Ultraluminous galaxies at high redshifts Jingwen Wu (NAOC / UCLA) Collaborators: Peter Eisenhardt (JPL) Edward. N. Wright (UCLA) Andrew Blain (Univ. Leicester UK) Daniel Stern (JPL) Chao-Wei Tsai (JPL) Roberto Assef (U. Diego Portales Chile) Guiyang 7/31/2015

The origin of high luminosity in galaxies Essentially from Star burst BH accretion Dust can re-process UV/opt photons to IR Cartoon credit: Chao-Wei, Tsai

Ultra-Luminous galaxies: Classification By bolometric luminosity A milestone: IRAS (1983) We we think about luminous galaxies: Optically bright (I band mag)/Radio loud: not necessary Bolometric luminosity: energy output is very high Ultra-luminous: compared to noraml-dwarf galaxies: An milestone for this work is IRAS ELIRGs (Tsai+2015)

Ultra-Luminous galaxies: Classification 2) By selections IRAS at Far-IR: LIRGs; ULRGS (e.g. Sanders & Mirabel 1996) mostly are local SCUBA at 850um: Submillimeter galaxies (SMGs) (e.g. Blain+2002, Chapman+2005); z~2 Spitzer at mid-IR: Dust obscured galaxies (DOGs) (e.g. Dey et al. 2008); z~2 Color-selected galaxies at opt/NIR (e.g. BzK): z>1.5 Herschel at FIR Radio galaxies at radio; Quasars at optical Many well known ultra-luminous galaxies are based on their selection, luminosity may deal with different physical process

Ultra-Luminous galaxies: Classification 3) By physical nature Main-sequence (SFR-M*) galaxies * Local normal disk galaxies * Color selected star-forming galaxies: e.g. BzK galaxies Non-main sequence galaxies (Carilli & Walter 2013): Starburst dominated: LIRGs, some ULIRGs, SMGs, bump DOGs, some Herschel galaxies AGN dominated: QSOs; power-law DOGs, some ULIRGs; Radio galaxies

A popular galaxy evolution model through “merger” SMGs, DOGs SFR Lum (Hopkins et al. 2008)

Now we highlight a new type of hyperluminous galaxies discovered by WISE: Hot DOGs NASA’s Wide-field Infrared Explorer (WISE) surveyed all-sky in 2010 at 3.4, 4.6, 12, 22 um (W1, W2, W3,W4). WISE found there are more obscured AGNs than un-obscured ones in the universe, uncovering a surprisingly large populations of hidden super massive black holes (SMBHs). very useful for extragalactic study; it is a less sensitive, but all-sky version of Spitzer at IRAC1,2 to MIP1 bands. 5σ point- source sensitivities are better than 0.07, 0.1, 0.9, and 5.4 mJy WISE was re-actived in Sep 2013, for 3 more years for NEOWISE project 9.29.10-2.1.11, 125 days post cryogen, 70% sky on W1/W2 ALLWISE 2 times better in W1/W2 NEOWISE : 8 times better?

Fulfilled one of the WISE mission goals: We have successfully selected a new population of hyperluminous galaxies by searching the reddest, most obscured WISE galaxies, using the W1W2-dropout selection Fulfilled one of the WISE mission goals: Finding the most luminous galaxies in the universe Publications so far: Eisenhardt et al. 2012; Wu et al. 2012, 2014, 2015; Griffith et al. 2012; Bridge et al. 2013; Jones et al. 2014; Stern et al. 2014; Assef et al. 2015; 2015b Tsai et al. 2015; W1 W2 W3 W4

Intensive follow-up programs > 200 UV spectra with redshifts from Keck/GMOS-S/Palomar > 900 with warm Spitzer IRAC1+IRAC2 > 200 with Herschel PACS+SPIRE > 40 with CSO SHARCII+Bolocam > 10 with SCUBA2 > 200 with Opt/IR photometry with NOAO facilities > 30 with EVLA > 25 with HST+Keck/NIRC2 Some interesting individual with ALMA, CARMA, SMA, XMM, NuSTAR

Results: UV Spectroscopy Redshift peak at 2-3, similar to SMGs, DOGs Characteristic AGN lines, most are type II (Obscured).

Results: SEDs SED: Optical+Spitzer+WISE+Herschel+CSO Consistent SED shapes, but quite different from known galaxy templates Unusually high mid-IR to submm ratios, dominated by hot dust emission.

