Hubble Science Briefing CANDELS - Observing Galaxy Assembly with the Hubble Space Telescope Henry Ferguson 1 August 2013 1
Cosmology in a nutshell The universe had a beginning In the beginning it was small and hot and nearly uniform in density It is filled mostly with dark matter and dark energy We know how they behave, but don t know what they are. As it expanded, the high-density regions collapsed and formed galaxies. 2
The standard cosmological model is a huge success on large scales Motivation Predicted fluctuations in the Cosmic Microwave background match observations amazingly well These fluctuations are the seeds of galaxies. Theoretical predictions (red) reproduce the observed clustering of galaxies (blue) amazingly well. 3
Motivation Galaxy evolution within this cosmology is complicated! Governato et al. Simulations of a Milky-Way-like galaxy (blastwave feedback) http://www.youtube.com/watch?v=n0jrobc7_xo 4
Cosmology, power spectrum Merging of dark-matter halos Ingredients in theoretical models of galaxies Gas heating and cooling Star formation, black-hole formation Stellar winds Supernovae, feedback from black holes chemical enrichment Multiple generations of stars dust absorption & emission galaxy observables 5
Theoretical models tell us where and when galaxies should form. But are these models correct? GIF Simulation Kauffmann, Colberg, Diaferio & White 1999 6
A crude way to make the connection between galaxies and Pick a slice of the universe dark-matter halos Estimate the stellar mass of each galaxy in that slice Rank order the galaxies from most to least massive Rank order the dark-matter halos in a cosmological simulation of the same volume Assign the most-massive galaxy to the most massive dark-matter halo, and so on down the list 7
Fraction of the mass in the halo that is in the form of stars Result: The mass in stars compared to the mass in dark matter Mass of the Milky Way 10% 1% Mass of the dark-matter halo (relative to the sun) The conversion of gas into stars is inefficient for high-mass and low-mass dark-matter halos 8
Some kind of feedback is needed to prevent all the gas from turning into stars Feedback from supernovae? Feedback from black holes? The conversion of gas into stars is inefficient for high-mass and low-mass dark-matter halos 9
Open Questions Do galaxies form at dark-matter peaks? Really? All of them? Which feedback mechanisms are most important in governing star formation? Heating of gas by radiation from other galaxies? Expelling gas explosively? Injecting energy into the gas from a central black hole? What is needed to make the CDM cosmological model consistent with all the observables? 10
The need for large surveys Galaxy formation/evolution is inherently statistical Making the link between galaxy-scale physics and cosmology is all about measuring distributions: Need to know what kinds of galaxies are common and what kinds are rare. Need to measure correlations between the structure of galaxies and their stellar content. Need to measure correlations between galaxy properties and their environment. 11
CANDELS Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey ~175 team members ~45 institutions 12 countries candels.ucolick.org Builders: Harry Ferguson, Sandra Faber, Adam Riess, Steve Rodney Norman Grogin, Dale Kocevski Anton Koekemoer 12
CANDELS in a nutshell CANDELS observes representative slices of the universe. These slices include Hubble s deep fields, but cover more area These are the reference fields for studies of the distant universe Near-infrared images provide crucial insight into galaxy assembly CANDELS works in concert with other surveys to provide as much information as possible on each galaxy. Searching for distant supernovae as we go along. 13
Looking back in time CANDELS sees about 250,000 galaxies Most are at high redshift (very distant) But for many of them, it s devilishly hard to determine exact distances. Redshift (z) Light reaching us today left these galaxies billions of years ago, providing a historical record of galaxy evolution. CANDELS 14
What The Hubble WFC3 Can Do 15
What WFC3 Can Do 16
Multi-wavelength slices of the universe 17
Hubble 0.6, 1.25, 1.6 microns 18
Chandra X-ray observatory 0.5-2, 2-8, 5-8 kev (0.0002-0.002 microns) 19
