Search for [CII] emission in z=6.5-11 star-forming galaxies

0.42 MB·

by  Jorge González-López

Accepted for publicationin the Astrophysical Journal.
PreprinttypesetusingLATEXstyleemulateapjv.04/17/13
SEARCH FOR [CII] EMISSION IN Z =6.5−11 STAR-FORMING GALAXIES.
Jorge Gonza´lez-Lo´pez1,3,9, Dominik A. Riechers2, Roberto Decarli3, Fabian Walter3, Livia Vallini4, Roberto
Neri5, Frank Bertoldi6, Alberto D. Bolatto7, Christopher L. Carilli8, Pierre Cox5, Elisabete da Cunha3,
Andrea Ferrara4, Simona Gallerani4, and Leopoldo Infante1,9
Accepted for publication in the Astrophysical Journal.
ABSTRACT
4
1 We present the search for the [CII]emission line in three z > 6.5 Lyman-alpha emitters (LAEs)
and one J-Dropout galaxy using the Combined Array for Research in Millimeter-wave Astronomy
0
2 (CARMA) and the Plateau de Bure Interferometer (PdBI). We observed three bright z ∼ 6.5−7
LAEs discovered in the SUBARU deep field (SDF) and the Multiple Imaged lensed z ∼ 11 galaxy
n
candidate found behind the galaxy cluster MACSJ0647.7+7015. For the LAEs IOK-1 (z = 6.965),
a
SDF J132415.7+273058(z = 6.541) and SDF J132408.3+271543(z = 6.554) we find upper limits
J
for the [CII]line luminosity of < 2.05, < 4.52 and < 10.56×108L⊙ respectively. We find upper
4
limits to the FIR luminosity of the galaxies using a spectral energy distribution template of the local
1
galaxy NGC 6946 and taking into account the effects of the Cosmic Microwave Background on the

mm observations. For IOK-1, SDF J132415.7+273058and SDF J132408.3+271543we find upper
]
A limits for the FIR luminosity of < 2.33, 3.79 and 7.72×1011L⊙ respectively. For the lensed galaxy
MACS0647-JD, one of the highest redshift galaxy candidate to date with z = 10.7+0.6 we put an
G ph −0.4
. upperlimitinthe[CII]emissionof<1.36×108×(µ/15)−1L⊙andanupperlimitintheFIRluminosity
h of<6.1×1010×(µ/15)−1L⊙ (whereµisthemagnificationfactor). Weexplorethedifferentconditions
p relevant for the search for [CII]emission in high redshift galaxies as well as the difficulties for future
- observations with ALMA and CCAT.
o
Keywords: galaxies: high-redshift– galaxies: individual (IOK-1, SDF J132415.7+273058, SDF
r
t J132408.3+271543,MACS0647-JD) –ISM: lines and bands
s
a
[
1. INTRODUCTION expectedthat the LAE fractiondecreasesas the amount

1 Lyman-alpha Emitters (LAE) are galaxies selected of neutral Hydrogen (HI) increases, due to the incom-
v plete reionization of the Intergalactic Medium (IGM)
through strong Lyα emission and are among the most
8 (Ota et al.2008;Stark et al.2010;Pentericci et al.2011;
studied galaxy populations at high redshift. The use of
2 Ono et al.2012;Schenker et al.2012). Thisisconsistent
narrowbandfiltersoverawideareaontheskyhasproven
32 tobeaveryeffectivemethodtofindgalaxiesuptoz ∼7 with the comparatively low success rate of detection of
Lyα emission at z &7.
1. (Iye et al.2006;Fontana et al.2010;Vanzella et al.2011; If Lyman-alpha photons from redshifts z ≥ 7 are ab-
Rhoads et al. 2012; Shibuya et al. 2012; Schenker et al.
0 2012; Ono et al. 2012). The possibility of finding LAEs sorbedbyHI inthe IGM(Dayal & Ferrara2012),itwill
4 from z ∼ 1 to z ∼ 7 shows that this type of galaxies be difficult to spectroscopically confirm the candidates
1 at high redshift, such as the candidate z ∼ 12 galaxy
can be used to understand galaxy evolution over cosmic
: UDFj-39546284 discovered in the Hubble Space Tele-
v time. It has been observed that the LAE fraction in
i UV selected galaxies increases with redshift up to z ∼6 scope (HST) Ultra Deep Field (UDF) (Bouwens et al.
X 2011;Ellis et al.2013;Brammer et al.2013;Capak et al.
(Stark et al.2010),whichisexpectedduetothedecreas-
r ing dust content at higher redshifts. Beyond z ∼ 6 it is 2013), and the candidates found behind galaxy clus-
a ters at z ∼ 9.6 MACS1149-JD and ∼ 10.7 MACS0647-
1Instituto de Astrof´ısica, Facultad de F´ısica, Pontificia Uni- JD (Zheng et al. 2012; Coe et al. 2013).
versidad Cat´olica de Chile, Av. Vicun˜a Mackenna 4860, 782- Among the usual Interstellar medium (ISM) tracers
0436Macul,Santiago, Chile;[email protected] at optical/UV wavelengths, the only line that has been
2Astronomy Department, Cornell University, 220 Space Sci-
observed at z > 4 in galaxies is Ly-alpha. The emis-
ences Building,Ithaca, NY14853, USA
3MaxPlanckInstitutefu¨rAstronomieHeidelberg,K¨onigstuhl sionofLy-alphais complicatedby its highopticaldepth
17,D-69117Heidelberg,Germany in the emission region and its escape through reso-
4Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 nant scattering, by dust absorption, and by the con-
Pisa,Italy
tribution from outflows. Therefore direct constrains on
5Institut de RadioAstronomie Millim´etrique, 300 Rue de la
Piscine, Domaine Universitaire, 38406 Saint Martin d’Heres, the gas properties from the Ly-alpha line strength and
France shape are difficult to derive. This motivates the explo-
6ArgelanderInstituteforAstronomy,UniversityofBonn,Auf ration of alternative means to study the highest red-
demHu¨gel71,53121Bonn,Germany
7Department of Astronomy, Universityof Maryland, College shift galaxies. Promising candidates include far-infrared
Park,MD20742,USA fine structure emission lines, e.g., [CII](2P3/2 → 2P1/2)
8National Radio Astronomy Observatory, P. O. Box 0, So- at 157.74 µm, which is not affected by the increas-
corro,NM87801, USA ingly neutral IGM at z > 7 and can account for up
9Centro de Astro-Ingenier´ıa, Pontificia Universidad Cat´olica
to 1% of the total infrared luminosity in some galax-
deChile,V.Mackenna 4860,Santiago, Chile
2 Gonza´lez-Lo´pez et. al.
ies, especially in those with low luminosity andmetallic- is presented in Sect. 5. Throughout this paper we use
ity(Crawford et al.1985;Stacey et al.1991;Israel et al. a Λ-Cold Dark Matter cosmology with H = 70 km s−1
0
1996; Madden et al. 1997). Mpc−1, Ω =0.7 and Ω =0.3.
