J/ApJ/823/11 Candidate Lyα emitting galaxies at z∼3.8 (Dey+, 2016)
Spectroscopic confirmation of a protocluster at z∼3.786.
Dey A., Lee K.-S., Reddy N., Cooper M., Inami H., Hong S., Gonzalez A.H.,
Jannuzi B.T.
<Astrophys. J., 823, 11-11 (2016)>
=2016ApJ...823...11D 2016ApJ...823...11D (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, spectra ; Photometry, UBVRI ; Redshifts ;
Equivalent widths
Keywords: cosmology: observations; galaxies: clusters: individual;
galaxies: distances and redshifts; galaxies: evolution;
galaxies: formation; galaxies: high-redshift
Abstract:
We present new observations of the field containing the z=3.786
protocluster PC 217.96+32.3. We confirm that it is one of the largest
known and most overdense high-redshift structures. Such structures are
rare even in the largest cosmological simulations. We used the
Mayall/MOSAIC1.1 imaging camera to image a 1.2x0.6° area (∼150x75
comoving Mpc) surrounding the protocluster's core and discovered 165
candidate Lyα emitting galaxies (LAEs) and 788 candidate Lyman
Break galaxies (LBGs). There are at least two overdense regions traced
by the LAEs, the largest of which shows an areal overdensity in its
core (i.e., within a radius of 2.5 comoving Mpc) of 14±7 relative to
the average LAE spatial density ({bar}rho) in the imaged field.
Further, {bar}rho is twice that derived by other field LAE surveys.
Spectroscopy with Keck/DEIMOS yielded redshifts for 164 galaxies (79
LAEs and 85 LBGs); 65 lie at a redshift of 3.785±0.010. The velocity
dispersion of galaxies near the core is σ=350±40km/s, a value
robust to selection effects. The overdensities are likely to collapse
into systems with present-day masses of >1015M☉ and
>6x1014M☉. The low velocity dispersion may suggest a
dynamically young protocluster. We find a weak trend between
narrow-band (Lyα) luminosity and environmental density: the
Lyα luminosity is enhanced on average by 1.35x within the
protocluster core. There is no evidence that the Lyα equivalent
width depends on environment. These suggest that star formation and/or
active galactic nucleus (AGN) activity is enhanced in the
higher-density regions of the structure. PC 217.96+32.3 is a Coma
cluster analog, witnessed in the process of formation.
Description:
We used the MOSAIC1.1 camera at the f/3.1 prime focus of the 4m Mayall
Telescope at the Kitt Peak National Observatory on U.T. 2014 April
24-29 to obtain deep narrow- and broadband imaging of a field just
south of the region imaged by Lee et al. (2014ApJ...796..126L 2014ApJ...796..126L). The
new field (central pointing of RA=14:31:36.14 DE=+32:08:46.29, J2000)
overlaps the previously imaged area by 9arcmin. The field was imaged
through the WRC4 narrow-band filter (KPNO filter #k1024,
λcen=5819Å, Δλ=42Å), and the BW, R, and
I broadband filters used by the NOAO Deep Wide-Field Survey (NDWFS;
Jannuzi & Dey 1999ASPC..191..111J 1999ASPC..191..111J).
We obtained spectroscopy of the LAE candidates at the W. M. Keck II
Telescope on the nights of U.T. 2014 May 6 and 2015 April 18. We used
the DEIMOS spectrograph (FWHM∼6Å; wavelength range ∼4900Å-1um).
Spectroscopy of a few galaxies associated with PC 217.96+32.3 was
obtained using the Hectospec spectrograph on the MMT telescope on U.T.
2012 June 1, 2. The Hectospec observations yielded the redshift of 1
additional LAE at the redshift of the protocluster lying near the core
of the NW group.