Spitzer observatory 3.6+4.5, 5.6, 8 microns 20
Spitzer and Herschel observatories 24, 100, 160 microns 21
Herschel Observatory 250, 350, 500 microns 22
33 CANDELS submitted papers Lead Author Paper Title Yicheng Guo CANDELS Multi-Wavlength Catalogs: Source Detection and Photometry in the GOODS-South Field David O. Jones Discovery of the Most Distant Type Ia Supernova at Redshift 1.914 -- Telecon 12/10 A. Galametz The CANDELS UDS Multiwavelength catalog -- Telecon 10/11/12 A. Cooray CANDELS: Strong Lensing Galaxies In HST/WFC3 Imaging Data Of UDS AND GOODS-S J. Lotz The Assembly of Massive Cluster Galaxies at z=1.62 CANDELS Observations of the Color-Morphology Relation at z = 1.6 and its Dependence on Mass R. Bassett and Environment V. Tilvi LBGs at z~7 from the zfourge Survey J. Herrington No Significant Evolution of the Bar Fraction in Large Disk Galaxies from z=1.8 to z=0.6 T. Targett The properties of (sub)millimetre selected galaxies as revealed by CANDELS WFC3/IR imaging in GOODS-South G. Barro The progenitors of red nuggets at z>2 as seen by CANDELS E. Curtis-Lake D. Rosario V. Bruce The stellar populations of spectroscopically confirmed z~6 galaxies in the CANDELS UDS/GOODS-S field X-ray selected AGN Hosts are Similar to Inactive Galaxies out to z=3: Results from CANDELS/CDF- S Morphologies of Massive Galaxies at 1<z<3 in the CANDELS-UDS Field: The Rise and Fall of Massive Disks H. Yan Luminous and High Stellar Mass Candidate Galaxies at z~8 Discovered in CANDELS 23
CANDELS submitted papers Lead Author Paper Title A. van der Wel Galfit Structural Parameters of Galaxies from CANDELS S. Finkelstein CANDELS: The Contribution of the Observed Galaxy Population to Cosmic Reionization A. Grazian The size-luminosity relation at z=7 in CANDELS and its implication on reionization K. I. Caputi The nature of H-[4.5]>4 galaxies revealed with SEDS and CANDELS J. S. Kartaltepe Morphology of Herschel Selected ULIRGs at z~1-3 Smooth(er) Stellar Mass Maps in CANDELS: Constraints on the Longevity of Clumps in High-redshift S. Wuyts Star-forming Galaxies A Type Ia Supernova at Redshift 1.55 in Hubble Space Telescope Infrared Observations from S. Rodney CANDELS E. Bell T. Wang What turns galaxies off? The morphologies of intermediate-mass and massive quiescent galaxies during the last ten billion years using the CANDELS Survey CANDELS: Correlations of SEDs and Morphologies with Star-formation Status for Massive Galaxies at z ~ 2 S. Wuyts Galaxy Structure and Mode of Star Formation in the SFR-Mass Plane from z~2.5 to z~0.1 E. Vanzella On The Detection Of Ionizing Radiation From Star-Forming Galaxies At Redshift z~3-4 C. Papovich The Structural Properties and Evolution of Galaxies in a Cluster at z=1.62 S. Finkelstein Evolution of UV Spectral Slope from z=4-8 D. Kocevski CANDELS: Investigating the AGN-Merger Connection at z~2 A CANDELS WFC3 Grism Study of Emission Line Galaxies at z~2: A Mix of Nuclear Activity and Low- J.R. Trump Metallicity Star Formation A. van der Wel Extreme Emission Line Galaxies in CANDELS N. A. Grogin CANDELS: The Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey A. M. Koekemoer CANDELS: HST Imaging Data Products and Mosaics 24
CANDELS/CLASH high-z supernovae program Improve constraints on cosmic acceleration & Dark Energy Observe evolution of SNIa population Test for systematic biases as standard candles Measure rates of supernovae at high-z: test supernova theory Riess, Rodney, Strolger, Dahlen, Graur, Hayden, Frederiksen 25
Supernova Follow-up Program for CANDELS Brightness Discovery Days 26
CANDELS: Cosmic Dawn Finding some of the most distant galaxies Within 700 million years of the big bang Tracing the evolution of galaxies with larger samples than possible from deep fields Finding galaxies bright enough to detect with other observatories 27
Hotter stars Cooler stars One highlight: evolution of UV slopes High-mass galaxies already metal-rich Low-mass galaxies growing dust and metals Finkelstein+ 2011 28
Galaxy Morphology at cosmic high noon 29
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Morphology is important 33
Galaxy Morphology Elliptical or Spheroidal Spiral Irregular Nearby galaxies 34
