Unveiling the nature of bright z ~ 7 galaxies with HST and JWST Rebecca Bowler Hintze Fellow, University of Oxford Nicholas Kurti Junior Fellow, Brasenose College with Jim Dunlop, Ross McLure, Derek McLeod, Matt Jarvis, Elizabeth Stanway, JJ Eldridge, and the UltraVISTA and VIDEO teams
high-redshift galaxies with HST Hubble Ultra-Deep Field Hubble Frontier Fields
Bright galaxies into the EoR CANDELS 0.2 deg
Bright galaxies into the EoR CANDELS is not enough to find the very brightest galaxies Hubble Ultra Deep Field CANDELS GOODS North and South CANDELS EGS CANDELS COSMOS CANDELS UDS Ground-based near-infrared data from: UltraVISTA* in COSMOS, UKIDSS and VIDEO* in the UDS Total area = 1.7 sq. deg UltraVISTA Survey / COSMOS field UKIDSS Ultra Deep Survey / Subaru XMM-Newton Deep Survey *ESO Public Surveys
Bright galaxies into the EoR Lyman-break galaxies as bright as mab = 24, without lensing ~ few per sq. degree for the brightest LBGs Hubble Ultra Deep Field CANDELS GOODS North and South CANDELS EGS CANDELS COSMOS CANDELS UDS UltraVISTA Survey / COSMOS field UKIDSS Ultra Deep Survey / Subaru XMM-Newton Deep Survey HST surveys e.g. CANDELS, UDF+ Ground-based
Bright galaxies into the EoR Such galaxies are unlikely to be found in JWST surveys e.g. NIRCam/NIRSpec GTO surveys Deep ~ tens sq. arcmin Wide 400 sq. arcmin (< CANDELS) Hubble Ultra Deep Field CANDELS GOODS North and South CANDELS EGS CANDELS COSMOS CANDELS UDS UltraVISTA Survey / COSMOS field UKIDSS Ultra Deep Survey / Subaru XMM-Newton Deep Survey Bright z > 6 LBGs provide a unique probe of galaxy properties during the EoR: accessible by JWST, ALMA, ELTs
HST/WFC3 imaging of bright z ~ 7 LBGs S/N > 20 Ground-based HST/WFC3 Targeted follow-up: one object per orbit 17 galaxies z > 6.5, reaching Muv ~ -23
HST/WFC3 imaging of bright z ~ 7 LBGs 3 /16kpc Ground-based HST/WFC3
HST/WFC3 imaging of bright z ~ 7 LBGs 3 /16kpc Himiko Ouchi et al. 2009, 2013 CR7 Sobral et al. 2015
Bright galaxies in the most ionized regions? Fraction of LBGs with Lyα Faint Bright Curtis-Lake et al. 2012 Oesch et al. 2016 e.g. Schenker et al. 2014 + Stark et al. 2015, 2017, Zitrin et al. 2015 Roberts-Borsani et al. 2015 Lyα can escape the brightest galaxies at z > 7 - ionised bubbles? Also see other rest-frame UV lines, CIV, CIII] To study the Lyα escape will require wide-area (CANDELS+) surveys and targeted follow-up of the brightest sources
Bright LBGs : the view from JWST 1) Spectroscopy of rest-frame UV and optical nebular emission lines Maseda et al. 2014 Wuyts et al. 2012 2) Resolved imaging of the rest-frame optical
Bright LBGs : the view from JWST 1) Spectroscopy of rest-frame UV and optical nebular emission lines R =100, t ~ 8 min R=1000, t < 1hr [OII] [OIII] Hα Hβ [NII] c/o Marijn Franx NIRSpec will clearly detect these lines + the continuum Metallicity, Ionisation parameter, temperature indicators Balmer break measured directly Also access to rest-frame UV lines
1) Spectroscopy of rest-frame UV/optical nebular emission
1) Spectroscopy: Pop III/DCBH signatures in CR7 @ z = 6.6? [Direct collapse black hole] CR7 is extreme LAE @ z = 6.6 in COSMOS He II 1640 line observed EW0 = 80±20A He II is strong and narrow, no metal lines. Sobral et al. 2015
1) Spectroscopy: Pop III/DCBH signatures in CR7 @ z = 6.6? CR7 is extreme LAE @ z = 6.6 in COSMOS He II 1640 line observed EW0 = 80±20A He II is strong and narrow, no metal lines. Sobral et al. 2015 Sobral et al. 2015 Visbal et al. 2016 Pop III? DCBH? other? Bowler et al. 2017b Pallottini et al. 2015 Hartwig et al. 2015 Agarwal et al. 2016 Smidt et al. 2016 Smith et al. 2016 Dijkstra et al. 2016 Pacucci et al. 2017 Agarwal et al. 2017
