H-alpha Kinematics of the SINGS Nearby Galaxies Survey. II

0.76 MB·English

by  I. Dicaire

Mon.Not.R.Astron.Soc.000,1–15(XXXX) Printed2February2008 (MNLaTEXstylefilev2.2)
α
H Kinematics of the SINGS Nearby Galaxies Survey – II
I. Dicaire1 ∗ †, C. Carignan1,7, P. Amram2,7, O. Hernandez1,7, L. Chemin3,
O. Daigle1,2,7, M.–M. de Denus–Baillargeon1,4, C. Balkowski3, A. Boselli2,
5 6
K. Fathi and R. C. Kennicutt
1Laboratoired’AstrophysiqueExpe´rimentale,ObservatoiredumontMe´gantic&De´partementdephysique,Universite´deMontre´al,
8 C.P.6128,succ.centreville,Montre´al,Que´bec,CanadaH3C3J7.
0 2Laboratoired’AstrophysiquedeMarseille,ObservatoireAstronomiqueMarseille–Provence,Universite´deProvence&CNRS,2place
0 LeVerrier,13248MarseilleCedex4,France.
2 3ObservatoiredeParis,sectionMeudon,GEPI,CNRS–UMR8111&Universite´Paris7,5Pl.Janssen,92195Meudon,France.
4InstitutFresnel,CNRS&Universite´sAixMarseille,13397MarseilleCedex20,France.
n 5InstitutodeAstrofisicadeCanariasC/ViaLactea,s/nE38205–LaLaguna(Tenerife)–Spain.
a 6InstituteofAstronomy,UniversityofCambridge,MadingleyRoad,CambridgeCB30HA,UK.
J 7VisitingAstronomer,Canada–France–HawaiiTelescope,operatedbytheNationalResearchCouncilofCanada,theCentreNational

8 delaRechercheScientifiquedeFrance,andtheUniversityofHawaii.
1

]
h Accepted2007December14.Received2007December10;inoriginalform2007October30
p
-
o
ABSTRACT
r
t This is the second part of an Hα kinematics follow–up survey of the Spitzer Infrared Nearby
s Galaxies Survey (SINGS) sample. The aim of this program is to shed new light on the role of
a
baryonsandtheirkinematicsandonthedark/luminousmatterrelationinthestarformingregions
[
of galaxies, in relation with studies at other wavelengths.The data for 37 galaxiesare presented.

1 The observationswere made using Fabry–Perotinterferometrywith the photon–countingcamera
v FANTOMM on 4 differenttelescopes, namely the Canada–France–Hawaii3.6m, the ESO La Silla
1
3.6m, the William Herschel 4.2m, and the Observatoire du mont Me´gantic 1.6m telescopes.
7
The velocity fields are computed using custom IDL routines designed for an optimal use of the
9
data. The kinematical parameters and rotation curves are derived using the GIPSY software. It
2
is shown that non–circular motions associated with galactic bars affect the kinematical parame-
.
1 tersfitting andthe velocitygradientof the rotationcurves.Thisleadsto incorrectdeterminations
0
ofthebaryonicanddarkmatterdistributionsinthemassmodelsderivedfromthoserotationcurves.
8
0
: Key words: instrumentation: interferometers – techniques: radial velocities – galaxies: ISM –
v
galaxies:kinematicsanddynamics–galaxies:darkmatter–surveys
i
X
r
a
1 INTRODUCTION entificobjectivesconstitutethecorescienceprogramoftheSpitzerIn-
fraredNearbyGalaxiesSurvey(SINGS)(Kennicuttetal.2003).Since
Understandingstarformationmechanismsandtheirphysicalconnec-
the science drivers of the project are dependent of many variables,
tiontotheinterstellarmedium(ISM)propertiesofgalaxiesiscrucial
theSINGSprojectrequiresacomprehensivesetofdataincludingin-
for resolving astrophysical issues such as the physical nature of the
fraredimagingandspectroscopicdata,broadbandimaginginthevis-
Hubblesequence, thenatureandtriggering ofstarbursts,and thein-
ibleandnear–infraredaswellasUVimagingandspectrophotometry.
terpretationof observations of thehigh–redshift universe. Thesesci-
TheSpitzerdataandancillaryobservationsoftheSINGSgalaxieswill
also provide valuable tools for understanding the physics of galaxy
formationandevolution.
∗Basedonobservations madewiththeESO3.60mtelescope atLaSilla
ObservatoriesunderprogrammeID076.B-0859andonobservationsobtained
The formation of individual stars from the collapse of dense
at the Canada–France–Hawaii Telescope (CFHT) which is operated by the
molecular clouds is relatively well known, e.g. the intensity of star
National Research Council of Canada, the Institut National des Sciences de
formation is strongly correlated with the column density of gas and
l’UniversoftheCentreNationaldelaRechercheScientifiqueofFrance,and
theUniversityofHawaii stars (Kennicutt 1998b). However, the large–scale processes driving
†E–mail:[email protected] starformationarestillpoorly understood. Forinstance, theeffect of
(cid:13)c XXXXRAS
2 I. Dicaireet al.
gas dynamics on the regulation of star formation is somewhat un- emission lines. Hα kinematics for 28 galaxies of the SINGS sam-
known. Sinceyoung starsareoftenassociatedwithspiralarms,it is ple have already been published in Daigleetal. (2006a). This paper
thoughtthatprotostarsareformedfromcompressedgasalonglarge– presentsthesecondpartofthefollow–upsurvey,namelytheHαkine-
scaleshockfronts.Moreover,thestarformationhistoryvariesgreatly maticsoftheremaining37galaxies.Table1presentsthebasicgalaxy
along the Hubble sequence. Ellipticalgalaxies, being gravitationally parameters.
supported by velocity dispersion, have exhausted their gas reservoir
and hence star–forming processes have ceased (Kennicutt 1998a).
