1 / 18

SFR density from Lya emitters in VVDS

SFR density from Lya emitters in VVDS. Paolo Cassata (UMASS Amherst) Olivier Le Fevre (LAM Marseille) & VVDS collaboration. Heidelberg, 6-10 ottobre 2008. Outline. Introduction to VVDS Observational issues: completeness & slit loss Properties of the sample: EW, Luminosities, SFR

media
Download Presentation

SFR density from Lya emitters in VVDS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. SFR density from Lya emitters in VVDS Paolo Cassata (UMASS Amherst) Olivier Le Fevre (LAM Marseille) & VVDS collaboration Heidelberg, 6-10 ottobre 2008

  2. Outline • Introduction to VVDS • Observational issues: completeness & slit loss • Properties of the sample: EW, Luminosities, SFR • Luminosity functions from z=2 to z=6 • Star Formation Density

  3. VVDS DEEP 20 pointings 80 quadrants 8000 targets with I<24 16000 s exposure time (4.5h) Red grism: 5600-9500 A Slits 1” cover 22.2 arcmin2 VVDS ULTRADEEP 3 pointings 12 quadrants 1200 targets with I<24.75 65000 s exposure time (18h!!!) Blue+red grisms: 3600-9500 A Slits 1” cover 3.3 arcmin2 VVDS: VLT VIMOS DEEP SURVEY PI: Le Fevre; www.oamp.fr/virmos/vvds.htm Multi-object spectroscopic survey

  4. Slits: 1”x5-20” VVDS target Lya @ 1216AA Target spectrum Photometrically invisible Lya emitter What are we looking for? We have 1200 of these slits, covering 3.3 arcmin2, 3500-9500 AA, int. times of 65000s We have 8000 of these slits, covering 22.2 arcmin2, 5500-9500 AA, int. times of 16000s

  5. With Blue grism: 3600-6500; z=2-4; texp=18 h With Red grism: 5600-9500; z=3.5-6.6; texp=18 h Adding all the slits together… Effective area 3.3arcmin2 22.2arcmin2 With Red grism: 5600-9500; z=3.5-6.6; texp=4.5 h

  6. Looking for “serendipitous” Lya emitters Visual inspection on 10000 slits… • Indipendently made by two of us • No continuum at the left of the line • Check for other lines (OIII, Ha, Hb…) to rule out the OII • Continua masked to better constrain the effective volume accessible to each Lya

  7. Some example z=3.43 Flux=1.9x10-18erg s-1 cm-2; log(L)=41.3 erg s-1 z=2.35 Flux=4.2x10-17erg s-1 cm-2; log(L)=41.2 erg s-1 z=5.72; Flux=1.1x10-17erg s-1 cm-2; log(L)=42.6 erg s-1

  8. Completeness • 1000 simulated galaxies per quadrant • Random spatial positions • Grid of z (wavelenght)& luminosity • Log(lum)=40.5-43.5 • z=2-6.5 • Ultradeep blue 50% complete at 41.75 • Ultradeep red 50% complete at 42 • Deep 50% complete at 42.65

  9. Slit flux loss Preliminar. Needs to be revisited Starting point: the bulk of our Lya emitters are resolved in The spatial direction Monte-Carlo simulation of 1” galaxies; 1000 realizations Slit loss~45%

  10. The final sample • 86 Lya from UDeep blue • 25 Lya from UDeep red • 27 Lya from Deep • We added 66 primary targets (mainly from UDeep blue; mi<24.75) • 204 Lya emitters!!! The largest Lya sample with spectroscopy?

  11. Redshift distribution • UDeep blue • UDeep red • Deep

  12. Luminosity - SFR - EW • 80% of serendipitous sample doesn’t show any detectable continuum: EW just lower limit • We reach quite deep limits: L(Lya)~1041

  13. SFR - EW • SFR=Lum/1.1x1042 (Kennicutt) Moderate SFR; average 1.5M/yr Not extreme EW; but many lower limits

  14. Redshift - luminosity • Computing volumes to build LF • Complicate selection function • For each galaxy we measure the accessible volume in each of the three sub-sample (UDblue, UDred, Deep) • Vtot=V1+V2+V3

  15. Luminosity functions • Black: literature z=3-6 • z=2-3 • z=3-4.4 • z=4.4-5.5 • z=5.5-6.6 • Mild evolution, or consistent with no evolution from z=2 to z=6 • we reach L=2x1041erg/s:we can constrain  No correction for IGM

  16. Luminosity functions: Schechter fits • z=2-4 (first 2 bins): , , L* free parameters • z=4-6.6 (last 2 bins):  fixed to z=2-4 values, , L* free parameters 87 gals 66 gals 27 gals 12 gals Very steep faint end: =-1.6 -1.8

  17. Star formation density from Lya If Lya emission comes just from Star Formation… • No correction for dust • No correction for IGM absorption • Constant SFD from z=2 to z=6 • Lya contributes to 20% of the SFD at z=2.5, 30% at z=5, 50% at z=6

  18. Conclusions • The largest spectroscopic survey of z>2 Lya emitters • Complementary to narrow band searches • The faint end of the LF is very steep: = -1.7 -1.8 • No or mild evolution of the Lya LF from z=2 to z=6.5 • Lya SFR Density constant with cosmic time • Lya contributes to 20% of the SFD of the universe at z=2.5, 30% at z=5, 50% at z=6 Next steps: • Build composite spectra • Constrain UV fluxes from CFHTLS imaging • Better model the slit loss

More Related