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Evolution of protoplanetary disks Some new rules for planet- and star-formers, from the bounty of the Spitzer and Herschel missions.Dan WatsonUniversity of RochesterFor the Spitzer Infrared Spectrograph (IRS) Team and the Herschel Orion Protostar Survey (HOPS). H/t to Neal Evans and his Cores to Disks (c2d) and DIGIT teams.

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Outline and conclusionsSpitzer-IRS and Herschel-PACS had poor spatial and spectral resolution by Townes-group standards, but their limitations did not prevent the making of substantial discoveries in the domain of protoplanetary disk evolution and planet formation:Giant planets form within a few Myr of their stars.Disks dissipate photo-evaporatively in 3-5 Myr.Prebiotic molecules are abundant in the planet-formation regions of protoplanetary disks.Dust in disks settles to midplane during the protostellar phase (< 0.5 Myr).Crystalline-dust mass fraction of disks increases with age, 0.7-5 Myr.

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Giant planets form within a few Myr of their stars.Transitional disks: mid-IR spectral gaps in Class II YSOs = 3-30 AU, sharp-edged gaps in disks = carved by recently-formed giant planets. Gap verified: SMA, CARMA, PdBI and ALMA.Time scale consistent with Saturn. Up to 20% of Class II objects, even in the youngest clusters (e.g. NGC 1333, Orion). Many TDs in ALMAs grasp; many of their planets in the grasp of GPI, SPHERE, etc.

DAlessio et al 2005; Calvet et al. 2005; Brown et al. 2007; Espaillat et al. 2007, 2008, 2010, 2012; Kim et al. 2009, 2013; Merin et al. 2010.

3Espaillat et al. 2007

rgap = 46 AUGiant planets form within a few Myr of their stars.Transitional disks: mid-IR spectral gaps in Class II YSOs = 3-30 AU, sharp-edged gaps in disks = carved by recently-formed giant planets. Gap verified: SMA, CARMA, PdBI and ALMA.Time scale consistent with Saturn. Up to 20% of Class II objects, even in the youngest clusters (e.g. NGC 1333, Orion). Many TDs in ALMAs grasp; many of their planets in the grasp of GPI, SPHERE, etc.

DAlessio et al 2005; Calvet et al. 2005; Brown et al. 2007; Espaillat et al. 2007, 2008, 2010, 2012; Kim et al. 2009, 2013; Merin et al. 2010.

4Andrews et al. 2011

rgap = 49 AU Giant planets form within a few Myr of their stars.Transitional disks: mid-IR spectral gaps in Class II YSOs = 3-30 AU, sharp-edged gaps in disks = carved by recently-formed giant planets. Gap verified: SMA, CARMA, PdBI and ALMA.Time scale consistent with Saturn. Up to 20% of Class II objects, even in the youngest clusters (e.g. NGC 1333, Orion). Many TDs in ALMAs grasp; many of their planets in the grasp of GPI, SPHERE, etc.

DAlessio et al 2005; Calvet et al. 2005; Brown et al. 2007; Espaillat et al. 2007, 2008, 2010, 2012; Kim et al. 2009, 2013; Merin et al. 2010.

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IapetusCastillo-Rogez et al. 2013Giant planets form within a few Myr of their stars.Transitional disks: mid-IR spectral gaps in Class II YSOs = 3-30 AU, sharp-edged gaps in disks = carved by recently-formed giant planets. Gap verified: SMA, CARMA, PdBI and ALMA.Time scale consistent with Saturn. Up to 20% of Class II objects, even in the youngest clusters (e.g. NGC 1333, Orion). Many TDs in ALMAs grasp; many of their planets in the grasp of GPI, SPHERE, etc.

DAlessio et al 2005; Calvet et al. 2005; Brown et al. 2007; Espaillat et al. 2007, 2008, 2010, 2012; Kim et al. 2009, 2013; Merin et al. 2010.

6Kim et al. 2013

Giant planets form within a few Myr of their stars.Transitional disks: mid-IR spectral gaps in Class II YSOs = 3-30 AU, sharp-edged gaps in disks = carved by recently-formed giant planets. Gap verified: SMA, CARMA, PdBI and ALMA.Time scale consistent with Saturn. Up to 20% of Class II objects, even in the youngest clusters (e.g. NGC 1333, Orion). Many TDs in ALMAs grasp; many of their planets in the grasp of GPI, SPHERE, etc.

