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The Millimeter Continuum Size-Frequency Relationship in the UZ Tau E Disk
Tripathi, Anjali,Andrews, Sean M.,Birnstiel, Tilman,Chandler, Claire J.,Isella, Andrea,Pé,rez, Laura M.,Harris, R. J.,Ricci, Luca,Wilner, David J.,Carpenter, John M.,Calvet, N.,Corder, S. A.,Del American Astronomical Society 2018 The Astrophysical journal Vol.861 No.1
<P>We present high spatial resolution observations of the continuum emission from the young multiple star system UZ Tau at frequencies from 6 to 340 GHz. To quantify the spatial variation of dust emission in the UZ Tau E circumbinary disk, the observed interferometric visibilities are modeled with a simple parametric prescription for the radial surface brightnesses at each frequency. We find evidence that the spectrum steepens with radius in the disk, manifested as a positive correlation between the observing frequency and the radius that encircles a fixed fraction of the emission (R-eff proportional to nu(0.34 +/- 0.08)). The origins of this size-frequency relation are explored in the context of a theoretical framework for the growth and migration of disk solids. While that framework can reproduce a similar size-frequency relation, it predicts a steeper spectrum than that observed. Moreover, it comes closest to matching the data only on timescales much shorter (<= 1 Myr) than the putative UZ Tau age (similar to 2-3 Myr). These discrepancies are direct consequences of the rapid radial drift rates predicted by models of dust evolution in a smooth gas disk. One way to mitigate that efficiency problem is to invoke small-scale gas pressure modulations that locally concentrate drifting solids. If such particle traps reach high-continuum optical depths at 30-340 GHz with a similar to 30%-60%. filling fraction in the inner disk (r less than or similar to 20 au), they can also explain the observed spatial gradient in the UZ Tau E disk spectrum.</P>
Dust properties across the CO snowline in the HD 163296 disk from ALMA and VLA observations
Guidi, G.,Tazzari, M.,Testi, L.,de Gregorio-Monsalvo, I.,Chandler, C. J.,Pé,rez, L.,Isella, A.,Natta, A.,Ortolani, S.,Henning, Th.,Corder, S.,Linz, H.,Andrews, S.,Wilner, D.,Ricci, L.,Carpenter, Springer-Verlag 2016 Astronomy and astrophysics Vol.588 No.-
Spiral density waves in a young protoplanetary disk
Pé,rez, Laura M.,Carpenter, John M.,Andrews, Sean M.,Ricci, Luca,Isella, Andrea,Linz, Hendrik,Sargent, Anneila I.,Wilner, David J.,Henning, Thomas,Deller, Adam T.,Chandler, Claire J.,Dullemond, American Association for the Advancement of Scienc 2016 Science Vol.353 No.6307
<P>Gravitational forces are expected to excite spiral density waves in protoplanetary disks, disks of gas and dust orbiting young stars. However, previous observations that showed spiral structure were not able to probe disk midplanes, where most of the mass is concentrated and where planet formation takes place. Using the Atacama Large Millimeter/submillimeter Array, we detected a pair of trailing symmetric spiral arms in the protoplanetary disk surrounding the young star Elias 2-27. The arms extend to the disk outer regions and can be traced down to the midplane. These millimeter-wave observations also reveal an emission gap closer to the star than the spiral arms. We argue that the observed spirals trace shocks of spiral density waves in the midplane of this young disk.</P>
CARMA LARGE AREA STAR FORMATION SURVEY: DENSE GAS IN THE YOUNG L1451 REGION OF PERSEUS
Storm, Shaye,Mundy, Lee G.,Lee, Katherine I.,Ferná,ndez-Ló,pez, Manuel,Looney, Leslie W.,Teuben, Peter,Arce, Hé,ctor G.,Rosolowsky, Erik W.,Meisner, Aaron M.,Isella, Andrea,Kauffmann American Astronomical Society 2016 The Astrophysical journal Vol.830 No.2
<P>We present a 3 mm spectral line and continuum survey of L1451 in the Perseus Molecular Cloud. These observations are from the CARMA Large Area Star Formation Survey (CLASSy), which also imaged Barnard. 1, NGC 1333, Serpens Main, and Serpens South. L1451 is the survey region with the lowest level of star formation activity-it contains no confirmed protostars. HCO+, HCN, and N2H+ (J = 1 -> 0). are all detected throughout the region, with HCO+ being the most spatially widespread, and molecular emission seen toward 90% of the area above N(H-2) column densities of 1.9 x 10(21) cm(-2). HCO+ has the broadest velocity dispersion, near 0.3 km s(-1) on average, compared with similar to 0.15 km s(-1) for the other molecules, thus representing a range of subsonic to supersonic gas motions. Our non-binary dendrogram analysis reveals that the dense gas traced by each molecule has a similar hierarchical structure, and that gas surrounding the candidate first hydrostatic core (FHSC), L1451-mm, and other previously detected single-dish continuum clumps has similar hierarchical structure; this suggests that different subregions of L1451 are fragmenting on the pathway to forming young stars. We determined that the three-dimensional morphology of the largest detectable dense-gas structures was relatively ellipsoidal compared with other CLASSy regions, which appeared more flattened at the largest scales. A virial analysis shows that the most centrally condensed dust structures are likely unstable against collapse. Additionally, we identify a new spherical, centrally condensed N2H+ feature that could be a new FHSC candidate. The overall results suggest that L1451 is a young region starting to form its generation of stars within turbulent, hierarchical structures.</P>