Objects:
------------------------------------------------------------------
RA (ICRS) DE Designation(s)
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08 56.3 +10 15 PC 217.96+32.3 = NAME PC 217.96+32.3
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 79 165 Photometry of LAE candidates
table4.dat 83 72 Keck/DEIMOS redshifts and luminosities
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See also:
J/A+A/572/A41 : VUDS Dicovery of a high-redshift protocluster (Lemaux+, 2014)
J/ApJ/779/137 : HST NIR spectrosc. of ISCS z>1 gal. clusters (Zeimann+, 2013)
J/ApJ/743/9 : z=3.1 LAEs morphological properties (Gronwall+, 2011)
J/ApJ/736/31 : HETDEX pilot survey. II. 1.9<z<3.8 LAEs (Blanc+, 2011)
J/ApJ/684/905 : z>1 gal. clusters from IRAC Shallow Survey (Eisenhardt+, 2008)
J/ApJS/176/301 : Subaru/XMM-Newton deep survey IV. (SXDS) (Ouchi+, 2008)
J/ApJ/673/143 : HST photometry of TN J1338-1942 (Overzier+, 2008)
J/A+A/461/823 : Candidate Lyα emitting galaxies (Venemans+, 2007)
J/A+A/431/793 : Ly-alpha emitters around MRC 0316-257 (Venemans+, 2005)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Lyman Alpha Emitting (LAE) galaxy name
10- 19 F10.6 deg RAdeg Right Ascension in decimal degrees (J2000)
21- 28 F8.5 deg DEdeg Declination in decimal degrees (J2000)
30- 34 F5.2 mag WRC4mag [21.8/25] WRC4/KPNO MOSAIC1.1 (5819Å)
narrow-band AB magnitude (1)
36- 39 F4.2 mag e_WRC4mag [0.04/0.3] Uncertainty in WRC4mag
41- 41 A1 --- l_WRC4-R Limit flag on WRC4-R color
43- 47 F5.2 mag WRC4-R [-4.1/-0.6] WRC4-R color index;
R/KPNO NDWFS mag (2)
49- 52 F4.2 mag e_WRC4-R [0.05/1]? Uncertainty in WRC4-R color
54- 54 A1 --- l_BW-R Limit flag on BW-R color
56- 60 F5.2 mag BW-R [0.1/4.4] BW-R color index;
B_W/KPNO NDWFS mag (2)
62- 65 F4.2 mag e_BW-R [0.09/1]? Uncertainty in BW-R color
67- 67 A1 --- l_R-I Limit flag on R-I color
69- 73 F5.2 mag R-I [-1.3/1.9]? R-I color index;
I/KPNO NDWFS mag (2)
75- 79 F5.2 mag e_R-I [0.05/12]? Uncertainty in R-I color
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Note (1): WRC4 narrow-band filter is KPNO filter #k1024,
Central Wavelength = 5819Å, FWHM = 42Å;
see also Lee et al. (2014ApJ...796..126L 2014ApJ...796..126L).
Note (2): B_W, R, and I magnitudes in the NDWFS system of Jannuzi & Dey
(1999ASPC..193..258J 1999ASPC..193..258J). See also Lee et al. (2014ApJ...796..126L 2014ApJ...796..126L).
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Name Lyman Alpha Emitting (LAE) galaxy name
10- 19 F10.6 deg RAdeg Right Ascension in decimal degrees (J2000)
21- 28 F8.5 deg DEdeg Declination in decimal degrees (J2000)
30- 35 F6.4 --- z [3.76/3.81] Spectroscopic Redshift (1)
37- 37 A1 --- l_W0(Lya) Limit flag on W0(Lya)
39- 44 F6.1 0.1nm W0(Lya) [19/1068] Rest-frame equivalent width of
Lyman Alpha, Angstroms (2)
46- 50 F5.1 0.1nm e_W0(Lya) [0.6/110]? Uncertainty in W0(Lya) (2)
52- 56 F5.2 10-20W/m2 F(Lya) [1.1/16.7] Lyman Alpha Flux, 10-17erg/s/cm2
58- 61 F4.2 10-20W/m2 e_F(Lya) [0.1/4] Uncertainty in F(Lya)
63- 67 F5.2 10+35W L(Lya) [1.6/24.2] Lyman Alpha Luminosity,
10+42erg/s
69- 72 F4.2 10+35W e_L(Lya) [0.2/6] Uncertainty in L(Lya)
74- 77 F4.2 10+22W/Hz L(1700) [0.1/7.7] Continuum Luminosity at 1700Å,
10+29erg/s/Hz
79- 83 F5.2 10+22W/Hz e_L(1700) [0.09/16] Uncertainty in L(1700)
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Note (1): All redshift measurements are based on gaussian fits to the Lyman
Alpha emission line.
Note (2): Rest-frame equivalent width. In the cases where no significant
continuum flux is detected, 3-sigma lower limits to the rest-frame
equivalent width are estimated using 3-sigma upper limits to the
continuum flux.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 08-Aug-2016