Λ m
doTmhinea[CtedII)]lirneegitornasce(sPpDhRotso)-,diasssowciealltioans (dai.ffku.as.epHhoItaonnd- 2. OBSERVATIONS
HII regions. In PDRs, the far-UV radiation produced 2.1. Source Selection
byOBstarsheats the surfacelayersofmolecularclouds,
The three Lyman-α emitters targeted in this study
which cool preferentially through [CII]emission. It has were discovered in the Subaru Deep Field (SDF). Two
been observed that most of the [CII]emission in IR- of the LAEs observed belong to the sample of LAEs at
brightgalaxiesis coming fromPDRs, andthat the PDR z ∼ 6.6 discovered by Taniguchi et al. (2005). The tar-
gas mass fraction can be up to 50% in starbursts like
getsarethebrightestLAEs(sources3and4intheircat-
M82 (Crawford et al. 1985).
alog) and have a narrow and bright Lyman-α emission
Modeling of FIR emission lines observed in starburst line. The third LAE (IOK-1) was discovered at z ∼ 7
galaxiesshowedthatatleast70%ofthe [CII]emissionis by Iye et al. (2006). It is one of the brightest and most
produced in PDRs (Carral et al. 1994; Lord et al. 1996;
distant LAEs known to date.
Colbert et al. 1999). In the low-metallicity system Haro
The fourth target, MACS0647-JD,is a lensed Lyman-
11, on the other hand, at least 50% of the [CII]emission breakgalaxy(LBG)discoveredbehindthegalaxycluster
arises from a more diffuse, extended ionized medium
MACSJ0647.7+7015atz =0.591(Coe et al.2013). The
(Cormier et al. 2012). The different conditions in which
galaxywas discoveredas a J-Dropoutgalaxylensed into
the [CII]emission is produced, and the direct or indi- 3 magnified images as part of The Cluster Lensing And
rect relation of these conditions with the star forma-
SupernovasurveywithHubble(CLASH)(Postman et al.
tion process, suggest that [CII]emission should be a 2012). The three images of the galaxy MACS0647-JD1,
goodtracerof the globalgalactic star formationactivity
MACS0647-JD2and MACS0647-JD3,have a magnifica-
(de Looze et al.2011),atleastforgalaxieswithlowTdust tion of ∼8,∼7 and ∼2 respectively. The photometric
or low ΣIR = LIR/πrm2id−IR (Diaz-Santos et al. 2013). redshift of the galaxy is 10.7+−00..64 (95% confidence lim-
[CII]is found to be the strongest emission line, stronger its). Thisisoneofthehighestredshiftgalaxycandidates
than CO, and thus is the most promising tracer of the
known to date.
dense, star forming regions in distant galaxies where
[CII]can be detected with ground-based telescopes due 2.2. CARMA Observations
to the redshift into observable atmospheric windows.
Observations of the three z ∼ 6.5 − 7 LAEs were
In the past years, the [CII]158 µm emission
carried out using the Combined Array for Research
line has been established as a promising observ-
in Millimeter-wave Astronomy (CARMA) between 2008
able in high-redshift galaxies (Maiolino et al. 2005;
July and 2010 July. The array configurations used were
Iono et al. 2006; Maiolino et al. 2009; Walter et al.
the mostcompact, D andE,to minimize phase decoher-
2009; Hailey-Dunsheath et al. 2010; Stacey et al.
2010; Ivison et al. 2010; Wagg et al. 2010; Cox et al. enceandmaximizepointsourcesensitivity. The[CII]line
has a rest frequency of 1900.54 GHz (157.74 µm). For
2011; De Breuck et al. 2011; Valtchanov et al. 2011;
the redshifts of the targets, the line is shifted to the 1
Gallerani et al. 2012; Venemans et al. 2012; Wagg et al.
mmband. Thereceiversweretunedtoafrequency∼150
2012;Walter et al.2012a;Carilli et al.2013;Wang et al.
kms−1bluer than the expected frequency from the red-
2013; Willott et al. 2013; Riechers et al. 2013). Most
shift determined by the peak of the Lyman-α line. This
of the high-z detections were for infrared-luminous
is for taking into account the possible absorptionby the
starbursts, many of which also show signatures of AGN.
IGMintheLyman-αline. Thesetupsprovideaninstan-
See the review by Carilli & Walter (2013) for more
taneous bandwidth of ∼ 1.5 GHz (∼ 1800kms−1) with
details.
WithstarformationratesofafewtensM⊙yr−1,based a spectral resolution of 31.25 MHz (∼37−39 kms−1).
ontheLyα andUVcontinuumemission,LAEsareclassi- The observations were processed using MIRIAD
fied as “normal” star forming galaxies. Different studies (Sault et al. 1995). The absolute flux calibrators used
claimthatLAEsareyoung,dustfree,starburstinggalax- are 3C84, MWC349, 3C273 and Mars, the latter being
ies, supported by UV observations (Gawiser et al. 2006; themostused. AspassbandcalibratorstheQSOs3C273,
Finkelstein et al.2007; Lai et al.2008). Recent MIRde- 3C345 and 0854+201 were used. As gain calibrator the
tection of LAEs at z ∼2.5 and z <0.3 show that a sig- QSO 1310+323 was used. The time on source for IOK-
nificantfractionofthestarformationinthesegalaxiesis 1 was 58.5 hours, for SDF J132415.7+273058was 15.9
strongly obscured by dust (Oteo et al. 2012a,b). Thus, hours and for SDF J132408.3+2715434.6 hours. The fi-
LAEs are promising targets for the detection of [CII]at nalcubesweremadeusingnaturalweightingtomaximize
high redshift. pointsourcesensitivity. Theobservationsresultedinthe
Previous attempts to detect [CII]in a small sample of followingbeamsizes: IOK-1: 1.86”×1.33”,PA=−0.34◦,
LAEs at z ∼6.6 were unsuccessful (Walter et al. 2012b; SDFJ132415.7+273058: 1.92”×1.56”,PA=83.45◦,SDF
Kanekar et al. 2013; Ouchi et al. 2013). J132408.3+271543: 2.54”×2.01”, PA= 88.02◦ (all tar-
Herewe presentthe resultofasearchfor[CII]inthree gets: D and E configurations). For D configuration the
LAEs at z > 6.5 and in a lensed galaxy at z ∼ 11. In minimum baseline is 11 meters and the maximum is 150
Sect. 2wedescribethetargetselectionandobservations. meters. For E configuration the minimum baseline is 8
The data is shown in Sect. 3 together with some impli- meters and the maximum is 66 meters. Table 1 summa-
cationsandanalysisinSect. 4. Asummaryofthe paper rizes the sensitivities reached for the observations of the
LAEs.
