A LARGE-SCALE VIEW OF THE DISTANT UNIVERSE STEVE FINKELSTEIN THE - PowerPoint PPT Presentation

A LARGE-SCALE VIEW OF THE DISTANT UNIVERSE STEVE FINKELSTEIN THE UNIVERSITY OF TEXAS AT AUSTIN IMAGE CREDIT: JASON JAACKS

A LARGE-SCALE VIEW OF THE DISTANT UNIVERSE PRIMER: REDSHIFT AND LOOKBACK TIME Lookback time = Lookback time = Lookback time = 13.3-13.6 Gyr 12.9-13.3 Gyr 12.9-13.3 Gyr 200-500 Myr after 0.5-1 Gyr after 1-3 Gyr after Big Bang Big Bang Big Bang 13.5 Hubble Sequence Epoch of 13 Emergence of Lookback Time (Gyr) Galaxy 12.5 Epoch of Formation 12 Reionziation 11 Epoch of 10 Galaxy Assembly 8 6 0 0 2 4 6 8 10 12 14 Redshift

A LARGE-SCALE VIEW OF THE DISTANT UNIVERSE (SOME) QUESTIONS WE HAVE ANSWERED WITH HUBBLE Time Since Big Bang (Gyr) 10 5 3 2 1.5 1 0.8 0.6 0.5 0.0 FINKELSTEIN 16 − 0.5 − 3 ) Unresolved − 1 Mpc Galaxies ▸ Galaxies exist in great number between − 1.0 log Cosmic SFRD (M yr − 1.5 500 Myr and 1 Gyr after the Big Bang, and Total SFR D e n s i t y r − 2.0 Reference Bouwens+15 the cosmic star-formation rate density − 2.5 r Finkelstein+15 McLeod+15 Reference Oesch+13/14 − 3.0 MD+14 evolves smoothly upward from z=8 to z=4 Oesch+14 MD+14 − 3.5 < 0 2 4 6 8 10 (e.g, work by Bowler+, Bouwens+, Redshift � Finkelstein+, McLeod+, Oesch+, McLure+, r ~ t � r Ishigaki+). BOUWENS+14 � � t ▸ Even the smallest galaxies we can see with t ~ r µ + - ~ r Hubble are still enriched by previous = � generations of star-formation (e.g., > r Bouwens+12,14, Finkelstein+12, r > Dunlop+13, Rogers+14, Smit+15). ▸ Galaxies alone could reionize the universe ROBERTSON+15 if their ionizing photon escape fractions are ��C�9�/2�2����:�6�����CCC 1/:0�72�� ����1��� �.�7����7��������D/���70�/�7����������,��������/��������������0��1������6���/:0�72�����������:����������/�/79/09��/��6�����CCC 1/:0�72�� ����1�������:� relatively high, >10% (e.g., Kuhlen 12, 6������2D 2�7 ������ ������/�/ ���� �� � Finkelstein+12, Robertson+13,15, - Bouwens+15b, Livermore+17). t = � 2 ~ r t ) r � � > ~

A LARGE-SCALE VIEW OF THE DISTANT UNIVERSE Oesch+14 Time [Gyr] 2 1.4 1 0.8 0.6 0.5 0.4 QUESTIONS WE HOPE TO ANSWER WITH JWST − 1 log SFR Density [M /yr/Mpc 3 ] − 1.5 − 2 − 2.5 > 0.7 M /yr ∝ ( 1 + z 3 ) − . 6 − 3 GOODS − N/S + HUDF09/XDF − 3.5 previous CDFS (Oesch+13) ▸ When is the epoch of the first galaxies? ∝ (1+z) − 10.9 Ellis+13 (corrected) − 4 CLASH − 4.5 3 4 5 6 7 8 9 10 11 12 13 Redshift ▸ What is the evolution of the cosmic SFR density at z > 8? Glazebrook+17 ▸ Are the galaxies we can see enriched by Population II star-formation? ▸ Have we missed anything with our UV-only view of the distant universe? 25.0 log ε 912 (erg s − 1 Mpc − 3 Hz − 1 ) AGN EMISSIVITY ▸ How do the conditions for star-formation 24.5 and black hole growth evolve with cosmic 24.0 time (e.g., spectroscopic studies)? 23.5 Finkelstein+17 23.0 0 2 4 6 Redshift

A LARGE-SCALE VIEW OF THE DISTANT UNIVERSE WHAT WFIRST BRINGS TO THE TABLE: SCIENCE ENABLED BY A ~100X INCREASE IN FOV 4 4 4 WFIRST HLS ~500 hr GO program 2 2 2 log Area (deg 2 ) log Area (deg 2 ) log Area (deg 2 ) WFIRST 3 deg 2 WFIRST 1 deg 2 0 0 0 CANDELS CANDELS CANDELS WFIRST WFC FOV Wide Wide Wide JWST JWST "CANDELS" "CANDELS" CANDELS CANDELS CANDELS UDF/HFF UDF/HFF UDF/HFF JWST JWST JWST JWST -2 -2 -2 Deep Deep Deep Parallels Parallels Parallels FFs FFs UDF UDF NIRCam FOV NIRCam FOV HFFs HFFs HFFs WFC3 FOV WFC3 FOV WFC3 FOV HUDF HUDF HUDF ( µ =5) ( µ =5) ( µ =5) 26 26 26 28 28 28 30 30 30 32 32 32 Apparent AB Magnitude Apparent AB Magnitude Apparent AB Magnitude

