The KMOS Redshift One Spectroscopic Survey (KROSS): rotational velocities and angular momentum of z~0.9 galaxies

1.5 MB·

by  C. M. Harrison

MNRAS000,1–19(2016) Preprint24January2017 CompiledusingMNRASLATEXstylefilev3.0
The KMOS Redshift One Spectroscopic Survey (KROSS):
rotational velocities and angular momentum of z≈0.9 galaxies⋆
C. M. Harrison,1,2,† H. L. Johnson,1,3 A. M. Swinbank,3,1 J. P. Stott,4,1 R. G. Bower,3,1
Ian Smail,1,3 A. L. Tiley,4,1 A. J. Bunker,4,5 M. Cirasuolo,2 D. Sobral,6,7 R. M.
7 Sharples,8,1 P. Best,9 M. Bureau,4 M. J. Jarvis,4,10 G. Magdis11,12
1
1CentreforExtragalacticAstronomy,DurhamUniversity,SouthRoad,Durham,DH13LE,U.K.
0
2EuropeanSouthernObservatory,Karl-Schwarzschild-Str.2,85748Garchingb.München,Germany
2
3InstituteforComputationalCosmology,DurhamUniversity,SouthRoad,Durham,DH13LE,U.K.

n 4Astrophysics,DepartmentofPhysics,UniversityofOxford,KebleRoad,Oxford,OX13RH,U.K.
a 5AffiliateMember,KavliInstituteforthePhysicsandMathematicsoftheUniverse(WPI),TodaiInstitutesforAdvancedStudy,TheUniversityofTokyo,
J 5-1-5Kashiwanoha,Kashiwa,Japan277-8583

3 6DepartmentofPhysics,LancasterUniversity,Lancaster,LA14YB,U.K.
2 7LeidenObservatory,LeidenUniversity,P.O.Box9513,NL-2300RALeiden,TheNetherlands
8CentreforAdvancedInstrumentation,DurhamUniversity,SouthRoad,Durham,DH13LE,U.K.

] 9SUPA,InstituteforAstronomy,RoyalObservatoryofEdinburgh,BlackfordHill,Edinburgh,EH93HJ,U.K.
A 10DepartmentofPhysics,UniversityoftheWesternCape,Bellville7535,SouthAfrica
G 11DarkCosmologyCentre,NielsBohrInstitute,UniversityofCopenhagen,JulianeMariesvej30,DK-2100Copenhagen,Denmark
12InstituteforAstronomy,Astrophysics,SpaceApplicationsandRemoteSensing,NationalObservatoryofAthens,GR-15236Athens,Greece
h. †Email:[email protected]
p
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AcceptedXXX.ReceivedYYY;inoriginalformZZZ
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a
[ ABSTRACT
We present dynamical measurements for 586 Ha detected star-forming galaxies from the
2
KMOS (K-bandMulti-ObjectSpectrograph)Redshift One SpectroscopicSurvey(KROSS).
v
Thesamplerepresentstypicalstar-forminggalaxiesatthisredshift(z=0.6–1.0),withame-
1
dianstarformationrateof≈7M yr−1 andastellarmassrangeoflog(M [M ])≈9–11.We
6 ⊙ ⋆ ⊙
find that the rotation velocity-stellar mass relationship (the inverse of the Tully-Fisher re-
5
5 lationship) for our rotationally-dominated sources (vC/s 0 > 1) has a consistent slope and
0 normalisation as that observed for z=0 disks. In contrast, the specific angular momentum
1. (j⋆;angularmomentumdividedbystellarmass),is≈0.2–0.3dexloweronaveragecompared
to z=0 disks. Thespecific angularmomentumscales as j (cid:181) M0.6±0.2, consistentwith that
0 s ⋆
7 expectedfordarkmatter(i.e., jDM (cid:181) MD2/M3).We findthatz≈0.9star-forminggalaxieshave
1 decreasing specific angular momentum with increasing Sérsic index. Visually, the sources
: withthehighestspecificangularmomentum,foragivenmass,havethemostdisk-dominated
v
morphologies.Thisimpliesthatanangularmomentum–mass–morphologyrelationship,sim-
i
X ilartothatobservedinlocalmassivegalaxies,isalreadyinplacebyz≈1.
r
a Keywords: galaxies:kinematicsanddynamics;—galaxies:evolution
1 INTRODUCTION mergers,inflows,outflowsandturbulence(e.g.,Fall1983;Moetal.
1998; Weiletal. 1998; Thacker&Couchman 2001). Wearenow
It has been suggested for several decades that galaxies form
inaneraoflargeintegral-fieldspectroscopy(IFS)surveysthaten-
at the centre of dark matter halos (e.g., Rees&Ostriker 1977;
ableustospatially-resolvetheseoutflows,inflowsandgalaxydy-
Fall&Efstathiou1980;Blumenthaletal.1984;seeMoetal.2010
namicsfor hundreds tothousands ofgalaxiesthatspan>10Gyrs
forareview).Thebaryonsmaycollapseintoagalaxydiskornot
of cosmological time (e.g., Cappellarietal. 2011; Sánchezetal.
dependingonhowtheangularmomentumisre-distributedthrough
2012;Bryantetal.2015;Bundyetal.2015;Wisnioskietal.2015;
Stottetal. 2016). In tandem tothis, thelatest supercomputers al-
low the modelling of cosmological volumes with sufficient res-
⋆ Basedonobservations obtainedattheVeryLargeTelescopeoftheEu- olution to study the evolution of these internal baryonic pro-
ropean Southern Observatory. Programme IDs: 60.A-9460; 092.B-0538; cessesoflargesamplesofmodelgalaxies(e.g.,Duboisetal.2014;
093.B-0106;094.B-0061;095.B-0035
(cid:13)c 2016TheAuthors
2 C. M. Harrisonet al.
Vogelsbergeretal.2014;Schayeetal.2015;Khandaietal.2015). ple and observations, in Section 3 we describe the analyses and
The fundamental test of the latest cosmological models and their measured quantities, inSection 4wegive our resultsand discus-
assumptions,istosuccessfullyreproducethepropertiesoftheob- sionontherotationalvelocity–M⋆andthe js–M⋆relationshipsand
servedgalaxypopulationovercosmictime. inSection5wepresentourmainconclusions.Withthisworkwe
Inthisstudywefocusonstudyingspecificangularmomentum releaseacatalogueofobservedandderivedquantitiesthatisavail-
(js;i.e.,theangular momentumdivided bystellarmass, M⋆)that able in electronic format (see Appendix A). Throughout, we as-
hasbeenproposedasoneofthemostfundamentalpropertiestode- sumeaChabrierIMF(Chabrier2003),quoteallmagnitudesasAB
scribeagalaxy(e.g.,Fall1983;Obreschkow&Glazebrook2014). magnitudesandassumethatH0=70kms−1Mpc−1,W M=0.3and
Correctlymodellinghowangularmomentumtransfersbetweenthe W L =0.7;inthiscosmology,1arcseccorrespondsto8kpcatz=1.
haloandthehostgalaxyisfundamentalforgalaxyformationmod- Unlessotherwisestated,theupperandlowerboundsprovidedwith
els to be successful, with early models having significant angu- quotedmedianmeasurementscorrespondtothe16thand84thper-
larmomentumloss(e.g.,Navarroetal.1995;Navarro&Steinmetz centilesofthedistribution.
