A study of a ULIRG-to-QSO transition object: possibly another gas-rich/gas-poor merger and a serendipitous line detection

Manuel Aravena, Jeff Wagg, Padelis Papadopoulos, Ilana Feain

OutlineIntroduction: the ULIRG to QSO

evolutionary scenarioA high-resolution search for molecular

gas in optically bright QSOs with elliptical hosts.

HE 0450-2958, the “naked” QSOFirst results: High-resolution CO imaging

of H1821+643 at z=0.3

An evolutionary scenario for galaxy evolution

Starbursting Ultra Luminous Infrared Galaxies (ULIRGs): • LIR > 0.9 LBOL

• LBOL > 1012 LSUN

• Powered mostly by star-formation• Interacting systems

QSOs (Quasi-Stellar Objects)• Lbol >1012 Lsun

• Point-like sources• Emission is powered by an AGN

An evolutionary scenario for galaxy evolutionObservations (Sanders et al. 1988a) and simulations (Mihos & Hernquist 1996)

Molecular gas in starbursts/QSOs

Early evidence for vast amounts of gas in merger-like systems and starburst-to-QSO transition objects.

Detections consistent with the evolutionary scenario.

Solomon et al. (1997)

Evans et al. (2002)

Molecular gas in late systems

Scoville et al. (2003): large amounts of gas in post-merger systems; optically luminous QSOs with MB<-23

Taken as evidence for late type spirals host galaxies.

Most optically luminous QSOs have elliptical-like light profiles (Dunlop 2001; McLeod & McLeod 2000; Floyd et al. 2004)

Possible that some of these sources are not optically luminous QSOs with gas rich host galaxy?

HE 0450-2958: the naked QSO

Magain et al. (2006): “We report … a quasar lying at the edge of a gas cloud, whose size is comparable to that of a small galaxy, but whose spectrum shows no evidence for stars. The gas cloud is excited by the quasar itself. If a host galaxy is present, it is at least six times fainter than would normally be expected for such a bright quasar. The quasar is interacting dynamically with a neighbouring galaxy – which matter might be feeding the black hole.”

-Host galaxy undetected- Based on Mbh vs Mbulge relation, the host galaxy should be >10x brighter

HE 0450-2958: the naked QSO

-CO imaging with Australia Telescope compact Array (ATCA) showed that lots of gas are associated with the companion galaxy and not with the AGN - Mid-IR high-resolution imaging confirmed this. The stellar mass of the companion would bring the system to the local Mbh to Mstar relation if it were to merge with the QSO.(Papadopoulos et al. 2008; Elbaz et al. 2009)

HE 0450-2958: the naked QSO

A series of arguments suggest that the radio jet has an important role in the formation of the companion galaxy (Elbaz et al. 2009)

Our little project: High-resolution CO imaging of optically luminous QSOs- Question: Is it possible that in some of the most optically luminous QSOs the gas is not coming from its elliptical host (as predicted by the Starburst/QSO scenario) but from a gas-rich companion? If so, what are the implications in the derivation of dynamical masses and the formation of a Mbh vs. Mstar relation?- CO imaging with CARMA and ATCA of the most optically luminous QSOs in the local Universe for which PSF subtracted HST images are available.

H1821+643: an interesting source

- H1821+643 is one of the most luminous objects in the local Universe with Mv=-27.1- Hosted by a giant elliptical galaxy 14 kpc in size.- Right at the middle of a cool-cluster core- Radio jet 250 kpc in size- Radio quiet, about to become radio-loud; jet structure in the transition between FRI and FRII

CARMA observations of H1821+643:A hyper-luminous IR starburst/QSO system at z=0.3

Aravena et al. (2011, submitted)

- CO emission offset by more than 1 beam from the nuclei position- Continuum 3mm does coincide with the radio-nuclei.- CO aligned with radio-jet?- Coincidence with optical feature: another gas-poor/gas-rich merger? Or tail structure from past merger?

CARMA observations of H1821+643:A hyper-luminous IR starburst/QSO system at z=0.3

Spectral energy distribution- Two components:

- optical/mid-IR resembles AGN

- FIR resembles starburst- radio: QSO emission

Needed to disentangle starburst:- Spatially resolved IR observations

- Hot dust with Td~130 K and Md~106 Msun- Cold dust with Td~50 K and dust mass of Md~1.4x108 Msun

CARMA observations of H1821+643:Implications for dynamical mass measurements

- Usually the line width of the CO line is used to estimate the dynamical mass of the system.- Can we recover the dynamical mass of this galaxy based on CO profile?- From the optical imaging Floyd et al. (2004) find a total mass of 2x1012 Msun.- Assuming a spherical geometry (usually assumed) we find a mass of ~9x1011 Msun (> 2x lower than the actual mass).- Apparently due to the complex dynamical configuration, we underestimate the dynamical mass of this system.- Only possible to measure this underestimation in the local Universe with good optical imaging- Consistent with similar results found with detailed modeling of disk galaxies at z=1.5, where the underestimation can amount up to 15-20% (Daddi et al 2010).

Any sign of cold gas flows?: A simple exercise

H1821+643 is right at the center of a massive cluster of galaxies (Abell class 2).Has any more gas been deposited in other galaxies in the environment of this QSO?

A simple exercise: stacking analysis

Upper limit to the molecular gas content of 1.1x109 MsunUpper limit to the continuum emission of 175 uJy.

Bonus point: Another CO bright QSO or molecular line in a carbon star?

Serendipitous detection of an emission line- Is it another QSO at a similar redshift?- Or a carbon star? Possible molec. Lines: C5H, HCO+, HCN, SiC4, etcs

- Small uncertainties – expect perfect fit - If it is a star, the spectral clasification (G5III) and B-Voptical color would imply and absolute magnitude of roughly +1 mag,and thus would imply a distance in the range 50=150 pc distance fromus- If a QSO, it must be at z=0.3.

Another CO bright QSO or molecular line in a carbon star?

Conclusions

- CO detection of H1821+643 at z=0.3

- CO is considerably offset from the nuclei: gas poor/rich merger or tail?

- SED presents evidence for two components: starburst and QSO

- Stacking analysis of galaxies in the field shows no detection, consistent with ellipticals

- Serendipitous detection of “gas” line emission: star or QSO at z=0.3?