2.2 Observingruns
Nevertheless, some elliptical galaxies having a rotating disc arestill
formingstars(e.g.NGC2974,Jeongetal.2007).Spiralgalaxies,on Theobservationshavebeenobtainedwiththesameinstrumentalset–
theotherhand,continuetoformstarsandaresupportedbyrotation. upconsistingofascanningFabry–Perot(FP)interferometer,animag-
Understanding the effect of gas dynamics on star formation would ingdevicedesignedforfaintfluxes,andanarrow–band(∼15A˚)inter-
certainlyhelp improving our understanding of galaxy formation. In- ferencefilter.Forimaging,aphoton–countingcamera(FANTOMM)and
deed,aSchmidtlawmodulatedbyrotationseemstobetterfitthedata anAndorcommercial(L3CCD)camerawereused.Eachinstrument
thanasimple(gascolumndensity)Schmidtlaw(Boissieretal.2003; wasattachedtoafocalreducerattheCassegrainorNasmythfocusof
Martin&Kennicutt2001;Kennicutt1989). thetelescope.ThefocalreducersusedwerePanoramixattheObser-
This paper presents the second part of an Hα kinematics sur- vatoiredumontMe´gantic(OmM)1.6mtelescope,CigaleattheEuro-
vey of the SINGS galaxies. The 37 galaxies showing Hα emission peanSouthernObservatory(ESO)LaSilla3.6mtelescope,MOS/FP
wereobservedbymeansofFabry–Perot(FP)interferometry.Thepa- attheCanada–France–Hawaii 3.6mtelescope (CFHT),and GHaFaS
perisorganizedasfollows.Section2describesthecompositionofthe attheWilliamHerschel4.2mtelescope(WHT).Table2describesthe
SINGSsampleandthehardwareusedfortheobservations. Thedata variouscharacteristicsoftheinstruments.
reductionprocess,usingacustomIDLpipelinedesignedforanopti- Thespectralprofilesforeverypixelinthefieldofviewwereob-
maluseofthedata,isintroducedinsection3.Insection4,thedetails tainedbyscanningthefreespectralrange(FSR)oftheFabry–Perot.
ofthekinematicalanalysisthathasbeendoneontheSINGSgalaxies TheFSRisthewavelengthintervalbetweentwoadjacenttransmission
aredescribed.Section5presentstheobservationalresultsintheform peaks:
of velocityfields,monochromatic maps, position–velocity diagrams,
androtationcurves.Insection6,theeffectofthebarontheobserved FSR=λ0/p (1)
kinematicsisdiscussed.Finally,thescientificapplicationsofthekine- whereλ0istherestwavelengthandptheinterferenceorder.Thenum-
maticalresultspresentedinthispaperarereviewedinsection7. ber of channels needed to scan the FSR must be at least 2.2 times
theFPfinesseFforagoodsampling(Nyquistcriteria).Thefinesseis
adimensionless parameter representing thespectral resolving power
Rofthescannedlineandisrelatedtothefull–widthhalf–maximum
2 OBSERVATIONS
(FWHM)ofthetransmittedline:
2.1 Thesample
R FSR
F= = (2)
Thesample, asdescribed by Kennicuttetal. (2003), iscomposed of p FWHM
75nearby(∆<30Mpc,forH0=70 kms−1Mpc−1)galaxiescover- TheFPetalonusedfortheobservationshasahighinterference
ing,inathree–dimensionalparameterspace,awiderangeofphysical order(typicallyp=765atHα)andiscapableofachievinghighvalues
properties: forthefinesseandspectralresolution.Atypicalobservationwouldbe
toscantheFPetalonin48channelswithanexposuretimeof15sper
• morphologicaltype:associatedwithgasfraction,starformation
channel,thenrepeattheprocessfor15cycles.However,whenthesky
rate(SFR)perunitmass,andbulge/discstructure;
transparencyisnotexcellentduringanexposure,theetalonisscanned
• luminosity : associated withgalaxy mass, internal velocity, and
morerapidlywithanexposuretimeof10sperchannelsothattheat-
meanmetallicity;
mosphericconditionscanbeaveragedoutmoreefficiently.Theresult-
• FIR/optical luminosity ratio : associated withdust temperature,
ingdatacubeisasetofinterferogramsstackedtogether,whereeach
dustopticaldepth,andinclination.
onerepresents animageof theobject modulated bytheinterference
Inparticular,thereareroughlyadozengalaxiesineachRC3type patternforagivenFPspacing.
(E–S0, Sa–Sab, Sb–Sbc, Sc–Scd, Sd–Sm, Im–I0) leading to an ex- The filter set used has 24 narrow–band Hα filters covering the
tensivesetofcombinationsofluminosityandFIR/opticalluminosity galaxies’systemicvelocitiesrangingfrom–300to100000 kms−1.
ratio.Inparticular,afactor of105 ininfraredluminosityand103 in Sometimes,thefilterwastiltedbyafewdegreestoadjustitscentral
LFIR/Lopt iscoveredbythesample.The75galaxiesalsorepresent wavelengthtotheDopplershiftedgalaxyemission.Narrow–bandfil-
avastrangeofothergalaxypropertiessuchasnuclearactivity,surface ters, used to select the proper order that will go through the etalon,
brightness,inclination,CO/HIratio,spiralarmstructure,barstructure, allow for the Hα emission to pass while at the same time blocking
andenvironment.Thegalaxieswerechosenasfaraspossiblefromthe mostofthenightskyemission.
GalacticplaneinordertoavoidGalacticextinctionandhighdensity Thephoton–countingcamerasFANTOMMI&II(Hernandezetal.
offoregroundstars. 2003) consist of a GaAs Hamamatsu photomultiplier tube having a
Since gas fraction is correlated with morphological type quantum efficiency of ∼23% coupled to a Dalsa commercial CCD.
(Bosellietal.2001),notallthe75galaxiesareHαemitters.Infact, Theabsenceofread–outnoiseforthiscameraenablesonetoscanvery
Hαwasnotdetectedfortengalaxies(E–S0andIrrtypes),thuskine- rapidlytheFPinterferometerwhereasCCDsneedlongexposuresto
matical information could not be extracted for those galaxies from overcometheirread–outnoise.Consequently,FANTOMMcanachieve
(cid:13)c XXXXRAS,MNRAS000,1–15
HαKinematicsof theSINGS Galaxies 3
Table1.ObservationaldatafortheSINGSHαkinematicssample
Galaxy α(J2000) δ(J2000) Type ∆a D2b,5ib BTb,ic MBb,id Vsyse
name (hhmmss) (◦ ′ ′′) RC3 (Mpc) (arcmin) (kms−1)
NGC24 000956.7 −245744 SA(s)c 8.2 5.8 12.19 −17.38 554
NGC337 005950.3 −073444 SB(s)d 24.7 2.9 12.06 −19.90 1650
NGC855 021403.6 +275238 E 9.6 2.6 13.30 −16.61 610
NGC1097 024619.0 −301630 SB(r’1)b 16.9 9.3 10.23 −20.91 1275
NGC1291 031718.6 −410629 SB(l)0/a 9.7 9.8 9.39 −21.75 839
NGC1482 035439.3 −203009 SA0 22.0 2.5 13.10 −18.61 1655
NGC1512 040354.3 −432056 SB(r)ab 10.4 8.9 11.13 −18.96 896
