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PRIN 2001: Summary of the activities of the Research Unit at the

PRIN 2001: Summary of the activities of the Research Unit at the Dipartimento di Astronomia dell’Università di Padova Giampaolo Piotto (Local PI) Sergio Ortolani Luigi Bedin Francesca De Angeli Yazan Momany Alejandra Recio Blanco

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PRIN 2001: Summary of the activities of the Research Unit at the

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  1. PRIN 2001: Summary of the activities of the Research Unit at the Dipartimento di Astronomia dell’Università di Padova Giampaolo Piotto (Local PI) Sergio Ortolani Luigi Bedin Francesca De Angeli Yazan Momany Alejandra Recio Blanco Contributions of: Christian Bidin, Giorgia Busso, Marco Riello, Manuela Zoccali Theoretical Support: Giuseppe Bono, Santi Cassisi, Fiorella Castelli

  2. Wide Field Photometric Survey • of Galactic Globular Clusters • Developed the photometric and astrometric • pipeline for WFI data reduction; • About 80 objects observed in with the WFI at the • 2.2m in at least 2 photometric bands; • About 20 objects with UBV photometry; • Calibrated photometric catalog for 21 objects; • Photometric and astrometric catalog for 14 • objects

  3. Wide Field Photometric Survey: Results • The final stellar catalogs satisfy the astrometric, photometric • and field coverage requirements for FLAMES follow-up • The second U-jump; • The post-HB sampling in BHB clusters; • The BHB “red incursion”; • Field WDs.

  4. Astrometric Capabilities

  5. The second • U-jump • There are clearly two jumps: • The first one, at T=11.600K, • corresponds to the Grundahl et al (1999) jump. • The second one, at T=23.000 K is a new discovered feature. Momany, Piotto, Recio-Blanco, Bedin, Cassisi, Bono, 2002, ApJL, 576, L65

  6. The second U-jump is An ubiquitous feature Momany et al. 2003, in prep. NGC 6752 The second U-jump has been Identifird in at least other Four globular clusters NGC 5139

  7. Is it an evolutionary effect? 0.505 0.504 0.510 30+3 stars 14 stars • Clearly there must be an evolutionary effect, but: • We expect a ratio of 0.80 between the stars in the lower and the upper box, while we observe 0.44+-0.20. • For T>23.000K the mass distribution of the HB stars in NGC 6752 must be sharply peaked around 0.505 solar masses, with all the stars within 0.006 solar masses.

  8. Also diffusion may be partially responsible of the second jump The first jump is the consequence of the onset of radiative levitation and diffusion after the disappearence of the envelope convective layers across the H and HeI ionization regions at T=10.000-11.000K. Canonical models predict that the HeII convective region approaches the stellar surface in the ZAHB structures at T=23.000. In addition, mass loss, which is a competing process to diffusion increases with effective temperature. As a result, radiative levitation is less and less effective in the temperature range 11.000-23.000K (supported by observational evidences). For stars with T>23.000K, as a consequence of the larger surface gravity and longer central He burning lifetime, one expects that atomic diffusion becomes more and more efficent in decreasing the envelope He abundance, implying the quenching of the HeII convection. At the same time, larger effective temperatures should enhance radiative levitation, producing a change in the surface composition. It is tempting to associate the second jump with this chemical discontinuity.

  9. Post-HB stars Momany et al. 2002 In the field covered by our data there are 13 post-HB stars. A comparison with the models shows that 11 of these should be classified as AGB-manquè. 84 HB stars are hot enough to evolve in AGB-manquè The ratio between the two populations is 0.13+-0.05, consistent, within the uncertainties, with the predicted value of 0.09, thus solving the discrepancy pointed out by Landsman et al. (1996).

  10. HBs with EBTs in far-UV 4 clusters with EBTs observed with WFPC2 In F255W, F336W, F439W, F555W (GO8718, PI Piotto) NGC 6388, Busso, Piotto, Cassisi 2003, Piotto et al. 2003, in prep.

  11. HBs with EBTs in far-UV The HB of NGC 6388 extends beyond Te=31.500K There is a clear presence of late helium flasher (blue hook) stars, for the first time identified in such metal rich clusters NGC 6388

  12. HBs with EBTs in far-UV It is not possible to simultaneusly fit the red and the blue part of the HB: the tilt of the HB is present also in the FUV CMDs. The HB tilt is not a reddening effect.

  13. The red incursion! Momany et al., 2003, A&A, in press

  14. To make things clearer:

  15. Problem: HB stars have hotter effective temp. than RGB stars with the same metallicity In a CMD the RGB corresponds to the Hayashi track: in stars in hydrostatic equilibrium and having convection, the Hayashi line separates between apermitted region(on its left) from aforbidden one(on its right).

  16. To make things more complicated: BHB red-incursion is not present in all BHB clusters (metallicity effect?) Moreover, some clusters show different HB morphology …. at different telescopes!

