RevealingtheoriginofextraplanarmolecularcloudsinarampressurestrippedgalaxythroughtheALMA

BumhyunLee&AereeChungDepartmentofAstronomy,YonseiUniversity,SouthKorea

East-AsiaALMAScienceWorkshop2017-Korea,November27-29,2017

Credit:ESO/B.Tafreshi(twanight.org)

Galaxyevolutioninclusterenvironment

Red

Blue

Density

Low High

• Elliptical&S0galaxies:90%intheclusterenvironment

2

Hoggetal.2004

• Clusterpopulation:passiveandred

Field Cluster

Rampressurestripping

✓ ICM(theintraclustermedium)–ISM(theinterstellarmedium)

Rampressurestripping(RPS,Gunn&Gott1972)rampressure>restoringforce→gasisstripped→red&passivegalaxy?

✓ HIgasstripping(e.g.Cayatteetal.1990;Chungetal.2007,2009)✓ Starformationquenching(Koopmann&Kenney2004a,b)

3

Moleculargas→adirectingredientforstarformation

Q.Whethermoleculargasisstripped/disturbedbytherampressure

Q.Whetherclusteraredeficientinmoleculargas(Starketal.1986,Kenny&Young1989vs.Fumagallietal.2009,Bosellietal.2014)

NGC4396

NGC4654

Chungetal.2009

Moleculargasunderstrongrampressure

4

SMAobservationsinordertoinvestigatedetailedCOproperties

12CO(2-1):blue,SMA,Lee&Chungetal.201712CO(2-1):green,IRAM30m,Vollmeretal.2008HI:red,Chungetal.2009D25intheopticalimage,RC3TheICMwinddirection:blackarrows

Virgocluster(16Mpc),threespiralsinactiveRPS

UsingSMA12CO(2-1)data,✓ 12COmorphology→highlyasymmetricanddisturbed→closelyrelatedtotheHImorphology

Lee&Chungetal.2017,MNRAS,446,1382

▶Strong rampressurecanaffectpropertiesofmoleculargas(evenwithinafewkpcofstellardisk)

ExtraplanarCOgasinNGC4522

5

• Activerampressurestrippingstage• Only25%ofexpectedHIgasmass• 40%oftotalHIgas(green)intheextraplanar• 25%oftotalCOgas(whitecontour)inthe

extraplanar• ExtraplanarCOgas&extarplanarHαpatches(Kenneyetal.2004;Vollmeretal.2008;Chungetal.2009)

✓ Aninterestingcase,asthenearestexampleamongonlythefewgalaxiesfoundwithextraplanarmoleculargas

✓ Moleculargaspropertiesandstarformationactivitiesinside&outsidethediskwiththefollow-upALMAobservations

ScientificquestionsintheALMAobservations

6

Q1.Whatarepropertiesofextraplanarmolecularclouds?(e.g.mass,linewidths,velocityfield,12/13COlineratio)

Q2.CanthemoleculargasgetstrippedbyrampressureduetotheICM?Ifso,isitstrippedascloudorisitre-crumpledafterstripping?Inaddition,canthemoleculargasbenewlyformedfromstrippedatomicgasoutsidethestellardisk?Q3.HowefficientlydostarsforminaRPSgalaxy?✓ Arelationbetweenthemoleculargassurfacedensityandthe

starformationrate(i.e.theKennicutt-Schmidtlaw)atsub-kpcscale

TheALMAobservations(Cycle3,PI:Lee,B)

7 Credit:ALMA(ESO/NAOJ/NRAO),B.Tafreshi

Using12marray,• January12,2016,12CO,46antennas• January19,2016,13CO,43antennas

Inband3andband6(MultiCOlines),• 12CO(1-0);115.271GHz• 13CO(1-0);110.201GHz• 12CO(2-1);230.538GHz

Intworegions,• onearoundthecenterofNGC4522• Onecenteredonthepeakofthe

extraplanarCOgas

On-sourcetime:• 12CO(1-0):0.9hrs,13CO(1-0):4.6hrs• 12CO(2-1):0.3hrs

Intotalobservationtime:~5.8hrs

FOV:~50arcsec(band3)~25arcsec(band6)

TheALMAdataofNGC4522

8

✓ Extraplanarcloudsdetectedinboth12COand13CO(C,D,E,G)

✓ Thefirstreportforextraplanar13COdetectioninaRPSgalaxy,usingALMA→importantdatatoconstraintheoriginofextraplanarcloudsandtheirphysicalstates

Leeetal.inprep.

