ALMA Science Highlights and Synergies with SKA

Daisuke Iono

National Astronomical Observatory of Japan

Atacama Large Millimeter/submillimeter Array

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•  Global project: 22 countries (from EA: Japan, Taiwan, Korea)•  66 antennas (12m array + ACA) located at the 5000m site in Chile.

•  12m main array: 50 x 12m•  ACA: 4 x 12m + 12 x 7m

•  Angular resolution: 0.01” (x10 of HST)•  Science operation begun in 2011•  235 papers published (11 Nature and 5 Science) from 2012 -‐‑‒

East Asian Contribution

ACA

•  All ACA antennas (4 x 12m, 12 x 7m), and ACA Correlator•  Bands 4, 8, 10 for all antennas•  Enhanced computing

Power of the ACA

12 m array 12m array + ACA

NORTH AMERICAN EAST ASIAN EUROPEAN

12m antenna 12m antenna – 7m antenna 12m antenna

Antennas with extremely precise surface

Science Capabilities

Cycle 0 Cycle 1 Cycle 2 Cycle 3

Time (12m time)

500 hours 800 hours 2000 hours (for 17 months)

2100 hours (for 12 months)

Bands 100, 230, 345, 690 GHz (Bands 3,6,7,9)

100, 150, 230, 345, 450, 690 GHz (Bands 3,4,6,7,8,9)

100, 150, 230, 345, 450, 690, 900 GHz (Bands 3,4,6,7,8,9,10)

Antennas > 16 x 12m •  32 x 12m •  9 x 7m•  2 x 12m TP

•  34 x 12m •  9 x 7m•  2 x 12m TP

•  36 x 12m •  10 x 7m•  2 x 12m TP

Baselines Max 400 m Max 1 km Max 1 km (B8,9)Max 1.5 km (B3,4,6,7)

Max 2 km (B8, 9,10)Max 5 km (B7)Max 10 km (B3, 4, 6)

Othercapabilities

•  Spectral scan•  Polarization

•  Spectral scan•  Polarization

Capabilities

Point Source Sensitivity

70

60

50

40

30

20

10

Cycle 1 Cycle 0 Cycle 2 Cycle 3 Cycle 4

Full ALMA

Point sou

rce sensi?vity

[1h, 8GH

z BW; m

icro Jy]

Angular Resolution

1

0.1

0.01

Cycle 1 Cycle 0 Cycle 2 Cycle 3 Cycle 4

Full ALMA

Maxim

um Angular Resolu?

on

[band 7; arcsec]

ALMA Science

From K. Kohno-san’s website

Redshifted Line Emission

Maiolino 2008

Negative K-‐‑‒correction

History of Cosmic Star Formation

Bouwens et al. 2011, ApJ, 737, 90; Oesch et al., 2012, ApJ, 745, 110 Dunlop 2013, Astrophysics and Space Science Library, Vol. 396, p. 223

“Main Sequence” of Galaxies

Rodighiero et al. 2011 Weinzirl et al. (2011)

D. Narayanan

Possible link to bright quasars and the most massive ellipticals

Evolution of MS galaxies with z

Whitaker et al .2012

Many SMGs are Multiples

Simpson et al. 2015

Figure 1. ALMA 870 μm continuum maps, at 0″. 8 resolution, of 30 bright sub-mm sources in the UDS field. These sources are selected to be representative of thebrightest sources detected in the S2CLS survey of this ∼0.8 deg2 field. The 18 × 18″ non-primary-beam-corrected maps (roughly 150 kpc × 150 kpc at the typicalSMG redshift, z = 2.5) are ordered by decreasing single-dish flux density and have a median 1-σ rms of 0.26 mJy beam−1. The dashed circle on each thumbnailrepresents the primary beam (FWHM) of ALMA at 870 μm. We detect 52 SMGs at >4σ (marked by a squares) in the 30 ALMA maps, with 870 μm flux densities of1.3–12.9 mJy. In 18/30 ALMA maps the single-dish sub-mm source fragments into two or more individual SMGs. In particular, we highlight UDS 57, 168, 286 and306, where the ALMA observations demonstrate that the single-dish source is comprised of three-or-four SMGs. In two ALMA maps, UDS 252 and 421, we do notdetect any SMGs, but note that both SCUBA-2 sources are detected in Herschel/SPIRE imaging. We plot contours representing the single-dish SCUBA-2 emission at3, 3.5, 4.0, 4.5 s´ for these sources, note that UDS 421 has a potential VLA/1.4 GHz counterpart (diamond; Arumugan et al. submitted) that is not detected in ourALMA maps.

4

The Astrophysical Journal, 807:128 (13pp), 2015 July 10 Simpson et al.

•  ALMA Survey of 52 SMGs. •  What were known as single sources

before were actually mul?ples. •  Sugges?ng merger origin, and/or

density peaks of large scale structure (cf. Tamura et al. 2008)

Number counts of Faint SMGs

Ono et al. (2014) Hatsukade et al. (2014)

Accoun?ng for ~80% of the extragalac?c background light

Optical properties of Bright SMGsThe Astrophysical Journal, 799:194 (28pp), 2015 February 1 Chen et al.

Figure 1. HST false-color images of 20 out of 25 H160-detected ALESS SMGs that have imaging in at least two HST bands, to demonstrate the diversity in morphologiespresent within the sample. In these maps the red and blue channels are WFC3 H160 and ACS I814, respectively, except for ALESS 55.1, where the blue is WFC3 J105.The green channel is WFC3 J125 if available, or if not, we made artificial green maps by interpolating H160 and I814. These images show that SMGs have a mix ofmorphology classes, but the majority, ∼80%, appear to be irregulars or interacting systems in the rest-frame optical. The contours show the submillimeter emissionfrom our ALMA 870 µm maps with levels at 3σ and 5σ . The size of each box is ∼70 × 70 kpc based on the photometric redshifts (∼8′′ × 8′′ at z ∼ 2).

5. Unclassified—sources that are contaminated by nearbybright stars, galaxies, or image artifacts, or are too faintto be classifiable.

Note that the first three classes are not mutually exclusive; onesource can be classified as a combination of different classes,such as Disk + Spheroid or Disk + Spheroid + Irregular.

If there are multiple counterparts located within the ALMAsynthesized beam of a single SMG, we tagged those sourcesas either “interaction” or “close companions.” Sources thathave tidal tails or low-level emission connecting multiplecounterparts were tagged as an interaction, while those thatdo not have apparent interacting features were tagged as closecompanions. An interaction tag may also represent a source thatappears to be in the final coalescent stage of a merger, withasymmetric merger remnants. We show examples for each classalong with the two additional tags in Figure 3 (see also Figures 4and 5 in Kartaltepe et al. 2014). These tags are independent fromthe main classifications described above. For example, an SMGsuch as ALESS 49.1 can be classified as Spheroid + Irregularwith an interaction tag.