1997). Sufficient numerical resolution and realisticfeedback pre-
scriptions are required to correctly reproduce galaxy sizes, ro-
tation curves, mass-to-light ratios and hence the observed js– 2 SURVEYDESCRIPTION,SAMPLESELECTIONAND
M⋆ relationship through the correct re-distribution of the angu- OBSERVATIONS
lar momentum (e.g., White&Frenk 1991; Navarro&Steinmetz
KROSSisdesignedtostudythegaskinematicsofastatisticallysig-
1997; Ekeetal. 2000; Weiletal. 1998; Thacker&Couchman
2001;Governatoetal.2007;Agertzetal.2011;Brooketal.2012; nificantsampleoftypicalz≈1star-forminggalaxiesusingKMOS
data.Thefulldetailsofthesampleselection,theobservationsand
Scannapiecoetal.2012;Crainetal.2015;Geneletal.2015).
thedatareductionareprovidedinStottetal.(2016);however,we
Furthermore, the distribution of angular momentum may be
give an overview here in thefollowing sub-sections. Wealso de-
fundamental in determining a galaxy’s morphology. For exam-
scribethefinalsampleselectionusedforthisstudy.
ple, the relative prominence of the bulge relative to the disk
of galaxies (i.e., the morphology), for a fixed mass, appears
to be a function of the specific angular momentum for local
2.1 TheKROSSsurveyandsampleselection
galaxies (e.g., Sandageetal. 1970; Bertola&Capaccioli 1975;
Fall1983; Romanowsky&Fall2012;Obreschkow&Glazebrook KROSS is an IFS survey of 795 z=0.6–1.0 typical star-forming
2014;Corteseetal.2016).Thespecificangularmomentumoflocal galaxies designed to spatially-resolve the Ha emission-line kine-
ellipticalsisafactorof≈3–7lessthanspiralgalaxiesofequalmass matics. The targets were selected from four extragalactic deep
(Romanowsky&Fall 2012; Fall&Romanowsky 2013). There- fields that are covered by a wide range of archival multi-
fore, the angular momentum distribution may be fundamental wavelength photometric and spectroscopic data: (1) Extended
in the formation of the Hubble sequence of galaxy morpholo- Chandra Deep Field South (E-CDFS; see Giacconietal. 2001;
gies (e.g., Romanowsky&Fall 2012; Obreschkow&Glazebrook Lehmeretal. 2005); (2) Cosmological Evolution Survey (COS-
2014). Indeed, models have shown that very different morpholo- MOS; see Scovilleetal. 2007); (3) UKIDSS Ultra-Deep Sur-
gies can be produced using the same initial conditions but with vey (UDS; see Lawrenceetal. 2007) and (4) SA22 field (see
a different redistribution of angular momentum due to different Steideletal.1998 andreferences there-in). Most targetswerese-
feedbackprescriptions(e.g.,Zavalaetal.2008;Scannapiecoetal. lected using new or archival spectroscopic redshifts; however,
2008,2012).Placingobservational constraintsonthespecifican- ≈25percent of the sample were selected as z = 0.84 narrow-
gular momentum over a large range of cosmic epochs is there- band Ha emitters from the HiZELS and CF-HiZELS surveys
fore fundamental for constraining galaxy formation models and (Sobraletal. 2013a; Sobraletal. 2015). Targets were selected so
understanding the formation of galaxies of different morpholo- thattheHa emissionlineisredshiftedintotheJ-band,withahigher
gies. However, whilst js measurements have been made for local priority given to targets where the wavelength range of the red-
galaxiesandarewellconstrained,onlyafewattemptsto-datehave shiftedemissionlineisfreeofbrightskylines.Themedianredshift
been made tomake similar measurements of high-redshift galax- ofthesampleisz=0.85+0.11.Thedetailsoftheredshiftcatalogues
−0.04
ies(z&0.5;e.g., FörsterSchreiberetal. 2006; Continietal.2016; usedforselectionareprovidedinStottetal.(2016).
Burkertetal. 2016; Swinbank et al. 2017) an epoch where angu- Inadditiontotheredshiftcriteria,thetargetswereprioritised
larmomentumre-distributionmaybecrucialforgalaxyformation iftheyhaveobservedmagnitudesofKAB<22.5,correspondingto
(e.g.,Danovichetal.2015;Lagosetal.2016). a stellar mass limit of approximately log(M⋆[M⊙])&9.5 (see be-
In this paper we investigate specific angular momentum low)andtheyhavea‘blue’colourofr−z<1.5(seeFigure1).The
of high-redshift galaxies using the KMOS Redshift One Spec- r−zcolour cut reduces thechance of observing passive galaxies
troscopic Survey (KROSS; Stottetal. 2016), This survey con- and, potentially, very dusty star-forming galaxies for which it is
sists of ≈600 Ha detected typical star-forming galaxies. Such challengingtoobtainhighsignal-to-noiseHa observations.How-
a large survey has only become possible in recent years thanks ever, we show how our final sample represents typical z≈1 star-
to the commissioning of KMOS (K-band Multi Object Spectro- forminggalaxiesinSection2.3.
graph; Sharplesetal. 2004, 2013). This instrument that is com-
posed of 24 individual near-infrared integral field units (IFU)
2.2 Stellarmasses
has made it possible to map the rest-frame optical emission-line
kinematics of large samples of z≈0.5–3.5 galaxies (Sobraletal. The KROSS targets are located in extragalactic deep fields with
2013b; Wisnioskietal. 2015; Harrisonetal. 2016; Stottetal. archivaloptical–infraredphotometricdata.Thereforeitispossible
2016; Masonetal. 2016), an order of magnitude faster than was tomeasureopticalmagnitudesandestimatestellarmasses(seede-
possiblewithsurveysusingindividualnear-infraredIFUs. tails in Stottetal. 2016). For this work, we avoid using individ-
InSection2wedescribetheKROSSsurvey,thegalaxysam- ual stellar mass estimates from the spectral energy distributions
MNRAS000,1–19(2016)
KROSS:angularmomentumofz≈0.9 galaxies 3
M
-19.5 H-22.0 -24.5
33..00
22..55 Parent sample RUHaensr euosnlvodelevdtee vdcC tv e(cQd ( Q1(Q/3Q5/Q2) )[4 2[)71 [0%9%%]]] -1s] H[58a 6 ]detected RUAGensrNeo/slIvorerlevdeg vduC lav (CrQ (1Q/Q3/2Q)4)
22..00 erg 1042 22.9-1Myr]O •
11..55 bs) [ L*Ha ate [
r-z 11..00 sity (o 1041 2.3 mation r
00..55 mino 0.1 L*Ha ar for
00..00 u st
l
--00..55 aH 1040 0.2
1199 2200 2211 2222 2233 2244 10 9 10 10 10 11
K stellar mass [M ]
AB O •
Figure1.Left:Ther−zcolourversusobservedKABmagnitudefortheparentKROSSsample.Thesquaresymbolsrepresentthe586Ha detectedsourcesused
fordynamicalanalysesinthiswork;withgreensymbolsrepresentingsourceswhichhavespatially-resolvedvelocitymeasurements(dark/lightcorresponds
to quality 1/quality 2 [Q1/Q2]; see Section 3.4)and grey symbols representing sources that have spatially-unresolved velocity measurements (dark/light
correspondstoquality3/quality4[Q3/Q4]).Thedashedlinesshowtheselectioncriteriaforthehighestprioritytargets.Right:ObservedHa luminosityversus
stellarmass(scaledfromMH;topaxis;Section2.2)fortheHa detectedtargets.Thesymbolsarecolouredasintheleftpanel.Systematicerrorbarsareshown
inthebottomright.Thesolidlineshowsthe“mainsequence”ofstarforminggalaxiesatz=0.85(Speagleetal.2014;seeSection2.3)andthegreydashedlines
areafactoroffiveaboveandbelowthis.Thedottedlinesshow0.1×and1×L⋆Ha forthisredshift(Sobraletal.2015).Thetargetshaveamedianstar-formation
rateof7M⊙yr−1andarerepresentativeoftypicalstar-forminggalaxies.
