Star Formation around Active Galactic Nuclei: Lessons from the mid-IR
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Star Formation around Active Galactic Nuclei: Lessons from the mid-IR D. Alloin & E. Galliano
description
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. HST revealed Young Massive Star Clusters (YMC) in local starburst galaxies - PowerPoint PPT Presentation
Transcript of Star Formation around Active Galactic Nuclei: Lessons from the mid-IR
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?