Four of our team members (C.-C.C., I.R.S., J.M.S., C.-J.M.)determined visual classifications of the H160-detected SMGs,as well as the comparison sample, and we derived from theirclassifications the median fraction of all main morphologicalclasses and the bootstrapped errors, which are later used in ouranalysis.

3.2. galfit

To quantify the morphology of the SMGs, we fitted a Sersicprofile to the H160-band surface brightness of each individualcounterpart galaxy, using the most recent version of GALFIT(v3.0.5; Peng et al. 2010). galfit is a two-dimensional (2D)fitting algorithm that is designed to fit the surface brightnessdistribution of a source with various predefined models, such asthe Sersic profile (de Vaucouleurs 1948; Sersic 1968), which isdescribed as

Σ(r) = Σe exp

!

−κ

"#r

re

$1/n

− 1

%&

, (1)

7

•  HST morphological analysis of 48 ALMA detected SMGs in the ECDFS •  82% +/-­‐ 9% SMGs at z=1-­‐3 appear disturbed. •  Significant displacement in HST posi?on and 870 micron emission -­‐>

dusty region is not seen in HST.

Chen et al. 2015

8 Ikarashi et al.

Figure 6. Size distribution of z ! 3 SMGs, as measured directly in dustcontinuum at 1100µm, in comparison with the radio sizes (Biggs & Ivison2008) and CO emission-line sizes (Tacconi et al. 2006) of z∼ 1–3 SMGs. Thesizes measured for z ! 3 SMGs are on average about half of those measuredin the radio and CO for z∼ 1–3 SMGs. In this plot, we have not applied anycorrection by a possible difference between CO line, millimeter and radiocontinuum emissions which is discussed in Section 4.

show smaller FIR continuum sizes of star forming region ofSMGs than the previous radio and CO sizes in spite of thedifferent luminosity and redshift distributions in the two sam-ples. In order to reveal the possible relation in FIR-continuumsize and redshift (and LIR), we need higher-angular resolutionimaging of SMGs with various properties by ALMA.

5. Z ! 3 SMGS AS PROGENITORS OF THE COMPACTQUIESCENT GALAXIES AT Z ∼ 2

Toft et al. (2014) suggested a plausible evolutionary con-nection between z ∼ 3–6 SMGs as merger-driven ULIRGsand z ∼ 2 cQGS, based on the following facts: i) the star-formation history of z ∼ 2 cQGs (Krogager et al. 2014)matches z ! 3–6 SMGs; ii) the NIR sizes of z ! 3 SMGsare compact enough for them to be progenitors of cQGs; iii)simulations suggest that major mergers at z ! 3 can generatecompact stellar components (e.g. Wuyts et al. 2010). Our re-sults provide direct evidence that starbursts in z ! 3 SMGsare compact. We plot the sizes of z ! 3 SMGs alongside theNIR sizes of compact star-forming galaxies (cSFGs) at z∼ 2–2.5 (Barro et al. 2014b) and cQGs (Krogager et al. 2014) as afunction of redshift in Figure 9. The size of the starburst re-gion in z ∼ 3–6 SMGs is comparable to (or smaller than) the(NIR) size of the stellar component in z ∼ 2 cQGs, support-

Figure 7. Comparison between flux at uv-distance ≥ 200 kλ expected fromthe size by uv-amplitude plot and flux measured by imfit on the high-res im-age. Error in flux by visibility comes from the measured size uncertaintyshown in Figure 4. Error in flux by IMFIT is output by imfit. The dashed grayline shows flux by IMFIT = 1.07×flux by visibility.

ing the idea that compact dust-obscured starbursts in z∼ 3–6SMGs generate the extremely compact, dense stellar compo-nents of cQGs.Compact star-forming galaxies at z ∼ 2–2.5 were reported

recently as a possible progenitors of cQGs, based on NIRspectroscopy of emission lines and NIR source size mea-surements, but without direct size measurements of the star-forming region. cSFGs have similarities with cQGs: cSFGshave similar NIR structural profiles as cQGs (Nelson et al.2014) and the formation redshift of cSFGs is also similar tothat of cQGs (Barro et al. 2014a). These facts could imply thatz! 3 SMGs evolve into cQGs via cSFGs (Figure 9). Note thatBarro et al. (2014a) suggests the posibility of disk instability(e.g. Dekel et al. 2009; Ceverino et al. 2010) as another pathto make cSFGs and cQGs, based on simulations, in additionto major mergers at z ! 3. Our results make the evolution-ary scenario suggested by Toft et al. (2014) more plausible.Given that z ∼ 2 cQGs are thought to evolve into local giantellipticals mostly via dry mergers (e.g. Bezanson et al. 2009;Newman et al. 2012; Oser et al. 2012; Krogager et al. 2014),our results indicate that local giant ellipticals probably expe-rienced an SMG phase at z∼ 3–6.

6. SURFACE STAR FORMATION RATE DENSITY OFZ ! 3 SMGS SIMILAR TO THAT OF LOCAL

(U)LIRGSA discussion based on the surface SFR density (ΣSFR) is

helpful to understand the origin of the compact but huge star-formation activity in z ! 3 SMGs. We derived ΣSFR of oursample using estimated Rc,e (Table 1). ΣSFR of our sampleare in the range of ∼30–600M⊙ yr−1 kpc−2 with a medianof 100+42−26 M⊙ yr−1 kpc−2. We can find that ASXDF sourceswith a millimeter size of ∼ 0′′.10 (FWHM) show large un-certainty in their ΣSFR (Table 1). These large uncertainties in

High Resolution SMG Studies

•  ALMA images of 13 SMGs at z = 3 – 6 •  LIR ~ 2 – 6 x 1012 Lsun (ULIRGs) •  200-­‐600 Msun/yr •  Median size 0.2” ~ 1.6 kpc

•  Compact starbursts •  Median SFR surface density ~ 100 Msun/yr/kpc2

•  Consistent with centers of local ULIRGs

Ikarashi et al. 2015

Compact starbursts in high-redshift SMGs 5

Figure 4. Size measurements for six of the sources with long-baseline data (400–1200 kλ) in our sample and stacked visibility data. Stacked (all) includes all ofASXDF sources with long-baseline data (ASXDF1100.013.1, 27.1, 45.1, 45.2, 49.1 and 53.1). Stacked (faint) includes faint ASXDF sources with long-baselinedata (ASXDF1100.027.1, 45.1, 45.2 and 49.1). (Left:) Black and grey points show the uv visibilities up to 400 and 1200 kλ, respectively. The black line is auv-amp model of the best-fitted Gaussian component. The blue line and shaded area are possible solutions for the corrected source size, with errors listed inTable 1. The blue line and shaded area are plotted for the total amplitude of the best-fitted model. (Right:) ALMA 1100-µm continuum images with synthesizedbeam sizes of∼ 0′′.2, generated by using 200–1200 kλ data. The r.m.s. in images of ASXDF1100.053.1, 13.1, 27.1, 45.1, 45.2, 49.1 and stacked faint and stackedall are 126, 124, 124, 122, 122, 126, 88 and 67 µJy beam−1, respectively. Contours are shown at +4σ and +8σ. These uv-amp plots and high-angular-resolutionimages using ≤ 1200-kλ data imply that these sources have a single, compact component, as shown by our source size analysis using ≤ 400-kλ data.