Search for [CII] emission in z =6.5−11 star-forming galaxies. 3
2.3. PdBI Observations Velocity offset [km s-1]
500 400 300 200 100 0 -100 -200 -300 -400 -500
All MACS0647-JD observations were carried out in
2012 November as part of a DDT (Director’s Discre- 4.0 IOK-1
tionary Time) program with the Plateau de Bure Inter- m]
a
ferometer(PdBI).Thetargetwasobservedwith4WideX Be 2.0
frequency setups (3.6 GHz bandwidth each), covering y/
mJ
80%of the photometric redshift range (z =10.1−11.1). y[ 0.0
Two of the three lensed images (JD1 and JD2) are sit
n
within 18” of each other and they were covered in a e
common 2 mm pointing. The absolute flux calibrators x d-2.0
u
used are MWC349, 2200+420, 3C279 and 0716+714. Fl
As gain calibrator the QSO 0716+714 was used. The -4.0
total on source time for all tunings was 7.4 hours (6-
238.5 238.6 238.7 238.8 238.9 239.0 239.1 239.2 239.3
antennas equivalent). The observations were processed Frequency [GHz]
using GILDAS. The beamsize of the observations is the Velocity offset [km s-1]
following: MACS0647-JD:2.10”×1.76”,PA=102.0◦(C 500 400 300 200 100 0 -100 -200 -300 -400 -500
10.0
configuration). For C configuration the minimum base- SDF J132415.7+273058
line is 22 meters and the maximum is 184 meters. Table m]
2summarizesthesensitivityreachedfortheobservations ea 5.0
B
of MACS0647-JD . y/
mJ
3. RESULTS sity[ 0.0
n
e
d
ux -5.0
3.1. Line Emission Fl
The spectra of the three z ∼ 6.5−7 LAEs are pre-
-10.0
251.8 251.9 252.0 252.1 252.2 252.3 252.4 252.5 252.6
sented in Fig. 1 and the spectrum of MACS0647- Frequency [GHz]
JD is shown in Fig.2. No significant emission is de- Velocity offset [km s-1]
tectedattheredshiftedlinefrequenciesorclosetothem. 500 400 300 200 100 0 -100 -200 -300 -400 -500
The observations were sampled to a channel resolution 25.0
SDF J132408.3+271543
of 50 kms−1similar to the expected FWHM of the m] 20.0
[CII]emission line (see Sect. 4.1). We use our non- a
e 15.0
detections to put constrains on the luminosities of the B
y/
[CII]lines for all targets. The results for the LAEs can mJ 10.0
bblees2e.enThinetuhpepTeralbimlei1tsawnedrefoersttihmeaMteAdCasSs0u6m47in-JgDthiantTthae- nsity[ 5.0
e 0.0
sourceswere unresolved. For MACS0647-JD the spectra d
of the two images were corrected by the primary beam ux -5.0
Fl
pattern before combination. The [CII]luminosities were -10.0
estimated assuming that the velocity integrated flux of
-15.0
the line is I =S ∆v, with S being 3 times the 251.2 251.3 251.4 251.5 251.6 251.7 251.8 251.9 252.0
line line line Frequency [GHz]
r.m.s. of the 50 kms−1channel and ∆v = 50kms−1
Figure 1. Spectra of the LAEs with a velocity resolution of 50
the range in velocity (details on Tab. 1 notes). Using kms−1. The relative velocities are with respect to the frequency
3σ over a 50 kms−1channel to estimate the upper limit expected for the [CII]line including absorption by the IGM (150
in the luminosities can result in a underestimation. We kms−1totheblueofzLyα). Theredshiftsofthetargetarez=6.965
pointoutthatforamoreconservativeestimationthe lu- for IOK-1, z=6.541 for SDF J132415.7+273058 and z=6.554 for
SDFJ132408.3+271543 .
minosities should be multiplied by a factor 2. (i.e. 3σ
over 200 kms−1channel). Assuming a channel width of 4. DISCUSSION
200 kms−1, our IOK-1 [CII]limit is ∼10%deeper than 4.1. Width of the [CII] emission line.
the previous PdBI limit (Walter et al. 2012b).
Previous studies have presented the non-detection
3.2. Continuum Emission of [CII](Walter et al. 2012b; Ouchi et al. 2013) with a
channelresolutionof200 kms−1, a choice motivatedby
Nocontinuumemissionis detectedinourobservations
of the three LAEs and the z ∼ 11 LBG. The sensitivity the width of the Lyα emission line. We argue that re-
reached for the continuum observations is given in the cent observations and models of [CII]in LAEs suggest
Tab. 1 for the LAEs and a continuum map for the three that the [CII]line could be narrowerthat the previously
assumed value.
LAEsisshowninFig. 3. TheresultsfortheMACS0647-
JD aregiveninTab. 2andthe continuummapis shown
4.1.1. [CII]detection on a LAE z=4.7.
in Fig. 4. In Sect. 4.2 we discuss how the CMB affects
our continuum observations and in Sect. 4.3 we use our In support of a the narrow emission line is the de-
continuum measurements to constrain the nature of our tection of [CII]in a LAE at z = 4.7 (Lyα -1) with
targets. ALMA (Carilli et al. 2013). The FWHM of the emis-
4 Gonza´lez-Lo´pez et. al.
Table 1
SummaryofObservations andResultsfortheLAEs
source RA DEC za νobsb σcontc σlined L[CII]e LNIR6,9C4M6Bf SFRdust,CMBg SFRUVh
J2000.0 J2000.0 GHz mJyb−1 mJyb−1 108L⊙ 1011L⊙ M⊙yr−1 M⊙yr−1
IOK–1 13:23:59.80 +27:24:56.0 6.965 238.881 0.19 1.17 <2.05 <6.34 <109.1 ∼24
SDFJ132415.7 13:24:15.70 +27:30:58.0 6.541 252.154 0.37 2.82 <4.52 <10.3 <177.2 ∼34
SDFJ132408.3 13:24:08.30 +27:15:43.0 6.554 251.594 0.75 5.67 <10.56 <21.0 <360.9 ∼15
Note. —Allluminositiesupperlimitsare3σ.
a References: IOK–1:Iyeetal.(2006);Onoetal.(2012)–SDFJ132415.7+273058andSDFJ132408.3+271543: Taniguchietal.(2005)
b ObservingFrequencies;tuned∼125MHzbluewardoftheLy–αredshiftsforalltargets.
c 1σcontinuumsensitivityat158µmrestwavelength.
d 1σ[CII] linesensitivityoverachannelwidthof50kms−1.
ies3mσe[aCsuIIr]edluimniLno⊙s;ittyhleimveitloocvietyraincthegarnanteeldwflidutxh, Iolfin5e0=kSmlinse−∆1va,ssinumJiyngkmLlsi−ne1=; t1h.e04re×st10fr−e3quIleinnecyν,reνsrte(s1t+=zν)−ob1s(D1L2+,wz)h,erinetGhHezli;naenldumthineolsuitmy,inLolsinitey,
distance,DL,inMpc. (e.g. Solomonetal.(1992)
f 3σlimitbasedontheSEDofNGC6946andincludingtheeffectoftheCMB.
g 3σlimitbasedonLN6946 includingtheeffectoftheCMB.
IR
h UV–basedSFRfromJiangetal.(2013a)
[CII] Redshift
11.0 10.8 10.6 10.4 10.2
8
6
] 4
y
J
m
[ 2

y
t
i
s 0
n
e
d
-2
x
u
l
F-4
-6
-8
158 160 162 164 166 168 170
Observed frequency [GHz]
Figure 2. Spectrum of MACS0647-JD. The spectrum shows the added fluxes measured on the positions of the two lensed images JD1
andJD2(combinedmagnificationµ∼15). Thespectraofthetwoimageswerecorrectedbytheprimarybeampatternbeforecombination.
The 4 setups are plotted in different colors, blue, red, green and orange the colors for the setups A, B, C and D respectively. The error
bars correspond to the quadrature of the errors of the individual measurement of the fluxes for JD1 and JD2 in each frequency channel.
