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					 The VLT-FLAMES Survey of Massive Stars
                      Chris Evans (ING, La Palma)




Tartu – August 2005
                    Main collaborators

 Steve Smartt, Philip Dufton, Ian Hunter (Belfast)

 Danny Lennon (ING)

 Carrie Trundle, Artemio Herrero (IAC)

 Alex de Koter, Rohied Mokiem (Amsterdam)

 Mike Irwin (Cambridge)




                                                      2
           FLAMES survey of massive stars
 ESO Large Programme (PI: S. Smartt)

 112hrs on the VLT with FLAMES

 FLAMES has 137 fibres which ‘feed’ the Giraffe spectrograph




                                                            3
                        Target fields

Fields chosen to sample a range of Z and ages:

                      ‘Young’ clusters      ‘Old’ clusters
                      (<5 Myr)              (10-20 Myr)


Milky Way             NGC 6611              NGC 3293, 4755


LMC                   N11 (inc. LH 9/10)    NGC 2004


SMC                   NGC 346               NGC 330
                                                             4
                 Some of our motivations

 Obtain CNO abundances for a large, homogenous OB sample

 Determine vsini distributions, evidence for Z-dependence?

 Armed with vsini, explore CNO cf. evolutionary models

 Tests of the Z-dependence of O star mass-loss rates

 Un-planned, but interesting: Binary detection!




                                                              5
                        Target fields

Fields chosen to sample a range of Z and ages:

                      ‘Young’ clusters      ‘Old’ clusters
                      (<5 Myr)              (10-20 Myr)


Milky Way             NGC 6611              NGC 3293, 4755


LMC                   N11 (inc. LH 9/10)    NGC 2004


SMC                   NGC 346               NGC 330
                                                             6
                        Target fields

Fields chosen to sample a range of Z and ages:

                      ‘Young’ clusters      ‘Old’ clusters
                      (<5 Myr)              (10-20 Myr)
Evans et al. (2005)
Milky Way             NGC 6611              NGC 3293, 4755


LMC                   N11 (inc. LH 9/10)    NGC 2004


SMC                   NGC 346               NGC 330
                                                             7
                        Target fields

Fields chosen to sample a range of Z and ages:

                      ‘Young’ clusters      ‘Old’ clusters
                      (<5 Myr)              (10-20 Myr)


Milky Way             NGC 6611              NGC 3293, 4755


LMC                   N11 (inc. LH 9/10)    NGC 2004


SMC                   NGC 346               NGC 330
                                                             8
               Observational information

 High resolution: R~20,000

 800 stars observed over the 7 fields:
   – @ 6 λ-settings, coverage from 3850-4750, 6400-6650 Å
   – LMC/SMC fields observed 6 times at each λ-setting

 Obtained in service mode, often different observational epochs
   – for each λ-setting
   – for repeat observations at each λ-setting


                                                               9
                    Observational information

 High resolution: R~20,000
 800 stars observed over the 7 fields:
    – @ 6 λ-settings, coverage from 3850-4750, 6400-6650 Å
    – LMC/SMC fields observed 6 times at each λ-setting
 Obtained in service mode, often different observational epochs:
    – for each λ-setting
    – for repeat observations at each λ-setting


                                                             V = 15.29

                                                                 O9.5 V




                                                                          10
Targets in NGC 346




          V-band DSS
                       11
                 Targets in NGC 346




ACS (HST/Nota)             V-band DSS
                                        12
                      Targets in N11




NIR (from R. Barba)           V-band DSS
                                           13
                      Targets in N11
                                           LH 10




                              LH 9

NIR (from R. Barba)           V-band DSS
                                               14
          Census of young MC clusters

Field       O    B<5   B5+   Be   AFG Total

N11         43   67    0     10   4     124

NGC 346     19   57    2     27   11    124




                                              15
                Census of young MC clusters

    Field           O       B<5       B5+      Be       AFG Total

    N11             43      67        0        10       4        124

    NGC 346         19      57        2        27       11       124



 Incidence of Be-stars:
   – there is a selection effects for the Be-stars, one cannot simply take the
     above numbers at face value!



                                                                                 16
Be-type spectra in   Hα
    NGC346




                     17
               Census of young MC clusters

   Field          O       B<5       B5+      Be    AFG Total

   N11            43      67        0        10    4    124

   NGC 346        19      57        2        27    11   124



 62 O-type stars, ~half of them previously unknown

 Analysis now underway in Amsterdam
      [more in Alex de Koter’s talk later today]

                                                               18
New O2-type star




                   19
New O2-type star




         O2-2.5 III(f*)

         Still small number statistics
          at earlier than O3 (~10 stars)




                                      20
N11 field




            21
N11 field




            22
N11 field




            23
N11 field   O2 star




                      24
                           Binary detection

 Service observations @ multiple epochs » checks for binarity

 Single/double-lined binaries found from simple methods:
   – from visual inspection when classifying the spectra
   – from radial velocity measurements of the H, He & Si lines
       [accurate to ~10 km/s]


 More sophisticated methods now being used to cross-correlate
  the individual spectra at each λ-setting
      [accurate to ~5 km/s, which will no doubt find further binaries]



                                                                         25
Binaries in the young MC clusters

Field     O    B<5   Be    Total

N11       43   67    10    120

NGC 346   19   57    27    103




                                    26
           Binaries in the young MC clusters

           Field        O      B<5    Be     Total

           N11          43     67     10     120
           Binaries     20     20      4      44
           NGC 346      19     57     27     103
           Binaries      4     18      5      27

 Note that these numbers do not include those found from
  cross-correlation methods – expect them to go up slightly


                                                              27
           Binaries in the young MC clusters

           Field        O      B<5    Be     Total

           N11          43     67     10     120
                                                        37%
           Binaries     20     20      4      44
           NGC 346      19     57     27     103
           Binaries      4     18      5      27
                                                        26%

 Note that these numbers do not include those found from
  cross-correlation methods – expect them to go up slightly


                                                              28
           Binaries in the young MC clusters

           Field        O      B<5    Be     Total

           N11          43     67     10     110
                                                        36%
           Binaries     20     20      4      40
           NGC 346      19     57     27       76
           Binaries      4     18      5       22
                                                        29%

 Note that these numbers do not include those found from
  cross-correlation methods – expect them to go up slightly


                                                              29
Binary detection: time sampling




                             N11
     57 days


     84 days


                                   NGC 346


               Julian Date
                                             30
            Binaries in the young MC clusters

            Field         O      B<5     Be      Total

            N11           43     67      10      110
                                                            36%
            Binaries      20     20       4       40
            NGC 346       19     57      27       76
            Binaries       4     18       5       22
                                                            29%

 Firm lower limits on binary fraction, to then compare with
  different star formation scenarios (eg Bally & Zinnecker, 2005)


                                                                    31
   N abundances in B stars in NGC 346




Provisional results from TLUSTY analysis, (Ian Hunter, Belfast)
                                                                  32
   N abundances in B stars in NGC 346



                                     Binaries




Provisional results from TLUSTY analysis, (Ian Hunter, Belfast)
                                                                  33
                              Summary

 Lots of interesting objects in these young clusters!

 Overview paper of LMC/SMC data, binary detection, radial
  velocities, etc: Evans et al., in prep.

 Parallel studies:
   –   LMC/SMC O-star analysis: Amsterdam
   –   Galactic vsini paper: Belfast
   –   Analysis of narrow-lined stars: Ian Hunter (Belfast)
   –   Analysis of O stars in NGC 6611: Herrero/Villamariz (IAC)


                                                                   34

				
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posted:10/18/2012
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