What are the redshifts of the SMGs?

•  ALMA/Herschel photo-­‐z of 77 SMGs (850 micron flux > 1.4 mJy)

•  Median z = 2.5 +/-­‐ 0.2. •  35% of the sources are at z > 3. •  Median Mstar ~ 8 x 1010Msun

Simpson et al. 2014

The Astrophysical Journal, 788:125 (43pp), 2014 June 20 Simpson et al.

Figure 3. Comparison of the photometric redshifts derived in this work, tospectroscopically confirmed redshifts drawn from the literature and from ourredshift follow-up of the original LESS sources (zLESS; A. L. R. Danielsonet al. in preparation). The inset shows the distribution of ∆z/(1 + zspec) fora 3.6 µm selected training sample with spectroscopic redshifts. For the fieldsample we find good agreement between the photometric and spectroscopicredshifts, with a median ∆z/(1 + zspec) of 0.011 ± 0.002 and a 1σ dispersionof 0.06. In the main panel we compare the photometric redshifts for 22 ALESSSMGs with confirmed spectroscopic redshifts. We again find good agreement,with a median ∆z/(1 + zspec) of −0.004 ± 0.026. We identify spectroscopicredshifts as robust where they are calculated from multiple strong emissionlines, and tentative where multiple weak lines or single line IDs are used. Weidentify three outliers, at | ∆z/(1 + zspec) | > 0.3. Of the three sources only one,ALESS 66.1, has a robust spectroscopic redshift and is an optically bright QSO.The remaining two sources have spectroscopic redshifts drawn from single lineidentifications.

Previous studies indicate that the majority of the ALESSSMGs lie at z > 1.0 (see Wardlow et al. 2011), and so we alsoinvestigate the accuracy of our photometric redshifts limitingjust to this redshift range. For the z > 1.0 sources in the trainingsample the median ∆ z/(1 + zspec) is 0.033 ± 0.005, marginallyhigher than for the training sample as a whole. We definecatastrophic failures as sources with ∆ z/(1 + zspec) > 0.3, andwe find that the failure rate for the 1077 sources at z > 1.0 is 4%.Importantly, the z > 1.0 training sample has a median 3.6 µmmagnitude of m3.6 = 21.2 ± 0.1, which is similar to the median3.6 µm magnitude of the ALESS sample, m3.6 = 21.8 ± 0.2.

Although Hyperz returns a best-fit model and 1σ error, forour sample of field galaxies we determine that the Hyperz“99%” confidence intervals provide the best estimate of theredshift error, yielding ∼68% agreement between the photo-metric and spectroscopic redshifts at 1σ , and so we adopt theseas our 1σ error estimates (see also Luo et al. 2010; Wardlowet al. 2011).

3.2. ALESS Photometric Redshifts

Before deriving the redshift distribution for all ALESS SMGs,we next make use of the existing spectroscopy of ALESSsources to test the reliability of our photometric redshifts forSMGs. Combining our results with a small number from theliterature, we have spectroscopic redshifts for 22 ALESS SMGs(Zheng et al. 2004; Kriek et al. 2008; Coppin et al. 2009;Silverman et al. 2010; Casey et al. 2011; Bonzini et al. 2012;Swinbank et al. 2012; A. L. R. Danielson et al. in preparation).We run hyperz on these SMGs to derive their photometricredshifts, and in Figure 3 we compare the spectroscopic resultsto our photometric redshifts (Figure 3) and find a median

Figure 4. Photometric redshift distribution of ALESS SMGs with individuallyderived photometric redshifts. For comparison we show the spectroscopicredshift distribution from Chapman et al. (2005), a radio-selected sample ofSMGs. We find that the ALESS SMGs lie at a median redshift of z = 2.3 ± 0.1,consistent with the result from Chapman et al. (2005). In contrast to Chapmanet al. (2005), we do not find a significant number of SMGs at z ! 1, and weidentify a high-redshift tail at z " 3.5, not seen in Chapman et al. (2005).The hatched box represents the area missing from the ALESS histogram dueto 19 SMGs with insufficient photometry to derive photometric redshifts. InSection 3.2.3 we identify these sources as belonging to the high-redshift tailof the distribution (i.e., z " 3). Including these 19 SMGs raises the medianredshift to z = 2.5 ± 0.2; see Figure 12.(A color version of this figure is available in the online journal.)

∆ z/(1 + zspec) = −0.004 ± 0.026 and σNMAD = 0.099. Thespectroscopically confirmed ALESS SMGs have a medianredshift zspec = 2.2 ± 0.2 and a median 3.6 µm magnitudeof m3.6 = 20.5 ± 0.5. Together with the results for the 5924galaxies in the spectroscopic training sample, we can thereforebe confident that the photometric redshifts we derive provide areliable estimate of the SMG population.

3.2.1. Reliability of SMG Redshifts

Running Hyperz on the photometry catalog of 77 ALESSSMGs, with detections in >3 wavebands, we derive a medianphotometric redshift of zphot = 2.3 ± 0.1, with a tail to z ∼ 6(Figure 4) and a 1σ spread of zphot = 1.8–3.5. In Table 3 weprovide the redshifts for individual sources. We note that wewill return to discussing the 19 SMGs detected in fewer thanfour wavebands in Section 3.2.3. We caution that five SMGs(ALESS 5.1, 6.1, 57.1, 66.1, and 75.1) have best-fit solutionswith anomalously high values of χ2

red (>10). We inspect thephotometry for each of these and find that ALESS 57.1, 66.1,and 75.1 have an 8.0 µm excess consistent with obscuredAGN activity (ALESS 66.1 is an optically identified QSO,ALESS 57.1 is an X-ray-detected SMG, and ALESS 75.1 hasexcess radio emission consistent with AGN activity; Wang et al.2013). As we do not include AGN templates in our model SEDs,it is unsurprising that we find poor agreement for these sources.For the remaining two sources, the photometry of ALESS 5.1is dominated by a large nearby galaxy, while ALESS 6.1 is apotential lensed source; the 870 µm emission is offset by ∼ 1.′′5from a bright optical source at zphot ∼ 0.4. We therefore advisethat the photometric redshifts for ALESS 5.1 and 6.1 are treatedwith caution, and we highlight these SMGs in Table 3.