DAlessio et al 2005; Calvet et al. 2005; Brown et al. 2007; Espaillat et al. 2007, 2008, 2010, 2012; Kim et al. 2009, 2013; Merin et al. 2010.

7Kim 2013, Ph.D. dissertation, University of Rochester

Disks dissipate photoevaporatively in 3-5 Myr.Late stage: photoevaporative flow, visible in mid-IR fine structure and recombination lines, particularly [Ne II] and Hu .

Getting there: linear relation between mass-loss rate and accretion rate runs all the way through Class 0 and Class II, as measured with [O I], [Si II] and [Fe II].

Hollenbach said it all along, but:

Alexander et al. 2006, Najita et al. 2009, Hollenbach & Gorti 2009, Pascucci et al. 2011, Watson et al. 2015.

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Disks dissipate photoevaporatively in 3-5 Myr.Late stage: photoevaporative flow, visible in mid-IR fine structure and recombination lines, particularly [Ne II] and Hu .

Getting there: linear relation between mass-loss rate and accretion rate runs all the way through Class 0 and Class II, as measured with [O I], [Si II] and [Fe II].

Hollenbach said it all along, but:

Alexander et al. 2006, Najita et al. 2009, Hollenbach & Gorti 2009, Pascucci et al. 2011, Watson et al. 2015.

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Watson et al. 2015Prebiotic molecules are abundant in the planet-formation regions of protoplanetary disks.Well, duh, but now we can see it:

WaterHCN, CO2, C2H2PAHsIce line: the far-infrared lines of water which would be most prominent in cooler gas at larger r are much fainter, and ice emission features are observed.

e.g. Carr & Najita 2007, Najita et al. 2013, Sargent et al. 2014, McClure et al. 2015.

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AA Tau, FM Tau, DH Tau (top-bottom)Prebiotic molecules are abundant in the planet-formation regions of protoplanetary disks.Well, duh, but now we can see it:

WaterHCN, CO2, C2H2PAHsIce line: the far-infrared lines of water which would be most prominent in cooler gas at larger r are much fainter, and ice emission features are observed.

e.g. Carr & Najita 2007, Najita et al. 2013, Sargent et al. 2014, McClure et al. 2015.

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Prebiotic molecules are abundant in the planet-formation regions of protoplanetary disks.Well, duh, but now we can see it:

WaterHCN, CO2, C2H2PAHsIce line: the far-infrared lines of water which would be most prominent in cooler gas at larger r are much fainter, and ice emission features are observed.

e.g. Carr & Najita 2007, Najita et al. 2013, Sargent et al. 2014, McClure et al. 2015.

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McClure et al. 2015Dust in disks settles to midplane during the protostellar phase (< 0.5 Myr).Range of HCN/H2O = range of degree of self-extinction, and thus sedimentation.Models of spectra demand similar dust settling, suggest continuum spectral indices to measure it.Degree of sedimentation same for all clusters of Class II objects, 0.5-5 Myr: sedimentation complete by then, as long expected theoretically. Thus its no wonder that planets have already formed in the embedded disk of the Class I protostar HL Tau: dust concentration at mid-plane enhances core-accretion processes very early.

DAlessio et al. 2001, 2006; Furlan et al. 2005, 2006, 2008, 2011.

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Dust in disks settles to midplane during the protostellar phase (< 0.5 Myr).Range of HCN/H2O = range of degree of self-extinction, and thus sedimentation.Models of spectra demand similar dust settling, suggest continuum spectral indices to measure it.Degree of sedimentation same for all clusters of Class II objects, 0.5-5 Myr: sedimentation complete by then, as long expected theoretically. Thus its no wonder that planets have already formed in the embedded disk of the Class I protostar HL Tau: dust concentration at mid-plane enhances core-accretion processes very early.

DAlessio et al. 2001, 2006; Furlan et al. 2005, 2006, 2008, 2011.

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5 10 20 50GO Tau = 0.001 = 0.01 = 0.1 = 1Star10-9

10-10F (erg sec-1 cm-2)Wavelength (m)Models

HSTModelDust in disks settles to midplane during the protostellar phase (< 0.5 Myr).Range of HCN/H2O = range of degree of self-extinction, and thus sedimentation.Models of spectra demand similar dust settling, suggest continuum spectral indices to measure it.Degree of sedimentation same for all clusters of Class II objects, 0.5-5 Myr: sedimentation complete by then, as long expected theoretically. Thus its no wonder that planets have already formed in the embedded disk of the Class I protostar HL Tau: dust concentration at mid-plane enhances core-accretion processes very early.

