Hubble Space TelescopeImaging and Keck Spectroscopy ofz≈ 6i‐Band Dropout Galaxies in the Advanced Camera for Surveys GOODS Fields

Abstract

We measure the surface density of i 0 -band dropout galaxies at z $ 6 through wide-field Hubble Space Telescope (HST ) Advanced Camera for Surveys (ACS) imaging and ultradeep Keck DEIMOS spectroscopy. Using deep HST ACS SDSS i 0 (F775W) and SDSS z 0 (F850LP) imaging from the Great Observatories Origins Deep Survey-North (GOODS-N; 200 arcmin 2 ), we identify nine i 0 -drops satisfying (i 0 Àz 0 ) AB > 1:5 to a depth of z 0 AB ¼ 25:6 (corresponding to L Ã UV at z $ 3). We use HK 0 imaging data to improve the fidelity of our sample, discriminating against lower redshift red galaxies and cool Galactic stars. Three i 0 -drops are consistent with M/L/T dwarf stars. We present ultradeep Keck DEIMOS spectroscopy of 10 objects from our combined GOODS-N and GOODS-S i 0 -drop sample. We detect Ly emission at z ¼ 5:83 from one object in the GOODS-S field, which lies only 8 0 (i.e., 3 h À1 70 Mpc) away from a previously confirmed z ¼ 5:78 object. One possible Ly emitter at z ¼ 6:24 is found in the GOODS-N field (although identification of this spatially offset emission line is ambiguous). Using the rest-frame UV continuum from our six candidate z $ 6 galaxies from the GOODS-N field, we determine a lower limit to the unobscured volume-averaged global star formation rate at z $ 6 of (5:4 AE 2:2) ; 10 À4 h 70 M yr À1 Mpc À3 . We find that the cosmic star formation density in Lyman break galaxies (LBGs) with unobscured star formation rates greater than 15 M yr À1 falls by a factor of 8 between z $ 3 and z $ 6. Hence, the luminosity function of LBGs must evolve in this redshift interval: a constant integrated star formation density at z > 3 requires a much steeper faint-end slope, or a brighter characteristic luminosity. This result is in agreement with our previous measurement from the GOODS-S field, indicating that cosmic variance is not a dominant source of uncertainty.

The Impact of JWST Broadband Filter Choice on Photometric Redshift Estimation

“…Our first galaxy sample contains 2422 galaxies with secure spectroscopic redshifts (z spec ) from the ESO public compilation in the Chandra Deep Field South (CDFS; Cristiani et al 2000;Croom et al 2001;Bunker et al 2003;Dickinson et al 2004;Stanway et al 2004aStanway et al , 2004bStrolger et al 2004;Szokoly et al 2004;van der Wel et al 2004;Doherty et al 2005;Le Fèvre et al 2005;Mignoli et al 2005;Ravikumar et al 2007;Popesso et al 2009;Balestra et al 2010;Silverman et al 2010;Kurk et al 2013;Vanzella et al 2014) and from Morris et al (2015). In order to obtain multiwavelength photometry for these galaxies, we cross-matched this sample with the public Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS; Grogin et al 2011;Koekemoer et al 2011) catalog for the Great Observatory Origins Deep Survey South field (GOODS-S) obtained by Guo et al (2013).…”

The great observatories origins deep survey

“…The area common to all the observing programs is 320 arcmin 2 , equally divided between the North and South fields. In the last five years the CDF-S has been the target of several spectroscopic campaigns (Cristiani et al 2000;Croom et al 2001;Bunker et al 2003;Stanway et al 2004;Strolger et al 2004;van der Wel et al 2004;Dickinson et al 2004;Szokoly et al 2004;Le Fevre et al 2005;Mignoli et al 2005;Ravikumar et al 2007). This is the third paper in a series presenting the results of the GOODS spectroscopic program carried out with the VLT/FORS2 spectrograph.…”

Star forming galaxies at z≈6 and reionization

“…Our spectroscopic redshifts for these objects confirms the validity of the i ′ -drop selection technique to select star-forming galaxies at z ≈ 6. Subsequently, a programme of spectroscopy with GMOS "nod & shuffle" on Gemini (GLARE, Stanway et al 2004b) has confirmed more galaxies in GOODS-South. Slitless spectroscopy of the UDF with HST/ACS (GRAPES, Malhotra et al 2005) has also confirmed the spectral breaks of the i ′ -drop galaxies, although the spectral resolution of R ≈ 70 is insufficient to see the Lyman-α emission lines.…”

“…The asterisk is the only unresolved i ′ -drop in our UDF sample, a probable star. The solid circle is the brightest i ′ -drop in the UDF, the spectroscopically-confirmed galaxy SBM03#1 at z = 5.83, with our discovery spectrum from Keck/DEIMOS shown (right, Stanway et al 2004b. 3 The star formation rate density at z ≈ 6…”

“…Subsequent papers by the GOODS team (Dickinson et al 2004;Giavalisco et al 2004) reproduced many of these i ′ -drop candidates. To address potential cosmic variance issues, we performed a similar analysis in the GOODS-North field, which yielded a consistent estimate of the surface density of z ≃ 6 star forming sources (Stanway et al 2004b). …”