8

SMG redshift determination

Vieira et al. 2013

Primordial Galaxy (Himiko)

Ouchi et al. (2013) See also Ota et al. (2014) for a similar non-­‐detec?on

Primordial Galaxy (Himiko)

1710 H. Hirashita et al.

dust species adopted. From our calculations, we have successfullyobtained upper limits of md,SN < 0.15–0.45 M⊙ depending on thedust species; these limits are discussed in the next section.

4 D ISCUSSION

4.1 Comparison with theoretical dust yields in SNe

Now that we have obtained constraints on md,SN (md,SN < 0.15–0.45 M⊙), we can compare our results with theoretically expectedvalues in the literature, as shown in Fig. 3. We compare to thetheoretical data from Nozawa et al. (2007), who consider dustcondensation in SNe and its subsequent destruction by reverseshocks (referred to as reverse shock destruction) under various hy-drogen number densities of the ambient medium (nH). Bianchi &Schneider (2007) have also calculated the dust condensation andreverse shock destruction in SNe based on Todini & Ferrara (2001),obtaining similar results; therefore, the following discussion doesnot change even if we adopt the data from Bianchi & Schneider(2007). Amongst the cases studied by Nozawa et al. 2007, we showthe case with the unmixed helium core, but the case with the mixedhelium core predicts similar dust masses with a tendency towardshigher destruction with increasing nH.

Figure 3. The formed dust mass in an SN as a function of progenitor mass atthe zero-age main sequence. The range of upper limits obtained from Himikois shown by the shaded area (0.15–0.45 M⊙ with the progenitor mass rangeappropriate for SNe, 8–40 M⊙). The range corresponds to the differentdust species adopted. The arrow indicates that the shaded area gives upperlimits. The crosses connected by the solid, dotted, dashed and dot–dashedlines show the theoretical predictions of dust condensation and destructioncalculation by Nozawa et al. (2007), for various hydrogen number densitiesof the ambient medium, nH = 0, 0.1, 1 and 10 cm−3, respectively (note thatnH = 0 corresponds to the case without reverse shock destruction). To avoidcomplication on the diagram, we simply plot the results for the unmixedhelium core in Nozawa et al. (2007). Note that, with the mixed helium core,similar dust masses are predicted for nH = 0, while the dust tends to be moredestroyed for nH > 0. Bianchi & Schneider (2007) also produce similar dustmasses, but less dependent on the progenitor mass. The filled squares witherror bars show the observed dust mass detected by Herschel (Table 2).

From Fig. 3, it is clear that the md,SN constraint obtained forHimiko favours the theoretical dust mass including destruction.Taking the weighted average of md,SN for the Salpeter IMF adoptedabove, we obtain 0.44, 0.31, 0.13 and 0.036 M⊙ for nH = 0, 0.1, 1and 10 cm−3, respectively (nH = 0 indicates no reverse shock de-struction). Therefore, the upper limit obtained for Himiko favoursreverse shock destruction with an ambient density of nH ! 1 cm−3,although a scenario with no dust destruction is still permitted pro-vided we use low-κν dust species such as SNcon (Table 1).

4.2 Comparison with nearby SNe

In Fig. 3, we also plot the dust masses observed in nearby SNe. Al-though there are a large number of SNe observed in the mid-infraredby Spitzer and AKARI, we limit the sample to the SNe detected by theHerschel FIR bands. This is because the mid-infrared observationsonly trace the warm dust component, while it is the cold componenttraced by FIR observations that dominates the total newly formeddust budget (Matsuura et al. 2011); indeed, mid-infrared observa-tions obtain dust masses of ∼10−5–10−3 M⊙ (Gall et al. 2011,and references therein), systematically well below the data fromHerschel detections. Further, the newly formed dust component inSNe should be isolated from the ISM dust component, which lim-its the sample to objects in the Galaxy and Magellanic Clouds. Wetherefore use the data for Cas A and Crab for Galactic SN remnants,and SN 1987A and N 49 for SN remnants in the Large MagellanicCloud (LMC) as summarized in Table 2. In fact, although it is dif-ficult to separate the dust emission from the new and pre-existingcomponents for the SNe in the LMC with the spatial resolutionof Herschel, recent observations of SN 1987A by ALMA haveconfirmed that the emission comes from the inner region, i.e. thedust observed by Herschel is indeed the newly formed component.Due to possible contamination, we interpret the dust mass of N 49to be an upper limit on the newly formed component.

Comparing the observational data (filled squares) with the upperlimits obtained for Himiko (yellow area) in Fig. 3, we find thatthe data are broadly consistent with our limits, although the largedust mass derived for SN 1987A exceeds the upper limits of md,SN

obtained for silicate and AC (0.15–0.33 M⊙, Table 1). Matsuura

Table 2. Data of nearby SN remnants observed by Herschel.

Object m a Ref. b md,SNc Ref. d

(M⊙) (M⊙)

Cas A 15–25 1 0.075 ± 0.028 1Crab 9–12 2, 3, 4 0.08–0.24 2SN 1987A 16–22 5 0.4–0.7 3, 4e

N 49 20 6 <0.4 f 5

Note: aMass of the progenitor at the zero-age main sequence.bReferences for the progenitor mass: (1) Krause et al. (2008); (2)Nomoto et al. (1982); (3) MacAlpine & Satterfield (2008); (4) Gomezet al (2012); (5) Arnett et al. (1989); (6) Hill et al. (1995).cInferred dust mass for the newly formed component.dReferences for the inferred dust mass: (1) Barlow et al. (2010); (2)Gomez et al (2012); (3) Matsuura et al. (2011); (4) Indebetouw et al.(2014); (5) Otsuka et al. (2010).eIndebetouw et al. (2014) derived a dust mass of 0.23 ± 0.05 M⊙ byassuming AC while Matsuura et al. (2011) obtained 0.35 ± 0.06 M⊙for the same species. The difference is explained by the differentmass absorption coefficients adopted in these papers.fBecause of possible contamination with the molecular cloud withwhich this SN remnant is interacting, we regard this dust mass as anupper limit for the newly formed dust.

MNRAS 443, 1704–1712 (2014)

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nH=0 cm-­‐3

0.1

1

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•  Dust ejec?on ~ < 0.15 – 0.45 Msun •  Smaller than SN 1987A •  Favors dust destruc?on due to

reverse shock with an ambient density > 1cm-­‐3

Mdust (Msun) Mdust,SN

Cas A 15 -­‐ 25 0.075 Crab 9 -­‐ 12 0.08 – 0.24 SN 1987A 16 -­‐ 22 0.4 – 0.7 N 49 20 < 0.4

[CII] in the Distant Universe

“Normal” Galaxy at z = 7 -‐‑‒ Abell 1689 -‐‑‒

Gravitational Lensing Galaxy Abell 1689

•  A1689-zD1, a dusty, normal galaxy in the epoch of re-ionization at z=7.5±0.2 (spectroscopic detection of the Lyα Break – Xshooter with VLT)

•  Detected with ALMA at ~230 GHz Sν = 0.61± 0.12 mJy

•  Highly evolved galaxy: large stellar mass (1.7x109 MO), dust enriched (4x107 MO), and gas-to-dust ratio close to MW.