NGC1566 042000.4 −545616 SAB(rs) 18.0 8.3 10.33 −20.95 1496
NGC1705 045413.5 −532140 SA0 5.8 1.9 12.77 −16.05 628
HoII 081905.0 +704312 Im 3.5 7.9 11.10 −16.62 157
DDO053 083407.2 +661054 Im 3.5 1.5 14.70 −13.02 19
NGC2841 092202.6 +505835 SA(r)b 9.8 8.1 10.09 −19.87 638
HoI 094032.3 +711056 IAB(s)m 3.5 3.6 13.00 −14.72 143
NGC3034 095552.2 +694047 I0 3.5 11.2 9.30 −18.42 203
HoIX 095732.0 +690245 Im 3.5 2.5 14.30 −13.42 46
NGC3190 101805.6 +214955 SA(s)a 17.4 4.4 12.12 −19.08 1271
IC2574 102821.2 +682443 SAB(s)m 3.5 13.2 10.80 −16.92 57
NGC3265 103106.8 +284747 E 20.0 1.3 13.00 −18.50 1421
Mrk33 103231.9 +542403 Im 21.7 1.0 13.20 −18.50 1461
NGC3351 104357.7 +114213 SB(r)b 9.3 7.4 10.53 −19.31 778
NGC3627 112015.0 +125930 SAB(s)b 8.9 9.1 9.65 −20.10 727
NGC3773 113813.0 +120643 SA0 18.3 1.2 12.90 −18.40 987
NGC4254 121849.6 +142459 SA(s)c 20.0 5.4 10.44 −21.07 2407
NGC4450 122829.6 +170506 SA(s)ab 20.0 5.2 10.90 −20.61 1954
NGC4559 123557.7 +275735 SAB(rs)cd 11.6 10.7 10.46 −19.86 816
NGC4594 123959.4 −113723 SA(s)a 13.7 8.7 8.98 −21.70 1091
NGC4631 124208.0 +323226 SB(s)d 9.0 15.5 9.75 −20.02 606
NGC4736 125053.0 +410714 SA(r)ab 5.3 11.2 8.99 −19.63 308
DDO154 125405.2 +270859 IB(s)m 5.4 3.0 13.94 −14.72 376
NGC4826 125643.7 +214052 SA(rs)ab 5.6 10.0 9.36 −19.38 408
DDO165 130624.8 +674225 Im 3.5 3.5 12.80 −14.92 37
NGC5033 131327.5 +363538 SA(s)c 13.3 10.7 10.75 −19.87 875
NGC5408 140320.9 −412240 IB(s)m 4.5 1.6 12.20 −16.07 509
NGC5474 140501.6 +533944 SA(s)cd 6.9 4.8 11.28 −17.91 273
NGC6822 194456.6 −144721 IB(s)m 0.6 15.5 9.31 −14.58 −57
NGC7552 231611.0 −423459 SB(s)ab 22.3 3.4 11.25 −20.49 1585
NGC7793 235749.8 −323528 SA(s)d 3.2 9.3 9.63 −17.90 230
a ∆:distance.TakenfromKennicuttetal.(2003).
b Db,i:apparentmajordiameteratthe25magarcsec−2inB.TakenfromtheRC3.
25
c Bb,i:totalapparentmagnitudeinB.TakenfromtheRC3.
T
d Mb,i:totalabsolutemagnitudeinB.Calculatedfrom∆andBb,i.
e VsyBs:systemicvelocity.TakenfromKennicuttetal.(2003). T
highsignaltonoiseratios(S/N)andthusisidealforfaintfluxeslike tails about the L3CCD can be found in Daigleetal. (2004) and in
theemissionfoundingalaxies(Gachetal.2002).Additionally,acam- Daigle,Carignan,&Blais–Ouellette(2006).
erausingalowlightlevelcharge–coupleddevice(L3CCD)madeby
Theobservations of thesample werespread over nine different
Andor Technology was also used as the imaging device. L3CCDs
observing runs over a three year period. Five runs took place at the
havehighquantumefficiency(∼80per cent)andsub–electron read-
OmM1.6mtelescopewhereFANTOMMisapermanentinstrument.A
out noise (σ <0.1 e-). This kind of sensor differs from traditional
secondgenerationinstrument,calledFANTOMMII,hasbeenbuiltre-
CCDs in the sense that the signal isamplified before it reaches the
centlyandwastestedsuccessfullyonthefaintdwarfgalaxyDDO154
output circuitry which is the major source of noise. Gain is created
duringoneoftheseruns.Also,anewinstrumentfortheLaSillaNTT
bypassingelectronsthroughamultiplicationregisterwhereanelec-
is under development and regarding this matter, the L3CCD cam-
tron will create a second one by avalanche multiplication. More de-
erawasusedtotestitscapabilitiesonveryfaintfluxeslikegalaxies.
Therefore, four galaxies were observed with this camera during the
(cid:13)c XXXXRAS,MNRAS000,1–15
4 I. Dicaireet al.
bythediscretesampling.Afterthat,thestrongnightskyemissionlines
Table2.Telescopeandinstrumentcharacteristics
weresubtracted.Themethodusedforthisistoreconstructaskycube
using the sky dominated regions and interpolating it in the galaxy
Telescope Instrument PixelSize FOV
region. This sky cube was then subtracted from the data cube. This
(arcsec) (arcmin)
methodhasproventobeverysuccessfulateliminatingskyresiduals
OmM FANTOMM 1.61 19.43 comparedwithsubtractingamedianskyspectrumwherebothspatial
OmM FANTOMMII 1.54 18.55 andspectralinhomogeneitiesintheinterferencefiltercanleadtohigh
OmM L3CCD 1.07 12.89 skyresiduals.
ESO FANTOMM 0.42 5.02
CFHT FANTOMM 0.48 5.84
WHT GHaFaS 0.40 4.82 3.3 Adaptivespatialbinningandmapextraction
In order to increase the signal–to–noise ratio (S/N) in the diffuse
samerunattheOmMObservatory. Tworunstookplaceat theESO and/orfaintinterstellarregions(e.g.inter–armregions)oftheobserved
La Silla 3.6m telescope and one at the CFHT 3.6m telescope, both galaxies, an adaptive spatial binning was applied to the data cubes.
whereFANTOMM Iisavisitorinstrument.A lastobserving runtook ThistechniqueisbasedonVoronoidiagramswherepixelsareaccreted
place at the WHT 4.2m telescope with the new instrument GHaFas intobinsuntil thedesired S/N (∼5, typicallychosen) isreached. In
(Carignanetal. 2007). The Fabry–Perot observations parameters for highintensityemissionregionslikethegalacticcenterandspiralarms,
eachgalaxycanbefoundinTable3. theS/Nexceedsbyfarthetargetedminimalvalueandhencethehigh
spatialresolutionismaintained.Thisisanimprovementovertheusual
gaussiansmoothingwherethekernelconvolutionwoulddilutethesig-
3 DATAREDUCTION nalinhighS/Nregions.
Next,thefinalstepsaretheintegrationofthefluxundertheHα
Thissectionintroducesthefewstepstowardsobtainingradialveloci- linefor every bin, yielding amonochromatic map, and the barycen-
tiesandmonochromaticmapsfromrawinterferograms.Inparticular, tercomputation,yieldingavelocityfield,followingtheprocedurede-
• wavelengthcalibration; scribedbyDaigleetal.(2006b).Theradialvelocities(RV)aregiven
• spectralsmoothingandskyemissionsubtraction; intheheliocentricrestframe.Acontinuummapandavelocitydisper-
• adaptivespatialbinningandmapextraction; sion map are also computed by the algorithm. The determination of
• WCSastrometry. thecontinuumthresholdisacriticalstepinthedatareductionasitde-
finesthepositionofthebarycenteroftheline.Thisisdonebyiterative
Foramorecompletedescriptionofthedatareductionsteps,we procedures.
refer to Hernandezetal. (2005a), Daigleetal. (2006a), Daigleetal.