3.03”X2.34” 3.14”X2.31”

12CO(1-0)intensitymap 13CO(1-0)intensitymap 12CO(1-0)velocityfieldmap

F

TheALMAdataofNGC4522

9

Leeetal.inprep.

3.03”X2.34” 3.14”X2.31”

12CO(1-0)intensitymap 13CO(1-0)intensitymap 12CO(1-0)velocityfieldmap

F

Lineratioof12CO&13CO

10

Arrow:theICMwinddirectionEllipse:theopticaldisk

✓ Meanlineratioofextraplanarclouds:~11.1(i.e.comparabletothelineratioofthemaindisk:~10.8)

✓ UGC12914/5interactingsystem:~50inthetidalbridge(cf.~15inthecenterofUGC12915)

▶Theexternalpressure:rampressure?(Alataloetal.2015)

✓ Lineratiogradientinextraplanarclouds(C,D,E,G;easttowest)

✓ Lowineast→highinwest

▶DiffuseCOgasisstripped?(Alataloetal.2015)

12CO/13CO(1-0)ratiomap

Twopotentialoriginsofextraplanarclouds

11

1.MoleculargasformationfromstrippedHIgas

2.Strippingmoleculargas

ascloudORreassemble(Sivanandametal.2010)

✓ Rampressure>restoringforceformolecularcloudsinthestellardisk

→strippingmolecularclouds(Leeetal.2017)

Leeetal.inprep.

✓ Consideringvarioustimescales(e.g.GMCformationtimescale(30Myr),strippingtimescale(100Myr))(Vollmeretal.2006;Crowl&Kenney2008)

✓ Thecombinationoftwopotentialorigins?

Twopotentialoriginsofextraplanarclouds

12 Leeetal.inprep.

✓ 13COdetection→ahintfortheoriginoftheextraplanarmoleculargas?

13C13C13C13C

Marigo2006

TheKennicutt-Schmidt(KS)relationofNGC4522

13

Bluesolidline:gasdepletiontime(=1/SFE)

1)Sub-linearrelation(slope:0.76)ontheKSplot✓ Inefficientstarformationactivityduetoinjectingturbulenceintomoleculargasby

rampressureAlataloetal.2015,Leeetal.2017,Shettyetal.2013Leeetal.inprep.

TheKennicutt-Schmidt(KS)relationofNGC4522

14

Bluesolidline:gasdepletiontime(=1/SFE)

Leeetal.inprep.

Summary

15

Jachymetal.2014

IC3418

Kenneyetal.2014

Ebelingetal.2014

Recentstudiesformanyjellyfishgalaxies

✓ Thefirstreportfor13COdetectionoutsidethemaindiskoftheRPSgalaxythankstohigh-sensitivityofALMA

✓ Extraplanarmolecularcloudsareaccelerated(40km/sblueshifted)towardVirgocluster

✓ Lineratiogradient,east(low)towest(high)inextraplanarclouds,diffuseCOgasisstripped?

✓ Twopotentialoriginsofextraplanarclouds,butextraplanr13CO→extraplanrmolecularcloudsarestrippedbyrampressure

✓ Sub-linearslopeintheKSplotandrelativelylonggasdepletiontimeinextraplanarmolecularclouds

ThisALMAdatawillgiveanopportunitytobetterunderstandthefateofISMandstarformationactivityintheextraplanarspace

Thankyou