•  SFR~12 MO yr-1

Watson(et(al.(Nature((2015)(

•  Dusty normal galaxy at z = 7.5 +/-­‐ 0.2

•  ALMA dust con?nuum of 0.61 +/-­‐ 0.12 mJy

•  SFR ~ 12 Msun/yr •  Mstar = 1.7 x 109 Msun •  Mdust = 4 x 107 Msun •  Gas to dust ra?o similar to

MW, sugges?ng an evolved system (in contrast to Himiko) Watson et al. (2015)

Galaxies at z > 6 with mm/smm observations

From Watson et al. 2015

Galaxy z Stellar mass (109 Msun)

SFR (UV) (Msun/yr)

Dust Mass (107 Msun)

Ref

HFLS3 6.34 50 1.3 30 Cooray et al. 2014

HCM6A 6.56 -­‐ 9 < 10 Hu et al. 2002

Himiko 6.60 15 30 < 4.72 Ouchi et al. 2013

A1703-­‐zD1 6.8 0.7 – 1.5 7.3 < 5.7 Bradley et al. 2012

IOK-­‐1 6.96 < 40 23.9 < 6.4 Iye et al. 2006 ,Ota et al. 2014

Z8-­‐GND-­‐5296 7.51 1 330 < 50 Finkelstein et al. 2013

A1689-­‐zD1 7.5 1.7 2.7 4 Watson et al. 2015

HG090423 8.2 < 0.05 < 0.38 < 2 Tanvir et al. 2009

Interstellar Gas

•  The amount of gas can control the degree of star formation and the stellar mass

•  High fraction of gas (against stars) can alter the dynamics/star formation characteristics

•  Kinematical information •  Chemistry in the ISM •  PDR Tracers (atomic lines) •  Molecular excitation (physical condition of gas)

4 Silverman et al.

Figure 3. (a) CO luminosity versus total infrared luminosity. (b) CO luminosity and specific star formation rate with each normalizedto the typical values of MS galaxies. Empirical model curves and 1σ errors (grey region) are described in Sargent et al. (2014). (c) Gasdepletion time (τdel ≡ SFE−1; units Gyr) versus SFR. Colored symbols with error bars show our starburst sample with two (819 and830) in bright red having dynamical mass measurements. Grey symbols represent published samples with αCO estimates as compiled inSargent et al. (2014) and shown in all panels.

With a redshift of the CO emission (z = 1.647) veryclose to that of the FMOS source, this system appearsto be in the early stages of a merger given the projectedseparation of 18.7 kpc. The lower limit for the stellarmass of the system as reported in Table 1 refers to themass of the object observed with FMOS, and encircledin Figure 2.

3.1. CO-to-IR ratio

Our primary interest is to determine whether high-redshift starbursts have a CO to IR luminosity ratioL′CO/LTIR dissimilar to that of MS galaxies at these

epochs, which may be indicative of a higher efficiencyof converting gas into stars, similar to that observed inlocal starbursts. To begin, we use observed quantitiesas opposed to derived values such as the gas mass sur-face density that relies on an assumed conversion fac-tor of CO luminosity to H2 gas mass. Moreover, wedo not have size information for our entire sample tomeasure the gas surface density. However, we note that

L′CO/LTIR ∼ Mgas/SFR, hence this luminosity ratio is a

fair proxy for the gas depletion time which in turn is theinverse of the SFE.In Figure 3a, we plot L′

CO as a function of LTIR, in-dicative of the obscured SFR, and include both low- andhigh-redshift galaxies with measurements available in theliterature and compiled in Sargent et al. (2014). All lineluminosities are converted to CO 1-0 using values of 0.85and 0.7, respectively for CO 2-1 and CO 3-2 (Daddi etal. 2015).All galaxies in our sample have L′

CO/LTIR below thewell-established relation for MS galaxies. These obser-vations indicate, for the first time, the existence of anoffset in the L′

CO/LTIR ratio for high-redshift starburstsas found by Solomon et al. (1997) for local ULIRGs.In Figure 3b, we plot these quantities, normalized tothe mean value of galaxies on the MS. In addition, onthe abscissa we replace LTIR with its implied specificSFR (sSFR=SFR/M∗), also normalized to the MS value.We measure the median value of L′

CO/ < L′CO >MS=

Gas Mass in MS Outliers

•  Observed 7 SB galaxies (100 – 800 Msun/yr) at z ~1.5 in the CO(2-­‐1) line

•  Finds that the total molecular gas content is smaller than MS galaxies at same z

•  This means that the deple?on ?me (SFR/Mgas) is shorter

•  Gas mass frac?on ~ 28 – 52%

CO observations of high-z starbursts 3

Figure 2. HST/ACS F814W images of our seven starbursts. CO emission is shown as contours in blue starting at 3σ and in steps of 1σabove the rms noise level. Spitzer/IRAC 3.6µm detections are marked with red contours to illustrate the association of peak CO emissionwith their IR counterparts. CO beam size is indicated in the lower left corner. Small black circles show the placement of FMOS fibers. ForPACS-164 the K-band image is shown to illustrate, in comparison with the HST image, the heavily-obscured nature of the CO-emittingregion. The angular size of the cutouts can vary.

Table 1Sample data and CO measurementsa

PACS RA Dec zCO zspecb log M∗ SFRc ICO L′CO

d ∆ve Beamf CO Gasg

ID (CO) (CO) M⊙ Jy km s−1 size (′′) size (′′) fraction

299 09:59:41.31 02:14:42.91 1.650 1.646 10.44 554 0.67±0.08 10.44 590 4.5×2.0 <2.4 0.52325 10:00:05.47 02:19:42.61 1.657 1.657 10.29 139 0.28±0.06 10.07 764 5.4×2.7 0.32819 09:59:55.55 02:15:11.70 1.444 1.445 10.61 783 1.10±0.07 10.55 592 1.3×1.0 0.34±0.08 0.34830 10:00:08.75 02.19.01.90 1.462 1.461 10.86 517 1.18±0.10 10.59 436 1.3×1.0 0.97±0.17 0.46867 09:59:38.12 02.28.56.56 1.567 1.567 10.67 358 0.46±0.04 10.24 472 4.4×2.0 <1.5 0.29282 10:00:01.54 02:11:24.27 2.192 2.190 10.88 581 0.75±0.12 10.44 660 5.6×4.9 <3.4 0.28164 10:01:30.53 01:54:12.96 1.647 1.650 >10.28 358 0.61±0.11 10.40 894 5.7×5.5 <4.8 0.52

a The first five targets are observed with ALMA while the remaining two with PdBI.b Spectroscopic redshifts are based on Hα with the exception of #282.c Units of M⊙ yr−1.d Log base 10; units of K km s−1 pc2e Velocity channel width of the CO line in units of km s−1.f FWHMg fgas = Mgas/(M∗ + Mgas)

properties and CO measurements.

