Globular Clusters: hot stellar populations and internal dynamics

Transcription

1 Globular Clusters: hot stellar populations and internal dynamics Giornate dell Osservatorio, Bologna February 2016 Emanuele Dalessandro

2 Globular clusters: I. hot stellar populations OABO people involved: E. Dalessandro, L. Origlia UniBO (Ferraro, Lanzoni), UniPD, University of Liverpool, STScI, ESO GOAL Understanding the origin and the frequency of hot stars for the interpretation of blue integrated spectra of galaxies Galactic GCs are ideal templates Hot stars in GCs are mainly Horizontal Branch stars and their progeny PHOTOMETRIC SURVEYS 1) HST- WFPC2 Survey of Galactic GCs 177 orbits (PI: Ferraro) 2) HST - UV Legacy Survey 130 orbits (PI:Piotto) 3) SPITZER - MIR Survey of GCs for mass-loss 25hr (PI: Rood)

3 1) HST WFPC2 UV Survey of Galactic GCs: High-quality optical and UV photometry and the most efficient color combinations to derive the HB star T eff distribution constrain the effect of internal He variations 1. An extensive use of synthetic HBs obtained with 2 free parameters: ML and σ ML 2. A proper treatment of radiative levitation (BC for [Fe/H]=0.5 for T>11000K)

4 2) HST UV Legacy Survey: The most complete photometric view of the multiple population phenomenon in GCs insights on the HB stars structure ( ) ALMOST UNIVERSAL FEATURES

5 3) SPITZER MIR Survey: The stellar mass-loss problem The first empirical mass-loss law for PopII RGB implementation in the available models NEXT STEPS: Link to multiple populations Sampling of the entire RGB extension (IR phot + spec) with JWST

6 Globular clusters: II. Internal dynamics OABO people involved: E. Dalessandro, L. Origlia, M. Bellazzini UniBO (Ferraro, Lanzoni, Mucciarelli, Sollima, Alessandrini, Miocchi, Lapenna, Pallanca) Indiana University, UCLA, ESO, STScI PRIN-INAF 2014: Probing the internal dynamics of GCs (PI: Origlia) GOAL Perform a leap forward in the knowledge of the physics and internal dynamics of dense stellar systems From the observational point of view we need 3 ingredients: 1. STAR DENSITY PROFILES è CLUSTER STRUCTURE 2. RADIAL VELOCITIES + PROPER MOTIONS è KINEMATICS 3. BINARY STAR CONTENT è FORMATION AND EVOLUTION

7 1) STAR DENSITY PROFILES star density profiles and 2D density maps from resolved star counts Core size Central cusp (CC or IMBH?) Cluster size Tidal tails Extra-tidal halos ENTIRE CLUSTER EXTENSION!

8 1) STAR DENSITY PROFILES High-res: HST 1 deg2 Wide-field ground-based imaging 25 DATA SETS ESO-VLT: FORS2 + VIMOS 72 hr (PI: Dalessandro) LBT: LBC 40 hr (PIs: Dalessandro + Beccari + Lanzoni) HST: WFPC2 + ACS + WFC3 + HRC

9 2) RADIAL VELOCITIES A new generation of velocity dispersion and rotational profiles from individual stars by using a multi-instrument approach ESO Large Programme 193.D-0232 (PI: Ferraro) 194 hr acquired with KMOS+FLAMES for 30 Milky Way GCs ESO Large Programme 195.D-0750 (PI: Ferraro) 101 hr with SINFONI for 15 high-density GCs Additional (PI: Rich) 20 hr OSIRIS + DEIMOS SINFONI KMOS FLAMES

10 2) RADIAL VELOCITIES: A MULTI-INSTRUMENT APPROACH SINFONI very central regions (AO) AO-assisted IFU, 0.1 spatial resolution, FoV=3.2 x3.2, mid-spectral resolution (R=4000), K-band grating ( µm), CO band-heads One spectrum for every (exposed) spaxel SINFONI

11 2) RADIAL VELOCITIES: A MULTI-INSTRUMENT APPROACH KMOS 24 deployable IFUs, FoV=3 x3 each, mid-spectral resolution (R=3400), YJ-band grating ( µm),atomic lines (TiI, MgI, FeI,..) very central regions (AO) SINFONI intermediate regions KMOS 1-3 stars per IFU

12 2) RADIAL VELOCITIES: A MULTI-INSTRUMENT APPROACH FLAMES GIRAFFE/MEDUSA: multi-object spectrograph (132 fibres), 25 FoV high spectral resolution (R>10,000), optical band (Ca triplet, Fe, MgI) very central regions (AO) intermediate regions external regions SINFONI KMOS FLAMES

13 2) RADIAL VELOCITIES: A MULTI-INSTRUMENT APPROACH Crucial constraints on the SINFONI KMOS FLAMES MP IMBH formation (?) scenarios High-velocity stars FG SG Rotation Dark-Matter (?) internal proper motions from multi-epoch + HST observations (also with GAIA) provide the FIRST 3D velocity map of the cores radial anisotropy profiles

14 3) BINARY STAR CONTENT Binary stars are a crucial ingredient for the formation and dynamical evolution of GCs Derive binary stars radial distribution and constrain the primordial binary fraction with the secondary MS method ESO-VLT: FORS2 + VIMOS 72 hr (PI: Dalessandro) FORS2 LBC@LBT: 40 hr ACS 1. Deep and accurate photometry wide spatial coverage 2. Control of completeness and blends (artificial stars experiments)

15 3) BINARY STAR CONTENT Binary stars are a crucial ingredient for the formation and dynamical evolution of GCs Derive binary stars radial distribution and constrain the primordial binary fraction with the secondary MS method ESO-VLT: FORS2 + VIMOS 72 hr (PI: Dalessandro) LBC@LBT: 40 hr 6 mag!! 1. Deep and accurate photometry wide spatial coverage 2. Control of completeness and blends (artificial stars experiments)

16 3) BINARY STAR CONTENT The radial distribution of binary stars shows three different behaviors (as for BSS) FLAT BIMODAL UNIMODAL This suggests that: they are shaped with the same efficiency by the same mechanism (dynamical friction) the evolution of binaries is an important formation channel for BSS