Properties summary High redshift: mostly 1<z<4.6, peak at z~2-3 Hyperluminous: Most L>1013 L (HyLIRGs), ~10% > 1014L(ELIRGs) Comparable to the most luminous SDSS QSOs known No sign of lensed W2246-05 at z=4.6 is the currently luminosity record holder (3.5x1014L) Hot dust temperature Tdust ~ 60-100K, compare to ~30-40K for SMGs or DOGs; Milky Way ~20K Rare Only about ~1000 in the all-sky Highly Obscured, AGN dominated Av ~ 20-60; Compton thick. Since they do qualify DOG selection (Dey+08), but much hotter, 10 x more luminous, and 10,000 X rarer, we named them hot dust-obscured galaxies, or Hot DOGs (Wu et al. 2012)

An evolutionary connection to SMGs and DOGs at z~2 ? PL DOGs Hot DOGs An evolutionary connection to SMGs and DOGs at z~2 ? An Evolution driven by the growth of the central SMBHs (Melbourne 2012) (Magnelli 2012) Log(350um) Log(24um)

They may be experiencing a rare seen evolutionary phase: the blow-out phase. Very hot dust Growing SMBHs 3) Unusually high ratio of LyA blobs (Hot DOG LABs, Bridge et al. 2013) 4) The extreme luminosity mostly come from AGN, suggesting either their BH masses are too massive, well above local BH-Bulge relation, or their accretion rates are very high, even exceed Eddiington limit (Assef+ 2015). To break-up the degeneracy of explaining their high IR luminosity (more massive BHs or higher Eddington ratios) and reveal their nature, a direct measurement of their BH masses are necessary.

An on-going MOSFIRE project to measure BH masses Check SMG, Lin’s DOG, lensing Broad Ha lines from Keck/MOSFIRE (Wu et al. 2015) Agree with an evolution along SMGs—>DOGs—>Hot DOGs—>QSOs

From Hot DOGs to SDSS QSOs: Time BH accretion rate Hot DOG SDSS QSOs From Hot DOGs to SDSS QSOs: Staying at high luminosity, when BH accretion rates reach and cross a peak. (Wu et al. 2015) (Tsai et al. 2015)

BH masses in Hot DOGs: About half way in accreting towards QSOs at similar luminosity The suggesting time scale (a few x 107 yrs) of high accreting Hot DOGs is comparable to time scales of SDSS QSOs. Agree with the result from a luminosity function study of Hot DOGs (Assef et al. 2015) that they are as common as SDSS QSOs at high luminosities. Hot DOGs may be an obscured version of luminous unobscured QSOs caught at high accreting phase.

These Hot DOGs are quite different from any other z~2 galaxy populations, but close to a well known Eddington limit accreting population at a different epoch: the z~6 quasars.

Hot DOGs & z~6 QSOs actually share some common features. BH-Host relation BH mass & Luminosity Hot Dust emission (SED of a z~6 qso from Leipski+14) Accretion rates

? Catching the high-accreting phase of SMBHs throughout cosmic time Accretion rate is one of the most important factors to shape AGN properties (e.g. Shen & Ho, 2014 Nature) The key common feature for z~2-3 Hot DOGs and z~6 QSOs is that they all reach an maximum level of BH accretion, leading to amount of hot dust and high luminosity, making themselves the most luminous objects in their own epoch. Time BH accretion rate Hot DOG SDSS QSOs Z~2 Z~6 ? Lower z Z~6 QSOs Earliest generation Gas-rich environment Duty cycle~1 Peak generation Feedback terminate Accretion & starburst Recent generation Catching the high-accreting phase of SMBHs throughout cosmic time

Related to FAST Possible projects Detecting HI at higher-z is hard ! Go to absorption lines a. Some Hot DOGs have strong radio continuum; HI absorption can reveal kinematic information of the host galaxies. b. Other radio laud non-main sequence galaxies Go to lower-z Hot DOGs Although rare, there should be high-accreting obscured Hot DOGs at lower-z. FAST It’s always hard to use single dish radio telescope to study high-z HI, due to sensitivity. But FAST will be the most sensitive one when available to lead such study

Summary We have discovered a new type of z~2 galaxies using WISE, dubbed “hot dust-obscured galaxies” or “Hot DOGs.” They are rare, hot, and hyperluminous, possibly tracing a transitional “blow-out” phase during galaxy evolution through merging. The measured BH mass & derived Eddington ratio agree with the scenario that Hot DOGs are experiencing an very high accreting phase, follows the SMG-DOG phases and right before optical QSOs. Hot DOGs share some key features with z~6 quasars, they may both trace the highest accreting stage of galaxy evolution, and become the most luminous objects in their own cosmic epoch. Hot DOGs provide an alternative approach to study high-accreting SMBHs at high redshifts. FAST may be able to study the HI absorption lines in these high-z Hot DOGs, and explore HI emission in their lower-z analogies.