An IRAM PdBI CO Survey of Luminous Submm Galaxies A spearhead project for ALMA IDA Meeting, Copenhagen Dec Thomas R. Greve (Caltech) R. Genzel (MPE), R. J. Ivison (ROE), R. Neri (IRAM), I. Smail (Durham), S. Chapman (Caltech), A. W. Blain (Caltech), F. Bertoldi (MPIfR), L. Tacconi (MPE), P. Cox (Orsay), A. Omont (AIP)
Outline A Brief History of CO at high z Why CO? High-z CO detections to date An interferometric CO survey of (sub)mm galaxies (SMGs) Duty cycle and current status Bulk gas properties of SMGs Comparison with ULIRGs Implications for galaxy formation models Conclusions and future directions IDA Meeting, Copenhagen Dec. 2004
The symmetry of H 2 makes electric dipole transitions strictly forbidden and thus the cool H 2 gas is not directly observable. We need tracer molecules to trace the cool gas (CO) A Brief History of CO at high z - Why CO? IDA Meeting, Copenhagen Dec. 2004
CO is powerful tool for probing molecular gas at high redshifts Abundance Strong rotational transitions Rotational ladder, small rotational energy-spacing, which goes as 115GHz/(1+z) CO has been studies in detail in GMCs in the Galaxy and in local starburst galaxies, e.g. (U)LIRGs A Brief History of CO at high z - Why CO? IDA Meeting, Copenhagen Dec. 2004
High-z CO detections to date IDA Meeting, Copenhagen Dec QSOs, including IRAS F the first ever high-z CO detection (Brown & Vanden Bout 1991) 6 High-z Radio Galaxies (HzRGs) 1 Lyman Break Galaxy (LBGs)
High-z CO detections to date IDA Meeting, Copenhagen Dec Omont et al. (1996) z= QSOs, including IRAS F the first ever high-z CO detection (Brown & Vanden Bout 1991) 6 High-z Radio Galaxies (HzRGs) 1 Lyman Break Galaxy (LBGs)
High-z CO detections to date IDA Meeting, Copenhagen Dec De Breuck et al. (2003) z= QSOs, including IRAS F the first ever high-z CO detection (Brown & Vanden Bout 1991) 6 High-z Radio Galaxies (HzRGs) 1 Lyman Break Galaxy (LBGs) Omont et al. (1996) z=4.69
High-z CO detections to date IDA Meeting, Copenhagen Dec Baker et al. (2003) z= QSOs, including IRAS F the first ever high-z CO detection (Brown & Vanden Bout 1991) 6 High-z Radio Galaxies (HzRGs) 1 Lyman Break Galaxy (LBGs) De Breuck et al. (2003) z=3.52 Omont et al. (1996) z=4.69
High-z CO detections to date IDA Meeting, Copenhagen Dec Omont et al. (1996) De Breuck et al. (2003) Baker et al. (2003) 13 QSOs, including IRAS F the first ever high-z CO detection (Brown & Vanden Bout 1991) 6 High-z Radio Galaxies (HzRGs) 1 Lyman Break Galaxy QSOs+HzRGs show strong CO emission from extended (~10kpc) starburst regions Typical gas and dynamical masses of ~1x10 11 M o Co-eval growth of stellar bulges and massive black holes Rapid enrichment before z~7
High-z CO detections to date IDA Meeting, Copenhagen Dec Omont et al. (1996) De Breuck et al. (2003) Baker et al. (2003) 13 QSOs, including IRAS F the first ever high-z CO detection (Brown & Vanden Bout 1991) 6 High-z Radio Galaxies (HzRGs) 1 Lyman Break Galaxy QSOs+HzRGs show strong CO emission from extended (~10kpc) starburst regions Typical gas and dynamical masses of ~1x10 11 M o Co-eval growth of stellar bulges and massive black holes Rapid enrichment before z~7 However, most high-z CO detections are a mixed bag of non-uniformly selected (and often strongly lensed) QSOs and HzRGs
High-z CO detections to date IDA Meeting, Copenhagen Dec Omont et al. (1996) De Breuck et al. (2003) Baker et al. (2003) 13 QSOs, including IRAS F the first ever high-z CO detection (Brown & Vanden Bout 1991) 6 High-z Radio Galaxies (HzRGs) 1 Lyman Break Galaxy QSOs+HzRGs show strong CO emission from extended (~10kpc) starburst regions Typical gas and dynamical masses of ~1x10 11 M o Co-eval growth of stellar bulges and massive black holes Rapid enrichment before z~7 However, most high-z CO detections are a mixed bag of non-uniformly selected (and often strongly lensed) QSOs and HzRGs. SMGs: 2+1 sources detected in CO prior to our survey.