Fordisplaypurposes,thespectrumissampledatachannelresolutionof200 kms−1,butthesearchofthe[CII]lineaswellastheanalysis
wasmadewiththespectrumsampledto50 kms−1.
sion line is 56 kms−1, which is one order of magni- conclude that the quasar is unlikely the source of heat-
tude narrower than the width of the Lyα emission line ing and ionization in the LAE.
of ∼ 1100 kms−1of the same source (Petitjean et al. Based on deep, spatially resolved optical spectroscopy
1996; Ohyama et al. 2004). Despite of the LAE being of the LAE, Ohyama et al. (2004) argue that the LAE
at a separation of 2.3′′ (∼ 15 kpc) to the quasar BRI islikelythe compositionofanormalstar-forminggalaxy
1202-0725, there is no evidence for a significant influ- and an extended nebula with violent kinematic status.
ence of the quasar on the properties of the LAE from This nebula emissionwouldproducea broadeningofthe
the observations. Carilli et al. (2013) tried to model the Lyα emission. Thisnebulacanbeexplained,atleastina
emission of the LAE taking into account the radiation qualitativeway,asasuperwindcausedbythesupernovae
coming from the luminous nearby quasar. All the mod- explosion of OB stars in the late phase of the evolution
elsthatreproducethe[CII]andLyα luminositiespredict of a starburst.
higher luminosities for other UV lines that are not de- In conclusion, this LAE is not intrinsically different
tected (Ohyama et al. 2004). Given this results, they from the generalpopulation of LAE. The [CII]detection
Search for [CII] emission in z =6.5−11 star-forming galaxies. 5
8.0
SDF J132415.7+273058 SDF J132408.3+271543 IOK-1
6.0
) 4.0
c
e
s 2.0
c
r
a -0
(
C
E-2.0
D
∆-4.0
-6.0
-8.0
-8.0-6.0-4.0-2.0 0.0 2.0 4.0 6.0 8.0 -8.0-6.0-4.0-2.0 -0 2.0 4.0 6.0 8.0 -8.0-6.0-4.0-2.0 0.0 2.0 4.0 6.0 8.0
∆RA (arcsec) ∆RA (arcsec) ∆RA (arcsec)
Figure 3. Rest-frame 158 µm continuum maps of the LAEs. Each contour level represents 1σ steps (±1σ levels are not shown). Solid
contoursarepositivesignalanddashedcontourarenegativesignals. The1σlevelsare0.75mJybeam−1 forSDFJ132408.3+271543 ,0.37
mJybeam−1 for SDFJ132415.7+273058 and 0.19 mJybeam−1 for IOK-1. The bluecrosses represent the position of each LAE as given
inTab. 1.
15.0
Table 2
SummaryofObservationsandResultsforMACS0647JD
JD1
10.0
Parameter MACS0647-JD1,JD2
Coordinates(J2000) JD1 06:47:55.731,+70:14:35.76
Coordinates(J2000) JD2 06:47:53.112,+70:14:22.94
µ(JD1+JD2) ∼15 c) 5.0
RUeVdsShFifRt ∼110[M.7+−⊙00y..r64−1] rcse
ν 156.7-171.1[GHz] a 0.0
σcont a 0.17mJyb−1 C (
σline (SetupA)b 3.31mJyb−1 E JD2
σσlliinnee ((SSeettuuppCB))bb 34..1192mmJJyybb−−11 DΔ -5.0
σline (SetupD)b 6.42mJyb−1
L[CII] (SetupC)c <6.78×107×(µ/15)−1[L⊙]
L[CII] (SetupD)c <1.36×108×(µ/15)−1[L⊙] -10.0
LNIR6946,d (CorrectedCMB) <1.65×1011×(µ/15)−1[L⊙]
SFR(LIR)(CorrectedCMB)e <28×(µ/15)−1 [M⊙yr−1]
SFR(L[CII])(Setup C)f <5×(µ/15)−1 [M⊙yr−1] -15.0
SFR(L[CII])(Setup D)f <9×(µ/15)−1 [M⊙yr−1] -15.0 -10.0 -5.0 0.0 5.0 10.0 15.0
ΔRA (arcsec)
Note. —Allluminositiesupperlimitsare3σ.
References: Coordinates, magnification, redshift and UV-SFR from Figure 4. Continuum map of the field of MACS0647-JD. Each
Coeetal. 2013. contourlevelrepresents1σsteps(±1σlevelsarenotshown). Solid
AlltheluminositiesandSFRarecorrectedbymagnification. contours are positive signal and dashed contour are negative sig-
a 1σcontinuumsensitivityat158µmrestwavelength. nals. The 1σ level is 93 µmJybeam−1. The blue plus signs rep-
b 1σ[CII] linesensitivityoverachannelwidthof50kms−1. resentthepositionsofthetwolensedimagesMACS0647-JD1and
c 3σ [CII] luminositylimitover achannelwidthof 50kms−1 asin MACS0647-JD2asgiveninTab. 2.
Tab. 1. The two results correspond to the most sensitive and the
leastsensitivesetups. clumps of individual size ≤3 kpc. They present a spec-
d 3σ limitbased on the SED of NGC 6946 and includingthe effect
oftheCMB. trumforthe simulated[CII]emission,where the FWHM
e 3σlimitbasedonLN6946 includingtheeffectoftheCMB. of the main peak is ∼ 50 kms−1, very similar to the
IR
f BasedontheDeLoozeetal.,2011L[CII]−SFRrelation. Thetwo 56 kms−1of the LAE at z=4.7. This suggests that the
resultscorrespondtothemostsensitiveandthelestsensitivesetups. width of the [CII]line is to first orderdetermined by the
in this LAE can thus be used as a reference for gravitationalpotentialofthe clumps. The [CII]emission
[CII]searches in other LAEs at high redshift. producedinthe CNM followsthe gravitationalpotential
of the clumps, resulting in narrow emission lines associ-
4.1.2. Himiko simulations. ated with each clumps. An ensemble of emitting clumps
Simulations also suggest narrow[CII]emission lines at movingthroughthe galaxyfollowingthepotentialofthe
high redshift for LAEs. Vallini et al. (2013) combine a galaxy could combine and produce a broader line. Such
high resolution cosmological simulation with a sub-grid behavioris not observedin the simulations,where justa
multi-phasemodeloftheinterstellarmediumtosimulate small number of clumps dominate the [CII]emission.
the[CII]emissioninahalosimilartotheLAEHimikoat Weconcludethattheadoptedwidthof∼50 kms−1for
z =6.6. They find that 95%of the [CII]emission is gen- the[CII]lineinLAEsagreeswithrecentobservationsand
erated in the Cold Neutral Medium (CNM), mainly in simulations. Nevertheless, we do not discard the possi-
6 Gonza´lez-Lo´pez et. al.
ν [GHz] observationsofhigh-redshiftgalaxies. Herewewillfollow
obs
105 104 1000 100 theprescriptionformulatedbyda Cunha et al.(2013)to
103 take into account the effects of the CMB in the contin-
Arp220
IOK-1 uum observations of galaxies at high redshift in the mm
102 M82
z = 7.0 andsub-mm. WewillapplythisprescriptiontotheSED
M51
101 NGC6946 of the local galaxies, as if they would be observed at a
given redshift z.
