1. Evolution of protoplanetary disks Some new rules for planet- and star-formers, from the bounty of the Spitzer and Herschel missions. Dan Watson University of Rochester For 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. 1

2. Outline and conclusions Spitzer-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. 2

3. 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 ALMA’s grasp; many of their planets in the grasp of GPI, SPHERE, etc. D’Alessio 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. 3 Espaillat et al. 2007 r gap = 46 AU

4. 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 ALMA’s grasp; many of their planets in the grasp of GPI, SPHERE, etc. D’Alessio 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. 4 Andrews et al. 2011 r gap = 49 AU

5. 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 ALMA’s grasp; many of their planets in the grasp of GPI, SPHERE, etc. D’Alessio 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. 5 Iapetus Castillo-Rogez et al. 2013

6. 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 ALMA’s grasp; many of their planets in the grasp of GPI, SPHERE, etc. D’Alessio 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. 6 Kim et al. 2013

7. 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 ALMA’s grasp; many of their planets in the grasp of GPI, SPHERE, etc. D’Alessio 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. 7 Kim 2013, Ph.D. dissertation, University of Rochester

8. 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. 8

9. 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. 9 Watson et al. 2015

10. Prebiotic molecules are abundant in the planet- formation regions of protoplanetary disks. Well, duh, but now we can see it:  Water  HCN, CO 2, C 2 H 2  PAHs  Ice 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. 10 AA Tau, FM Tau, DH Tau (top-bottom)

11. Prebiotic molecules are abundant in the planet- formation regions of protoplanetary disks. Well, duh, but now we can see it:  Water  HCN, CO 2, C 2 H 2  PAHs  Ice 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. 11

12. Prebiotic molecules are abundant in the planet- formation regions of protoplanetary disks. Well, duh, but now we can see it:  Water  HCN, CO 2, C 2 H 2  PAHs  Ice 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. 12 McClure et al. 2015

13. Dust in disks settles to midplane during the protostellar phase (< 0.5 Myr).  Range of HCN/H 2 O = 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 it’s 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. D’Alessio et al. 2001, 2006; Furlan et al. 2005, 2006, 2008, 2011. 13

14. Dust in disks settles to midplane during the protostellar phase (< 0.5 Myr).  Range of HCN/H 2 O = 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 it’s 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. D’Alessio et al. 2001, 2006; Furlan et al. 2005, 2006, 2008, 2011. 14 5 10 20 50 GO Tau ε = 0.001 ε = 0.01 ε = 0.1 ε = 1 Star 10 -9 10 -10 νF ν (erg sec -1 cm -2 ) Wavelength (μm) Models HSTModel

15. Dust in disks settles to midplane during the protostellar phase (< 0.5 Myr).  Range of HCN/H 2 O = 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 it’s 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. D’Alessio et al. 2001, 2006; Furlan et al. 2005, 2006, 2008, 2011. 15 Molecular-line fluxes from Najita et al. 2013; n 13-31 from Furlan et al. 2011.

16. Dust in disks settles to midplane during the protostellar phase (< 0.5 Myr).  Range of HCN/H 2 O = 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 it’s 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. D’Alessio et al. 2001, 2006; Furlan et al. 2005, 2006, 2008, 2011. 16 Data: n 13-31 vs. 10-  m silicate equivalent width for 750 protoplanetary disks in six nearby associations. Contour intervals are linear. Models: ε = 1 ε = 0.1 ε = 0.01 ε = 0.001 Radially- continuous disks Transitional disks

17. Dust in disks settles to midplane during the protostellar phase (< 0.5 Myr).  Range of HCN/H 2 O = 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 it’s 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. D’Alessio et al. 2001, 2006; Furlan et al. 2005, 2006, 2008, 2011. 17 HL Tau at 870  m ALMA Early Science Team 2015

18. The 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 18 OriA-254 Large warm grains Koch et al. 2015

19. The 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 19 ZZ Tau Courtesy Dave Joswiak, Don Brownlee, and Graciela Matrajt Sargent et al. 2009

20. The 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 20 Koch et al. 2015