(2006b),andCheminetal.(2006a).Thesoftwareusedcanbefound
athttp://www.astro.umontreal.ca/fantomm/reduction. 3.4 WCSastrometry
Finally, WCS coordinates are attached to the computed maps using
3.1 Wavelengthcalibration the task koords in the KARMA package (Gooch 1996). No refer-
encestotheWorldCoordinateSystemareobtainedduringtheacqui-
Therawdatacube,obtainedduringanacquisition,mustbewavelength sitionand arenecessary since themajor axes positionangle (PA) of
correctedsincethetransmittedwavelengthλisafunctionoftheangle thegalaxy isfield–orientation dependent. Besides, WCSastrometry
θoftheincominglightbeam: isneededtocombinetheHαkinematicswithancillarySINGSsur-
veys.Thecoordinates areadded bycomparing positionsofstarsbe-
pλ=2necosθ (3)
tweenareferencefile(aredbandDSSimageforinstance)andtheFP
where p is the interference order at λ0(6562.78 A˚), n the index of non–binnedcontinuumimage.
the medium, and e the distance between the parallel plates of the
etalon.Thewavelengthcalibrationismadebyscanningtheneonline
at6598.95A˚ justbeforeandafterathreehouracquisition,inthesame
4 KINEMATICALPARAMETERSFITTING
conditionsastheobservationitself.Thisenablesonetocalculatethe
phaseshiftneededtoassignawavelengthtoaparticularFPspacing, Rotation curves are computed using the task rotcur available in the
foreverypixelofthefield.Thisphasemaptransformsrawinterfero- GIPSYsoftware(Vogelaar&Terlouw2001).Rotcurderivesthekine-
gramsintoawavelength–sorteddatacube.Sinceonecanonlyknow maticalparametersforaparticulargalaxybyfittingtilted–ringstothe
the transmittedwavelength value ± FSR,anuncertainty remains on observedvelocityfield.Moreprecisely,aleast–squares–fittingisdone
thezero–pointofthevelocityscale.Comparisonwithotherkinemati- tothefunction:
calworkwillremovethisuncertainty.Notethatthedatacubesarenot
flux–calibrated. Vobs(x,y)=Vsys+Vrot(r)cosθsini+Vexp(r)sinθsini (4)
Here V (x,y) denotes the radial velocity at the pixel coordi-
obs
3.2 Spectralsmoothingandskyemissionsubtraction nates(x,y),Vsysthesystemicvelocity,Vrot(r)therotationalvelocity
forthecorresponding radiusr,θ theazimuthal anglefromthemajor
A Hanning smoothing was performed on every spectrum of the axisintheplaneofthegalaxy,itheinclinationangleofthegalaxy,and
wavelength–sorteddatacubesinordertoremoveanyartifactscaused Vexp theexpansionvelocity.SinceGIPSY doesnottakeintoaccount
(cid:13)c XXXXRAS,MNRAS000,1–15
HαKinematicsof theSINGS Galaxies 5
Table3.JournaloftheFabry–Perotobservations.
Galaxy Date λc FWHM Tmax texp tch p FSR F R nch stepλ
a b c d e f g h i j k
NGC24l 2005/11/04 6581 19.8 60 150 2.50 765 392 19.7 15071 60 0.14
NGC337l 2005/11/02 6598 18.2 73 150 2.50 765 392 20.5 15657 60 0.14
NGC855m 2003/11/27 6584 15.5 74 190 4.75 609 492 13.2 8010 40 0.27
NGC1097l 2005/11/07 6598 18.2 73 470 7.83 765 392 20.0 15321 60 0.14
NGC1291l 2005/11/06 6584 15.5 74 385 6.42 765 392 20.5 15669 60 0.14
NGC1482l 2005/11/08 6608 16.2 69 115 1.92 765 392 20.3 15561 60 0.14
NGC1512l 2005/11/03 6584 15.5 74 740 2.67 765 392 17.5 13389 60 0.14
NGC1566l 2005/11/02 6598 18.2 73 150 2.50 765 392 20.7 15864 60 0.14
NGC1705l 2005/11/03 6581 19.8 60 130 2.17 765 392 20.0 15282 60 0.14
HoIIm 2005/02/05 6563 30.4 80 204 4.25 765 392 17.7 13527 48 0.18
DDO053n 2006/04/07 6563 30.4 80 96 2.00 765 392 18.1 13885 48 0.18
NGC2841m 2005/02/03 6584 15.5 74 240 5.00 765 392 12.7 9731 48 0.18
HoIn 2006/04/05 6563 30.4 80 176 3.67 765 392 14.2 10869 48 0.18
NGC3034m 2007/03/01 6581 19.8 60 384 8.00 765 392 17.2 13181 48 0.18
HoIXm 2005/05/10 6563 30.4 80 228 4.75 765 392 15.9 12185 48 0.18
NGC3190m 2004/11/03 6598 18.2 73 144 3.00 765 392 15.6 11905 48 0.18
IC2574m 2005/02/03 6563 30.4 80 180 3.75 765 392 16.6 12713 48 0.18
NGC3265m 2007/03/01 6598 18.2 73 100 2.08 765 392 18.8 14396 48 0.18
Mrk33n 2006/04/08 6598 18.2 73 48 1.00 765 392 16.7 12798 48 0.18
NGC3351m 2005/02/03 6584 15.5 74 156 3.25 765 392 18.0 13750 48 0.18
NGC3627m 2005/02/06 6584 15.5 74 144 3.00 765 392 16.6 12670 48 0.18
NGC3773n 2006/04/08 6584 15.5 74 76 1.58 765 392 17.2 13127 48 0.18
NGC4254m 2005/02/14 6621 18.0 68 240 5.00 765 392 17.4 13825 48 0.18
NGC4450l 2002/04/07 6607 12.0 69 60 2.50 793 381 12.1 4604 24 0.35
NGC4559m 2005/02/06 6584 15.5 74 408 8.50 765 391 16.5 12631 48 0.18
NGC4594o 2007/07/05 6585 15.5 75 64 5.00 765 392 16.5 12623 48 0.18
NGC4631m 2005/02/01 6584 15.5 74 180 3.75 765 392 18.0 13757 48 0.18
NGC4736m 2005/05/11 6563 30.4 80 216 4.50 765 392 16.7 12745 48 0.18
DDO154m 2007/02/22 6581 19.8 60 320 8.00 765 392 17.1 13097 40 0.21
NGC4826n 2006/04/07 6563 30.4 80 128 2.67 765 392 17.2 13121 48 0.18
DDO165n 2006/04/06 6563 30.4 80 172 3.58 765 392 17.1 13091 48 0.18
NGC5033m 2005/05/10 6584 15.5 74 460 9.58 765 392 16.7 12782 48 0.18
NGC5408n 2006/04/07 6581 19.8 60 108 2.25 765 392 17.1 13083 48 0.18
NGC5474m 2007/02/28 6581 19.8 60 108 2.25 765 392 17.2 13157 48 0.18
NGC6822l 2005/11/08 6563 30.4 80 60 1.00 765 392 19.8 15121 60 0.14
NGC7552l 2005/11/02 6598 18.2 73 120 2.00 765 392 19.8 15160 60 0.14
NGC7793l 2005/11/08 6563 30.4 80 100 1.67 765 392 19.7 15040 60 0.14
a λc:Non–tiltedfiltercentralwavelengthat20◦C(inA˚)
b FWHM:Non–tiltedfilterFull–WidthHalf–Maximumat20◦C(inA˚)
c Tmax:Non–tiltedfiltertransmissionatλcandat20◦C(in%)
d texp:Totalexposuretime(inmin)
e tch:Totalexposuretimeperchannel(inmin)
f p:InterferenceorderatHα
g FSR:FreespectralrangeatHα(in kms−1)
h F:Finesse
i R:Resolutionaccordingtothefinesse
j nch:NumberofFPchannels
k stepλ:wavelengthdifferencebetweenchannels(inA˚)
l ESO:EuropeanSouthernObservatory,LaSilla,Chile,3.6mtelescope.
