star formation around active galactic nuclei: lessons from the mid-ir d. alloin & e. galliano

32
Star Formation around Active Galactic Nuclei: Lessons from the mid-IR D. Alloin & E. Galliano

Upload: roberta-oneal

Post on 27-Dec-2015

213 views

Category:

Documents


0 download

TRANSCRIPT

Star Formation around Active Galactic Nuclei:

Lessons from the mid-IR

D. Alloin & E. Galliano

Embedded Young Massive Star Clusters

M82: Archetypal starburst galaxy

Embedded Young Massive Star Clusters

o HST revealed Young Massive Star Clusters (YMC) in local starburst galaxieso 100s to 1000s in some galaxieso 0.5pc to 200pc, mass~10^6Msolo Age, few Myr to 10 Myr

o Are they adolescent GC ?

Embedded Young Massive Star Clusters

o On the GC time scaleo YMCs are very young

o On stellar formation time scaleo YMCs are already evolved

o Comparison with star formationo First stages of YMCs

expected to be embedded

ESC…SSC…GC?

o We expect the cluster to be embedded ino Dense region of ionized gas

(UDHII)o Cocoon of heated dust

o We can observeo Radio cm emissiono IR nebular lineso MIR continuumo PAH

Embedded Young Massive Star Clusters

o Not yet identified in observationso Giant molecular cloudso Sub-mm emission of cold

gas

o Future: observations with ALMA

NGC1365, NGC1808, visible

D=18.6Mpc, 1”=90pc D=10.9Mpc, 1”=53pc

From HST archive

F814WF658N

NGC1365, NGC1808, visible

D=18.6Mpc, 1”=90pc D=10.9Mpc, 1”=53pc

+ radio

Radio data: Forbes & Norris 1998 & Collison et al. 1994

NGC1365, NGC1808, visible

D=18.6Mpc, 1”=90pc D=10.9Mpc, 1”=53pc

=-0.75

=-0.4 =-0.4

=-0.3

=-0.5

=-0.6

+ radio

Radio data: Forbes & Norris 1998 & Collison et al. 1994

F814WF658N

3.6cm 3.6cm

NGC1365, NGC1808, N-band*

*TIMMI2 data

NGC1365, NGC1808, N-band

*TIMMI2 data

MIR templates

N-Band colors

N_band colorsMuch redder than HII

regions or PDR

Deep silicate absorptionAv of several 10s

Strong [NeII] emission

Interpretation:Embedded Star Clusters

o Few objects knowno Antennae, NGC5253, SBS0335-052, IIZw40o 106 to 107 solar masseso Radio index =-0.1

o Radio emission =-0.1 : thermal free-free emission from HII

regions =-0.8 : non-thermal emission from SNR

Interpretation:Embedded Star Clusters

o In NGC1365 and NGC1808 clusters?o negative cm indices: -0.4 to -0.9o share of thermal and non-thermal

emission

Fν thermal ionizing photon production rate

Fv non-thermal SN rate

Starburst99 model

o Model from Leitherer et al. 1999*o 106 solar masseso Instantaneous star formationo Salpeter IMFo We use:

o Supernova rateo Ionizing photon production rateo Total star luminosity

* www.stsci.edu/science/starburst99

Starburst99 model

SN rate

Non-thermal radio flux

Ionizing photon rate

Thermal radio flux

Star Luminosity

BB flux

Cluster age

Predicted cm flux

Cluster mass

Predicted 12.9µm F

Av

Weighing and dating the clusters?

Weighing and dating the clusters?

NGC1365o 3-6 Myro 2 106 solar masseso Av=20-40 mag

NGC1808o 3-5 Myro 0.3 106 solar masseso Av=20-40 mag

Simple model confirms that these objects are likely to be young embedded clusters: proto-globular clusters??

ISAAC data

o Imaging in K, L and M bandso SED of the objects

o LR spectroscopy in K(2.2µm) and L(3.5 µm)o Measure Br (K) and Br (L)o Measure extinction: deredden line fluxeso Detect PAHo Compare with more complex models

NGC1365

K L N

NGC1808

K L N

Improved Modeling ?

o GRASILo code for

spectrophotometry of evolving stellar populations taking into account the effects of dust

Silva & Granato 1998

Survival ofEmbedded Star Clusters

o Cluster lifetime dependence on mass and environmental effects (Gieles et al, Portegies et al 2002, Baumgardt & Makino 2003).

o N-body simulations, Galactic center: D=34 pc, density~700 solar mass/pc3

o 105 solar mass cluster: < 40-120 Myro 106 solar mass cluster: < 180-500 Myr

o Effect of molecular cloud interactionso decrease lifetime by a factor 5-10o hence lifetimes less than 50 Myr

NGC1068, N band, VISIR SV:knots identification & inner

spiral

NGC1068, N band, deconvolved

NGC1068, [NeII]

NGC1068, comparison with Subaru

NGC1068, comparison with NACO/VLT

NGC1068, comparison with [OIII] HST

Survival of Embedded Star Clusters in strong X/UV field?

o NLR clouds: high density o Ionization cone: protected cloud back-side

o Dust emissiono PaH emission

o Star formation?o Jet-induced gas compressiono Transient micro-bar?o Only minor flux contribution in NGC1068, but size consistent (~14 pc)

Concluding remarks

o Observational side: high-resolution imaging &

MIR-NIR spectroscopy, mm/cm interferometry

o Modeling side:o Codes DUSTY or GRASIL (radiation transfer)o N-body simulations for lifetime estimates

o Statistical approacheso Frequency of e-clusters occurrence around AGNo Age sequence versus location?