1) Spectroscopy: Pop III/DCBH signatures in CR7 @ z = 6.6? CR7 is extreme LAE @ z = 6.6 in COSMOS He II 1640 line observed EW0 = 80±20A He II is strong and narrow, no metal lines. Sobral et al. 2015 Pop III? DCBH? other? Bowler et al. 2017b Sobral et al. 2015 Visbal et al. 2016 Pallottini et al. 2015 Hartwig et al. 2015 Agarwal et al. 2016 Smidt et al. 2016 Smith et al. 2016 Dijkstra et al. 2016 Pacucci et al. 2017 Agarwal et al. 2017
1) Spectroscopy: Pop III/DCBH signatures in CR7 @ z = 6.6? UltraVISTA DR3 + deconfused Spitzer SPLASH data Sobral et al. 2015 Bowler et al. 2017b
1) Spectroscopy: Pop III/DCBH signatures in CR7 @ z = 6.6? Hβ [OIII] 4959, 5007 UltraVISTA DR3 + deconfused Spitzer SPLASH data Lower HeII EW = 40±30A Hα Sobral et al. 2015 Bowler et al. 2017b
1) Spectroscopy: Pop III/DCBH signatures in CR7 @ z = 6.6? Pop III DCBH Pop III? DCBH? other? Normal stellar populations or an AGN, with strong [OIII] 5007 emission can reproduce the colours
1) Spectroscopy: Pop III/DCBH signatures in CR7 @ z = 6.6? IRAC colour of CR7 is exactly what you expect for contamination of ch1 by [OIII] (as in other z ~ 6-8 LBGs) Pacucci et al. 2017, also Agarwal et al. 2017 CR7 He II 1640 emission is still a puzzle. Could be AGN (as supported by line ratios in the UV + point-like core) Or young stellar population with binary populations (e.g. BPASS models) More objects with rest UV/optical spectroscopy will be key: JWST
1) Spectroscopy: bright galaxies or faint quasars? Bowler et al. 2014 Galaxies Quasars z ~ 6 quasar search by Matsuoka et al. 2016 Potential region of overlap
1) Spectroscopy: combination with far-ir measurements Measured with ALMA e.g. the dusty normal galaxy at z = 7.5 from Watson et al. (2015) bluer Bowler+ in prep. ALMA band 6 imaging of six bright LBGs at z ~ 7 redder Balmer decrement and β measured by NIRSpec can be directly compared to ALMA results
2) Resolved imaging of the rest-frame optical Rest-frame UV Rest-frame optical SF galaxies at z ~ 1 Wuyts et al. 2012 The brightest LBGs into the EoR, are they: Merging galaxies or clumpy galaxies? Merging could explain high SFRs Clumps are expected in gas rich high-z galaxies
2) Resolved imaging of the rest-frame optical z = 2-3 SF galaxies Elmegreen et al. 2005 Guo et al. (2015) Rest-frame UV `chain `clump-cluster double-core galaxies Rest-frame optical NIRCam will reveal the underlying rest-frame optical profile WFC3 FWHM ~ 0.2, NIRCam <~ 0.1 S/N ~ 50 for < 10 min
2) Resolved imaging of the rest-frame optical Deep data required below the break to confirm that the clumps are at high-z: e.g HST/ACS imaging at z ~ 6 [regime where Hα is covered by NIRSpec] Lower redshift galaxies along the line-of-sight to high-z galaxy (centre)
2) Resolved imaging of the rest-frame optical Size-luminosity relation at z ~ 7 from the rest-frame UV (HST/WFC3)
2) Resolved imaging of the rest-frame optical Size-luminosity relation at z ~ 7 from the rest-frame UV (HST/WFC3) Large range of sizes for the brightest galaxies, driven by clumpy morphology Is there a smoother underlying older population: mergers or clumps?
Summary Using ground-based data from the UltraVISTA + UDS we now have samples of extremely bright star-forming galaxies at z = 7 The sample is ideal for detailed follow-up with HST, ALMA, and JWST HST reveals a clumpy, extended morphology, deep F814W essential CR7 - inferred [OIII] emission argues against Pop III or DCBH interpretation With JWST: Rest-frame optical emission lines Test of PopIII/DCBH nature of CR7- like objects Detection of faint quasars? The impact of dust at z > 6 Underly morphology of the rest-frame optical A more robust measure of galaxy size at early times