100 The templates that we use are those presented by
]
y Silva et al. (1998) for the galaxies Arp 220, M82, M51
mJ 10-1 and NGC 6946. For the galaxies assume cold dust
[ with temperature Tz=0 and an emissivity index β. For
Fν10-2 dust
Arp 220 we used Tz=0 = 66.7 K and β = 1.86
dust
10-3 (Rangwala et al.2011),forM82Tz=0 =48Kandβ =1
dust
(Colbert et al. 1999), for M51 Tz=0 =24.9 K and β =2
10-4 (Mentuch Cooper et al.2012)anddusftorNGC6946weused
10-5 Tdzu=st0 = 26 K and β = 1.5 (Skibba et al. 2011). At a
given redshift the CMB contributes to the dust heating
0.001 0.01 0.1 1 10
λ [mm] such that the equilibrium temperature is:
obs
ν [GHz]
obs 1
103 105 104 1000 100 Tdust(z)= (Tdzu=st0)4+β+(TCzM=B0)4+β (1+z)4+β−1 4+β .
Arp220 MACS0647-JD (cid:16) (cid:2) (cid:3)(cid:17) (1)
102 MM8521 z∼11.0 Tdzu=st0 isameasurementofthemeandusttemperatureas
101 NGC6946 determined by a modified blackbody fit to an observed
galaxy IR SED at z = 0, representing the total IR lu-
100 minosity of the galaxy. As a representative fit, this is
]
y equallyapplicabletobothopticallythingalaxiesandop-
mJ 10-1 ticallythickasinArp220. Solongasthegalaxyistrans-
[
parenttotheCMBradiation(trueforevenArp220),Eq.
Fν10-2 1 holds. The additional heating by the CMB affects the
SEDs such that the peak of the emission is shifted to a
10-3
shorter wavelength and the total luminosity associated
10-4 to the cold dust is higher by [Tdust(z)/Tdzu=st0](4+β). We
need to modify the intrinsic SED of the galaxies to in-
10-5 cludethisnewT (z). Thefluxdensitydependsonthe
dust
0.001 0.01 0.1 1 10
black body radiation for the given temperature,
λ [mm]
obs
Figure 5. Top: SpectralenergydistributionofIOK-1. Thepho- Fν/(1+z) ∝Bν(Tdust(z)), (2)
tometricpointscorrespondtothosemeasuredbyIyeetal.(2006);
Otaetal.(2010);Caietal.(2011);Onoetal.(2012). Theredtri- Toinclude Tdust(z)wehavetoapplythe followingfac-
angle corresponds to the 3σ upper limit given by the CARMA tortoconverttheintrinsicSEDflux densitytotheemis-
observations. The colored lines correspond to the SEDs of local sion associated with the new temperature F∗ .
galaxies shifted to the redshift of IOK-1 and scaled to the ob- ν/(1+z)
servations in the UV band. The dashed lines correspond to the
observedSEDofthelocalgalaxiesaftertheeffectsoftheCMBon F∗ =Fint × Bν(Tdust(z)). (3)
theobservations aretaken intoaccount. Bottom: Spectral energy ν/(1+z) ν/(1+z) B (Tz=0)
distributionofMACS0647-JD.Thephotometricpointscorrespond ν dust
to those presented by Coeetal. (2013). The SED of the galaxies This factor will only apply to the part of the SED
followthesameprescriptionasintheupperpanel. Theredtriangle
that correspond to the emission of the cold dust. To
corresponds tothe3σ upper limitcalculated asthequadrature of
theerrorsoftheindividualfluxesofJD1andJD2,inthesameway accomplish this, we scale a modified black body (MBB)
as the errors presented by Coeetal. (2013). The 1σ photometric to the peak of the FIR emission of the SED at Tz=0,
uncertainty of the observations is 0.093 mJy, and the errorof the dust
and then use this MBB emission to estimate the ratio
addedfluxesis0.13mJy.
(R )ofemissionassociatedwiththe colddustatagiven
ν
bility of [CII]lines being broader than our assumption, frequency,
but thatthe occurrenceofunusually narrowlines in this
population appears plausible. KνβB (Tz=0)
R = ν dust , (4)
ν Fint
4.2. CMB effects. ν
where K is just the scaling factor. The flux density as-
The CosmicMicrowaveBackgroundRadiation(CMB)
sociated to the new temperature of the cold dust will
emits as a black body with a temperature of Tz=0=
CMB be:
2.7 K. The temperature of the CMB increases linearly
with (1 + z), becoming an important factor to take F∗ =M ×Fint (5)
into account for observations of objects at high redshift. ν/(1+z) ν ν/(1+z)
da Cunha et al.(2013) showedthe effect of the CMB on with
Search for [CII] emission in z =6.5−11 star-forming galaxies. 7
1999). WeconcludethattheCMBeffectsonthe[CII]line
M = (1−R )+R × Bν(Tdust(z)) . (6) observations are negligible for our observations.
ν (cid:20) ν ν B (Tz=0) (cid:21)
ν dust 4.3. Spectral energy distribution of the galaxies.
Finally, following da Cunha et al. (2013), we have to
Using the upper limits on the continuum, we compare
take into account the effect of the CMB as an observ-
the targets with the spectral energy distribution tem-
ing background. For this we have to multiply the flux
plates oflocalgalaxies(SEDs). For the LAEs,the SEDs
associated with T (z) by C ,
dust ν of the local galaxies are scaled to the flux of a near-IR
filter that is not contaminatedby the Lyα emission line.
B (T (z))
C = 1− ν CMB , (7) For MACS0647-JD , the filter used for the scaling is the
ν
(cid:20) Bν(Tdust(z))(cid:21) onenexttotheLymanBreak. ThephotometryofIOK-1
andMACS0647-JDtogetherwiththeSEDoflocalgalax-
resulting in the flux observed of the galaxies as:
iesareshowninFig. 5. ForSDFJ132415.7+273058and
SDFJ132408.3+271543(notshown)thesituationisvery
Fobs =C ×M ×Fint , (8)
ν/(1+z) ν ν ν/(1+z) similar: the sources have a similar redshift, the contin-
withC ×M representingtheeffectoftheCMBinthe uum upper limits are comparable and the CMB effects
ν ν
observations at a given frequency. The same corrections areofthesameorder. OurupperlimitforIOK-1iscom-
parabletotheupperlimitfoundbyWalter et al.(2012b)
arederivedwhen anoptically thick emissionis assumed,
as in the case of Arp 220. using PdBI observations.
AswecanseeinFig. 5,theeffectoftheCMBdecreases UsingtheSEDofNGC6946asatemplate,weestimate
the IR luminosity given the upper limit flux densities,
the observable flux density at 2 mm by up to a factor of
5× (in the case of M51) for the galaxy at z ∼ 11, when similar to the approach shown by Walter et al. (2012b).
thetemperatureoftheCMBishigher,asexpected. Also, We scale the SED of NGC 6946 to the 3 sigma upper
limits of the mm observations and integrate from 8 µm
the effect is higherfor galaxieswitha lowertemperature
of the cold dust. Galaxies with temperature of order of to 1 mm (rest frame) to compute the IR luminosity.
