Target Selection for DESpec Filipe Abdalla, Stephanie Jouvel, With input from many from the DESpec target selection team.

A DESspec target selection? 1)100% spectroscopic completeness of DES galaxies to r=21stmagnitude with resolution 50 km/s. 2)Case 1 plus 50% completeness to r=22.5 magnitude evenly distributed over all redshift bins 3)~300 km/s redshift precision with 100% completeness to r=22ndmagnitude Q: on what parameters give the most improvement on FoM and advice as to what new techniques are opened up.

Largest FOM’s are always with a constant number density. 1- Constant density 0.2<z<1.7, 10^7galaxies 2- Constant density 0.2<z<0.5, plus I<22.5 for eff’y. Total 10^7galaxies. Note redshiftcut- off (right) 3- Constant density 0.2<z<0.7, plus emission line galaxies for 0.7<z<1.7. Total 10^7galaxies. Is FOM the best way to asses these Large difference between different target selection techniques. Best is to reach a magic number of n=~2.10^-4Mpc^-2 This magic number ranges from a few hundred to a few thousand galaxies per sqdeg depending on z range

LRG target selection

Strawman LRG target selection from Jim...

- Sensitivities for 30 mins exposure time on 2 arcsec ø fibers (70% light fraction) - Resolution R=2500 at 0.9um. - Calculation include DES throughput + sky noise and atmospheric lines from Hanuschik (2003) Line sensitivities from Huan Lin

Line sensitivities from Huan Lin 0.6-1um - Sensitivities for 30 mins exposure time on 2 arcsec ø fibers (70% light fraction) - Resolution R=2500 at 0.9um. - Calculation include DES throughput + sky noise and atmospheric lines from Hanuschik (2003)

Redshift distribution / em lines gal

Redshift distribution from em lines Redshift distribution of emission line galaxies selected with : - I (DES) < < photoz < 2 - at least one em line detected at 5 sigma Photoz with Le Phare (template fitting method) u DES+VISTA Can we select the emission line galaxies based on DES+VISTA photometry only ? Total of roughly 1200 gal/deg2

Can we do color-color cut ? g-r vs r-i r-i vs i-z It looks difficult to select the OII line in a color-color cut. We need a higher dimensional kind of cut such as photoz codes can provide

Multidimensional method based on NN selection

Photo-z’s, target selection and Neural networks: Has an architecture: defined by a number of inputs/ outputs and nodes in hidden layers Collister & Lahav Internally values range from 0 to 1 roughly

Use of NN to select em line galaxies We assign a value of : - 1 for targetted em line galaxies - 0 for non targetted galaxies We then use ANNz and train a NN on a sample of galaxies from the CMC (DES+VISTA) Results for i(DES) < 24 Using Huan Lin sensitivities cut between 0.6-1um

Which ANNz selection criterion ? Fig : Cumulated nbr galaxies/deg2 fct ANNz target probability We suggest a selection criterion of 0.8 yielding to : emission line galaxies / deg2 i(DES)<24 - and a contamination of 800 gal/deg2 i(DES)< Using sensitivities cut between 0.6-1um

Which ANNz selection criterion ? Solid : percentage of galaxies for which we will measure a redshift/total nbr gal & Dashed : SSR fct ANNz target probability We suggest a selection criterion of 0.8 yielding to : emission line galaxies / deg2 i(DES)<24 - and a contamination of 800 gal/deg2 i(DES)<24 Using sensitivities cut between 0.6-1um

Redshift distribution of ANNz sel 0.8 Using sensitivities cut between 0.6-1um

Redshift distribution / em lines gal

Target selection

Target selection in words Out of the high redsfhit EL galaxies, use the photo-z to obtain a nP=1 survey out to z=1.7 use photo-z from DES to “shape that distribution” ~1000 sq deg? Obtain a high nP sample at low z as it overlaps the lensing kernel. ~1500 sq deg? Some could be EL galaxies to have low bias for RSDs ~750 deg sq? Can be Ha or OIII lines Some could be LRG’s & RG’s ~ 750 deg sq? so that we probe down the luminosity function of groups and relate lenses and lensing galaxies.

Conclusion We simulated a DES+VISTA catalogue using the CMC which include emission line fluxes. Used derived a fiber sensitivities including all instruments troughput and sky noise including astmospheric lines for a DESpec instrument (Huan Lin). Using these sensitivities we can select emission line galaxies from DES+VISTA photometry using ANNz. They are complementary to the LRG selection. We suggest a selection criterion of 0.8 with a yield of 8000gal/deg2 for i(DES) 1. To do this would need a pilot survey to identify the successful galaxies or trust the mocks. A color-color cut does not seem the optimal solution to select target for DESpec.