Seamless Astronomy Alyssa A. Goodman

Transcription

1 Semless Astronomy Alyss A. Goodmn Hrvrd-Smithsonin Center for Astrophysics Inititive in Innovtive Hrvrd Collbortors Hrvrd-Smithsonin Center for Astrophysics & SEAS: Alberto Accomzzi, Eli Bressert, Dougls Burke, Rhul Dvé, Pepi Fbbino, Michel Kurtz, Gus Muench, Pvlos Protopps Msschusetts Generl Hospitl: Tim Clrk & Sudeshn Ds Microsoft Reserch: Jonthn Fy, Curtis Wong RPI: Jim Hendler & Deborh McGuinness STScI: Alberto Conti & Crol Christin UCLA: Christine Borgmn

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3 Semless Astronomy Literture Viewer Semntic Serch Info Viz for Serch Results Dt Viewer (e.g. WWT) Archive Browser Mockup bsed on work of Eli Bressert, excerpted from NASA AISRP proposl by Goodmn, Muench, Christin, Conti, Kurtz, Burke, Accomzzi, McGuinness, Hendler & Wong, 2008

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19 3D PDF LETTERS NATURE Vol Jnury 2009 c T mb (K) 0 d 8 T mb (K) Self-grvitting leves v z y (dec.) x (RA) CLUMPFIND segmenttion dt, CLUMPFIND typicllyfinds fetures on limited rngeofscles, bovebutclosetothephysiclresolution ofthedt, nd its results cn be overly dependent on input prmeters. By tuning CLUMPFIND s two free prmeters, the sme moleculr-line dt set 8 cn be used to show either tht the frequency distribution of clump mss is the sme s the initil mss function of strs or tht it follows the much shllower mss function ssocited with lrge-scle moleculr clouds (Supplementry Fig. 1). Four yers before the dvent of CLUMPFIND, structure trees 9 were proposed s wy to chrcterize clouds hierrchicl structure b Click to rotte Self-grvitting structures All structure v z y (dec.) x (RA) Figure 2 Comprison of the dendrogrm nd CLUMPFIND fetureidentifiction lgorithms s pplied to 13 CO emission from the L1448 region of Perseus., 3D visuliztion of the surfces indicted by colours in the dendrogrm shown in c. Purple illustrtes the smllest scle selfgrvitting structures in the region corresponding to the leves of the dendrogrm; pink shows the smllest surfces tht contin distinct selfgrvitting leves within them; nd green corresponds to the surfce in the dt cube contining ll the significnt emission. Dendrogrm brnches corresponding to self-grvitting objects hve been highlighted in yellow over the rnge of T mb (min-bem temperture) test-level vlues for which the viril prmeter is less thn 2. The x y loctions of the four selfgrvitting leves lbelled with billird blls re the sme s those shown in Fig. 1. The 3D visuliztions show position position velocity (p p v) spce. RA, right scension; dec., declintion. For comprison with the bility of dendrogrms (c) to trck hierrchicl structure, d shows pseudodendrogrm of the CLUMPFIND segmenttion (b), with the sme four lbels used in Fig. 1 nd in. As clumps re not llowed to belong to lrger structures, ech pseudo-brnch in d is simply series of lines connecting the mximum emission vlue in ech clump to the threshold vlue. A very lrge number of clumps ppers in b becuse of the sensitivity of CLUMPFIND to noise nd smll-sclestructurein the dt. In the online PDF version, the 3D cubes ( nd b) cn be rotted to ny orienttion, nd surfces cn be turned on nd off (interction requires Adobe Acrobt version or higher). In the printed version, the front fce of ech 3D cube (the home view in the interctive online version) corresponds exctly to the ptch of sky shown in Fig. 1, nd velocity with respect to the Locl Stndrd of Rest increses from front (20.5 km s 21 ) to bck (8 km s 21 ). 64 using 2D mps of column density. With this erly 2D work s inspirtion, we hve developed structure-identifiction lgorithm tht bstrcts the hierrchicl structure of 3D (p p v) dt cube into n esily visulized representtion clled dendrogrm 10. Although well developed in other dt-intensive fields 11,12, it is curious tht the ppliction of tree methodologies so fr in strophysics hs been rre, nd lmost exclusively within the re of glxy evolution, where merger trees re being used with incresing frequency 13. Figure 3 nd its legend explin the construction of dendrogrms schemticlly. The dendrogrm quntifies how nd where locl mxim of emission merge with ech other, nd its implementtion is explined in Supplementry Methods. Criticlly, the dendrogrm is determined lmost entirely by the dt itself, nd it hs negligible sensitivity to lgorithm prmeters. To mke grphicl presenttion possible on pper nd 2D screens, we fltten the dendrogrms of 3D dt (see Fig. 3 nd its legend), by sorting their brnches to not cross, which elimintes dimensionl informtion on the x xis while preserving ll informtion bout connectivity nd hierrchy. Numbered billird bll lbels in the figures let the reder mtch fetures between 2D mp (Fig. 1), n interctive 3D mp (Fig. 2 online) nd sorted dendrogrm (Fig. 2c). A dendrogrm of spectrl-line dt cube llows for the estimtion of key physicl properties ssocited with volumes bounded by isosurfces, such s rdius (R), velocity dispersion (s v ) nd luminosity (L). The volumes cn hve ny shpe, nd in other work 14 we focus on the significnce of the especilly elongted fetures seen in L1448 (Fig. 2). The luminosity is n pproximte proxy for mss, such tht M lum 5 X 13CO L 13CO, where X 13CO cm 2 K 21 km 21 s (ref. 15; see Supplementry Methods nd Supplementry Fig. 2). The derived vlues for size, mss nd velocity dispersion cn then be used to estimte the role of self-grvity t ech point in the hierrchy, vi clcultion of n observed viril prmeter, obs 5 5s v 2 R/GM lum. In principle, extended portions of the tree (Fig. 2, yellow highlighting) where obs, 2 (where grvittionl energy is comprble to or lrger thn kinetic energy) correspond to regions of p p v spce where selfgrvity is significnt. As obs only represents the rtio of kinetic energy to grvittionl energy t one point in time, nd does not explicitly cpture externl over-pressure nd/or mgnetic fields 16, its mesured vlue should only be used s guide to the longevity (boundedness) of ny prticulr feture. Intensity level Locl mx Test level Locl mx Merge Locl mx Merge 2009 Mcmilln Publishers Limited. All rights reserved Lef Trunk Figure 3 Schemtic illustrtion of the dendrogrm process. Shown is the construction of dendrogrm from hypotheticl one-dimensionl emission profile (blck). The dendrogrm (blue) cn be constructed by dropping test constnt emission level (purple) from bove in tiny steps (exggerted in size here, light lines) until ll the locl mxim nd mergers re found, nd connected s shown. The intersection of test level with the emission is set of points (for exmple the light purple dots) in one dimension, plnr curve in two dimensions, nd n isosurfce in three dimensions. The dendrogrm of 3D dt shown in Fig. 2c is the direct nlogue of the tree shown here, only constructed from isosurfce rther thn point intersections. It hs been sorted nd flttened for representtion on flt pge, s fully representing dendrogrms for 3D dt cubes would require four dimensions. Lef Brnch Lef Goodmn et l. Nture, 2009

20 Semless Astronomy Literture Viewer Semntic Serch Info Viz for Serch Results Dt Viewer (e.g. WWT) Archive Browser Mockup bsed on work of Eli Bressert, excerpted from NASA AISRP proposl by Goodmn, Muench, Christin, Conti, Kurtz, Burke, Accomzzi, McGuinness, Hendler & Wong, 2008

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