The 6dF Galaxy Survey: Initial results on large-scale structure and ...

<strong>The</strong> <strong>6dF</strong> <strong>Galaxy</strong> <strong>Survey</strong>:<strong>Initial</strong> <strong>results</strong> on large-scale structureand galaxy evolutionHeath Jones (AAO)Matthew Colless, Bruce Peterson, Will Saunders,Tom Jarrett, Rob Proctor, Philip Lah, Mike Read & the <strong>6dF</strong>GS team

<strong>The</strong> Anglo-Australian Observatory• <strong>The</strong> Anglo-Australian Observatorywas created in 1974 as part of a binationalagreement between Australiaand Britain, to operate the 3.9m Anglo-Australian Telescope• It employs around 70 people based attwo sites:–Siding Spring Observatory,located ~450 km northwest ofSydney in the WarrumbungleMountains,– its Headquarters, located in theSydney suburb of Epping• In 1988 it took over management ofthe 1.2m UK Schmidt Telescope (fromthe Royal Observatory in Edinburgh)

<strong>The</strong> Anglo-Australian Telescope (AAT)• 3.9 m diameter Ritchey-Chretien telescope with focal stations at prime (f/3.3),cassegrain (f/8 and f/15) and coude (f/36).• Open to international subscription with successful proposals charged timeproportional to Aus/UK/other participation: over-subscription rate ~3 to 5 times.Instrument workload:AAOmega (68%), IRIS2 (17%),UCLES (8%), SPIRAL (7%)• Current instrumentation:IRIS2: infrared imager/spectrograph(7.7’ x 7.7’ FOV in JHK)SPIRALIRIS2SPIRAL: 512-element, 22.4” x11.2” FOV integral field unitUCLES / UHRF: high resolutionechelle spectrograph (R ~ 40k to100k and ~300k to 940k)AAOmega: 392-fibre, 2 o FOV,multi-object optical spectrograph

AAOmega• <strong>The</strong> centrepiece of AAOmega (andits predecessor, 2dF) is a roboticfibre-positioner at prime focus• It can configure fibres for ~400sources in ~70 mins -- the same timeit takes to complete an observationX• As there are 2 switchable field plates,no time is lost between observations• <strong>The</strong> transformation of 2dF to AAOmegasaw both spectrographs replacedX

AAOmega• <strong>The</strong> centrepiece of AAOmega (andits predecessor, 2dF) is a roboticfibre-positioner at prime focus• It can configure fibres for ~400sources in ~70 mins -- the same timeit takes to complete an observation<strong>The</strong> 2dF <strong>Galaxy</strong>Redshift <strong>Survey</strong>221,414 redshiftsz 1/2= 0.11b J< 19.5• As there are 2 switchable field plates,no time is lost between observations• <strong>The</strong> transformation of 2dF to AAOmegasaw both spectrographs replaced2dF <strong>Galaxy</strong> Redshift <strong>Survey</strong>(1998 - 2003): 221k redshifts,>130 publications, >600 citations formain survey paper alone

<strong>The</strong> United Kingdom Schmidt Telescope (UKST)• Built around the same time as theAAT, as a wide-field photographicsurvey telescope• Managed by AAO since 1988• Six-Degree Field instrument (2001):multi-object spectroscopy of up to150 objects over a 5.7 o FOV• Current survey: RAVE - the RAdialVelocity Experiment (2004 to ~2011)– Radial velocities, metallicities andabundances for up to a million diskand halo stars• Previous survey: <strong>The</strong> <strong>6dF</strong> <strong>Galaxy</strong><strong>Survey</strong> (2001 to 2006)

Ongoing Instrumentation Projects“STARBUGS”(McGrath & Haynes 2006)Integrated PhotonicSpectrographsNight-Sky Line Suppressing Fibres(Bland-Hawthorn & Horton 2006)• Aiming to suppress 98% skyemission over z, J, H bands–Need to solve for single-modeand then multi-mode

<strong>The</strong> AAO in 2008 and beyond• <strong>The</strong> AAO and its facilities are now 33years old• <strong>The</strong> UK will withdraw from the AATagreement on 30 June 2010• A government review of theAAO in 2007 recommended thatthe AAT continue operating for atleast a decade• <strong>The</strong> AAO and all facilities will thentransfer to Australian ownership andcontrol• It also recommended that theAAO become Australia’s nationaloptical observatory, (serving theAAT, and also Gemini & Magellan)• However, the UK is steeply rampingdown for the AAT, starting 2006-07• Meanwhile, the AAO was also successful inobtaining $10M in special government funding–$4M to refurbish the AAT for the coming decade–$6M for a new AAT instrument