(SEDs)duetothevarying qualitydataacross thefour fields.For mass range of this sample is log(M⋆[M⊙])=8.7–11.0, with a me-
consistency we use interpolated absolute rest-frame H-band AB dianoflog(M⋆[M⊙])=10.0−+00..44.ThemedianobservedHa luminos-
tmo-algignhittudraetsio(M(¡HH)=and0.c2o)nfvoelrlotwtoinsgtelMla⋆r=ma¡sHse×sw10it−h0a.4×fi(xMedH−m4.a7s1s)-. aittyzi≈sl1og(S(LobHraa[leergtsa−l.12])0=1451)..15−+O00v..33e,rawllh7ic9hpecrocrreenstpoofntdhsetsoam≈p0l.e6hLa⋆Hvae
Thismass-to-lightratioisthemedianvalueforthesamplederived luminositiesbetween0.1L⋆Ha andL⋆Ha (seeFigure1).Themedian
usingtheHYPERZSED-fittingcode(Bolzonellaetal.2000)witha Ha derivedstar-formationrateofoursampleis7+7M yr−1,fol-
suiteofspectraltemplatesfromBruzual&Charlot(2003)andthe −4 ⊙
lowingKennicutt(1998)correctedtoaChabrierinitialmassfunc-
U-bandtoIRAC4.5µmphotometry.Theinner68percentrangeis
0.3dexaroundthemedianmass-to-lightratiowhichwetaketobe tionandassuminganextinctionof AHa =1.73(themedianfrom
our SED fitting, following Wuytsetal. 2013 to convert between
thesystematicuncertaintyonthestellarmasses(seeFigure1).Our
stellarand gasextinction; seeStottetal.2016).Themedian star-
targetsaredominatedbybluegalaxies(Figure1)thatarelikelyto formation rate of our Ha detected sample is consistent with the
havesimilarmass-to-lightratios;however,theimplicationsonour
averagestar-formationandscatterof“mainsequence”galaxiesfor
angular momentum versus galaxy morphology results of the po-
themedianmassandmedianredshift(z=0.85)ofourtargetsfrom
tentiallysystematicdifferentmass-to-lightratiosforredderversus various works; e.g., SFR =5+5 M yr−1 from Schreiberetal.
bluergalaxiesisdiscussedinSection4.4. MS −2.5 ⊙
(2015)orSFR =8+5M yr−1 fromSpeagleetal.(2014),where
MS −3 ⊙
wehaveconvertedtoaChabrierIMFinbothcases(seeFigure1).
Forthefollowinganalyses ofthispaper weonly discussthe
2.3 Arepresentativesampleofstar-forminggalaxies ≈80percentofthefinalsamplethatareHa detectedsources.How-
ever,basedontheabove,weconcludethatthestar-formationrates
Forthisworkweapplyadditionalcutstotheoriginalsamplepre-
of this sample are representative of the “main sequence” of star-
sentedinStottetal.(2016).Firstlyweremove19sourcesforwhich
forminggalaxiesandthesesourcescanbeconsideredtobetypical
therewerepointingerrorswiththeIFUssuchthattheyhaveunreli-
star-forminggalaxiesatthisredshift(alsoseeStottetal.2016and
ablekinematicmeasurements.Secondly,weconsidertheobserved
Magdisetal.2016).
magnitude range of 19 <KAB <24.5 and remove any sources
whichhavephotometrythatisflaggedasunreliableinr,zorK .
AB
Thisleavesafinalsampleof743targets(93percentoftheorigi-
2.4 KMOSobservations
nalsample).Overall552(74percent)ofthefinalsamplelieinthe
highpriorityselectioncriteriaofr−z<1.5andKAB<22.5(see TheKROSSobservationsweretakenusingtheKMOSinstrument
Figure 1). As expected, the Ha detection rate is higher for these onESO/VLT.KMOSconsistsof24integralfieldunits(IFUs)that
targetswith478(87percent)detectedforthehighpriorityand108 canbe placed withina7.2arcminute diameter field. EachIFUis
detected(57percent)forthelowerprioritytargets(seeSection3.2
fordetectioncriteria).Overall586targets(79percent)fromthefi-
nalsamplearedetectedinHa (seeSection3.2). 1 Weremovethe22targets identified ashavinganAGNcontribution to
In Figure 1 we plot Ha luminosity (see Section 3.2) versus theiremissionlineswhencalculating averageluminosities,star-formation
estimatedstellarmassfortheHa detectedtargets.Thefullstellar ratesandmasses(seeSection3.4).
MNRAS000,1–19(2016)
4 C. M. Harrisonet al.

C-HiZ_z1_195 2 Ha intensity 2 vel. (km s-1) 2 s (km s-1) 100 8800 RT+ O
obs
ec 1 1 1 1 -1m s) 50 -1-1m s)m s) 6600
arcs -10 QID1:13 --210 --210 -95 0 95 --210 0 40 81 vel. (k -500 ss (k (kobsobs 2424000000
- 2 - 1 0 1 2 - 2 - 1 0 1 2 - 2 - 1 0 1 2 - 2 - 1 0 1 2 -10-5 0 5 10 --1100--55 00 55 1100
2 U-zvipe_z 1_1071 2 Ha int ensity 2 vel. (k m s-1) 2 s obs (k m s-1) 112200 DN O
arcsec -101 Q2 -101 -101 -101 -1el. (km s) 500 -1-1 (km s) (km s)obsobs 110046846800000000
ID:669 -77 0 77 0 76 152 v -50 ss 2200
-2 -2 -2 -2 00
- 2 - 1 0 1 2 - 2 - 1 0 1 2 - 2 - 1 0 1 2 - 2 - 1 0 1 2 -10 -5 0 5 10 --1100 --55 00 55 1100
2 C-zcos_z 1_652 2 Ha int ensity 2 vel. (k m s-1) 2 s obs (k m s-1) 40 5500 DN M
arcsec -011 Q1 -101 -101 -101 -1el. (km s) 1230000 -1-1 (km s) (km s)obsobs 234234000000
ID:146 -40 0 40 0 31 62 v -10 ss 1100
-2 -2 -2 -2 -20 00
- 1 0 1 - 2 - 1 0 1 2 - 2 - 1 0 1 2 - 2 - 1 0 1 2 -10 -5 0 5 10 --1100 --55 00 55 1100
E-zmus_z 1_119 2 Ha int ensity 2 vel. (k m s-1) 2 s obs (k m s-1) 200 115500 RT+ M
ec 1 1 1 1 -1m s) 100 -1-1m s)m s) 110000
arcs -10 QID1:183 --210 --210 -200 0 200 --210 0 78 156 vel. (k -1000 ss (k (kobsobs 550000
- 1 0 1 - 2 - 1 0 1 2 - 2 - 1 0 1 2 - 2 - 1 0 1 2 -10-5 0 5 10 --1100--55 00 55 1100
2 E-zmus_z 1_12 2 Ha int ensity 2 vel. (k m s-1) 2 s obs (k m s-1) 200 115500 RT+ M
arcsec -101 Q1 -101 -101 -101 -1el. (km s) -1100000 -1-1 (km s) (km s)obsobs 1100550000
ID:184 -202 0 202 0 68 135 v -200 ss
-2 -2 -2 -2 00
- 2 - 1 0 1 2 - 2 - 1 0 1 2 - 2 - 1 0 1 2 - 2 - 1 0 1 2 -10-5 0 5 10 --1100--55 00 55 1100
2 E-zmvvd_ z1_67 2 Ha int ensity 2 vel. (k m s-1) 2 s obs (k m s-1) 100 110000 RT+ M
arcsec --0121 QID1:316 --2101 --2101 -141 0 141 --2101 0 50 100 -1vel. (km s) --11-555000000 ss-1-1 (km s) (km s)obsobs 246824680000000000
- 1 0 1 - 2 - 1 0 1 2 - 2 - 1 0 1 2 - 2 - 1 0 1 2 -10 0 10 --1100 00 1100
ec 12 SS-MC1F4H-1IZ6E4 L2S90- 12 Ha int ensity 12 vel. (k m s-1) 12 s obs (k m s-1) -1m s) 50 -1-1m s)m s) 68680000 RT M
arcs -10 Q3 -10 -10 -63 0 63 -10 0 43 85 vel. (k -500 (k (kobsobs 24240000
ID:337 ss
-2 -2 -2 -2 00
- 2 - 1 0 1 2 - 2 - 1 0 1 2 - 2 - 1 0 1 2 - 2 - 1 0 1 2 -10 -5 0 5 10 --1100 --55 00 55 1100
arcsec -1012 SSQ-MC11F4H-8IZ5E7 L9S7- -1012 Ha int ensity -1012 -v15e1l. (k0 m s1-15)1 -1012 s 0obs (k5 0m s1-100) -1vel. (km s) 1-5500000 -1-1 (km s) (km s)obsobs 1100246824680000000000 RT+ M
ID:359 -100 ss
-2 -2 -2 -2 00
- 2 - 1 0 1 2 - 2 - 1 0 1 2 - 2 - 1 0 1 2 - 2 - 1 0 1 2 -10 0 10 --1100 00 1100
arcsec arcsec arcsec arcsec r (kpc) rr ((kkppcc))

Figure2.Examplespatially-resolvedgalaxiesfromtheKROSSsample(withexamplesfromeachfieldstudiedandcoveringtherangeindataquality).From
lefttoright:(1)broad-bandimage(3-colourwhenavailablefortheHSTcoveredtargets)wherethedashedorangelinerepresentsPAim(IDsandqualityflags
arealsoshown);(2)Ha intensitymapwheretheoverlaidcontoursshowthedistributionofcontinuumemissionandthedashedcirclerepresentstheseeing
FWHM;(3)observedHa velocity mapwherethesolidblacklinerepresents PAvel andthedashedorangelinerepresents PAim;(4)observedHa velocity
dispersionmap(s obs)wherethelinesareasinpanel3;(5)velocityprofilesextractedalongPAvel wherethesolidcurveisthediskmodelandthevertical
dashedlinesaretheradiiatwhichtherotationalvelocitiesaremeasured(averageofhorizontaldashedlines);however,forquality3sourcesthevelocitiesare
estimatedfromthegalaxy-integratedspectra(e.g.,ID337);(6)observedvelocitydispersionprofileextractedalongPAvelwherethehorizontaldottedlineis
ats 0,obs,thedot-dashedlineisats 0.Thesolidhorizontallinesinpanels1and2represent5kpcinextent.Theequivalentfiguresforallspatially-resolved
targetsareavailableonline(seeAppendixA).