3. RESULTS

We detect CO emission in all seven targeted galaxieswith integrated flux densities (ICO) ranging from 0.28to 1.18 Jy km s−1. All but one have a high level ofsignificance (> 5σ) and those resulting from ALMA ob-servations are above the 8σ level with the exception ofPACS-325 (S/N = 4.7). In Figure 2, we display the opti-cal HST/ACS i-band image cutouts with CO and 3.6µmemission overlaid as contours. Using a large beam forthe majority of the sample, the CO emission is essen-tially unresolved with the exception of two observationstaken at higher resolution (∼ 1′′). PACS-819 has half ofthe emission coming from a region of 3.2±0.8 kpc, whilePACS-830 is more extended (9.0±1.6 kpc). This maysuggest that there is diversity in the size distribution ofmolecular gas at high redshift, dissimilar to local star-bursts (e.g., Scoville et al. 1989).Upon close inspection of the maps in Figure 2, it is

evident that the centroid of the CO emission is not alwayscoincident with the brightest regions of UV emission asseen in the HST/ACS image (i.e., PACS-164, PACS-830,PACS-867). This is likely evidence that a fair fractionof the star formation is obscured as supported by theimproved alignment of the CO emission with the peakinfrared emission detected by Spitzer in both the IRACand MIPS channels, and clear association with highlysignificant radio emission at 1.4 GHz (Schinnerer et al.2010).We note that the Herschel far-IR (and possibly the CO)

emission of PACS-164 is likely the sum of two separatecomponents seen in the IRAC image. The peak of theCO emission, detected by IRAM, is located somewhatbetween two IR sources, as made particularly clear bythe K-band image also shown in Figure 2, and slightlyelongated possibly indicating a contribution from bothsources. The FMOS spectrum that provides the redshift(z = 1.650) refers to the western IR component that is co-spatial with the UV-bright source seen in the HST image.

Silverman et al. 2015 Also see Seko et al. 2014 for G/D ra?o

Gas Mass Fraction

Dessauges-­‐Zavadsky et al. 2015

•  Molecular gas mass frac?on increases at z > 1

•  Scoville et al. (2014) uses op?cally thin mm (ALMA) dust measurements and find a similar trend.

•  Decline in SFR at z = 0 is in response to the low gas reservoirs in low z systems

Gas Mass Fraction and Disk Formation

Hopkins et al. 2009

Gas mass frac?on is correlated with disk survival in merger simula?ons

Springel et al. 2005

Gas

Stars

Formation of Disk Galaxies Through Mergers

•  CO Survey of 37 optically selected merger remnants using ALMA, SMA and CARMA

•  More than 50% show signature of large disks (some as large as MW)

•  No clear correlation with gas mass fraction

•  Major mergers can possibly produce disk dominated late type galaxies

Ueda et al. 2014

[CII] in the Distant Universe

ALESS 73.1 (z=4.8) De Breuck et al. (2014)

High-‐‑‒z [CII]

[CII] in a z=5.3 ClusterALMA imaging of [CII], OH, and far-infrared emission in a z=5.3 galaxy protocluster 9

Figure 9. ALMA spectra of the [CII](2P3/2→2P1/2) (left), OH(2Π1/2 J=3/2→1/2) (middle), and CO(J=16→15) (right) lines toward

AzTEC-3. Spectra (histograms) are shown at resolutions of 20MHz (20 kms−1; [CII]) or 40MHz (41 km s−1; OH and CO). The velocityscales are relative to z=5.2988. Detected lines are shown along with Gaussian fits to the line emission (black curves). In the case of OH,zero velocity corresponds to the central frequency between the P components of the Λ doublet. The [+/–] and [–/+] labels at ±249 km s−1

indicate the P components of the Λ doublet (i.e., JP=3/2+→1/2− and 3/2−→1/2+, respectively). Due to the narrow splitting (∼14and 2MHz observed-frame, respectively), labels for hyperfine structure splitting of the P components are omitted for clarity. OH andcontinuum emission as quantified by the Gaussian fit in the middle panel have been subtracted from the CO(J=16→15) spectrum. Thedashed gray histogram shows the CO(J=5→4) emission (R10) for comparison, which demonstrates that the bulk of the CO(J=16→15)line is covered by the 1.875GHz bandpass shown.

Figure 10. ALMA [CII](2P3/2→2P1/2) spectra toward LBG-1 (left) and its components LBG-1a, LBG-1b, and LBG-1c (middle; see

Fig. 7), as well as LBG-2 and LBG-3 (right). Spectra (histograms) are shown at resolutions of 19.5MHz (19 km s−1; left and middle) or39MHz (39 km s−1; right). The velocity scales are relative to z=5.2988. Detected lines are shown along with Gaussian fits to the lineemission (black curves). The bottom right panel shows a stack of the spectra of LBG-2 and LBG-3. The dashed gray histogram shows the[CII](2P3/2→

2P1/2) emission from the strong nearby source AzTEC-3 (Fig. 9), scaled by a factor of 0.25, for comparison.

Figure 11. VLA spectrum covering the redshifted CO(J=2→1)frequency toward LBG-1 (D.A. Riechers et al., in prep.). Spectrum(histogram) is shown at a resolution of 16MHz (131 km s−1). Thevelocity scale is relative to z=5.2988. The dashed gray histogramshows the [CII](2P3/2→

2P1/2) emission (Fig. 10), scaled by a factorof 1/50, for comparison.

3.5. Derivation of Further Galaxy Properties

We derive line luminosities from the observed [CII] in-tensities using standard relations (e.g., Solomon & van-den Bout 2005; Carilli & Walter 2013). We assume aChabrier (2003) stellar initial mass function (IMF) toderive star formation rates from LFIR. For AzTEC-3, weuse the measured continuum size to estimate the averagestar formation rate surface density. Based on the linewidth and [CII] galaxy sizes measured along the majoraxis, we then use an isotropic virial estimator (e.g., En-gel et al. 2010) to derive dynamical masses for all [CII]–detected sources (see Table 2).

4. ANALYSIS

4.1. The Massive Starburst Galaxy AzTEC-3

Despite its high LFIR, both the continuum and [CII]line emission in the massive starburst galaxy AzTEC-3

yield a 12% higher limit for Mdust, and thus, would have a minorimpact compared to other sources of uncertainty.