L1L2 R.A. (2000) Dec. (2000) SMMJ (z=2.81) 11 Ivison et al. 1998, MNRAS 298, 583 Frayer et al. 1998, ApJ, 506, L7 Genzel et al. 2003, ApJ, 584, 633 M dyn (R<8kpc) ~ 2-3x10 11 M O Most of which is baryonic IDA Meeting, Copenhagen Dec. 2004
SMMJ (z=2.51) Ivison et al ApJ 561, L45 Frayer et al. 1999, ApJ, 514, L13 Downes & Solomon 2003 ApJ 582, 37 IDA Meeting, Copenhagen Dec. 2004
An IRAM PdBI CO Survey of SMGs (Genzel, Ivison, Neri, Bertoldi, Blain, Chapman, Cox, Greve, Neri, Omont, Smail, Tacconi) We are undertaking a first systematic CO survey of dust-enshrouded starburst galaxies at high redshifts Bright (S 850 >5mJy) submm-selected galaxies detected in the radio. This population is responsible for ~25% of the submm background. IDA Meeting, Copenhagen Dec. 2004
Duty-cycle and current status: SCUBA/MAMBO sources with VLA 1.4GHz counterparts (Lockman E, ELAIS N2, SSA 22, SSA13, HDF-N etc). Keck follow-up spectroscopy with LRIS-B: ~70 redshifts, =2.4 We are undertaking a first systematic CO survey of dust-enshrouded starburst galaxies at high redshifts An IRAM PdBI CO Survey of SMGs (Genzel, Ivison, Neri, Bertoldi, Blain, Chapman, Cox, Greve, Neri, Omont, Smail, Tacconi) IDA Meeting, Copenhagen Dec. 2004
Keck (LRIS-B + NIRSPEC) spectroscopy Chapman et al. (2003) Ivison et al. (2002) IDA Meeting, Copenhagen Dec. 2004
Duty-cycle and current status: An IRAM PdBI CO Survey of SMGs SCUBA/MAMBO sources with VLA 1.4GHz counterparts (Lockman E, ELAIS N2, SSA 22, SSA13, HDF-N etc). Keck follow-up spectroscopy with LRIS-B: ~70 redshifts, =2.4 PdBI follow-up for redshift confirmation (2-3 tracks each) High-resolution PdBI follow-up for spatially resolved CO dynamics IDA Meeting, Copenhagen Dec. 2004
Duty-cycle and current status: SCUBA/MAMBO sources with VLA 1.4GHz counterparts (Lockman E, ELAIS N2, SSA 22, SSA13, HDF-N etc). Keck follow-up spectroscopy with LRIS-B: ~70 redshifts, =2.4 PdBI follow-up for redshift confirmation (2-3 tracks each) High-resolution PdBI follow-up for spatially resolved CO dynamics Status winter 2004: 7 (+1) new CO detections, 6 non-detections - the number of SMGs detected in CO almost tripled! An IRAM PdBI CO Survey of SMGs IDA Meeting, Copenhagen Dec. 2004
An IRAM PdBI CO Survey of SMGs First results Neri et al. (2003) z=2.509z=3.349 z=2.380 IDA Meeting, Copenhagen Dec. 2004
An IRAM PdBI CO Survey of SMGs Greve et al. (2005) IDA Meeting, Copenhagen Dec. 2004
An IRAM PdBI CO Survey of SMGs ID Transition z spec z CO FWHM I CO Our Detections km/s Jy km/s SMMJ (2-1) SMMJ (4-3) SMMJ (3-2) SMMJ (3-2) SMMJ (3-2) SMMJ (3-2) SMMJ (4-3) SMMJ (3-2) (7-6) Non-detections SMMJ (3-2) SMMJ (3-2) (3-2) (7-6) SMMJ (3-2) (3-2) EROJ (2-1) (5-4) (1-0)
IDA Meeting, Copenhagen Dec Greve et al. (2005) Genzel et al. (2003) Neri et al. (2003) Downes & Solomon (2003) An IRAM PdBI CO Survey of SMGs Neri et al. (2003)Greve et al. (2005) z=1.062z=2.803 z=2.562z=3.405z=3.349 z=2.509
IDA Meeting, Copenhagen Dec An IRAM PdBI CO Survey of SMGs Neri et al. (2003)Kneib et al. (2004)Greve et al. (2005) Andreani et al. (2000)Greve et al. (2005) z=2.380z=2.517z=2.454 z=3.098z=1.439z=3.098
IDA Meeting, Copenhagen Dec An IRAM PdBI CO Survey of SMGs 7 (+1) out of 13 (+1): detection rate of 54-57%. Remarkably good - comparable to the radio-ID fraction. This confirms the =2.4 redshift distribution of the bright, radio-detected SMG population (Chapman et al. 2003).