A LARGE-SCALE VIEW OF THE DISTANT UNIVERSE THE KINDS OF NUMBERS WE’RE DEALING WITH Expected # Expected # Redshift ▸ Predictions assume smoothly evolving (HLS) (deg 2 GO) Schechter UV LF (Finkelstein 16). 6 ~3,300,000 ~21,000 ▸ Limiting magnitudes = 26.5 for HLS (except for z=7, which is limited by z’ LSST =26.2 depth), 7 ~530,000 ~9200 with empirically derived (from HST) magnitude-dependent completeness applied. 8 ~280,000 ~4000 2 ▸ GO deg survey is a roughly 500 hr survey observing one square degree to m~29. 9 ~75,000 ~1700 ▸ To survey a sq. deg. with JWST to this 10 ~19,000 ~700 depth would take several 1000’s of hours of integration, plus extensive overheads. 10000 10 5 z=7 z=10 HLS 1000 10 4 Number per bin Number per bin 10 3 100 10 2 GO 10 10 1 1 10 0 -23 -22 -21 -20 -19 -18 -17 -23 -22 -21 -20 -19 -18 -17 Absolute UV Magnitude Absolute UV Magnitude

A LARGE-SCALE VIEW OF THE DISTANT UNIVERSE OPEN QUESTIONS FOR WFIRST ▸ HST and JWST are severely limited in volumes that they can simultaneously probe. The following are some high priority questions likely to remain open in ~a decade: ▸ How do the physics which regulate star-formation evolve with cosmic time? ▸ How has cosmic variance affected our current results, particularly at faint luminosities? ▸ What is the impact of environment on reionization and galaxy evolution? ▸ What is the large-scale distribution of the detectability of Ly α emission in the epoch of reionization? ▸ What is the contribution of AGNs to reionization?

A LARGE-SCALE VIEW OF THE DISTANT UNIVERSE OPEN QUESTIONS FOR WFIRST 0.1 ▸ How do the physics which regulate star-formation 0.01 BEHROOZI+15 evolve with cosmic time? M * / M h z = 4, Behroozi et al. (2013) ▸ A phenomenological model which assumes that the z = 5, Behroozi et al. (2013) z = 6, Behroozi et al. (2013) 0.001 star-formation rate tracks the halo mass accretion z = 7, Behroozi et al. (2013) z = 8, Behroozi et al. (2013) z = 9.6, Median Prediction rate predict that the ratio of stellar-mass formed to z = 10.8, Median Prediction z = 12.5, Median Prediction z = 15.0, Median Prediction halo mass (SMHM) increases with increasing redshift 0.0001 9 10 11 12 10 10 10 10 at z > 4 (Behroozi+13, Behroozi & Silk+15). M h [M O • ] ▸ This implies that galaxies are perhaps better at 10 − 3 converting gas into stars at higher redshifts, counter z = 7 to a variety of theoretical predictions (e.g., lower-Z Currently permitted ϕ (# Mag − 1 Mpc − 3 ) should reduce SF efficiency). Other factors, such as 10 − 4 range of models reduced negative feedback effects, could be at play. 10 − 5 ▸ One example - changing the timescale for converting gas into stars (Somerville+12) by a factor Finkelstein+15 of four results in large changes at the bright end! 10 − 6 Bouwens+15 UltraVISTA ▸ Current volumes probed do not contain (Bowler+14) 10 − 7 enough galaxies to constrain these physics! − 23 − 22 − 21 − 20 − 19 M UV

A LARGE-SCALE VIEW OF THE DISTANT UNIVERSE OBSERVATIONAL EVIDENCE? HARIKANE+17 ▸ Galaxy clustering results have observationally found a similar trend - higher SMHM at fixed halo mass (Harikane+16,17). ▸ A similar result was found via abundance matching the UV luminosity function, and looking at evolution at fixed UV magnitude (~fixed stellar mass; Observed Data 0.06 Finkelstein+15b), though this is subject to UV scatter, Stellar Mass/Halo Mass (M UV =-21) Observed Fit (4<z<7) Observed Fit (z>6) 0.05 FINKELSTEIN+15B and nebular contamination in M* estimates. Predicted 0.04 ▸ Stefanon+17 found less evolution via Unknown 0.03 Evolution rest-z’ luminosity function abundance at z > 6 0.02 matching, though they were exploring 0.01 progenitors/descendants, and had small 0.00 0 2 4 6 8 10 Redshift numbers at z > 5. ▸ Most of these studies are limited by small STEFANON+17 sample sizes (the clustering study used HSC, so had large samples, but potentially much higher sample contamination), so conclusions remain difficult.

A LARGE-SCALE VIEW OF THE DISTANT UNIVERSE FURTHER OBSERVATIONAL EVIDENCE? ▸ There is now some evidence that the bright end of the UV luminosity function may be “super”-Schechter, e.g., a double power law (e.g., Bowler+14, 15; Ono+17, Stefanon+17, Stevans in prep). ▸ Interesting physics? Dust attenuation? Contamination by Stevans+17 AGNs? z=4 UV luminosity function BY UT student Matt Stevans, using ~20 deg 2 SHELA survey data, and simultaneously fitting AGN and star- forming galaxy luminosity functions.

A LARGE-SCALE VIEW OF THE DISTANT UNIVERSE COSMIC VARIANCE ▸ Fractional uncertainty due to cosmic variance is ~40% in the HUDF. ▸ Will be similar in a JWST UDF- style observation due to small volume probed. ▸ How much are our conclusions on faint galaxies biased by cosmic variance? ▸ Lensing helps provide independent lines-of-slight, though volumes are tiny, so still Finkelstein+15 CV issues. s s ¢ ´ ¢ ¢ ´ ¢ ¢ � 2 ¢ � ¢ 2 1 ¢ 1 s s ¢ ¢ = - = - = - = -