MNRAS000,1–19(2016)
KROSS:angularmomentumofz≈0.9 galaxies 5
2.8 × 2.8 arcsec in size with 0.2 arcsec pixels. The observation Corteseetal.(2016)recentlypresentedIFSresultsonthean-
weretaken during ESOperiods P92–P95using Guaranteed Time gularmomentumof≈500z<0.1galaxieswithlog(M⋆[M⊙])>8
Observations (Programme IDs: 092.B-0538; 093.B-0106; 094.B- from the SAMI survey (Bryantetal. 2015). Although this sample
0061; 095.B-0035). The sample is also supplemented with sci- is larger than Romanowsky&Fall (2012), their specific angular
enceverificationdata(ProgrammeID:60.A-9460;seeSobraletal. momentum measurements are constructed using a very different
2013b; Stottetal. 2014). The median J-band seeing for the ob- method(followingEmsellemetal.2007)andarerestrictedbylim-
servationswas0.7arcsec, with92percentof thetargetsobserved itations such as only measuring the angular momentum within a
duringseeingthatwas<1arcsec.Theindividualseeingmeasure- small radii of R and removing small galaxies from their sam-
1/2
mentsaretakenintoaccountduringtheanalyses.Allobservations ple.Therefore,forthisstudy,weusetheirsampleforaqualitative
weretakenusingtheYJ bandwithatypicalspectralresolutionof comparisononly(Section4.3).
R=l /Dl =3400. We correct for the instrumental resolution in the In Section 4.2 we compare our rotation velocity-mass rela-
analysespresentedhere.Individualframeshaveexposuretimesof tionshiptotherelationshippresentedfor189z<0.1diskgalaxies
600sandachoptoskywasperformedeverytwoscienceframes. inReyesetal.(2011).TheReyesetal.(2011)sampleisidealasit
Mosttargetswereobservedwith9ksonsource,withaminimum alsousesHa emissionasatracerofrotationalvelocityandcovers
of1.8ksandamaximumof11.4ks(seeStottetal.2016). thesamestellarmassrangeasoursample(seeTileyetal.2016for
The data were reduced using the standard ESOREX/SPARK furtherdiscussiononlow-redshiftsamples).
pipeline(Daviesetal.2013).However,eachABpairwasreduced
individually, with additional sky subtraction being performed on
each pair using residual sky spectra obtained from dedicated sky 3 ANALYSIS
IFUs. These AB pairs were flux calibrated using corresponding
observationsofstandardstarsthatwereobservedduringthesame In this study we investigate the rotational velocities and specific
nightasthesciencedata.TheindividualABpairswerethenstacked angularmomentum(js)ofHa detectedgalaxies.Towardsthiswe
using a clipped average and re-sampled onto a pixel scale of 0.1 makemeasurements ofthegalaxy sizes,intrinsicvelocitydisper-
arcsec(Stottetal.2016).Thesecubeswereusedtocreatethespec- sions and inclination-corrected rotational velocities. We combine
tra,thelineandcontinuum imagesandtheHa intensity, velocity archival high spatial resolution broad-band imaging, which trace
and velocity dispersion maps used intheanalyses presented here thestellarlightprofile(Section3.1),withHa velocityandvelocity
(seeSection3.2). dispersionmapsderivedfromourKMOSIFUdata,whichtracethe
galaxykinematics(Section3.2).Theseanalysesbuildupontheini-
tialkinematicanalysesoftheKROSSdata,whichdoesnotinclude
the broad-band imaging analyses, presented in Stottetal. (2016)
2.5 Comparisonsamples
whoinvestigateddiskpropertiesandgasanddarkmattermassfrac-
For our specific angular momentum measurements, we fo- tions and in Tileyetal. (2016) who investigated the Tully-Fisher
cus on a comparison to the local galaxy sample presented in relationship.Forallofthe586Ha detectedtargetstherawandde-
Romanowsky&Fall(2012)(seeSection4.3).Thiscomprehensive rivedquantities,alongwithallofthenecessaryflagsdescribedin
study contains kinematic measurements (primarily from longslit thefollowingsubsections,aretabulatedinelectronicformat(see
data) for ≈100 nearby bright galaxies including a range of mor- AppendixA).
phologiesfromearly-typegalaxiestodisk-dominatedspiralgalax-
ies. They calibrate global relationships between observed veloci-
3.1 Broad-bandimagingandalignmentofdatacubes
ties,radiiandintrinsicspecificangularmomentum.Therefore,we
usethisstudytoguideouranalysistechniques,usingvelocitiesob- Tomake measurements of thehalf-light radii (R ),morpholog-
1/2
tained at the same physical radii as in their study (i.e., 2×R ) ical axes(PA ) and inclination angles (q ) wemake use of the
1/2 im im
andthesameglobalrelationshipstoestimatespecificangularmo- highest spatial resolutionbroad-band imaging available. Withthe
mentum using velocity, inclination angle and radii measurements aimof obtaining the best characterisation of thestellar light pro-
(seeSection3).Whenquotingz=0diskangularmomentumweuse file for each target we prefer to use near infrared H- or K- band
the raw values of disk radii, velocity and inclination angle pro- images; however, we use optical images obtained using HST in
vided by Romanowsky&Fall (2012) for the spiral galaxies and preference to ground-based near infrared images, when applica-
apply consistent methods to that adopted for our sample (Sec- ble, due to the &5× better spatial resolution. Overall 46percent
tion4.3).Intheabsenceofanalternative,weusetheangularmo- ofthesamplehaveHSTcoverage,whilsttheremainderarecovered
mentummeasurementsfortheearly-typegalaxiesdirectlyquoted byhigh-qualityground-basedobservations(detailsbelow).Weper-
by Romanowsky&Fall (2012). We apply the colour-dependant formvariousteststoassessthereliabilityofourmeasurementsob-
correctionstotheRomanowsky&Fall(2012)totalstellarmasses tainedusingthesedifferentdatasets.Exampleimagesofourtargets
using(B−V)0coloursfromPatureletal.(2003)andEquation1of areshowninFigure2.
Fall&Romanowsky(2013).2Wenotethatourdatatracesangular
momentumusingHa emissionwhichmayresultin≈0.1dexlarger
3.1.1 Broad-bandimages
angularmomentumcomparedtostellarangularmomentum,based
onlow-redshiftmeasurements(e.g.,Corteseetal.2014,2016).We All of our targets in E-CDFS and COSMOS, and a subset of
discussthisfurtherinSection4.3. the targets in UDS have been observed with HST observations.