<strong>The</strong> <strong>6dF</strong> <strong>Galaxy</strong> <strong>Survey</strong> - an introduction• <strong>The</strong> <strong>6dF</strong>GS is a combined redshiftand peculiar velocity survey of thelocal volume of the universe…–Near-infrared selected primarysample (from 2MASS)–Also redshift survey of other‘interesting’ source samples–Peculiar velocities fromFundamental Plane distances• <strong>The</strong> survey uses the <strong>6dF</strong>spectrograph on the AAO’s UKSchmidt Telescope…–5.7º diameter FoV (25.5 deg 2 )–up to 150 objectssimultaneously

Redshift <strong>Survey</strong> - Goals! Measure the luminosity function of NIR-selected galaxies (i.e. thestellar mass function of collapsed structures) and its variation withlocal environment and spectral type.! Map the local galaxy distribution (especially close to the Galacticequator).! Quantify the small- and large-scale clustering of galaxies weightedby stellar mass, and so constrain the scale-dependence of thebiasing of the galaxies with respect to the dark matter.! Measure the power spectrum of galaxy clustering on very largescales, comparable to the scales achieved by the 2dFGRS andSDSS.! Construct a large, all-sky, volume-limited sample of early-typegalaxies as the basis for the peculiar velocity survey.

<strong>The</strong> <strong>6dF</strong> <strong>Galaxy</strong> <strong>Survey</strong> - an introductionField CoverageK-band redshiftcompleteness• <strong>Survey</strong> strategy…–Cover the whole southernsky with |b|>10º–Primary sample selectedfrom 2MASS to K tot

Additional targetsamplesSample2MASS K s< 12.752MASS H < 13.05Priority86Total1139883283Sampling94.1%91.8%• Additional target samplesextend science grasp and fullyexploit this whole-hemisphereredshift survey.• AT programs include targetsfrom:• 2MASS NIR sky survey• DENIS NIR sky survey• SuperCosmos galaxycatalogs• ROSAT All-Sky <strong>Survey</strong>(RASS)• HI Parkes Sky <strong>Survey</strong>(HIPASS)• IRAS Faint Source Catalog(FSC)• NVSS and SUMSS radiosurveys• Hamburg-ESO QSO survey2MASS J < 13.75SuperCosmos r F

Large Scale Structure:Redshift Maps

<strong>6dF</strong>GS view ofthe LocalUniverse:VirgoSouthRedshiftShapleyHydraCentaurusOphiuchusNormaPavo-IndusHorologium-ReticulumFornaxColumba<strong>6dF</strong>GS data have establishednew redshifts for over 430southern Abell clusters.(Andernach, et al.)SculptorGalactic planeimage courtesyof 2MASS

<strong>6dF</strong>GS NearbyStructures:(A. Fairall et al)Example <strong>6dF</strong>GSstructure seen in a1000 km/s-wideslice insupergalacticcoordinate space.Adjacent galaxiesare enclosed insurfaces to highlightstructure and texture(Labyrinth software:Hultquist/Perumal)Over 500 voids withdiameters rangingfrom 1500 to 6000km/s have beenidentified

<strong>6dF</strong>GS compared to other wide redshift surveys<strong>6dF</strong>GS17,000 "°K

Near-infrared Luminosity Functions• <strong>The</strong> <strong>6dF</strong>GS K-band LFextends 1.5-2 magsfurther at both brightand faint ends (covers afactor of 10 4 in L)• Agrees with otherrecent LF measurementsup to small differencesbetween magnitudesystems• Previous, smallersamples have largeruncertainties in theirnormalisations9500 sq deg<strong>6dF</strong>GS2MASS + 2dF2MASS + ZCAT2MASS + SDSSJones et al (2006)83028 galaxies

Final NIR and optical luminosity functionsJones et al, in prep83,028galaxies66,461galaxies69,293galaxies47,598galaxies49,118galaxies• Revised LFs for FINALsample in all bands(30% more galaxies)• Small recalibrations ofthe photometry (mostsignificant in K b J r F )• Otherwise consistentwith published LFs

Luminosity density in optical and NIR• <strong>The</strong> luminosity densitiesin optical and NIRestimated from <strong>6dF</strong>GSare broadly consistentwith the 2dFGRS andSDSS <strong>results</strong>• K-band luminositydensity lies at lower endof range• From optical through NIR,the variation ofluminosity density withwavelength is consistentwith models for an oldstellar populationStellar population withz old= 12 Gyr, ! = 4 Gyr