8 Riechers et al.

Figure 7. Velocity-integrated ALMA [CII](2P3/2→2P1/2) contours overlaid on HST/ACS F814W image (left) and [CII](2P3/2→

2P1/2)

velocity maps (right) toward LBG-1. Left: The map is averaged over ∼332MHz (330 km s−1). Contours start at ±3σ and are in stepsof 1σ (1σ=236 µJy beam−1 at the phase center). The synthesized beam size is the same as in Fig. 3. The plus signs indicate the samepositions as in Fig. 1. Right: Color-encoded velocity structure and first moment map of the [CII] emission. The channel maps in the topright panel include emission above 3σ significance (1σ=460 µJy beam−1 at the phase center). The colors indicate different velocity bins.Velocity ranges in km s−1 for each color are indicated in the top right corner. The velocity scale is the same as in Fig. 3. The colors in thefirst moment map (bottom right) indicate the velocity gradient. Contours are shown in steps of 40 km s−1, with dashed (solid) contoursshowing blueshifted (redshifted) emission relative to the central velocity of LBG-1 at z=5.2950. The arrows indicate the general directions(blue- to redshifted) of the two strongest velocity gradients.

Figure 8. ALMA [CII](2P3/2→2P1/2) velocity channel contours overlaid on HST/ACS F814W image toward LBG-1. Velocity channels

are averaged over 87.89MHz (87 km s−1). Contours start at ±3σ and are in steps of 1σ (1σ=460 µJy beam−1 at the phase center). Thenoise in the rightmost channel is slightly higher due to a weak atmospheric absorption feature (see Sect. 2). Velocity ranges in km s−1 areindicated in the top right corner of each panel. The synthesized beam size is the same as in Fig. 7. The velocity scale is the same as inFig. 7. The plus signs indicate the same positions as in Fig. 7.

Gunn-Peterson effect (Gunn & Peterson 1965). TheALMA continuum limit for LBG-1 is inconsistent withthe SED shapes of spiral, starburst and dust-obscuredgalaxies in the nearby universe, but is consistent withthe flatter SED shapes typically observed in nearby dwarfgalaxies. Similar results are found for LBG-2 and LBG-3when assuming the same redshift as for LBG-1 (Fig. 12,middle and right). To determine the LFIR of LBG-1,we thus integrated the dwarf galaxy templates over theirinfrared peaks.20 This results in LFIR limits of <1.1–3.4×1011L⊙.21 We conservatively scale the highest of

20 Corresponding to the rest-frame 42.5–122.5 µm range.21 We did not correct for effects due to the cosmic microwave

background (CMB), which has a temperature of Tz,CMB≃17Kat the redshift of AzTEC-3 and LBG-1. Any corrections to theLFIR limits required are small compared to other sources of uncer-tainty unless the dust temperature approaches Tz,CMB (see, e.g.,

these templates to the ALMA limits in the following.We then assume LBG-2 and LBG-3 to have the sameredshift and SED shape as LBG-1 to determine limits ontheir LFIR.Based on the upper limit for the rest-frame 157.7µm

continuum flux density, we assume standard relationsand the same dust absorption coefficient as for AzTEC-3 to place constraints on the dust mass of LBG-1.Assuming a dust temperature of Tdust=30K and anopacity power law index of β=1.5 yields Mdust<3.1–9.4×107M⊙,22 where the range indicates the differencebetween point source and extended source limits.

da Cunha et al. 2013). The dust temperatures of the dwarf galax-ies used as templates are Tdust≃26–37 K (e.g., Israel et al. 1996b;Skibba et al. 2011), which would require corrections at the few percent level at most.

22 Assuming Tdust=25 or 40K instead would yield ∼1.9× or∼0.44× the quoted Mdust limit. Assuming β=2.0 instead would

ΣSFR = 530 Msun/yr/kpc2 Close to Eddington limit (maximum SB)

SFR = 18 – 54 Msun/yr

Riechers et al. (2014)

2 Riechers et al.

Figure 1. HST/ACS F814W (left) and ALMA 1.0mm continuum image (rest-frame 157.7µm; right) of the targeted region. Two pointingswere observed to cover AzTEC-3 at z=5.3 and five candidate companion Lyman-break galaxies (positions are indicated by plus signs; LBG-1contains three components). The 1.0mm continuum image was obtained by averaging the three [CII] line-free spectral windows (correctedfor primary beam attenuation). The rms at the phase centers is ∼58µJy beam−1, and increases outwards due to the primary beam response.The synthesized beam size of 0.63 ′′×0.56 ′′ is indicated in the bottom left corner of the right panel.

the same redshift11 that extends out to >13Mpc on thesky, with >10 galaxies within the central (co-moving)∼2Mpc radius region (C11). The protocluster galax-ies alone (including the SMG) place a lower limit of4×1011M⊙ on the mass of dark and luminous matterassociated with this region (C11). However, our currentunderstanding of this exceptional cosmic environment isdominantly based on the rest-frame UV/optical proper-ties of all galaxies except the SMG, and thus, may beincomplete due to lacking information on the gas anddust in their interstellar media (ISM).Here we report [CII](2P3/2→2P1/2),

OH(2Π1/2 J=3/2→1/2), and rest-frame 157.7µmdust continuum imaging toward the center of thegalaxy protocluster associated with the z=5.3 SMGAzTEC-3 with ALMA. The [CII](2P3/2→2P1/2) line isthe dominant cooling line of the cold12 ISM in star-forming galaxies (where it can carry up to 1% of LFIR;e.g., Israel et al. 1996a), typically much brighter thanCO lines, and traces regions of active star formation(photon-dominated regions, or PDRs) and the cold,neutral atomic medium (CNM; e.g., Stacey et al. 1991).It thus is an ideal tracer for the distribution, dynamics,and enrichment of the ISM out to the most distantgalaxies, but it was only detected in some of the mostluminous quasars and starburst galaxies in the past(e.g., Maiolino et al. 2005, 2009; Walter et al. 2009;Stacey et al. 2010; Wagg et al. 2010; Valtchanov etal. 2011; Riechers et al. 2013; Wang et al. 2013) –i.e., systems that are much more extreme than typical

11 Based on photometric redshifts and several spectroscopic con-firmations (C11).

12 Cold here means ≪104 K, i.e., in the regime where dust cool-ing through (far-)infrared emission is prevalent, and below theregime where cooling through hydrogen lines dominates.

protocluster galaxies. Previous searches for [CII] emis-sion in typical and/or ultraviolet-luminous galaxies atz>5 have been unsuccessful (e.g., Walter et al. 2012b;Kanekar et al. 2013; Ouchi et al. 2013; Gonzalez-Lopezet al. 2014), and it is important to understand whatrole environment may play for the detectability of suchobjects. The far-infrared lines of the OH radical areimportant for the H2O chemistry and cooling budgetof star-forming regions, and they are critical tracers ofmolecular outflows (e.g., Sturm et al. 2011), but OHwas only detected in a single galaxy at cosmologicaldistances to date (Riechers et al. 2013). We use aconcordance, flat ΛCDM cosmology throughout, withH0=71 km s−1 Mpc−1, ΩM=0.27, and ΩΛ=0.73 (Spergelet al. 2003, 2007).

