Status of EROS baryonic dark matter search

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Status of EROS baryonic dark mattersearch

• J-F Glicenstein
• DAPNIA/SPP, CEA-Saclay

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• the EROS surveys
• monitoring of mlensing candidates
• differential photometry of the SMC
• limits on the MACHO content of the dark halo

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Event rate predictions from  standard 
isothermal halo model
standard model predictions
EROS LMC events (ltMgt 0.2 Mo)

• predicted rate depends on halo model (? MHalo)
•  standard halo model  optimistic
• (range in rate 1?5 depending on
  halo flattening etc.)
• rate/star (LMC) rate/star (SMC)

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The EROS surveys towards the Magellanic Clouds
0.5 Mo MACHOs fHalo1

• Papers
• LMC 3 yrsSMC 5yrs
• C.Afonso et al., A A 400, 951 (2003)
• LMC 2 yrs
• T.Lasserre et al., A A 355, L39 (2000)
• EROS 1
• C.Renault et al., A A, 324, L69 (1998)

P.Tisserand thesis (2004)
 
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Comparison of LMC and SMC candidates
Halo lenses Same tE distributions for LMC/SMC
lenses.  Self-lensing  LMC expect tE
40 days SMC expect tE 100 days

• SMC candidates not compatible with 0.5 Mo
  Machos.
• Optical depth towards SMC too large for
  self-lensing
• ? some SMC candidates likely variable stars

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EROS1 candidates towards the LMC
EROS1 1

• data taking 1990 1994 ,
• with photographic plates
• 4.2 million stars
• 2 mlens candidates
• new fluctuation of EROS1 2
• in 1998 ? rejected.

R CCD camera down
EROS1 2
new bump
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What about EROS11 ?
EROS1 1

• New mlensing-like
• fluctuation of EROS1 1
• seen in EROS2 data
• rejected.
• All the EROS1 candidates
• eliminated !!

new bump
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LMC 3 year analysis mlensing candidates
EROS2 5
EROS2 3
uo0.580.01 te24 1 days blending0.91
uo0.230.01 te44 3 days blending0.75
EROS2 7
uo0.230.01 te33 2 days blending0.45
uo0.380.01 te36 2 days blending0.72
EROS2 6
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Follow-up of LMC 3 year analysis candidates
bumps
EROS2 3
LMC 3 yr
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Follow-up of other LMC candidates
First bump tmax-2450000-237.7
MACHO LMC-23
bump observed by EROS at tmax-2450000?2250.
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EROS2 SMC 5 year analysismlensing candidates
tE101 days
tE612 days
tE390 days
tE243 days
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Differential photometry of EROS2 SMC data

• SMC fields reprocessed with
• diff. photometry. (L. LeGuillou thesis)
• 5 seasons
• dedicated substraction program
• written (TRITON)
• 600000  variable  objects
• detected
• preliminary lensing/dark clouds
• analyses
• 8 mlensing candidates found,
• 4 associated with resolved stars
• no convincing candidate except SMC-1

bumpers
red giants
SMC-1
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EROS2 SMC diff. photometrymlensing candidates
same as SMC-1
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EROS2 SMC diff. photometrymlensing candidates (2)
killed by CMD cut
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Constraints on MACHO mass fraction in halo from
EROS
central value MACHO 5.7 years
excluded by EROS2 (95CL)

• fMACHO lt 20 (95 CL)
  (MMACHO 0.5 Mo)
•  Standard  halo fMACHO 100 excluded
  (MMACHO lt 10 Mo)
• lt 20 Brown dwarfs (MMACHO in
  10-2 0.08Mo)
• EROS central value f MACHO 15 BUT no signal
  claimed

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Conclusions

• Limits
• lt 10 MACHOs with mass in 10-6-10-2 Mo
• lt 10 brown dwarfs
• lt 20 0.5 Mo MACHOs
• Possible MACHO signal still unresolved.
• The comparison between LMC and SMC may give a
  strong constraint on 0.5 Mo Machos.
• Follow-up of microlensing candidates shows that
  LMC-1,LMC-2 and LMC-3 are variable stars. Also
  true for MACHO-LMC-23.
• variable star background obviously
  non-negligible.
• Preliminary differential photometry of SMC
  brings no new event.