These data come from four separate surveys (1) CANDELS
(Groginetal. 2011; Koekemoeretal. 2011); (2) ACS COSMOS
2 Wenotethat13oftheRomanowsky&Fall(2012)sampledonothave (Leauthaudetal.2007);(3)GEMS(Rixetal.2004)and(4)obser-
(B−V)0 colours in Patureletal. (2003) and therefore we remove these vationsunderHSTproposalID9075(seeAmanullahetal.2010).
sourcesfromthesample. Overall, WFC3-H-band observations are available for 36percent
MNRAS000,1–19(2016)
6 C. M. Harrisonet al.
of the HST observed targets (CANDELS fields) with a PSF of
FWHM≈0.2arcsec. For the remainder, we use the longest wave- Ha detected [586]
lengthdataavailable,thatis,ACS-Ifor57percentandACS-z′for 111555000 R measured (no upper limits) [94%]
1/2
7percent,whichhaveaPSFofFWHM≈0.1arcsec.
Duetothedifferentrest-framewavelengthsbeingobservedfor
thedifferentsetsofimageswetestforsystematiceffects.Wemea-
surethekeypropertiesof R1/2,q im andPAim (seeSection3.1.2) berber 111000000
usingboththeH-bandandI-bandimagesforthe128targetswhere mm
thesearebothavailable.Wefindthatthemedianratiosandstandard uu
nn
deviation between the two measurements to be: R /R =
1/2,I 1/2,H
1.1±0.2;q im,I/q im,H=1.0±0.2andPAim,I/PAim,H=1.0±0.1. 555000
This test indicates that our position angle and inclination an-
glemeasurements arenot systematically affectedby thedifferent
bands.However,theobservedI-bandsizesmeasurementsaresys-
000
tematically higher than the observed H-band size measurements
000 222 444 666 888 111000
by ≈10percent. This isconsistent withthe HST-based resultsof
hhaallff--lliigghhtt rraaddiiii [[kkppcc]]
vanderWeletal. (2014) (using their Equation 1) who find that
z≈0.9,log(M⋆[M⊙])=10galaxiesareafactorof≈1.2±0.2larger Figure3.Distributionofcontinuumhalf-lightradii,includingupperlimits,
intheobservedI-bandcomparedtointheobservedH-band,where fortheHa detected targets.Thedistributionforthe94percentoftargets
the quoted range covers the results for the stellar mass range withmeasuredradii(i.e.,excludingupperlimits)isshownastheoverlaid
log(M⋆[M⊙])=9–11.Weapplya10percentcorrectiontoaccount filledgreenhistogram.Themajorityofourgalaxieshavespatially-resolved
forthiseffectinSection3.1.2. radiimeasurements.
For the UDS targets, which are not covered by HST ob-
servations, we make use of Data Release 8 K-band observa-
targetsareHa detectedtargetsthatarespatially-resolvedintheIFU
tions taken with the UKIRT telescope as part of the UKIDSS
data(Section3.2)andhaveinclinationanglesandpositionangles
survey (Lawrenceetal. 2007). The stacked image has a PSF of
measureddirectlyfromthebroad-bandimaging(detailedbelow).
FWHM=0.65arcsec. Finally, for the SA22 targets we make use
Toobtainmorphological positionangles(PA ) andaxisra-
oftheK-bandimagingfromtheUKIDSSDeepExtragalacticSur- im
tiosofourtargetsweinitiallyfitthebroad-bandimageswithatwo-
veyofthisfield(Lawrenceetal.2007).Theseimageshaveatypi-
dimensionalGaussianmodel.Toobtaininclinationangles(q )we
calPSFofFWHM=0.85arcsec.Wedeconvolvedthesizemeasure- im
correct the axis ratios (b/a) for the PSF of each image and then
mentstoaccountfortheseeingineachfield(Section3.1.2).
converttheseintoinclinationanglesbyassuming,
To assess the impact of the poorer spatial resolution of
the ground based images compared to the HST images we con- (b/a)2−q2
volve the HST H-band images from our sample to a Gaus- cos2q im= 1−q2 0, (1)
0
sian PSF of: (1) FWHM=0.65arcsec (i.e., the UDS PSF) and
where q is the intrinsic axial ratio of an edge-on galaxy (e.g.,
(2) FWHM=0.85arcsec (i.e., the SA22 PSF), before making 0
Tully&Fisher1977)andcouldhaveawiderangeofvalues≈0.1–
the measurements of radius, positional angle and inclination an-
0.65(e.g.,Weijmansetal.2014;seediscussioninLawetal.2012).
gle (described below). On average, position angles are unaf-
fected by the convolution in both cases, with a median ratio of Weuseq0=0.2,whichisapplicableforthickdisks;however,asa
PAim,conv/PAim,HST =1.0; however an introduced 1s scatter of guide,afactoroftwochangeinq0resultsina<7percentchange
intheinclination-correctedvelocitiesforourmedianaxisratio.To
10percentand20percentfortheUDSPSFandSA22PSF,respec-
beveryconservativeinouruncertaintiesarisingfromtheassumed
tively.Similarlytheinclinationanglesareunaffected,onaverage,
by the convolution, with q im,conv/q im,HST =1.0, but with an in- intrinsicgeometrywesettheuncertaintiesoftheinclinationangles
troduced1s scatterof15percentand20percent,respectively.We tobeaminimumof20%.
We compared our morphological position angles and in-
includethesepercentagescattersasuncertaintiesonthemeasured
clination angles to those presented in vanderWeletal. (2012)3
inclination angles from the ground based images. Following the
for the 142 targets that overlap with the parent KROSS sam-
methodsdescribedinSection3.1.2wefindasmallsystematicfrac-
ple (see Section 2.3). vanderWeletal. (2012) fit Sérsic models
tional increase the measured half-light radii after the convolution
of5%; however, thisisnegligiblecompared totheintroduced 1s to the HST near-infrared images using GALFIT that incorporates
PSF modelling. Excluding the 4 targets flagged as poor fits by
scatterof25percentand35percent.Weincludethesepercentage
vanderWeletal.(2012),wefindexcellentagreementbetweenthe
scattersasuncertainties onthemeasuredhalf-light radiifromthe
groundbasedimages. GALFIT results and those derived using our method. The median
differenceintheinclinationanglesareDq im=0.4+−53degrees.For
thepositionanglesthemediandifferenceis|D PAim|=1.8degrees
3.1.2 Positionangles,inclinationanglesandsizes with84percentagreeingwithin6degrees.Thisdemonstratesthat
therearenosystematicdifferencesbetweenthetwomethods. We
Weaimtoapplyauniformanalysisacrossalltargetsirrespectiveof
alsocomparedourinclinationanglesfor152ofourCOSMOStar-
thevarying spatialresolutionof thesupporting broad-band imag-
getswithI-bandimagestothosederivedusingtheaxisratiospre-
ing.However,weareabletomakeuseofmorecomplexanalyseson
sentedinTascaetal.(2009)forthesamesources.Again,wefind
theHST-CANDELSsubsetoftargetsforabaselineforcomparison
(vanderWeletal. 2012). Furthermore, we define various quality
flags,detailedbelow,tokeeptrackofthequalityandassumptions 3 WeconverttheaxisratiospresentedinvanderWeletal.(2012)toincli-
oftheanaylsesthatwereappliedforindividualtargets.“Quality1” nationanglesfollowingEquation1.