m OmM:ObservatoiredumontMe´gantic,Que´bec,Canada,1.6mtelescope.
n CFHT:Canada–France–HawaiiTelescope,Hawaii,USA,3.6mtelescope.
o WHT:WilliamHerschelTelescope,LaPalma,Spain,4.2mtelescope.
(cid:13)c XXXXRAS,MNRAS000,1–15
6 I. Dicaireet al.
thefieldrotationof thesupplied velocityfieldwithrespect toWCS
Table4.Photometricandkinematicalparameters
coordinates, the velocity fields were all rotated in order to compute
accuratepositionangles(PAs)ofthekinematicalmajoraxis.
Galaxy Phot Kin
Fittingthekinematicalparameterswasdoneinathree–steppro-
name PA i PA i
cess. First, the systemic velocity Vsys and the kinematical center
(xpos,ypos)arefittedwhilekeeping fixedtheinclinationi andposi- NGC24 225 78 226±1 75±3
tionanglePA.Thestartingparametersusedarethephotometriciand NGC337 130 53 121±5 52±6
PAgivenbythehyperledacatalogandforVsys,thevalueusedforse- NGC1097 140 37 133±1 55±1
lectingtheinterferencefilter.Thestartingvaluesforthegalacticcenter NGC1512 253 65 260±1 35±14
NGC1566 212 56 214±2 32±14
arethephotometriccentercorrespondingtothemaximumvaluenear
NGC2841 147 68 150±1 70±1
thegalacticcenterinthecontinuummapforspiralgalaxiesorinthe
NGC3351 193 42 193±1 41±2
Spitzer3.6µmimagefordistortedandirregulargalaxies.Then,asec-
NGC3627 173 57 173±7 65±7
ond fittingisdone by lettingi, PA, and Vrot vary withradius while NGC4254 45 28 69±3 31±6
keepingfixedthenew–foundvaluesforVsys,xpos,and,ypos.Finally, NGC4450 355 43 353±5 49±17
rotcurisrunagain,withonlyVrotasthevaryingparameter.Thecom- NGC4559 330 67 323±3 68±5
putedrotationcurveisthusderivedwithfixedkinematicalparameters NGC4736 285 35 292±2 36±7
sothatthesamplecouldbehomogeneous,eventhoughsomevelocity DDO154 219 48 236±17 59±32
fields(e.g.NGC3627)werebettermodeledwithparametersvarying NGC4826 295 60 291±1 53±1
withradius. NGC5033 351 66 353±2 71±2
NGC7793 264 53 277±3 47±9
Theringwidthusedinthefittingprocedurewassettobegreater
than3timesthepixelwidthforagoodsampling.Theresultis5′′for
theOmMobservationsand2′′fortheESO,CFHTandWHTobserva-
tions.Also,additionalrotcurrunsweredonefortheapproachingand responding Hα velocity field (middle–right). The blue images show
receding sides separately in order tomodel any asymmetries arising theintermediate(∼109yrs)stellarpopulationandthe3.6µmtheold
betweenthetwosides.Finally,theexpansionvelocityVexpwasfixed stellarpopulation, tracer of thetotal massof galaxies, whiletheHα
tozeroforallgalaxies,thusassumingpurecircularrotation.Letting monochromaticmapsshowthegasionizedbymassive(M>8M⊙),
Vexpvarywithradiusdidnotchangesignificantlytherotationveloci- young (∼ 106 yrs) OB stars (Kennicutt 1998a; Bosellietal. 2001).
tiesinthecomputedregions. These four maps are WCS–oriented and represent the same field of
Tworotcur parametersremaintobeexplained, namelythefree view.Foreachgalaxy,thefieldofviewisadjustedsothattheHαmor-
angleandtheweightingfunction. Todiminishtheimportanceofde- phologyandkinematicsaswellasthelargescalestellarmorphology
projectionerrors,radialvelocitiesinanopeningangle(calledthefree aredisplayedwithgreatdetail.Themapsandtherotationcurvescan
angle) of typically 35◦ about the minor axis were rejected from the befoundathttp://www.astro.umontreal.ca/fantomm/singsII/
least–squarefittingandacos(θ)(whereθ=anglefromthemajoraxis) Moreover,aposition–velocity(PV)diagramisprovidedforeach
weightingfunctionwasappliedtogivemoreimportancetopointsnear galaxy when the extraction of the kinematical parameters was pos-
themajoraxis.Naturally,formoreface–ongalaxies,theprojectedve- sible. They represent a slice in the data cube along the kinematical
locitiesalong theline–of–sight possess littleinformation about rota- majoraxis.Theblackline,superposedonthediagrams,representsa
tionalvelocitiesresultinginlargeerrorsfor thekinematical parame- cutinthemodelvelocityfield.Adatacubeslicealongthekinematical
ters. majoraxisshowingarotationcurvewhichsuperposeswellontheve-
Afterwards, the GIPSY output was analyzed by IDL routines locitiesofthemaximumintensityoftheionizedgasemissionimplies
(mainlycomputingaveragesandstandarddeviations).Thedetermina- that there are no significant non–circular motions nor any kinemat-
tionofconstantvaluesforiandPAthroughoutthegalaxyisperformed ical twist. Lastly, rotation curves can be found in Appendix C. The
byeliminatingradiiwherenon–circularmotionsandwarpscanoccur. definitionoftheerrorsusediseitherthelargestvelocitydifferencebe-
Foranon–barredgalaxy,thisresultsindiscardingradiilocatedinthe tweenbothsidesandtheapproaching orrecedingsideseparately, or
galacticcenterandouterspiralarmswhereoneusuallyfindsasubstan- therotcurintrinsicerrorifitisgreater.