IDA Meeting, Copenhagen Dec An IRAM PdBI CO Survey of SMGs 7 (+1) out of 13 (+1): detection rate of 53-57%. Remarkably good - comparable to the radio-ID fraction. This confirms the =2.3 redshift distribution of the bright, radio-detected SMG population (Chapman et al. 2003). Greve et al. (2005)
IDA Meeting, Copenhagen Dec An IRAM PdBI CO Survey of SMGs 7 (+1) out of 13 (+1): detection rate of 54-57%. Remarkably good - comparable to the radio-ID fraction. This confirms the =2.4 redshift distribution of the bright, radio-detected SMG population (Chapman et al. 2003). H provides much more reliable estimate of the systemic (CO) redshift: V(CO-Ly ) V(CO-H ) blueshifted: 5 0 redshifted : 2 0 zero offset : 1 4
IDA Meeting, Copenhagen Dec Greve et al. (2005) An IRAM PdBI CO Survey of SMGs Bulk gas properties: CO luminosity: =( )x10 10 K km/s 4x ULIRGs Gas masses (including HI+He): =( )x10 10 M O 4x ULIRGs So SMGs contains 3-4x more gas than local ULIRGs. Depletion of Gas as the merger progresses (Gao et al. 1999)? Detection rate: z>2.4 : 5/7 (71%) z<2.4 : 2/6 (33%) Is this evidence for evolution in gas mass content?
IDA Meeting, Copenhagen Dec Starformation efficiency: SMGs extend the (non-linear) FIR-CO correlation to higher z and luminosities SMGs: =( ) L O M O -1 ULIRGs: =( ) L O M O -1 Starformation efficiency might be higher in SMGs than in ULIRGs Tentative evidence of a FIR- CO correlation within the SMG sample itself An IRAM PdBI CO Survey of SMGs log(LCO) = 0.6 log(LFIR) Greve et al. (2005)
IDA Meeting, Copenhagen Dec An IRAM PdBI CO Survey of SMGs Starformation efficiency: SMGs extend the (non-linear) FIR-CO correlation to higher z and luminosities SMGs: =( ) L O M O -1 ULIRGs: =( ) L O M O -1 Starformation efficiency might be higher in SMGs than in ULIRGs Tentative evidence of a FIR- CO correlation within the SMG sample itself Greve et al. (2005)
IDA Meeting, Copenhagen Dec An IRAM PdBI CO Survey of SMGs Dynamical masses: The double horn profiles are indicative of ordered orbital motion: either circum-nuclear disk or a merger. Assuming: 1) a conservative source size of D=0.5” (~3.7kpc at z=2.3) 2) random orbital inclinations (factor of /4) 3) Merger model* SMG = ( ) x M O * Toomre stability criterion: Q = v s G 1 for a gaseous disk to be stable. We find Q << 1 for M gas =3x10 10 M O and R~4kpc.
IDA Meeting, Copenhagen Dec Greve e al. (2005) An IRAM PdBI CO Survey of SMGs Dynamical masses: Velocity dispersion of SMGs is comparable to that of HzRGs and 3-4x that of ULIRGs. Assuming M dyn ~ R 2, and ULIRGs: M dyn (R<0.6kpc) ~ 6x10 9 M O, we find SMGs: M dyn (R<0.6kpc) ~ 4x10 10 M O The large line widths of SMGs strongly suggest that they are massive systems - with M dyn comparable to HzRGs.