MNRAS000,1–19(2016)
KROSS:angularmomentumofz≈0.9 galaxies 7
excellent agreement with Dq im =−0.4+−74degrees. We also note 3.1.3 Datacubealignment
that wefindgood agreement between themorphological position
ToalignourKMOSdatacubestothebroad-bandimagingwemade
anglesandkinematicpositionanglesforboththeHSTtargetsand
use of continuum measurements in the data cubes. We produced
ground-based targets (see Section 3.3.2), which provides further
continuum images by taking a median in the spectral direction,
confidenceonourderivedvalues.Motivatedbythesmallscatterof
avoiding spectral pixels in the vicinity of emission lines and ap-
theabovecomparisons,weenforceanadditionalerrorof5oonall
plying2-s clipping,toavoidregionswithstrongskylineresiduals.
oftheinclinationanglemeasurements.Thegroundbasedmeasure-
Weidentifythecontinuumcentroidsfor85percentoftheHa de-
mentshaveanadditionaluncertaintyof15percentand20percent
tectedtargets. Duetofaint continuum emissionfor 15percent of
respectively for UDS and SA22 due to the effects of the poorer
the targets we were required to obtain centroids from images in-
resolutionforthesetargets(seedetailsinSection3.1.1).
cludingthecontinuumandemissionlines.Examplesofcontinuum
For7percentoftheHa detectedtargetsweareunabletomea- imagesareshownascontoursinFigure2.Thesecontinuumcentres
werethenusedtoalignthedatacubestothecentresofthearchival
suretheinclinationanglesfromtheimagingduetopoorspatialres-
broad-bandimages.
olution.Forthesesourcesweassumethemedianaxisratioofthe
targetswithspatially-resolved HST images (b/a)=0.62+0.20 (i.e.,
−0.22
q im=53+−1178degrees). This median axis ratio is in agreement with 3.2 Emissionlinefittingandmaps
theresultsof Lawetal. (2012) whouse therest-frameHSTopti-
Inthissub-sectionwedescribethevariouskinematicmeasurements
cal images for z≈1.5–3.6 star-forming galaxies and find a peak
wemakeusingourIFUdata.Theseincludebothgalaxy-integrated
axis ratioof (b/a)≈0.6. Thisassumed inclination value for these
7percentofourHa detectedtargetsresultsinacorrectionfactor and spatially-resolved measurements (e.g., rotation velocities, in-
of1.2+0.5 totheobserved velocities.Thesetargetsareflaggedas trinsicvelocitydispersionsandkinematicmajoraxes).Weproduce
−0.2 both galaxy-integrated spectra and two dimensional intensity, ve-
“quality2”sources.
locityandvelocitydispersionmaps.Inthefollowingsub-sections
wedescribehowwefittheHa and[NII]6548,6583emission-line
Tomeasurethehalf-light radiiofthebroad-band imageswe
profiles, produce the spectra and maps and make the kinematic
adoptedanon-parametricapproach.Wemeasuredthefluxesinin-
measurements. Example maps are shown in Figure 2 and all ve-
creasinglylargeellipticalaperturescentredonthecontinuumcen-
locitymapsfor the552 targetsthatarespatially-resolvedsources
tresthathavepositionanglesandaxisratiosasderivedabove.We
intheIFUdataareshowninFigure4.
measureR asthePSF-deconvolvedsemi-majoraxisoftheaper-
1/2
ture which contained half of the total flux. For the targets where
the images are in the I or z′ band we apply a systematic correc- 3.2.1 Emissionlinefitting
tion of a factor of 1.1 to account for the colour gradients (see
Section 3.1.1). To test our technique, we compared to the GAL- WefittheHa and[NII]6548,6583emission-lineprofilesobserved
FITSérsicfitstothesameHSTdataofvanderWeletal.(2012)for in both galaxy-integrated spectra and spectra extracted from spa-
thetargetscoveredbybothstudies.Wefindthatthemedianoffset tialbinstoderiveemission-line fluxes,linewidthsand centroids.
betweenthetwomeasurementstobeD R /R =−0.01 Thesefitswereperformedusingac 2minimisationmethod,where
1/2 1/2,GALFIT
witha30percent1s scatter.Reassuringlywealsodidnotseeany we weighted against the wavelengths of the brightest sky lines
trend intheoffset between these toomeasurements asafunction (Rousselotetal. 2000). The emission-line profiles were charac-
of magnitude. This indicates that the two methods are in general terisedassingleGaussian components withalinear local contin-
agreement; however, we assume a minimum error of 30percent uum. The continuum regions were defined to be two small line-
(due to the method) on all of our half-light radii measurements. freewavelength regionseach sideof theemission linesbeing fit-
Thegroundbasedmeasurementshaveanadditionaluncertaintyof ted.Toreducethedegeneracybetweenparameters,wecouplethe
25percentand35percentrespectivelyforUDSandSA22dueto [NII]6548,6583doubletandHa emission-lineprofileswithafixed
theeffectsofthepoorerspatialresolutionofthebroad-bandimag- wavelengthseparationusingtherest-framevacuumwavelengthsof
ingforthesetargets(seedetailsinSection3.1.1). 6549.86Å,6564.61Å and6585.27Å.Wealsorequirethatallthree
emissionlineshavethesamelinewidthandwefixthefluxratioof
For84oftheHa detectedtargetswewereunabletousethe the[N II]doublet tobe3.06(Osterbrock&Ferland2006).These
imagingtodetermineR fromthebroad-bandimaging;however, constraints leave the intensity of the Ha and the [N II] doublet
1/2
wewereabletousetheturn-overradiusfromthedynamicalmodels freetovary,alongwiththeoverallcentroid,linewidthandcontin-
toestimateR ,calibratedusingtheimagingradiifortheresolved uum. The emission-line widthsare corrected for the instrumental
1/2
sources(seeSection3.3.3).Wehighlightthesesourcesas“quality dispersion, which ismeasured fromunblended sky linesnear the
2”sources(seeFigure1).Forafurther33targets(only6percent observedwavelengthoftheHa emission.
oftheHa detectedtargets),wherewewerenotabletoextractradii
fromtheIFUdataorthebroadbandimaging,weassumeconser-
3.2.2 Galaxy-integratedspectraandvelocitymaps
vativeupperlimitsonthehalf-lightradiiof1.8×s PSF.
Galaxy-integratedspectrawerecreatedfromthecubesbysumming
Ahistogramofthehalf-lightradiiforthe586Ha detectedtar- thespectrafromthespatialpixelsthat fallwithinacircularaper-
getsisshowninFigure3.Themedianhalf-lightradiiis2.9+1.8kpc tureofdiameter1.2arcseccenteredonthecontinuumcentroid.We
−1.5
(excludingupperlimits).Includingtheupperlimittargetswithzero thenfittheHa and[NII]emission-lineprofilesusingthemethods
radiiortheirmaximumpossibleradii,resultsinamedianof2.7kpc describedabovetoderive:(1)the“systemic”redshiftofeachtar-
or2.8kpc,respectively.Themedianhalf-lightradiifortheHa un- get;(2)theobservedvelocitydispersions tot and(3)theHa flux.
detectedtargetsis2.7+1.5kpcandtherefore,thesearenotsignifi- Sourceswereclassedasdetectedifthesignal-to-noiseratio,aver-
−1.1
cantlydifferentinsizetothosethatweredetected. agedover2×thederivedvelocityFWHMoftheHa line,exceeded
MNRAS000,1–19(2016)
8 C. M. Harrisonet al.
KROSS
]
1 (z~1)
-
r
y
O
•
M
[

e
t 10
a
r

n
o
i
t
a
m
r
o
f

r
a 1
t
s
9 10 11
10 10 10
stellar mass [M ]
O •
Figure4.Velocitymapsforallofour552spatially-resolved targets.Eachmapispositionedatthecorrespondingpositioninthestar-formationrateversus
stellarmassplaneasdescribedbytheaxes.Thesolidlineshowsthe“mainsequence”ofstar-forminggalaxiesatz=0.85fromSpeagleetal.(2014)andthe
dashedlinesareafactoroffiveaboveandbelowthis.Theverticaldottedlinecorrespondstoourselectioncriteriaforhighprioritytargets(seeFigure1and
Section2.1).Thehorizontaldottedlinerepresentsthe5thpercentileofthestar-formationratesofthespatially-resolvedtargets.
three. The emission-line profiles and the fits for all 586 targets wasmet(uptoamaximumspatialof0.7×0.7arcsec;i.e.,thetyp-
areavailableonline(seeAppendixA).The1.2arcsecaperturewas icalseeingoftheobservations).Forthiswork,thesemapsarefur-
chosenasacompromisebetweenmaximisingthefluxandsignal- ther masked by visual inspection, identifying clearly bad fitsdue
to-noiseratios.Weestimatetwomethodsforanaperturecorrection toskylinesordefects.Overall552(94percent)oftheHa detected
to themeasured fluxes and hence to obtain galaxy-integrated Ha sourcesshowspatially-resolvedemission(seeStottetal.2016).We
luminosities.First,weusetheHa fluxes(i.e.,with[NII]removed) assignalloftheunresolvedsourcesaflagof“quality4”.Example
presented inSobraletal. (2013a) for theHiZELSsourcesfor the Ha intensity,velocityandvelocitydispersionmapsareprovidedin
112 of our Ha detected targetsthat overlap between the surveys. Figure2andallvelocitymapsareshowninastar-formationrate
We obtain a median aperture correction of 1.7. Secondly, we re- versusstellarmassplaneinFigure4.
measurethefluxesagainfromourIFUdatabutusinganaperture
withadiameterof2.4arcsec.Usingthesourceswhicharedetected
in both apertures we obtain a median aperture correction of 1.3.