25-30 K are more affected than those with temperature The IRluminositycorrespondingto this intrinsic SED
and the SFR associated (Kennicutt 1998) are given in
of 40-50 K. The CMB effects will be important for esti-
mations of the flux densities of these type of galaxies in Tab. 1 for the LAEs and in Table 2 for MACS0647-JD .
the continuum and for the correct interpretation of the We note that estimating the IR luminosity using NGC
6946 without taking into account the CMB result in a
observations.
TheCMBeffectsonthe[CII]lineobservationsaresim- significant underestimation of the luminosity upper lim-
ilar to those on the continuum. The flux of an emission its. The IR luminosity limit corrected by the CMB of
the LAEsatz ∼6.6 is35%higherthanwithout correct-
line observed against the CMB is:
ing by the CMB. For IOK-1 at z ∼7, the IR luminosity
Sobs B (T (z)) limit is a 50% higher than the estimation without cor-
ν/(1+z) = 1− ν CMB , (9) rectingbytheCMB.ForMACS0647-JD atz ∼10.7,the
Sνin/t(1+z) (cid:20) Bν(Texc) (cid:21) IRluminositylimitcorrectedfortheCMBis∼3.5times
the IR luminosity limit not corrected by the CMB. For
withT beingtheexcitationtemperatureofthetran-
exc galaxies with cold dust temperature of ∼ 25 K, the ef-
sition. For the case of local thermal equilibrium (LTE),
fectoftheCMBontheobservationsisveryimportantat
when collisions dominate the excitation of the [CII]line, highredshift,anditwillsignificantlylimitthefeasibility
the excitation temperature of the transition is equal
of detecting not extremely starbursting galaxies in the
to the kinetic temperature of the gas (T ). The ki-
kin IR continuum, it will not greatly affect the detectability
netic temperature varies for the different [CII]emission of [CII]emission.
regions. Gas temperatures within PDRs are typically
T ∼ 100 − 500 K (Stacey et al. 2010), for the CNM 4.4. Ratio L /L
[CII] FIR
T ≈ 250 K, for the WNM T ≈ 5000 K and for the ion-
ized medium T ≈ 8000 K(Vallini et al. 2013). Since the Figure 6 presents our upper limits to L[CII]/LFIR and
CMBtemperatureatz =6.5−11ismuchlowerthanthe LFIR together with detections of [CII]in other galax-
gas temperature of the [CII]emitting region, it will not ies. The arrows represent the region of possible val-
contribute significantly to the [CII]excitation, but must ues for L[CII]/LFIR and LFIR (integrated from 42.5µm
be taken into account as the background against which to 122.5µm rest frame). If we used UV-based SFR
the line flux is measured. In most of the [CII]emission estimates to infer LFIR, our data points would move
regions, the temperatures are so high that the observed across the diagonal arrows towards the region where lo-
flux of the line against the CMB is similar to the intrin- cal galaxies are, putting our L /L upper limits
[CII] FIR
sic flux (Sobs /Sint ≈ 1). For the extreme case close to the average value found for the local galax-
ν/(1+z) ν/(1+z)
where all the [CII]emission is being produced in PDRs ies. The ratio L[CII]/LFIR is a measure of how effi-
with temperature of 100 K in a galaxy at z = 11, the cient the [CII]emission is in cooling the gas. The values
observed flux (using Eq. 9) would be 90% of the intrin- presented for our targets, log(L[CII]/LFIR) ∼ −2.9, do
sic flux. We found this case very unlikely, since in low not necessarily imply that [CII]is not efficient in cool-
redshift galaxies the [CII]emission produced in PDRs is ing the gas in these galaxies, it is most likely a conse-
50-70%ofthetotal[CII]luminosityandthegastempera- quence of the galaxies having much lower FIR luminosi-
turesassociatedtothePDRsarehigher(Crawford et al. ties than our conservative upper limits. Different pro-
1985; Carral et al. 1994; Lord et al. 1996; Colbert et al. cesses can affect the ratio L /L . In galaxies with
[CII] FIR
8 Gonza´lez-Lo´pez et. al.
lowextinctionandlowmetallicity,likeinHaro11,about -1.5
50% of the [CII]emission arises from the diffuse ionized Local Galaxies SDF J132415.7+273058
z > 2 ULIRGs/QSOs SDF J132408.3+271543
medium(Cormier et al.2012). Variationsonthefraction
1 < z < 2 Galaxies MACS0647-JD
of[CII]emissionassociatedwiththeionizedmediumwill z < 0.1 LIRGs Himiko
also affect the ratio L /L . In some galaxies, the -2.0
[CII] FIR IOK-1 HFLS3
internal dust extinction can affect the ratio L /L .
[CII] FIR
In Arp 220, the dust is optically thick at 158 µm and
can absorb part of the [CII]emission, decreasing the ra- )
R
tio L[CII]/LFIR (Rangwala et al. 2011). FI -2.5
L
Diaz-Santos et al. (2013) present the results of a sur- /
]
vey of [CII]in luminous infrared galaxies (LIRGs) ob- CII
served with the PACS instrument on board the Her- L[
schel Space Observatory. They found a tight corre- (g -3.0
lation between the ratio L /L and the far-IR o
[CII] FIR l
S (63µm)/S (158µm) continuum color, independently
ν ν
of their L . They found that the ratio decreases
IR
as the average temperature of dust increases, suggest- -3.5
ing that the main observable linked to the variation of
L /L is the average dust temperature. For the
[CII] FIR
galaxieswithdusttemperatures∼20K theaverageratio
liiskelogN(GLC[CI6I]9/4L6FIwRi)th∼a1d0u−s2t, tseumggpeesrtaintugrethoaft≈for26gaKla,xtihees -4.08 9 10 11 12 13 14 15
log(L )[L ]
ratio L[CII]/LFIR should be on the same order of mag- FIR ⊙
nitude. Diaz-Santos et al. (2013) also found a correla-
Figure 6. Ratio of the [CII]luminosity to the FIR luminosity
tion between L /L and luminosity surface density
[CII] FIR vs the FIR luminosity (integrated from 42.5µm to 122.5µm rest
of the mid-IR emitting region (Σ = L /πr2 ). frame) for galaxies at different redshifts. The green symbols cor-
IR IR mid−IR respondtotheupperlimitsoftheLAEspresentedhere. Theblue
LIRGs with lower L /L ratios are warmer and
[CII] FIR hexagon corresponds to the upper limit of MACS0647-JDusing
more compact. We can use this relation to find a rough themostsensitivesetup. TheFIRluminositiesforthegalaxiesare
estimation for L[CII]/LFIR of our targets. As rmid−IR upper limits estimated from the observations including the CMB
effects. The black diamond corresponds to the upper limit for
we use the size found in the UV observations of the
Himiko with ALMA observations (Ouchi etal. 2013). The hori-
targets. The half-light radius of IOK-1 is ≈ 0.62 kpc zontaldashedlineistheaveragevalueforL[CII]/LFIR onthelocal
(Cai et al.2011). Thefullwidthathalfmaximumsizeof galaxies. (Malhotraetal.2001;Negishietal.2001;Luhmanetal.