IDA Meeting, Copenhagen Dec An IRAM PdBI CO Survey of SMGs Gas mass fractions: Gas fraction: SMGs : M gas /M dyn ~ 0.3 ULIRGs: ~ 0.16 (Downes & Solomon 1998) So SMGs appear to be more gas-rich than local ULIRGs, although this is subject to uncertainties in the CO-H 2 conversion factor and dynamical mass estimates. But overall there is mounting evidence that SMGs are neither high-z replicas of local ULIRGs, nor simply scaled up versions. Rather SMGs are more gas-rich and seem to form stars more efficiently (caveat: CO doesn’t trace the dense starforming gas, HCN does!)
IDA Meeting, Copenhagen Dec An IRAM PdBI CO Survey of SMGs Gas consumption time-scale and baryonic masses: The median starformation rate is =720 M O yr -1, hence the duration of the ‘SCUBA/MAMBO’-phase is: = M(H 2 )/SFR ~ 40Myr This is a lower limit since it assumes continuous starformation and ignores negative feedback and the possibility of HI falling in from outer regions.
IDA Meeting, Copenhagen Dec An IRAM PdBI CO Survey of SMGs Gas consumption time-scale and baryonic masses: The median starformation rate is =720 M O yr -1, hence the duration of the ‘SCUBA/MAMBO’-phase is: = M(H 2 )/SFR ~ 40Myr This is a lower limit since it assumes continuous starformation and ignores negative feedback and the possibility of HI falling in from outer regions. The median V-band restframe luminosity is 2 x L O, which implies median stellar mass of M * ~ 3 x M O (Smail et al. 2004). So the typical baryonic mass is M bar ~ 6 x M O - comparable to the masses of local L* galaxies. And SMGs are baryon-dominated in their inner regions: M bar /M dyn ~ 0.5. Assembling that much baryonic matter so early is a severe challenge for models!
IDA Meeting, Copenhagen Dec Implications for Models of Galaxy Formation Greve et al. (2005) A fundamental test-bed for galaxy formation models is the assembly of massive baryonic galaxies. Co-moving number density of M bar = 6 x M O is n(M>M bar ) ~ 5 x Mpc -3 Corrected for our CO detection Fraction (0.53) and finite survey volume.
IDA Meeting, Copenhagen Dec Implications for Models of Galaxy Formation A fundamental test-bed for galaxy formation models is the assembly of massive baryonic galaxies. Co-moving number density of M bar = 6 x M O is n(M>M bar ) ~ 5 x Mpc -3 Corrected for our CO detection Fraction (0.53) and finite survey volume. This is a lower limit since we must correct for the finite life time of SMGs: ( )/ SMG = 1.5Gyr/(40-200)Myr = Mo 7x10 10 Mo 5x10 10 Mo Greve et al. (2005)
High-resolution PdBI observations of SMGs - a taste of ALMA IDA Meeting, Copenhagen Dec Tacconi et al. in prep. 1.3mm continuum, beam 0.7”x0.6” SMMJ : H6 + H7 (both radio sources) are part of the same physical structure - separation 22kpc
IDA Meeting, Copenhagen Dec Tacconi et al. in prep. SMMJ : CO(4-3) is detected in H7 (but not H6). Tentative evidence for a blueshifted filament of gas between H7+H6. High-resolution PdBI observations of SMGs - a taste of ALMA
IDA Meeting, Copenhagen Dec Tacconi et al. in prep. SMMJ : CO(4-3) is detected in H7 (but not H6). Tentative evidence for a blueshifted filament of gas between H7+H6. We have ‘tasted’ what we might expect to achieve with ALMA! High-resolution PdBI observations of SMGs - a taste of ALMA
IDA Meeting, Copenhagen Dec Tacconi et al. in prep. SMMJ : High-resolution PdBI observations of SMGs - a taste of ALMA
The Future… IDA Meeting, Copenhagen Dec CO is great! But… It doesn’t trace the dense starforming gas Need high-density tracers such as HCN Other molecular/atomic lines, e.g. CI Ultimate goal: detail ISM studies at high-z as well as ‘blind’ CO surveys. …is here and it’s interferometrical!
The Future… IDA Meeting, Copenhagen Dec …is here and it’s interferometrical! CO is great! But… It doesn’t trace the dense starforming gas Need high-density tracers such as HCN Other molecular/atomic lines, e.g. CI Ultimate goal: detail ISM studies at high-z as well as ‘blind’ CO surveys
IDA Meeting, Copenhagen Dec The Future…
IDA Meeting, Copenhagen Dec The Future… Courtesy Jesper Sommer Larsen