tialscatteriniandPAvalues.Forabarredgalaxy,thisiscomplicated Thekinematicalparametersinclinationandpositionanglefound
bythefactthatimportantnon–circularmotionsarepresentinthebar bythetechniquedescribedinsection4arepresentedinTable4.Figure
region,thereforethisregionwasexcludedfromthefit.Also,forbarred 1comparesthekinematicalparameterswithrespecttothephotometric
andnon–barredgalaxies,ringscontainingtoofewpointsordominated values.Asexpected, theagreement isbetterforthePAsthanforthe
byonesideofthegalaxywerediscarded. inclinations.ThetwopointsthatstandoutareNGC1512(iphot=65◦
& i = 35◦) and NGC 1566 (i = 56◦ & i = 32◦). In both
kin phot kin
cases, the explanation isquite clear: the photometric parameters are
mainlyrepresentativeofthebarwhichcontributesalargepartofthe
5 RESULTS
lightresultinginmoreedge–onvalues.OnlylookingattheBor3.6-
ThissectionpresentstheHαmonochromaticandRVmapsaswellas µmimagesinFiguresB7&B8,onecanseethattheouterisophotes
therotationcurvesforeachgalaxyinorderofincreasingrightascen- aremuchmoreface–on.
sion.AppendixAbrieflydescribestheobservedkinematicsforeach Finally,ontheoverall37galaxiesexhibitingHαemission,itwas
galaxyofthesample.InAppendixB,fourimagespergalaxyarefirst not possible to extract rotation curves for 21 of them due to either
shown:DSSblueimagewhenavailable(top–left),Spitzer3.6µmim- poor spatial coverage, absence of large–scale rotation or extremely
age(top–right),Hαmonochromaticimage(middle–left),andthecor- perturbeddiscs.
(cid:13)c XXXXRAS,MNRAS000,1–15
HαKinematicsof theSINGS Galaxies 7
In addition, all simulations find density profiles that are incon-
sistentwiththeisothermalprofilefoundinobservations.Intheouter
regions,thedeterminationofthedarkhaloslopebasedonmappingthe
outerdensityprofileofgalaxiesisdifficult,owingmainlytoalackof
masstracersatlargeradii.Intheinnerregions,theunknownvalueof
thestellarmass–to–lightratiofurthercomplicatesthedeterminationof
themassdistribution.Thishasledtodedicatedanalysisondwarfand
lowsurfacebrightness(LSB)galaxiesthatarebelievedtobedarkmat-
terdominatedatallradii(deBlok&McGaugh1997;Verheijen1997;
Swaters1999).Ithasbeensuggestedthatrotationcurvesofdwarfand
LSBgalaxiesriselesssteeplythanpredictedbynumericalsimulations
basedonthecolddarkmatter(CDM)paradigm(Moore1994;Flores
& Primack 1994; de Blok & McGaugh 1997; McGaugh & de Blok
1998;deBloketal.2001a,2001b).
However, a number of observational uncertainties cast doubt
overtheseearlyclaims.TheseincludebeamsmearingforHIrotation
curves(Swatersetal.2000;vandenBoschetal.2000),highinclina-
tionanglesandHαlong–slitalignmenterrors(Swatersetal.2003a),
andnon–circularmotionsclosetothecenterofgalaxies(Swatersetal.
2003b).Manyoftheseuncertaintiescanbequantifiedoreliminatedby
measuringhigh–resolutiontwo–dimensionalvelocityfields(Barneset
al. 2004). At optical wavelengths, these can be obtained via Fabry–
Perotinterferometry(e.g.,Blais–Ouelletteetal.1999)orintegralfield
spectroscopy(e.g.,Andersen&Bershady2003;Courteauetal.2003).
Therearewaystoextractthetruekinematicsthatreflectthegrav-
itationalpotential.Oneistoderivethepotentialdirectlyfromthe2D
velocity field or the 3D data cube (thisis work in preparation). The
other way is to derive the bar parameters using the Spitzer images,
comparewithnumericalsimulations,andapplythenecessarycorrec-
tionsfor,e.g.thestreamingmotionsinducedbythebars(seeHernan-
dez et al. 2005b; Perez, Fux & Freeman, 2004). This detailed work
Figure 1. Comparison between photometric and kinematical willbedoneinanotherpaper(Hernandezetal.2007inpreparation),
parameters.Top:PositionAngle.Bottom:Inclination.Thedot- butwecanillustratewhatneedstobedonebyusingthreeofthebarred
tedlinerepresentsagreeingparameters. systemsinoursample.
The galaxy NGC 3351, better known as Messier 95, is a SBb
galaxy,memberoftheLeogroup.Situatedatadistanceof9.3Mpc,
6 DISCUSSION thisstarburstgalaxyhasalarge–scalestellarbar whichhasadepro-
jected value of 47′′ for the semi–major axis (Martin 1995). Outside
In this paper, the rotation curves given in Appendix C were ob-
thisbar,theHαvelocityfieldisfairlyregularandthekinematicalPA
tainedfromthekinematicalparametersderivedusingtilted–ringmod-
andinclinationfoundbyGIPSYagreewellwiththephotometricval-
elswhichassumepurecircularmotions.Evenifwetriedtoavoidthe
ues. Thus, the gas outside the bar is thought to be in circular orbits
zones obviously affected by non–circular motions, thereisstill con-
sothattherotationcurverepresentsaccuratelythekinematicsofthis
siderableworkneeded toextractrotationcurvesthataretrulyrepre-
galaxy.Thesmalldeviationsfromcircularmotionsareduetostream-
sentativeofthemassdistribution,andcanbeusedformassmodeling
ingalongtheinnerring.TheHαrotationcurveshowsamoreorless
purposes.Thisisespeciallytrueforbarredsystems,whichaccountfor
constant velocity beginning at the end of the stellar bar with peaks
aboutonethirdofthegalaxiesinTable1.
correspondingtothe70′′ innerring.Figure2displaysthetilted–ring
Theideabehindobtaininganaccuratedeterminationofthegrav-
modelresultsandonecansee,outsidethebar,thefairlyregularvalues
itational potential is correlated with the dark halo modeling. For in-
forthepositionangleandinclinationasafunctionoftheradius.