SDFJ132415.7+273058andSDFJ132408.3+271543are 2003; Ionoetal. 2006; Maiolinoetal. 2009; Walteretal. 2009;
≈ 4.0 and 3.2 kpc respectively (Taniguchi et al. 2005). Staceyetal. 2010; Ivisonetal.2010; Waggetal. 2010; Coxetal.
2011;DeBreucketal.2011;Swinbanketal.2012;Venemans etal.
ForMACS0647-JD thedelensedhalf-lightradiusis.0.1
2012; Walter etal. 2012a; Wangetal. 2013; Riechersetal. 2013;
kpc (Coe et al. 2013). Using our LIR upper limits as Ouchietal.2013)
an approach to L we can estimate Σ . For IOK-1
the estimated ratioIRis log(L /L ) ∼IR−2.9, for SDF ence between the LAEs at z ∼ 4.5 with the higher red-
[CII] FIR shift population. The high magnification of MACS0647-
J132415.7+273058is log(L /L ) ∼ −2.5 and for
[CII] FIR JD allows us to explore an UV-SFR one order of mag-
SDF J132408.3+271543is log(L /L ) ∼ −2.6. For
[CII] FIR nitude lower than the ones of the LAEs, showing the
theLAEstheaverageofL[CII]/LFIRissimilartotheaver- advantage of observing lensed galaxies to cover the in-
agevalueforthelocalgalaxies(Fig. 6). ForMACS0647- trinsically faint population at high redshift.
JD the estimated ratio is log(L /L )∼−3.2.
[CII] FIR
4.6. IOK-1 Models
4.5. SFR-L[CII] Relation Using the same procedure presented in Vallini et al.
In Fig. 7 we present our L[CII] upper limits with the (2013) for the [CII]emission of Himiko, we estimate the
UV-SFR estimated for the targets together with upper emission of [CII]for IOK-1 at z ∼ 7. For this simu-
limits detections for published LAEs (Carilli et al. 2013; lation, the star formation rate was set to 20 M⊙yr−1
Kanekar et al. 2013; Ouchi et al. 2013). The black solid and a stellar population age of 10 Myr. The metallic-
linescorrespondstotherelationfoundbyde Looze et al. ity was set to solar to have a conservative estimation
(2011),withthegrayareacorrespondingto2σ scatterin of the [CII]emission. The simulation does not include
therelation. Ourupperlimitsforthe[CII]luminosityfall the emission from PDRs and should be seen as a lower
within the scatter of the SFR-L[CII], with the exception limit. In Fig. 8, we show the [CII]emission produced by
of SDF J132408.3+271543, where the upper limit falls the three modeled phases, cold neutral medium (CNM),
above the relation due to the moderate depth of its ob- warmneutral medium (WNM) andthe ionizedmedium.
servations. The detection of the LAE at z=4.7 (Lyα -1) Mostofthe[CII]emissioncomesfromtheCNM(∼50%),
agreeverywellwiththerelationfoundbyde Looze et al. therestiscomingfromthe WNM(∼20%)andfromthe
(2011) using the UV-SFR estimated by Ohyama et al. ionized medium (∼ 30%). For comparison, in Himiko,
(2004). The upper limits for the lensed LAE at z =6.56 95% of the emission is produced in the CNM and the
HCM 6A and Himiko suggest that LAEs at z >6 could restin the WNM. No emissionfromthe ionizedmedium
fallbelowtherelationfoundatlowredshift. Moreobser- was modeled in the simulation of Himiko (Vallini et al.
vationsareneededtoclarifyifthereisanintrinsicdiffer- 2013). We can also see in the emission that the FWHM
Search for [CII] emission in z =6.5−11 star-forming galaxies. 9
1044
Local Galaxies 0.8 Cold Neutral Medium
IOK-1 Warm Neutral Medium
SDF J132415.7+273058 0.7 Ionized Medium
1043 SDF J132408.3+271543
MACS0647-JD ]
y0.6
Himiko J
m
] HCM 6A [
-1s 1042 Lyα-1 z=4.7 ty 0.5
g nsi0.4
er e
d
[CII]1041 ux 0.3
L[ Fl
0.2
1040 0.1
0.0
−200 −100 0 100 200 300
1039 V [km s-1]
10-2 10-1 100 101 102 103
-1 Figure 8. Simulated[CII]spectrumofagalaxysimilartoIOK-1
SFR[M yr ] at z ∼ 7. The parameters set for this simulation were a SFR of
⊙ 20M⊙yr−1,andstellarpopulationageof10Myrandasolarmetal-
Figure 7. Relation of the [CII]luminosity with the UV-derived licity. Thebluespectrumcorrespondstotheemissionproducedin
starformationrateofgalaxies. Theblacksolidlinescorrespondto thecoldneutralmedium,theorangespectrumcorresponds tothe
the relation found by deLoozeetal. (2011), with the gray area emissionproducedinthewarmneutralmediumandthegreenspec-
corresponding to 2σ of the scatter in the relation. The black trumcorrespondstotheemissionproducedintheionizedmedium.
dots with error bars correspond to the data used to find the re- The main peak (at ∼ 80kms−1) of the cold neutral medium has
lation of [CII]- SFR. The green circle, square and pentagon cor- aFWHMof∼50 kms−1. Formoredetailsonthesimulationsof
respondtothe LAEswiththe[CII]upper limitspresented inthis [CII]emissioninhighredshiftgalaxies seeVallinietal.(2013).
paper assuming the star formation rate estimated from the UV
fluxes. The blue hexagon corresponds to the [CII]upper limit of
MACS0647-JDwithbasedinthemostsensitivesetupandthestar
formationrateestimated fromthe UV fluxes. Theredstar corre-
sponds to theLAE detected withALMAatz∼4.7(Carillietal. 100
2013). The black triangle corresponds to the upper limit of the
[CII]emission found for HCM-6A by Kanekar etal. (2013). The 90
blackdiamondcorrespondstotheupperlimitofthe[CII]emission
foundforHimikobyOuchietal.(2013).
80
of the main peak is ∼50 kms−1, just as expected.
70
In Fig. 9, we present the integrated flux of [CII]for
)
a different combination of metallicities and stellar pop- yr
ulation ages. This shows a strong dependency on the M 60
(
metallicity, which is expected, since it is treated linearly ge 50 5 10 15 20
withthe abundance of[CII]inthe gas. The secondmain A
feature of this results is the dependency with the stel- 40 25
lar population age. Here we assumed a continuum star
formation rate of 20 M⊙yr−1, for the older stellar pop- 30 30
ulations there is a higher amount of heating photons
5
coming from the UV part of the spectrum. This is a 20 3
result of using a continuum star formation mode, for a
10
givenSFR, olderpopulations havemoretime generating 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
young UV emitting stars. These extra heating photons Z/Z
⊙
avoid the cooling of the gas, which decrease the amount
Figure 9. Contour plot of the integrated [CII]flux of IOK-1 in
of gas in the cold neutral medium, where most of the
mJykms−1fordifferentsimulationconditions. Ascomparison,our
[CII]emission is produced. upper limit for integrated flux of IOK-1 is 175 mJykms−1. The
twoindependentparametersarethestellarpopulationageandthe
4.7. Spectral Resolution metallicity of the gas. The flux is integrated over the whole area
of the cube and inachannel resolutionof 500 kms−1around the
For a Gaussian emission line, with a FWHM of 50 peak of the emission. The integrated flux is a conservative upper
kms−1observed at a channel resolution of 200 kms−1, limit for the different parameters. We can see from the contour
emission lines will be significantly diluted. In the best plot that the [CII]emission is very sensitive to the metallicity of
the galaxy, and in a less significant way to the age of the stellar
case scenario of the line falling completely in one chan-
population. Thedifferentagescorrespondtoadifferentamountof
nel, we will recover 38% of the peak flux density of the heatingphotons comingfromtheyoungstars,whichiscriticalfor
line. Thissuggeststocarryoutobservationsasufficiently thecoolingofthegas.
