taurus Properties: K3 star 1.2 L ☉ 1 M ☉ 1.7 R ☉ Temp: 4730K Distance ~ 120pc Region: Ophiuchus Properties: G3 star 10 L ☉ 1 M ☉ 3.2 R ☉ Temp: 5830 K Distance: ~ 185 pc Region: Lupus Properties: K5 star 1.3 L ☉ 1.1 M ☉ 2 R ☉ Temp: 4400 K Distance: ~ 140 pc Region: Sco-OB2 Properties: F4 star 7.8 L ☉ 1.6 M ☉ 2.2 R ☉ Temp: 6590K Sources: simbad

DATA SPECIFICS VLA Project 13B-381 and Project 14B-361 Q band (40.06GHz-47.6GHz) observing X band ( GHz) pointing calibration Observing 7mm grains 64 spw (128MHz/ bandwidth polarization), 64 channels (2MHz in width); 35m-36km baseline in 3 configurations (B, CnB, BnA) Total bandwidth: 7.6 GHz ALMA Cycle 0 (June-July 2012) Observations: 0.5mm grains (690Hz) 4 spw (1.875 GHz/bandwidth polarization, 3840 channels (0.488MHz in width); m baseline range Total bandwidth: 7.5GHz

DATA REDUCTION CASA VLA and ALMA data calibrated with standard pipeline. Created Python/CASA scripts for 4 Terabytes of DATA! Implemented UV tapering for low detection data Continuum imaging of multi-configuration data sets for each object.

RESULTING CONTINUUM IMAGES LkCa15 SR21 RXJ SAO206462

Pinilla et al dP/dr < 0 dP/dr >0 dP/dr = 0 cm Dust Trapping: A Path for Planet Formation mm 0.5mm 7 mm

DATA ANALYSIS TECHNIQUES Azimuthal Average profile of Flux Density Average disk’s flux density in an elliptical shape between two radii starting from the center of disk to longer radii. FWHM of radial distribution of grain size Brightness Temperature Profile Computed brightness temperature profile with standard calculation to see if the disk is optically thick or thin. Azimuthal profile Snu (JY/Beam Disk Radius (AU) FWHM

RESULTS Object FWHM (ALMA)FWHM (VLA) LkCa1598 AU65 AU SR2190 AU58 AU SAO AU169 AU RXJ AU150 AU cm mm dP/dr >0 dP/dr = 0 dP/dr < 0 Kraus & Ireland 2011 VLA ALMA

FUTURE WORK Gaussian fits to azimuthal profiles Modeling of disk emission using visibilities (not images) Constrain optically thin vs thick emission with physical disk models of ALMA and VLA data.

MY NAC EXPERIENCE Highlight Learned more about academia and graduate school process. Made meaningful connections/networking with students and mentors. Lowlights Realizing the struggles underrepresented minorities in astronomy have to overcome. Recommendation for the future of NAC Program More publicity for NAC to gain more funding, participants/mentors, and recognition!

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