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

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, Myr. 2

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 Espaillat et al r gap = 46 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 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 Andrews et al r gap = 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 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 Iapetus Castillo-Rogez 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 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 Kim 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 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 Kim 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

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 Watson et al. 2015

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 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:  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

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 McClure et al. 2015

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, 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,

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, 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, GO Tau ε = ε = 0.01 ε = 0.1 ε = 1 Star νF ν (erg sec -1 cm -2 ) Wavelength (μm) Models HSTModel

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, 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, Molecular-line fluxes from Najita et al. 2013; n from Furlan et al

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, 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, Data: n 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 = Radially- continuous disks Transitional disks

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, 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, HL Tau at 870  m ALMA Early Science Team 2015

The crystalline-dust mass fraction of disks increases with age, 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 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 OriA-254 Large warm grains Koch et al. 2015

The crystalline-dust mass fraction of disks increases with age, 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 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 ZZ Tau Courtesy Dave Joswiak, Don Brownlee, and Graciela Matrajt Sargent et al. 2009

The crystalline-dust mass fraction of disks increases with age, 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 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 Koch et al. 2015