highspectralresolution. E.g. withalineofFWHMof50
10 Gonza´lez-Lo´pez et. al.
kms−1and a channel resolution of 10 kms−1, we expect 1. We have not detected [CII]emission line any of
to recover 97% of the peak flux density of the line. our targets. Given the recent observational re-
sults and simulations of the [CII]emission in
4.8. Atomic Mass Estimation high redshift LAE, we adopt a line width of
50 kms−1for the [CII]emission. We put con-
We use Equation 1 from (Hailey-Dunsheath et al.
strains on the luminosity of the line for the tar-
2010) to give rough upper limits to the atomic mass
gets. For the LAEs the 3σ L upper limit
associated with PDRs in our targets (Assuming all [CII]
[CII]wouldarisefromPDRs). AsapproachtothePDRs are < 2.05, < 4.52 and < 10.56 × 108L⊙
for IOK-1, SDF J132415.7+273058and SDF
conditions we use the result of Vallini et al. (2013) for
the temperature and density in the CNM of Himiko, J132408.3+271543respectively. Our [CII]upper
n = 5 × 104 cm−3 and T=250 K. Using our upper limitsareconsistentwiththerelationofSFR-L[CII]
limits for [CII]we obtain the following upper limits found by de Looze et al. (2011). The 3σ upper
tfoorthSeDFatoJm13ic24m15a.s7s+: 2F73o0r5I8OMKH-1I M.HI4.× 210×8M1⊙08,Mf⊙or, l<im5it.2i7n×th1e07[C×II(]µlu/m15i)n−o1sLit⊙y o(Af sMsuAmCinSg06t4h7a-tJDthies
SDF J132408.3+271543MHI . 1 × 109M⊙ and for redshift of the galaxy is within the most sensitive
MACS0647-JDMHI . 6×107M⊙. Assuming that the setup).
mass of atomic gas is similar to the mass of molecular
2. No detection of the FIR continuum is found
gas,we can compare our upper limits with the measure-
at a wavelength of 158 µm rest frame for any
ments of similar galaxies at lower redshift.
of the 4 targets. Assuming a spectral energy
The only molecular gas masses measured in high red-
distribution template for the local galaxy NGC
shift UV-selected star-forming galaxies come from the
6946 as a template for the high redshift galax-
detection of CO transition lines in lensed LBGs. The
measured values are, ∼ 4 × 108M⊙, ∼ 9 × 108M⊙ ies observed here, we present conservatives up-
caonsdm∼ic 1ey×e 1(0z9M=⊙ 3fo.0r7M) San1d51M2–Sc1B35588–(azrc=(z2.7=3),4t.h9e) p<er2.l3im3,it3s.7f9orantdhe7.F72IR×l1u0m11inLo⊙sitays. upWpeer lfiimnd-
its for IOK-1, SDF J132415.7+273058and SDF
respectively (Coppin et al. 2007; Riechers et al. 2010;
J132408.3+271543respectively, these values ac-
Livermore et al. 2012). Our upper limits for the LAEs
count for the effect of the CMB on the observa-
are similar to the values estimated for the observed
tions. For MACS0647-JD, the upper limit in the
LBGs. ForMACS0647-JD ourupperlimitforthemolec-
ularmassisatleast8×lowerthanintheobservedLBGs. FIRluminosityis<6.1×1010×(µ/15)−1L⊙,after
correcting for the CMB and the lensing magnifica-
Using the UV-SFR relation we can estimate the
tion.
gas depletion timescales for our targets, assuming
τ = M /SFR . We estimate upper limits for
dep gas UV 3. We present the results of simulations supporting
the depletion time of . 8Myr, . 11Myr and .
66Myr for IOK-1, SDF J132415.7+273058and SDF the brightest component of the [CII]line having a
width of the order of 50 kms−1. Here we want to
J132408.3+271543respectively. For MACS0647-JD the
emphasize the necessity of resolving such emission
depletion time is . 60Myr. The estimated depletion
lines in future ALMA observations, to not loose
times for the observed lower redshift lensed LBGs are
within the range of ∼ 7− 24 Myr, similar to our up- signal-to-noise ratio, by selecting a channel resolu-
tion that is too low.
per limits. The depletion times for the LAEs are consis-
tentwiththe agesestimatedforthe youngpopulationof
4. The effect of the CMB must to be taken into ac-
LAEs at z ∼4.5 of <15 Myr found by Finkelstein et al.
count in attempts to detect the FIR continuum in
(2009) and to the simulated LAEs at ∼ 3.1 with ages
galaxies at high redshift. The heating of cold dust
<100Myr(Shimizu et al.2011). Thedepletiontimesof
by CMB photons can shift the peak of the FIR
the LBGs are consistent with the LBG-phase predicted
continuum to values up to a ∼ 400 microns for
duration of 20−60 Myr (Gonz´alez et al. 2012).
galaxies with temperature of ∼ 25 K and redshift
Saintonge et al.(2013)presentedmoleculargasmasses
of z ∼ 11. We emphasize that not including the
anddepletiontimescalesforasampleoflensedstarform-
effects of the CMB on the observations results in
ing galaxies at z = 1.4−3.1. The range of measured
an underestimationof the FIR luminosities for the
molecular gas masses is 5.6×109−4×1011M⊙ and of targets. TheCMB correctedFIRluminositylimits
depletion timescales is 127−1089 Myr. The longer de-
are35%higherthanthosewithoutCMBcorrection
pletiontimescalesmeasuredforthelower-zsourcescould
at z ∼ 6.6, 50% higher at z ∼ 7, and 350% higher
indicatethattheyexperienceless‘extreme’burstsofstar
at z ∼11 for a T=26 K.
formation in comparison to our z > 6.5 sample. Al-
though,assumingahighermolecular-to-atomicgasratio
5. Simulations are already showing us that the task
(ofatleast5)wouldputourupper limits within the val-
of detecting [CII]in high redshift galaxies is go-
ues measured by Saintonge et al. (2013).
ing to be difficult even with ALMA, as confirmed
by the recent sensitive non-detection of Himiko by
5. SUMMARYANDOUTLOOK. Ouchi et al.(2013). AccordinglytoourIOK-1sim-
We have presented a search for [CII]emission in three ulations, a key parameter for the [CII]emission in
LAEs at z ∼ 7 and in a LBG at z ∼ 11 using CARMA LAEs is the metallicity, as we discussed in Sect.
andthePdBI.Wesummarizeourresultsandconclusions 4.6. If these simulations were applicable to all
as follows: high redshift LAEs, we should first try to detect