  17. Blue: measures the extent of the incursion (HB-RGB) • Red: measures (RGB-RGB[Z=0.0001]) • Black: measures (HB-HB[Z=0.0001])

  18. Field White Dwarfs

  19. High Precision Astrometry on WFPC2/ACS HST Images (Anderson and King 2002, 2003) Just the random error remains~ 0.02 pxl which corresponds to 1 mas(PC) on a single image with N images: N: ~1 mas /sqrt(N)(in the PC case)

  20. Multi-epoch WFPC2/HST images allows accurate proper motion (and proper motion dispersion) measurements for thousands of stars, and…

  21. …thanks to Multifiber High Resolution Spectrographs (like FLAMES at VLT) we are obtaining radial velocities with uncertainties << 1km/s for thousands of stars/night

  22. Combining the proper motion dispersion (an angular quantity) with the radial velocity dispersion (a linear quantity) we have: DISTANCES (sampling error for 3000 stars: 1.3%!) Ongoing projects on: NGC 2808, NGC 6121, NGC 6397, NGC 6752 Cluster modeling with Schwarzschild models (PhD thesis work of FDA, starting from Gebhardt code) Suitable multi-epoch WFPC2/ACS HST images available for 13 globular cluster in total.

  23. Ongoing work on proper motions: example HST observations scheduled for Cycle 12 GO9899, PI: Piotto

  24. Ongoing work on radial velocities: example NGC2808: 1283 stars observed 1000 prop. accepted (FLAMES@VLT) In addition: NGC6121 (2500*) NGC6752 (1500*) Prop. 71.D-0205 PI: Piotto (ongoing)

  25. ABSOLUTE MOTIONS

  26. …of M4: (U,V,W)LSR = ( 53+- 3, -202+-20, 0+- 4)Km/s (P, Q,Z)LSR = ( 54+- 3, 16+-20, 0+- 4)Km/s

  27. Once corrected m l cos b and mb for the Sun peculiar motion we can get Bedin, Piotto, King, Anderson 2003, AJ, in press

  28. Hunting the bottom of the Main Sequence (Bedin, Anderson, King, Piotto 2001, ApJL, 560, L75)

  29. Mass Functions down to the Hydrogen Burning Limit Ongoing Projects: 47 Tuc and w Centauri (HST Cyc. 11 and 13) NGC6791 (HST Cyc. 12 and 14) NGC6397 (King et al.1998 and HST archive) Example: M4, Bedin et al., in prep

  30. (Relative) Distances from the HST Snapshot Database • The method. I. • for [Fe/H]<-1.0 • The metal poor clusters have been divided in 5 bins (approx. 0.2 dex each) • To each bin we associated a cluster with accurate photometry, low reddening, and a sizable of RRLyrae sample • We identified the RRLyrae mean location on the (HST) CMD of the template clusters

  31. Templates -1.10 < [Fe/H] NGC 6362 Walker 2001, private communication -1.28 < [Fe/H] < -1.10 NGC 1851 Walker 1998 -1.50 < [Fe/H] < -1.28 NGC 5904 Caputo et al. 1999 -1.80 < [Fe/H] < -1.50 NGC 1904 - NGC 5272 Buonanno et al. 1994 [Fe/H] < -1.80 NGC 4590 Walker 1994

  32. (Relative) Distances from the HST Snapshot Database The method. I. for [Fe/H]<-1.0 In each group we registered the HB of each cluster to the corresponding template and therefore measured the location of the Mean RRLyrae level. Then: v_zahb = v_rr+ 0.152 + 0.041 [M/H] V_zahb = 0.9824 + 0.3008 [ M/H] + 0.0286 [ M/H]**2 NB: v = F555W

  33. (Relative) Distances from the HST Snapshot Database The method. II. for [Fe/H]>-1.0 v_zahb = v_le + 0.152 – 3 + 0.1 V_zahb = 0.9824 + 0.3008 [ M/H] + 0.0286 [ M/H]**2 NB: v = F555W

  34. (Relative) Distances from the HST Snapshot Database

  35. Relative ages: new groundbased data Plus 51 clusters from the HST snapshot database of Piotto et al. (2002)

  36. Relative ages 51 clusters from HST 34 clusters from Rosenberg et al. (1999) 18 clusters from new groundbased data

  37. CMDs for (relative) age determination: an example TNG+OIG

  38. Ages of single clusters: NGC6642 Piotto, Ortolani, Barbuy Bica, Saviane, 2003, A&A, submitted NGC 6642, a bulge cluster, is about 2 Gyr older than M5. As M5 is coeval with most of the Halo clusters (Rosenberg et al. 1999), NGC 6642 must have formed before most if not all the Halo globular clusters.

  39. Blue Stragglers from the snapshot catalog • Blue stragglers (BS) are present in all of our 74 CMDs; • Almost 3000 BSs have been extracted from 62 GCs; • The location of BSs in the CMD depends on metallicity; • The brightest BSs have always a mass less than 1.6 solar masses; • In all GCs, BSs are significantly more concentrated than other cluster stars.

  40. There is a dependence of the BSs relative frequency on the cluster total mass and on the expected collision rate The enviroment affects the number of BSs. Log Field Log Piotto et al. 2003

  41. The total number of BS stars varies only by a factor of about 10 while HB stars varies by a factor of about 100! BS formation must be affected by the environment. HOW?

  42. Production of Blue Stragglers in GCs Davies, Piotto, De Angeli 2003, A&A, in prep

  43. Blue Stragglers Luminosity Function

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