Within the uncertainties we did not find a significant correlation
betweenaperturecorrectionandgalaxysize.Therefore,weapply
afixedaperturecorrectionfactorof1.5tothemeasuredHa fluxes 3.3 Spatially-resolvedkinematicmeasurements
anda30percenterrortoreflecttheuncertaintyonthisvalue. 3.3.1 Kinematicmajoraxes
TheHa intensity,velocityandvelocitydispersionmapswere To identify the kinematic major axes for all of the targets in our
firstproducedbyStottetal.(2016).Thesewerecreatedbyfitting dynamical sample we make use of the Ha velocity maps. We
theHa and[NII]emissionlinesateachpixelfollowingtheproce- rotated the velocity maps around the continuum centroids (see
duredescribedaboveandthenindividualvelocitiesarecalculated Section 3.1.3) in 1degree steps, extracting the velocity profile in
withrespecttothegalaxy-integrated‘systemic’redshifts.Ifanin- 1.5arcsecwidth“slits”andcalculatingthemaximumvelocitygra-
dividualpixeldidnotresultinadetectedlinewithasignal-to-noise dient along the slit. The position angle with the greatest velocity
ratio of >5, the spatial binning was performed until this criteria gradientwasidentifiedasbeingthemajorkinematicaxis(PAvel).
MNRAS000,1–19(2016)
KROSS:angularmomentumofz≈0.9 galaxies 9
intheformof,
100 vvIrCCre//ssg00u><l11ar Quality 1 im=q v(r)2= r2p Gµ0(I0K0−I1K1)+voff, (3)
2 RD
80 5
g] o whereristheradialdistance,µ isthepeakmasssurfacedensity,
e 0
) [d 60 RBDessiselthfuendcitsioknrsadeivia,lvuoaftfeidsathte0.v5erl/oRcDity. Daturrin=g0thaenfidttIinnKgnwaereatlhsoe
y (el allowtheradialcentretovaryby0.2arcsec(i.e.,theKMOSpixel
m,v 40 scale). Thevelocity offset, voff,isapplied tothevelocity profiles
Ai beforemakingmeasurementsofdynamicalvelocities.
P
Theprimaryfunctionofthemodelvelocityprofilesistoex-
20
D tractvelocitiesbyinterpolatingthroughthedatapointsandnotto
derivephysicalquantities;however,in13%ofthecaseswearere-
0 quiredtoextrapolatethemodelbeyondthedata(seebelow).Focus-
ingonthe“quality1”sourceswithHSTimages(i.e.,thosewiththe
0.0 0.2 0.4 0.6 0.8
bestconstraintsonthehalf-lightradiifromthebroad-band imag-
image axis ratio
ing), we derive a median ratio of R /R =0.8+0.5. This is con-
1/2 D −0.4
Figure5.Thedifferencebetweenthephotometricandkinematicposition sistentwithourpredictionsforanintrinsicratioofR1/2/RD=1.68
angles(Y )asafunctionofbroad-bandimageaxisratio.Thelargersymbols thathasbeenbeam-smearedduringour≈0.7′′KMOSobservations
represent sources covered by broad-band HST imaging. The largest data (Johnsonetal.inprep.;seedetailsbelow).Weapplythismedian
points with the error bars show the running median for the rotationally- ratiotothederivedR valuestoestimatethehalf-lightradiiforthe
D
dominatedsystemsandthethincurveshowstherunning84thpercentile. “quality2”sourcesthatdonothavespatially-resolvedbroad-band
Fortherotationally-dominatedsourcesthemedianmisalignmentif13◦.The imagingdataandhencethatlackdirectR measurements(Sec-
1/2
good agreement between the positional angles observed for targets both
tion 3.1.1). Due to the uncertainty in this estimate we impose an
withandwithoutHSTimagingplacesconfidenceonourmeasurements(see
uncertaintyof60percent.Wenotethatweobtainconsistentveloc-
Section3.3.2).
itymeasurements (seebelow)ifweapplythecommonly adopted
arctan model (Courteau 1997; adopted for KROSS in Stottetal.
3.3.2 Morphologicalversuskinematicmajoraxes 2016) instead of the exponential disk model, with a median per-
Herewe compare the derived kinematics major axes, PA , with centagedifferenceof(vC,arctan−vC,disk)/vC,disk=0.5+−93percent.
vel Forconsistencyandtofacilitateafaircomparisontoourlow-
themorphologicalpositionalangles,PA forourtargets.Follow-
im redshiftcomparisonsamples(seeSection2.5)wemakemeasure-
ing Wisnioskietal. (2015) (c.f. Franxetal. 1991) we define the
mentsoftherotationalvelocitiesatthesamephysicalradiiforall
“misalignment”betweenthetwopositionanglesas,
targets.Wemake measurements at twodifferent radii of 1.3R
1/2
sinY =|sin(PAim−PAvel)|, (2) and2R1/2.Thesecorrespondto≈2.2RDand≈3.4RD,respectively,
foranexponentialdisk.Thefirstofthese,wecallv ,iscommonly
2.2
whereY isdefinedasbeingbetween0◦ and 90◦.InFigure5we adoptedintheliteratureasitmeasuresthevelocityatthe“peak”of
show Y as a function of image axis ratio for the sources where therotationcurveforanexponentialdisk(e.g.,Milleretal.2011;
we have measured the kinematic position angles, morphological Pellicciaetal.2016)andweincludethesevaluesforreferencefor
position angles and axis ratios (i.e., “quality 1” sources). As ex- interestedparties.Thesecondofthese,whichwecallv ,wascho-
C
pected, thedispersion-dominated systemswithalow rotationve- senforuseinourangularmomentummeasurementasitwasshown
locity,vC,tointrinsicvelocitydispersion,s 0,ratio(i.e.,vC/s 0<1; byRomanowsky&Fall(2012)(ourmaincomparisonsample;Sec-
seeSection4.1)havelargermisalignmentsduetoalackofawell tion2.5)tobeareliablerotationalvelocitymeasurement acrossa
definedkinematicaxis.Fortherotationally-dominatedsources,the wide range of galaxy morphologies. Furthermore, reaching large
median misalignment is13◦ and 81percent have a misalignment radii of &3RD can be crucial for measuring the majority of the
of .30◦. These values are comparable to those found by using total angular momentum (e.g., Obreschkowetal. 2015). We note
IFU data for high-z galaxies, all withcomplementary HST imag- that this measurement also roughly corresponds to another com-
ing(Wisnioskietal.2015;Continietal.2016).Encouragingly,our monly adopted value, v , which is the velocity measured at a
80
misalignment results are similar when only considering our tar- radiicontaining80percentofthelightforanexponentialdisk(i.e.
getswithoutHSTimaging,withamedianmisalignmentof15◦and at3.03RD;e.g.,Pizagnoetal.2007;Reyesetal.2011;Tileyetal.
82percent having a misalignment of .30◦. This provides confi- 2016).
denceinouranalysesbasedontheground-basedimages. Tomakethevelocitymeasurements,wefirstconvolvetheR
1/2
valueswiththePSFoftheindividualKMOSobservationsandthen
read off the velocity at the defined radii from the model velocity
3.3.3 Velocityprofilesandrotationalvelocities
profiles (see Figure 2). The observed velocities quoted, v , are
obs
Weextractone-dimensionalvelocityprofiles[v(r)]alongthemajor half the difference between the velocities measured at the posi-
kinematicaxes.Toachievethis,weextractthemedianvelocityin tiveandnegativesideoftherotationcurves.For13percentofthe
0.7arcsec“slits”alongthevelocitymaps,centredonthecontinuum targetsinthespatially-resolvedsamplewearerequiredtousethe
centroids (see Section 3.1.3). Examples can be seen in Figure 2 model(seeabove)toextrapolateto>0.4arcsecbeyondthedatato
wheretheerrorsbarsrepresentthescatteracrosstheslit. reach (i.e., >2 KMOS pixels). The uncertainties on the observed
To reduce the effect of noise in the outer regions of the ve- velocities are obtained by varying the radii by ±1s and then re-
locityprofilesweextrapolatethroughthedatapointsbyfittingan measuringthevelocities.
exponentialdiskmodel(seeFreeman1970)tothevelocityprofiles Forsourceswherewedonothavespatially-resolvedIFUdata
MNRAS000,1–19(2016)
10 C. M. Harrisonet al.
(i.e., “quality 4”) or we do not have a measured half-light radii imposeanuncertaintyof50percentforthosetargetswhereweuse
(i.e., “quality 3”) we are unable to measure the velocities at a themedianofthevelocitydispersion(s )maptoinfers .
