From Brown Dwarfs to Giant Planets

From Brown Dwarfs to Giant Planets Stan Metchev (Stony Brook Astronomy Group) PHY 688 seminar in Spring 2009 Artist’s rendition of a brown dwarf: R. Hurt (NASA)

Areas of Interest • Imaging of brown dwarf companions to stars • Properties of nearby brown dwarfs • Modeling of circumstellar disks

giant planet formation Brown Dwarfs: Link between Stars and Giant Planets • no H fusion • substellar objects • <0.08 M ~ 80 MJup • star-like formation • planet-like properties? 211 MJup = 0.2 M M 80 MJup 13 MJup 10 MJup 73 MJup 5 MJup stars brown dwarfs “planets” 1 MJup stars brown dwarfs “planets” Burrows et al. (2001)

The Stellar/Substellar Continuum stars brown dwarfs planets Sun (G dwarf) M dwarf L dwarf T dwarf Jupiter 5700 K ~3500 K ~2000 K ~1000 K 160 K visible light R. Hurt (Caltech/IPAC)

WMAP Brown Dwarfs: Population is Uncertain • detection is challenging • more numerous than stars? • relevance: • bottom of star-like formation • galaxy mass-to-light ratios • dark matter Reid et al. (1999); Allen et al. (2005)

Some Outstanding Questions ??? ??? • What are the properties of substellar companions? • can we image extrasolar planets? • What are the properties of isolated brown dwarfs? • do cooler, planetary-mass objects exist in isolation? • How do planetary systems evolve? • is the Solar System typical?

First L and T Dwarfs Discovered as Companions to Stars Gl 229 B: first T dwarf GD 165 B: first L dwarf J H K U Hawai’i 2.2 m telescope Palomar 1.5 m discovery Hubble Telescope confirmation Becklin & Zuckerman (1988); Nakajima et al. (1995)

HD 18940 A/B AO off 1″ AO on (AO) Palomar AO Brown Dwarfs Companions to Stars • independent constraints on substellar properties: • age • distance (luminosity) • internal chemistry • lowest mass substellar companions: planets • young stars are optimal targets Gl 229 B Nakajima et al. (1995)

What Planets May Look Like Neptune’s orbit (a = 30 AU) Palomar 5m telescope + AO Ks band (2.16µm); Ks = 11.3 mag (104.5) at 2.6” Ks = 13.6 mag (105.4) at 3.3”

planets 10–15% brown dwarfs <0.5% stars ~22% Planet Detection:Precision Radial Velocity Context Mazeh et al. (2003)

stars brown dwarfs conventional AO HST, Gemini, Keck, VLT: now planets Chauvin (2007) Planet Detection:Direct Imaging Has Lagged 100 brown dwarf desert <0.5% companion frequency 10 M2 (MJup) J 1 S Physical Separation (AU)

Companion Imaging Survey Success Rates Survey sensitivity: <13 MJup 13–30 MJup >30 MJup (r.v.) Metchev & Hillenbrand (2008)

Lick 3m California Project 1 Spitzer 0.9m Space Telescope • Search for faint substellar companions to stars • Characterize their atmospheres Keck 3m Hawaii

J H K CIA H2 Brown Dwarf Properties • L dwarfs (stars+brown dwarfs) • metallic hydrides, H2, H2O • T dwarfs (brown dwarfs) • CH4, H2, H2O IRTF Spectral Library, Cushing et al. (2005)

The Stellar/Substellar Continuum stars brown dwarfs planets Sun (G dwarf) M dwarf L dwarf T dwarf Jupiter 5700 K ~3500 K ~2000 K ~1000 K 160 K visible light R. Hurt (Caltech/IPAC)

The Stellar/Substellar Continuum stars brown dwarfs planets Sun (G dwarf) M dwarf L dwarf T dwarf Jupiter 5700 K ~3500 K ~2000 K ~1000 K 160 K near-infrared light R. Hurt (Caltech/IPAC)

L T0–T4 T5–T8 visible near-IR L T L T Brown Dwarf Properties • L dwarfs (stars+brown dwarfs) • metallic hydrides, H2, H2O • red in visible and in near-IR • Teff < 2300 K • T dwarfs (brown dwarfs) • CH4, H2, H2O • red in visible, vast color range in near-IR • Teff < 1400 K F1.6µm / F1.2µm F2.1µm / F1.6µm

2MASS J04454316+2540233 Finding Nearby Brown Dwarfs • near-IR SDSS i (0.8µm) 2MASS J (1.2µm) 2MASS H (1.6µm) 2MASS KS (2.1µm) SDSS z (0.9µm) POSS–I R (0.6µm) POSS–II R (0.6µm) Kirkpatrick et al. (1997) Strauss et al. (1999)

Most L’s and T’s Now Found from Large-Area Imaging Surveys >500 ~100 DwarfArchives.org

10–2 L 10–3 (SpT) [pc–3 SpT–1] 2MASS T0–T4 10–4 T5–T8 10–5 L0 L5 T0 T5 T8 ; Cruz et al. (2007) Cool Brown Dwarfs: Numerous but Difficult to Find Burgasser (2006)

10–2 SDSS i SDSS z 10–3 (SpT) [pc–3 SpT–1] z = 19.1 2MASS 10–4 2MASS J 2MASS KS 10–5 L0 L5 T0 T5 T8 J = 15.9 ; Cruz et al. (2007) ; Metchev et al. (2008) Cool Brown Dwarfs: Use Database Cross-Correlation Burgasser (2006)

Project 2 • complete nearby T dwarf census in SDSS + 2MASS • search for the coolest brown dwarfs NASA IRTF 3m Hawaii Palomar 5m California

Orion protoplanetary disks HST/WFPC2 1" = 400 AU O’Dell & Wien (1994)  Pictoris debris disk Bok globules in IC 2944 HST/WFPC2 500 AU 1´ = 0.5 pc 25" (Kalas & Jewitt 1996) Reipurth et al. (1997) From Stars to Disks to Planets Beckwith (1996)

Disk evolution movie

 Pictoris debris disk 500 AU 25" LIR / Lstar = 10–3 10 Myr (Kalas & Jewitt 1996) Solar System debris disk LIR / Lstar = 10–7 4.5 Gyr (P. Kalas, UC Berkeley) Debris Disks:Context for the Solar System • zodiacal light, asteroid belt, Kuiper belt analogs

Beichman et al. (2005) Debris Disks:Context for the Solar System • zodiacal light, asteroid belt, Kuiper belt analogs • comets

HD 107146 disk HST/ACS (Ardila et al. 2004) Solar System model 23 µm grains 60 AU (Liou & Zook 1999) Debris Disks:Context for the Solar System • zodiacal light, asteroid belt, Kuiper belt analogs • comets • embedded planets

Evidence for Embedded Planets is Strong: Fomalhaut Kalas et al. (2005) HST/ACS 13" 100 AU a = 119 AU planet(Quillen 2006)

Solar System model Liou & Zook (1999) HD 107146: A Face-on Ring (HST) 50–200 AU HST survey of 40 more debris disks Metchev et al., in preparation

Project 3 Hubble 2.4m Space Telescope • Analyze the properties of circumstellar debris disks • Search for dynamical evidence of embedded planets Spitzer 0.9m Space Telescope

Areas of Interest • Imaging of substellar companions • Properties of nearby brown dwarfs • Modeling of debris disks

From Brown Dwarfs to Giant Planets