Highlights from Cosmic high noon Quiescent vs. star-forming galaxies Compact spheroids Where did they come from, where did they go? The emergence of bulges within galaxy disks Clumpy star formation AGN host galaxies 35
Massive z~2 galaxies: morphology vs. SFR Passive (24-μm faint) galaxies tend to be compact spheroidals Star-forming galaxies tend to be more extended and more disk like Also, the correlation of star-formation with profile shape is much stronger than with stellar mass. (Bell+ 2012) Wang+ 2012 36
Compact quiescent galaxies At redshift z>1.5, most passive galaxies are compact. These compact galaxies mostly appear at 1<z<3. Many of these compact galaxies disappear by z=0 Cassata+13 37
How common was this kind of galaxy? Less common More common How rapidly were stars forming? rapidly slowly Blue and red nuggets Relative space densities evolve Densities suggest rapid quenching of blue nuggets (< 1 Gyr) Barro+13 How tightly packed are the stars? loosely tightly 38
Quiescent Galaxy Summary Morphology is strongly correlated with specific star-formation rate at z~2. Quiescent galaxies at this era are small: Red nuggets Small quiescent galaxies are disappearing by z=0 Reactivating or growing by mergers? There is a sufficient reservoir of small active galaxies at z~2 blue nuggets to form the red nuggets. 39
The Hubble Sequence at z~2 Bulge fractions Massive galaxies M*>10 11 M Bulges become dominant in massive galaxies at z~2 Bulges are smaller at fixed mass at z~2 than today. While most passive galaxies are bulge dominated, a few passive galaxies appear to be pure disks. Implications for quenching models? Era of massive disks at 2<z<3 Bruce+13 Mortlock+13 40
Emergence of clumpy disks Gas instabilities in gas-rich disks? Mergers? The seeds of bulges? Guo et al. 2011 Ravindranath et al. in prep. Mozena et al. in prepration 41
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Star-formation histories pixel by pixel Clumps in massive galaxies at 1<z<2 account for ~20% of the star formation but 7% of the mass Wuyts+13 43
More massive clumps are redder Massmetallicity relation for clumps? Winds only partially effective Hotter stars Cooler stars Clumps at z~3 More massive clumps Ravindranath+13 44
Redder Radial Trends Clumps near the center tend to be redder and higher mass. Preference for more massive clumps to form near the center? Migration coupled with aging of the clumps? Trends roughly agree with predictions Guo+11 Ravindranath+13 Closer to galaxy center 45
Inspecting thousands of galaxies by eye Help from Galaxy Zoo: 40 million classifications! Visual classifications 46
The AGN-Merger connection Are supermassive black holes part of the feedback loop that regulates star formation in galaxies? Strong feedback is needed to explain the inefficiency of star formation. Emerging testable paradigm AGN feedback: Mergers drive gas to galaxy centers Trigger starbursts (often IR luminous) Funnel gas onto central black hole Energy injection from BH quenches further star formation Resulting galaxy ends up as a red spheroid 47
Merger AGN connection: theory Bright Chandra source Bright Spitzer/Herschel source Distinct Hubble Morphology 48
One early result: Morphologies of X-ray-bright galaxies at z~2 X-ray-bright galaxies have hot gas flowing into a central super-massive black hole Kocevski+12 49
Morphologies of X-ray AGN hosts at z~2 AGN hosts are NOT disturbed. Kocevski+12 50
Morphologies of X-ray AGN hosts AGN hosts are mostly spheroids. Kocevski+12 51
Morphologies of X-ray AGN hosts AGN hosts have many disks. Kocevski+12 52
Morphologies of X-ray AGN hosts The lack of disturbances and high frequency of disks challenges the standard merger-driven AGN paradigm. AGN hosts have many disks. AGN demographics at z ~ 2 look like those at z ~ 1 internally driven BH growth and AGN triggering. Kocevski+ 2012 53
Unexpected Discovery 54
Bursting dwarfs at z ~ 1.7 van der Wel+ 2011 55
Bursting dwarfs at z ~ 1.7? Ubiquitous low-metallicity extreme starbursts. Can produce most of stellar mass in today s dwarf galaxies in only 4 billion years. 56
CANDELS is really just getting started Last observations complete August 10 About 1 year of work to get reliable catalogs Stay tuned! Follow our research blog at candels-collaboration.blogspot.com 57