DAlessio et al. 2001, 2006; Furlan et al. 2005, 2006, 2008, 2011.

15Molecular-line fluxes from Najita et al. 2013; n13-31 from Furlan et al. 2011.

Dust in disks settles to midplane during the protostellar phase (< 0.5 Myr).Range of HCN/H2O = range of degree of self-extinction, and thus sedimentation.Models of spectra demand similar dust settling, suggest continuum spectral indices to measure it.Degree of sedimentation same for all clusters of Class II objects, 0.5-5 Myr: sedimentation complete by then, as long expected theoretically. Thus its no wonder that planets have already formed in the embedded disk of the Class I protostar HL Tau: dust concentration at mid-plane enhances core-accretion processes very early.

DAlessio et al. 2001, 2006; Furlan et al. 2005, 2006, 2008, 2011.

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Data: n13-31 vs. 10-m silicate equivalent width for 750 protoplanetary disks in six nearby associations. Contour intervals are linear.Models: = 1 = 0.1 = 0.01 = 0.001 Radially-continuous disksTransitional disksDust in disks settles to midplane during the protostellar phase (< 0.5 Myr).Range of HCN/H2O = range of degree of self-extinction, and thus sedimentation.Models of spectra demand similar dust settling, suggest continuum spectral indices to measure it.Degree of sedimentation same for all clusters of Class II objects, 0.5-5 Myr: sedimentation complete by then, as long expected theoretically. Thus its no wonder that planets have already formed in the embedded disk of the Class I protostar HL Tau: dust concentration at mid-plane enhances core-accretion processes very early.DAlessio et al. 2001, 2006; Furlan et al. 2005, 2006, 2008, 2011.

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HL Tau at 870 mALMA Early Science Team 2015The crystalline-dust mass fraction of disks increases with age, 0.7-5 Myr.No statistically-significant difference in large-grain mass fractions, among clusters in this age range. Crystalline component of suspended submicron grains evolves.Notably silica, which increases from very small numbers to 5-10% of the crystalline silicates in the outer disk.Concordance: high-temperature silica demands the same formation conditions as chondrules, which in the presolar nebula were produced over the course of 0.5-5 Myr (Connelly et al. 2012). Sargent et al. 2006, 2009; Kessler et al 2006; Bouwman et al. 2008; Olofsson et al. 2013; Koch et al. 2015

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OriA-254Large warm grainsK-S testsDp (%)Taurus-ONC0.1116Taurus-L16410.1180Koch et al. 2015The crystalline-dust mass fraction of disks increases with age, 0.7-5 Myr.No statistically-significant difference in large-grain mass fractions, among clusters in this age range. Crystalline component of suspended submicron grains evolves.Notably silica, which increases from very small numbers to 5-10% of the crystalline silicates in the outer disk.Concordance: high-temperature silica demands the same formation conditions as chondrules, which in the presolar nebula were produced over the course of 0.5-5 Myr (Connelly et al. 2012). Sargent et al. 2006, 2009; Kessler et al 2006; Bouwman et al. 2008; Olofsson et al. 2013; Koch et al. 2015

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ZZ TauCourtesy Dave Joswiak, Don Brownlee, and Graciela MatrajtSargent et al. 2009The crystalline-dust mass fraction of disks increases with age, 0.7-5 Myr.No statistically-significant difference in large-grain mass fractions, among clusters in this age range. Crystalline component of suspended submicron grains evolves.Notably silica, which increases from very small numbers to 5-10% of the crystalline silicates in the outer disk.Concordance: high-temperature silica demands the same formation conditions as chondrules, which in the presolar nebula were produced over the course of 0.5-5 Myr (Connelly et al. 2012). Sargent et al. 2006, 2009; Kessler et al 2006; Bouwman et al. 2008; Olofsson et al. 2013; Koch et al. 2015

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Warm enstatiteDp (%)Taurus-ONC0.5210-8Taurus-L16410.4810-7Cold silicaDp (%)Taurus-ONC0.3710-5Taurus-L16410.4510-6Koch et al. 2015