stance,therehasbeensignificantdebateabouttheshapeofdarkmatter
densityprofiles,especiallyregardingtheirinnerslope.Basedoncos- However,insidethelarge–scalebar,theHαvelocityfieldshows
mological N–body simulations (Navarro et al. 1996, 1997, hereafter theperturbedkinematicsexpectedforthisbarredsystem.Thetwisted
collectivelyNFW),thedarkmatterhaloprofileappearstobeindepen- isovelocitycontours indicate that apure circular rotationmodel will
dentofhalomasswithaninnerlogarithmicslopeequalto−1.Nev- present a poor fit to the data and hence kinematical information ex-
ertheless,recenthigherresolutionsimulationssuggestthatthedensity tractedinthisregionwillbeincorrect.ThisisillustratedinFigure2
profilesdo not converge toasingle power lawat small radii.At the where the filled circles represent the values computed in the bar re-
smallest resolved scales (0.5% of the virial radius), profiles usually gion.Itisthusimperativetotakeintoaccountthebarlocationwhen
have slopes between –1 and –1.5 (Moore et al. 1999; Ghigna et al. derivingkinematicalparameters.
2000; Jing & Suto 2000; Fukushige & Makino 2001; Klypin et al. Furthermore, bar modeling is crucial in order to properly com-
2001;Poweretal.2003;Navarroetal.2004;Diemandetal.2004). pute the rotation curve in this region. Numerical computations were
(cid:13)c XXXXRAS,MNRAS000,1–15
8 I. Dicaireet al.
Figure 2. Tilted–ring model for NGC 3351. The dotted line Figure 4. Tilted–ring model for NGC 337. The dotted line
shows the fitted PA (193◦) and inclination (41◦). The stellar shows the fitted PA (121◦) and inclination (52◦). The stellar
barendsataradiusof47′′.So,thefilledcirclesgivethevalues barendsataradiusof35′′.So,thefilledcirclesgivethevalues
insidethe barandtheemptycirclesthe valuesoutsidethebar insidethebarandthe emptycirclesthe valuesoutsidethebar
region. region.
performedwithGADGET,atree–basedN–body+SPHcodedeveloped thisgalaxy willthereforebeobtained by correcting thisartificialin-
bySpringel,Yoshida&White(2001).Fortheneedsofthesimulations, crease in the velocity gradient. Until then, rotation velocities inside
aninitialstellarpopulationissetuptoreproduce adiscgalaxywith thebarregionarenotgivenforthefinalrotationcurve.Seethegalaxy
an already formed bulge. The initial positions and velocities of the description in Appendix A for additional evidences of non–circular
stellarparticlesaredrawnfromasuperpositionoftwoaxisymmetric motions.
Miyamoto–Nagai discs (Miyamoto & Nagai 1975) of mass respec- AnothergalaxydisplayingaperturbedvelocityfieldisNGC337.
tively1010 and1011M⊙,ofscalelengthsrespectively1and3.5kpc ThisasymmetricSBdgalaxyfeaturesanoff–centerstellarbarhaving
and common scale height of 0.5 kpc. Velocity dispersions are com- aPAof162◦ andadeprojectedvalueof35′′ forthebarsemi–major
puted solving numerically the Jeans equations. The total number of axis(Mene´ndez–Delmestreetal.2007).Sincethephotometricmajor
stellar particles is 1.1 ×106. The run includes a dark halo made of axisofthisgalaxyis130◦,thebarhasanintermediateorientationwith
2.2×106liveparticlesdistributedinaPlummersphereofscalelength respecttothemajor axis.Numericalsimulationshavebeendonefor
50 kpc and of mass respectively 2.42 and 6.46 ×1011M⊙. The to- thisbarpositionandtheresultsareillustratedinthemiddlepanelof
tal massof the gasis0.11×1011M⊙. Finally,the totalmass of the Figure 3. The simulated velocity field displays the characteristic Z–
simulatedgalaxyis7.67×1011M⊙. shape of the isocontours similar to what is seen in the Hα velocity
Numerical simulations of the kinematical effect of the bar are map.Onecharacteristicisthevelocitygradientalongtheminoraxis
shown in Figure 3. The input model for the galaxy is pure rotation (greenlineinFigure3).Anotherfeatureistherelativeagreementbe-
and thecorresponding rotationvelocitiesalong themajor and minor tweentheinputrotationvelocities(faintblueline)andthecomputed
axis are shown in faint blue and green lines. Afterwards, the code ones(trianglesymbolsshowaveragedredandbluepointscalculated
simulatesgalaxyevolutionwhereabarisdeveloping.Thedifference usingthemethodpresentedinsection4).Therotationcurveinthebar
inorientationbetweenthemajoraxisandthebarcorrespondstodif- region is thus provided for this galaxy since these perturbations are
ferentevolvingtimeswhicharegiveninunitsofmillionsyears. For confinedtotheminoraxiswhichisexcludedfromthefit.Thetilted–
NGC 3351, the kinematical PA (PA = 193◦) is almost perpen- ringmodelforthisgalaxy,presentedinFigure4,illustratesthesmall
kin
dicular to the bar, with PA = 113◦ using the value found by differencesforthefittedvaluesbetweenthebarregion(filledcircles)
bar
Mene´ndez–Delmestreetal.(2007).Theresultsofthesimulationsare andspiralarms(opencircles).
shown intheformof RVmaps andstellardensitiessuperposed. For Afterhavingcompletedthekinematicalfittingprocedure,onecan
an80◦ differencebetweenthemajor axisand thebar PAs,theover- lookattheSpitzerIRAC3.6µmimageinordertocomparethebarlo-
alleffectisanartificialincreaseinthevelocitygradient.Thiscanbe cationwiththevelocityresiduals.Sincetheeasternsideisapproaching
explained by gas moving along x1 orbits (parallel to the bar) where andthewesternsideisreceding,thespiralarmsseemtobetrailingin
the velocity is greater at the perigalacticon (near the center) than at ananti–clockwisedirection.Thevelocityresidualsfromthepurecir-
the apogalacticon (near the end of the bar). The true kinematics of cularrotationmodelindicatepositiveresidualseastofthebaraswell
(cid:13)c XXXXRAS,MNRAS000,1–15
HαKinematicsof theSINGS Galaxies 9
Figure 3. Three different bar orientations with respect to the major axis. Top: NGC 3351, perpendicularposition. Middle: NGC
337,intermediateposition.Bottom:NGC4559,parallelposition.(left)Densitycontoursofthebarsuperposedonthevelocityfield
ofthemodel.(middle)Thethinblueandgreenlinesrepresenttherotationvelocitiesalongthemajorandminoraxis,respectively,
foraninputmodelwithpurerotation.Thedots(bluefortheapproachingsideandredfortherecedingside)representtheobserved
velocities.(right)Rotationcurvesderivedinthisstudy.
asnegativeresidualsonthesouthernendofthebar,suggestinganin- Finally, the last barred system discussed in this paper is NGC
flowofgastowardsthebar. 4559, anSABcdgalaxyhavingasmallbar roughlyalignedwiththe
Twootherbarredgalaxieshavingabarorientationintermediateto major axis (PAbar ∼ 340◦ vs PAkin = 323◦). Numerical simu-
lations have been done for a bar parallel to the major axis and are
themajoraxisareNGC1566andNGC3627,buttheirSeyfertactivity
presentedinthebottompanelofFigure3.Thesmallvelocitygradient
and warped disc respectively make difficult the kinematical analysis
seeninthePVdiagramandintherotationcurveisinagreementwith
regardingtheeffectsofthebar.Theirrotationcurvesareprovidedat
thepredictedbehaviorseeninthesimulation.Therotationvelocities
theendofthispaper.