Stellar Mass Function• NIR luminosities are goodproxies for the total stellarmasses in galaxies, so we canestimate the stellar massfunction from the K-bandluminosity function…• NIR light is dominated by the older and coolerstars comprising the bulk of the stellar mass• NIR mass-to-light ratios are well constrained,and k-corrections & extinctions are smaller inNIRModel uncertaintiesdominate the errors

<strong>The</strong> present-day stellar mass density• <strong>The</strong> <strong>6dF</strong>GS data provides (up to systematic errors in the models) the mostprecise measurement of the stellar mass density today<strong>6dF</strong>GSEyles+ (2006)• Stellar mass density is! * h = (1.80 ± 0.04) x10 -3" * = (5.00 ± 0.11) x10 8 h M ! Mpc -3

Stellar and Dynamical Masses• <strong>The</strong> relation betweenvelocity dispersion andstellar mass isconsistent with M * # $ 2• This is implies thatstar-formationefficiency in galaxies isroughly independent oftheir dynamical masses- i.e. M * /M dyn % const(cf. Gallazzi et al 2006)• <strong>The</strong> scatter in therelation translates to ascatter in star-formationefficiency of about 40%log [! (km/s)]log ! " 0.5 log M *log [M * (M Sun h -2 )]

<strong>Galaxy</strong> colours and stellar populationsK-selectedb J -selectedRestframe b J -r F10 Gyr3 Gyr1Gyr10 Gyr3 Gyr1Gyr0.40.0[Z/H]0.40.0[Z/H]RedshiftRedshift• NIR and optical samples have different mixes of galaxy types• Age and metallicity are substantially degenerate w.r.t. colours

<strong>Galaxy</strong> ages and metallicities• For 7000 DR1 galaxies wecan measure Lick indicesand emission lines at highS/N and get ages &metallicities• <strong>The</strong> distribution of ages &metallicities shows…• Most galaxies have-0.2

Metallicity and Mass-to-Light Ratios• Old galaxies show a clear massmetallicityrelation. Younggalaxies do not.BYoung (10 Gyr)RK• Dynamical mass-to-light ratios ofthe old population alone, in the B,R, and K-bands.(Proctor et al, in prep)• While the effects of age have beeneliminated (by our deliberateselection), metallicity has not.

Metallicity and Mass-to-Light Ratios• Old galaxies show a clear massmetallicityrelation. Younggalaxies do not.BAfterYoung (10 Gyr)K trendBefore correctionRK(Proctor et al, in prep)• When metallicity is accounted for,all three bands show remarkableagreement in the (M dyn /L) relations• From the (M/L)#M 0.15 relationfound, one would expect(M/L)~L 0.18 . Infact, (M/L)~L 0 .• <strong>The</strong>refore simple (M/L) variationswith M or L can not be used toexplain the ‘tilt’ of the Fund Plane

<strong>6dF</strong>GS science from the redshift survey• Studies of large scale structure (Fleenor et al 20005, 2006; Proust ey al 2006,Radburn-Smith et al 2006, Doyle & Drinkwater 2006, Andernach et al 2005)• Luminosity and mass functions (Jones et al 2006; Jones et al in prep)• <strong>The</strong> influence of local density and velocity distributions (Erdogdu et al2006a,b; Inoue & Silk 2006)• <strong>Galaxy</strong> groups and their properties (Brough et al 2006a,b; Forbes et al 2006,Firth et al 2006, Kilborn et al 2006)• Studies of special interest samples such as radio sources (Sadler et al 2006,Mauduit & Mamon 2007, Mauch & Sadler 2007), infra-red luminous galaxies(Hwang et al 2007) among many others.<strong>6dF</strong>GS Peculiar Velocity <strong>Survey</strong>• To map in detail the density and peculiar velocity fields over half the localvolume to ~15,000 km/s.• To provide additional constraints on cosmological models, and bettermeasurements of fundamental parameters, from statistics of these fields.• To study the ages, metallicities and star-formation histories of early-typegalaxies over a wide range of masses and environments.

<strong>6dF</strong>GS Database• <strong>6dF</strong>GS online database• Searchable using either SQL query commands or a WWW form• Each source has its own multi-extension FITS file, of spectra & postage stamps• <strong>The</strong> different target catalogues are also fully searchable online• Current - Data Release 2• Released April 2005• Data Jan 2002-Oct 2004• 89211 spectra• 83014 unique redshifts• 936 fields• Final Data Release• Expected Feb 2008• Complete dataset fromMay 2001 to Jan 2006• 137k spectra• 120k unique redshifts• 1464 fieldshttp://www-wfau.roe.ac.uk/<strong>6dF</strong>GS/