0,obs
fixed radii from the IFU data. Therefore we estimate the veloci- Forbothoftheapproachesformeasurings weobtained
0,obs
tiesfromthewidthsofthegalaxy-integratedemission-lineprofiles theintrinsicvelocitydispersion,s ,byapplyingasystematiccor-
0
by applying correction factors derived from the resolved veloc- rection for the effects of beam-smearing based on mock KMOS
ity measurements; i.e., the median ratios of s tot/vC,obs=1.13 and data(Johnson etal.inprep; seedetailsabove). Thesecorrections
s tot/v22,obs=1.26.Inbothcasesthereis0.3dexscatteronthesera- areafunctionofboththeratioofhalf-lightradiitotheFWHMof
tios,whichweapplyasauncertaintyonthesemeasurements. the KMOS PSF and the observed velocity gradient. When using
Toobtaintheintrinsicvelocities,v andv ,weapplyacor- thevelocitydispersionsextractedfromtheouterregionsthebeam-
2.2 C
rectiontotheobservedvelocitiesfortheeffectsofinclinationangle smearingcorrectionshaveamedianof0.97+0.02andforthoseex-
−0.06
(q im)andbeamsmearingfollowing, tractedfromthesigmamapsthemediancorrectionfactoris0.8+0.1.
−0.3
e The intrinsic velocity dispersions of the sample will be provided
R,PSF
v=vobs×sin(q im), (4) anddiscussedindetailinJohnsonetal.(inprep).
wheree isthebeam-smearingcorrectionfactorthatisafunc-
R,PSF
3.4 Summaryofthefinalsampleforfurtheranalyses
tionoftheratioofhalf-lightradiitotheFWHMoftheKMOSPSF.
ThesecorrectionfactorsarederivedinJohnsonetal.(inprep.),by We detected Ha emission in 586 of our targets (79percent) and
creating mock KMOS data (also see Burkertetal. 2016 for sim- weshowed that thesearerepresentative of “mainsequence” star-
ilar tests). A sample of ≈105 model disk galaxies were created forming galaxies at z≈1 (Section 2.3). For the following analy-
assuming an exponential light profile, withadistributionof sizes ses,whicharebasedonvelocitymeasurements,weexcludethe50
andstellarmassesrepresentativeoftheKROSSsample.Theintrin- sourceswithaninclinationangleofq im≤25obecausetheinclina-
sicvelocityfieldswereconstructedassumingadarkmatterprofile tioncorrectionstothevelocitiesforthesesourcesbecomeveryhigh
plusanexponential stellardisk,witharangeof darkmatterfrac- (e.g.,>2.4for <25o and>10for <5o).Consequently, anysmall
tionsmotivatedfromtheEAGLEsimulations(Schayeetal.2015). errorsintheinclinationanglescanresultinlargeerrorsintheve-
Arangeofflatintrinsicvelocitydispersions,s 0werealsoassumed. locityvalues.Weremoveafurther20sourceswhichhaveeitheran
“ Intrinsic” KMOS data cubes were constructed using the model emission-lineratioof[NII]/Ha >0.8and/ora&1000kms−1broad
galaxiestopredictthevelocity,intensityandlinewidthofHa pro- linecomponentintheHa emissionlineprofiles(butnotthe[NII]
files.Eachsliceofthesecubeswasthenconvolvedwithavarietyof profile).Thesesourceshaveasignificantcontributiontotheemis-
seeingvaluesapplicablefortheKROSSobservations.Thesemock sion lines from AGN emission and/or shocks (e.g., Kewleyetal.
observationswerethensubjecttothesameanalysesasperformed 2013;Harrisonetal.2016).Finally,weremoveafurther30sources
ontherealdata.Differencesbetweeninputandoutputvalueswere which show multiple emission regions in the IFU data or broad-
usedtoderivedthecorrectionfactorsasafunctionoftheratioof band imaging that resulted in unphysical measurements for the
half-lightradiitotheFWHMoftheKMOSPSF.Fulldetailswill rotational velocitiesand/or thehalf-light radii.Thisleavesafinal
beprovidedinJohnsonetal.inprep.ForthemeasuredvC values sampleof486targetsforanalysesontherotationalvelocities(Sec-
these corrections range from e R,PSF=1.01–1.17 with a median of tion4.2)andspecificangularmomentum(Section4.3).
1.07.Wefollowthesameequationforv2.2butapplytheappropri- Of this final sample, only 33 (7percent) are unresolved in
atee R,PSF correctionfactorforthisradii.Theuncertaintiesonthe theIFUdata(“quality4”)andonly24(5percent)areresolvedin
intrinsicvelocitiesarecalculatedbycombining(inquadrature)the the IFU data but have only an upper limit on the half-light radii
uncertaintiesontheobservedvelocities(seeabove)withthevaria- (“quality3”;seeSection3.1.2).Inbothofthesecasesthevelocity
tionfromvaryingtheinclinationanglesby±1s . measurements are unresolved in that they are estimated from the
galaxy-integrated emission-line profiles (Section 3.3.3). We note
that 63 (13percent) are assigned “quality 2” because they have
3.3.4 Velocitydispersionprofilesandintrinsicvelocity fixed (unknown) inclination angle and/or a half-light radii that is
dispersions estimatedfromthevelocitymodelsasopposed tothebroad-band
imaging (see Section 3.1.2). Overall, the majority of the sources
Toclassify thegalaxy dynamics of our sources we need tomake (366;i.e.,75percent)areassigned“quality1”forwhichwehave
measurementsoftheintrinsicvelocitydispersions(s 0).Weextract spatially-resolvedIFUdataandboththehalf-lightradiiandincli-
velocitydispersionprofiles[s (r)]usingthesameapproachasfor nationanglesaremeasureddirectlyfromthebroadbandimaging.
thevelocityprofiles(seeabove)butusingtheobserveds maps(see
examplesinFigure2).Wethenmeasuretheobservedvalues
0,obs
intheouterregionsofthes (r)profilesbymeasuringthemedian
4 RESULTSANDDISCUSSION
valuesfromeither>2×or<−2×thehalf-lightradii(whichever
islowest).Attheseradiitheobservedvelocitydispersionwillonly In the previous sections we have presented our new analyses on
haveasmallcontributionfromthebeam-smearingofthevelocity ≈600Ha detectedgalaxiesfromtheKROSSsurvey.Thesetargets
field(seebelow).Theuncertaintiesaretakentobethe1s scatterin arerepresentativeoftypicalstar-forminggalaxiesatredshift≈0.9.
thepixelsusedtocalculatethismedian.Whentheextentofthedata Usingacombinationofbroad-bandimagingandourIFUdatawe
doesnotreachsufficientradii(orwedonothaveameasuredhalf- have measured inclination angles, half-light radii, morphological
lightradii),whichisthecasefor52percentofourHa sample,we andkinematicpositionangles,rotationalvelocitiesandintrinsicve-
adoptasecondapproachbytakingthemedianvalueofthepixelsin locitydispersions(seeAppendixAfordetailsofthetabulatedver-
thes maps.Afterapplyingtheappropriatecorrections(seebelow), sionofthesevalues).Afterremovinghighly-inclinedsourcesand
thesemethodsagreewithin4percent(whereitispossibletomake thosewithanAGNcontributiontothelineemission(Section3.4),
bothmeasurements)witha≈50percentscatter.Consequentlywe weareleftwithasampleof486targetsforwhichweanalysethe
MNRAS000,1–19(2016)