(cid:13)c XXXXRAS,MNRAS000,1–15
10 I. Dicaireetal.
The data have been obtained from high resolution Fabry–Perot
observationsusingtheFANTOMMcameraandaL3CCDdetector.The
SINGSsampleofgalaxieshasbeenobservedattheOmM1.6mtele-
scope,ESOLaSilla3.6mtelescope,CFHT3.6mtelescope,andWHT
4.2mtelescope.Thevelocityfieldswereobtainedbyusingadatare-
ductionpipelinewritteninIDLandtherotationcurveswerecomputed
bytherotcurtaskfromtheGIPSYsoftware.Whenfittingthekinemati-
calparameters,carewastakentoavoidthezonesobviouslyaffectedby
non–circularmotions.However,wehavedemonstratedthatforbarred
systems,differentbarcharacteristicsconsiderablymodifythecentral
velocitygradientofthecomputedrotationcurvesinthepurecircular
rotationhypothesis.Therefore,numericalmodelingofbarredgalaxies
iscrucialinordertoextractrotationcurvesthataretrulyrepresenta-
tiveof the gravitational potential and hence of the mass distribution
inthosegalaxies.Inthemeantime,thedarkmatterdistributionofthe
SINGSgalaxies, using therotation curves derived here, willbe pre-
sentedinaforthcomingpaper.
Notonlywilltheseobservationsprovidethehighspatialresolu-
tion data needed for constraining the dark matter density profiles of
galaxies,buttheywillbehelpfulforstudyingtheseprofilesasafunc-
tion of morphological type. Furthermore, they will help to delineate
the role of gas kinematics in regulating the star formation rate. For
Figure 5. Tilted–ring model for NGC 4559. The dotted line instance,Palousˇ,Ehlerova,&Elmegreen(2002)havearguedthatthe
shows the fitted PA (323◦) and inclination (68◦) values. The probabilityofcollapseofmolecularcloudsleadingtostarformation
stellarbarendsataradiusof∼30′′. isgreatlyenhancedinslowlyrotatinggasdiscscomparedtohighve-
locityrotation.Moreover,Cheminetal.(2003)andFathietal.(2007)
have suggested that the star forming inner and nuclear rings in the
areartificiallyloweredbytheradialmotionsinthebar,resultinginan
nearby galaxies NGC 3627 and NGC 628 (respectively) are driven
underestimationoftheluminousmassinthecentralregions.Itisthus
byarotatingasymmetrybecausetheirlocationinthehostdiskarein
vitaltomodelthebarinordertodeterminetheaccuratemassdistribu-
agreement with Lindblad resonances caused by a bar pattern speed.
tion.Theradialmassdistributionofthegaswasanalyzedbetweenthe
Gasdynamicalprocessesthereforeareimportantinregulatingthestar
3timestepstoverifythatmodificationsoftheinnerpartoftherotation
formationhistoryofgalaxiesandtheHαkinematicspresentedinthis
curvewasnotaneffectofmigrationofthegasduringtherun.
paperwillhelpunderstandingthestarformationprocesses.
Furtherbarmodelingenablesthebarlengthtobecalculated.Us-
ingtheFouriermoment analysisonazimuthal profilesderivedusing
J and K 2MASS images (see Aguerri,Beckman,&Prieto 1998 and
Aguerrietal.2000),thedeprojectedvalueforthebarsemi–majoraxis
is30±5′′.Forexample,thetilted–ringmodelforNGC4559shows
that it is difficult to assess which radii are affected by the bar (see
Figure5).However,theHαvelocityfielddisplaysstreamingmotions
ACKNOWLEDGMENTS
outsidethebaraswell,thereforethevelocitiesareperturbedtoatleast
aradiusof∼40′′.Derivingtheformofthegravitationalpotentialdi- WewouldliketothankJacquesBoulesteix,Jean–LucGach,Philippe
rectlyfrom2Dkinematicsand/orusingnumericalsimulationsofthe Balard and Olivier Boissin for helping withthe instrumentation and
bar,arethusessentialtoperforminordertostudyproperlythemass partoftheobservationsandthestaffofthefourObservatories,where
distributionandsolvethedarkhalodensityprofileinconsistencies. thedatawereobtained,fortheircontinuingsupport.TheWilliamHer-
schel Telescope is operated on the island of La Palma by the Isaac
NewtonGroupintheSpanishObservatoriodelRoquedelosMucha-
chosoftheInstitutodeAstrofisicadeCanarias.Weacknowledgesup-
7 CONCLUSIONS
portfromtheNaturalSciencesandEngineeringResearchCouncilof
We have presented in this paper the second and last part of the Hα CanadaandtheFondsQue´be´coisdelarecherchesurlanatureetles
kinematicsfollow–upsurveyoftheSpitzerInfraredNearbyGalaxies technologies.TheDigitizedSkySurveys(DSSimages)wereproduced
Survey(SINGS)sample.Thegoalofthiskinematicalfollowupisto attheSpaceTelescopeScienceInstituteunderU.S.Governmentgrant
betterunderstandtheroleofbaryonsandofthedark/luminousmatter NAGW–2166.Theimagesofthesesurveysarebasedonphotographic
relationinstarformingregionsofgalaxies.Theshapeofthevelocity dataobtainedusingtheOschinSchmidtTelescopeonPalomarMoun-
fieldinthecentralgalacticregions,drawnthroughitsHαcomponent, tainand the UK Schmidt Telescope. Theplates were processed into
is indeed directly related to the baryonic luminous disk and the star thepresentcompresseddigitalformwiththepermissionoftheseinsti-
formationprocesses.TheSINGSsamplewillprovideauniqueoppor- tutions.TheIRimageswereobtainedbytheSpitzerSpaceTelescope,
tunitytolinkthekinematicswithnumerousobservationsandstudies whichisoperatedbytheJetPropulsionLaboratory, CaliforniaInsti-
atotherwavelengths. tuteofTechnologyunderacontractwithNASA.
(cid:13)c XXXXRAS,MNRAS000,1–15