Star Formation around Active Galactic Nuclei Lessons from

  • Slides: 32
Download presentation
Star Formation around Active Galactic Nuclei: Lessons from the mid-IR D. Alloin & E.

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

Embedded Young Massive Star Clusters M 82: Archetypal starburst galaxy

Embedded Young Massive Star Clusters M 82: Archetypal starburst galaxy

Embedded Young Massive Star Clusters o HST revealed Young Massive Star Clusters (YMC) in

Embedded Young Massive Star Clusters o HST revealed Young Massive Star Clusters (YMC) in local starburst galaxies o 100 s to 1000 s in some galaxies o 0. 5 pc to 200 pc, mass~10^6 Msol o Age, few Myr to 10 Myr o Are they adolescent GC ?

Embedded Young Massive Star Clusters o On the GC time scale o YMCs are

Embedded Young Massive Star Clusters o On the GC time scale o YMCs are very young o On stellar formation time scale o YMCs are already evolved o Comparison with star formation o First stages of YMCs expected to be embedded

ESC…SSC…GC? o We expect the cluster to be embedded in o Dense region of

ESC…SSC…GC? o We expect the cluster to be embedded in o Dense region of ionized gas (UDHII) o Cocoon of heated dust o We can observe o o Radio cm emission IR nebular lines MIR continuum PAH

Embedded Young Massive Star Clusters o Not yet identified in observations o Giant molecular

Embedded Young Massive Star Clusters o Not yet identified in observations o Giant molecular clouds o Sub-mm emission of cold gas o Future: observations with ALMA

NGC 1365, NGC 1808, visible From HST archive F 814 W D=18. 6 Mpc,

NGC 1365, NGC 1808, visible From HST archive F 814 W D=18. 6 Mpc, 1”=90 pc F 658 N D=10. 9 Mpc, 1”=53 pc

NGC 1365, NGC 1808, visible + radio D=18. 6 Mpc, 1”=90 pc D=10. 9

NGC 1365, NGC 1808, visible + radio D=18. 6 Mpc, 1”=90 pc D=10. 9 Mpc, 1”=53 pc Radio data: Forbes & Norris 1998 & Collison et al. 1994

NGC 1365, NGC 1808, visible + radio =-0. 75 =-0. 4 F 814 W

NGC 1365, NGC 1808, visible + radio =-0. 75 =-0. 4 F 814 W 3. 6 cm F 658 N 3. 6 cm =-0. 4 =-0. 3 =-0. 5 =-0. 6 D=18. 6 Mpc, 1”=90 pc D=10. 9 Mpc, 1”=53 pc Radio data: Forbes & Norris 1998 & Collison et al. 1994

NGC 1365, NGC 1808, N-band* *TIMMI 2 data

NGC 1365, NGC 1808, N-band* *TIMMI 2 data

NGC 1365, NGC 1808, N-band *TIMMI 2 data

NGC 1365, NGC 1808, N-band *TIMMI 2 data

MIR templates

MIR templates

N-Band colors N_band colors Much redder than HII regions or PDR Deep silicate absorption

N-Band colors N_band colors Much redder than HII regions or PDR Deep silicate absorption Av of several 10 s Strong [Ne. II] emission

Interpretation: Embedded Star Clusters o Few objects known o Antennae, NGC 5253, SBS 0335

Interpretation: Embedded Star Clusters o Few objects known o Antennae, NGC 5253, SBS 0335 -052, IIZw 40 o 106 to 107 solar masses o Radio index =-0. 1 o Radio emission o =-0. 1 : thermal free-free emission from HII regions o =-0. 8 : non-thermal emission from SNR

Interpretation: Embedded Star Clusters o In NGC 1365 and NGC 1808 clusters? o negative

Interpretation: Embedded Star Clusters o In NGC 1365 and NGC 1808 clusters? o negative cm indices: -0. 4 to -0. 9 o share of thermal and non-thermal emission Fν thermal ionizing photon production rate Fv non-thermal SN rate

Starburst 99 model o Model from Leitherer et al. 1999* o 106 solar masses

Starburst 99 model o Model from Leitherer et al. 1999* o 106 solar masses o Instantaneous star formation o Salpeter IMF o We use: o Supernova rate o Ionizing photon production rate o Total star luminosity * www. stsci. edu/science/starburst 99

Starburst 99 model SN rate Non-thermal radio flux Ionizing photon rate Thermal radio flux

Starburst 99 model SN rate Non-thermal radio flux Ionizing photon rate Thermal radio flux Star Luminosity BB flux

Weighing and dating the clusters? Cluster age Predicted cm flux Cluster mass Predicted 12.

Weighing and dating the clusters? Cluster age Predicted cm flux Cluster mass Predicted 12. 9µm F Av

Weighing and dating the clusters? NGC 1365 o 3 -6 Myr o 2 106

Weighing and dating the clusters? NGC 1365 o 3 -6 Myr o 2 106 solar masses o Av=20 -40 mag NGC 1808 o 3 -5 Myr o 0. 3 106 solar masses o 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 bands o SED of the

ISAAC data o Imaging in K, L and M bands o 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 fluxes o Detect PAH o Compare with more complex models

NGC 1365 K L N

NGC 1365 K L N

K L N NGC 1808

K L N NGC 1808

Improved Modeling ? o GRASIL o code for spectrophotometry of evolving stellar populations taking

Improved Modeling ? o GRASIL o code for spectrophotometry of evolving stellar populations taking into account the effects of dust Silva & Granato 1998

Survival of Embedded Star Clusters o Cluster lifetime dependence on mass and environmental effects

Survival of Embedded 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/pc 3 o 105 solar mass cluster: < 40 -120 Myr o 106 solar mass cluster: < 180 -500 Myr o Effect of molecular cloud interactions o decrease lifetime by a factor 5 -10 o hence lifetimes less than 50 Myr

NGC 1068, N band, VISIR SV: knots identification & inner spiral

NGC 1068, N band, VISIR SV: knots identification & inner spiral

NGC 1068, N band, deconvolved

NGC 1068, N band, deconvolved

NGC 1068, [Ne. II]

NGC 1068, [Ne. II]

NGC 1068, comparison with Subaru

NGC 1068, comparison with Subaru

NGC 1068, comparison with NACO/VLT

NGC 1068, comparison with NACO/VLT

NGC 1068, comparison with [OIII] HST

NGC 1068, comparison with [OIII] HST

Survival of Embedded Star Clusters in strong X/UV field? o NLR clouds: high density

Survival of Embedded Star Clusters in strong X/UV field? o NLR clouds: high density o Ionization cone: protected cloud back-side o Dust emission o Pa. H emission o Star formation? o Jet-induced gas compression o Transient micro-bar? o Only minor flux contribution in NGC 1068, but size consistent (~14 pc)

Concluding remarks o Observational side: high-resolution imaging & MIR-NIR spectroscopy, mm/cm interferometry o Modeling

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 approaches o Frequency of e-clusters occurrence around AGN o Age sequence versus location?