2. OBSERVATIONS

We observed the [CII](2P3/2→2P1/2) transition line(νrest = 1900.5369GHz, redshifted to 301.72GHz, or994µm, at z=5.299), using ALMA. Observations werecarried out with 16–24 usable 12m antennas under good870µm weather conditions (precipitable water vapor of0.64–1.76mm) for 4 tracks in the cycle 0 extended config-uration (longest baseline: 402m) between 2012 April 11and May 17, and for 1 track in the cycle 0 compact config-uration13 (shortest baseline: 21m) on 2012 November 18(three additional tracks were discarded due to poor dataquality). This resulted in 125min on-source time, whichwas evenly split over two (slightly overlapping) pointings(primary beam FWHM diameter at 994µm: 20′′). Thenearby radio quasar J1058+015 was observed regularlyfor pointing, bandpass, amplitude and phase calibration.

13 Given the increased number of antennas available, this con-figuration also contained antennas on longer baselines than theoriginally advertised 125m.

[CII] in the Distant Universe

High-‐‑‒z [CII]

0 0.5 1 1.5 2 2.5 3log10(SFR) (Msun yr-1)

7

7.5

8

8.5

9

9.5

10

L [CII]

(Lsu

n)

LiteratureThis work

Extended Data Figure 1 | [C II] flux as a function of total star-formationrate, SFR. Our sample is consistent with the low-z SFR–L[C II] relation from theliterature at z 5 0–6 (ref. 6). The best fit to the literature points from ref. 44is indicated with a solid line. The SFRs are derived using the UV 1 FIR methodand a Chabrier IMF18. The dust-corrected ultraviolet estimates with a Meurerrelation typically used at these redshifts would increase the estimated SFR bya factor of ,2–10 (0.5–1 dex), leading to over-estimates of the expected[C II] flux. The L[C II] error bars are 1s standard measurement error, while theSFR errors are 1s from a combination of measurement error in LIR and LUV

converted to star formation added in quadrature.

LETTER RESEARCH

G2015 Macmillan Publishers Limited. All rights reserved

star-formation history is much smaller, ,40%, because the majority ofstar-formation is in low luminosity (,L*) galaxies that were alreadyassumed to have little or no dust extinction (see Methods section‘Effects of evolving dust on the global star-formation history’,Extended Data Fig. 4).

In contrast to the dust emission, we find .3s detections of the [C II]line in all nine normal galaxies (Fig. 3). The line emission is spectrallyresolved in all cases, with [C II] velocity dispersions of 63–163 km s21,and marginally resolved at our spatial resolution of ,0.5–0.9 arcsec,indicating galaxies with dynamic masses (Mdyn) of ,109–1011 solarmasses (M[; see Methods sections ‘Reduction of ALMA data’ and‘Derivation of physical parameters’). We also detect two optically faint[C II] emitters at redshifts consistent with the targeted objects. HZ5a isdetected near HZ5 at a redshift consistent with the in-falling gas seenin the optical spectra of HZ524. HZ8W corresponds to an optically faintcompanion to HZ8 and has a similar redshift. Taken together, thedirect and serendipitous detections suggest ubiquitous and enhanced[C II] emission in early galaxies similar to that seen in local low-metal-licity systems12 (Fig. 4).

The [C II] enhancement in local systems is caused by a lower dust-to-gas ratio which allows the ultraviolet radiation field to penetrate alarger volume of molecular cloud12. Our significantly lower IRXvalues and enhanced [C II]/FIR ratios would suggest a similar effectis happening in high redshift galaxies. But other possible causes ofthe transition in obscuration properties with redshift have beensuggested25: evolution in metal abundances that changes theintrinsic ultraviolet slope; changes in the dust properties; and dif-ferences in the dust geometry. The systems in this study wereselected to have broad ultraviolet absorption features in their spec-tra that indicate a relatively homogeneous metal abundance of,0.25 times the solar value. At this metallicity, the ultraviolet spec-tral slopes are expected to be similar to those of solar metallicity

1ʺ

HZ5a

N

E

HZ8W

HZ1 HZ2 HZ3 HZ4

HZ5 HZ6 HZ7 HZ8

HZ9 HZ10

Figure 1 | Optical, [C II] and continuum maps of the sources HZ1–HZ10.The [C II] line detections (red contours) and weak ,158 mm FIR continuumdetections (blue contours) are shown with the rest-frame ultraviolet images asthe background. The images are 50 3 50 (scale bar at bottom left) and thecontours are 2, 6 and 10 s with [C II] line profiles for each source shown in

Fig. 3. The background images are from HST-ACS in the F814W17 band wherethe morphologies will be affected by Lya, except for HZ10, which is Subaru z9band. All objects are detected in [C II], showing that a large amount of gas ispresent in these systems, but only four are detected in continuum.

–2 –1 0 1Ultraviolet slope, β

–2

–1

0

1

2

3

log 10

(LIR

/L16

00)

Ref. 29 (Calzetti like dust)Ref. 20 (SMC like dust)This work, detectionsThis work, upper limitsThis work, mean of undetectedA1689-zD1

Figure 2 | IRX–b measurements of z . 5 objects. The deficit of infraredemission in our sample is evident in the presented infrared excessversus ultraviolet slope (IRX–b) relation when compared with models.Detections are indicated in red, upper limits in orange, the mean IRXratio (obtained by combining undetected sources) in blue, andA1689-zD111 in maroon. Error bars are 1s, and include standardmeasurement error and systematic uncertainty added in quadrature.The Meurer29 relation, which assumes Calzetti-like dust and isconsistent with typical galaxies at z , 3, is shown as a black solid line,while a model for lower-metallicity SMC-like dust model20 is shown as adashed line.

RESEARCH LETTER

G2015 Macmillan Publishers Limited. All rights reserved

4 5 6 | N A T U R E | V O L 5 2 2 | 2 5 J U N E 2 0 1 5

Capak et al. 2015

•  Observed 9 typical SFGs at z = 5-­‐6 •  Dust content is < 10% than similar

systems at z < 3. •  Metalicity is consistent with z = 0 low

metallicity systems

[CII] in the Distant Universe

High-‐‑‒z [CII]Gullberg et al. 2015

•  17 [CII] detec?ons in z = 2.1-­‐5.7 SFGs in the SPT sample

•  CO and [CII] line profiles are consistent, possibly indica?ng spa?al coexistence

•  See also •  Ota et al. 2014 •  Riechers et al. 2014 •  Kimball et al. 2015 •  Schaerer et al. 2015

for [CII] at high-­‐z

2886 B. Gullberg et al.

Figure 1. Comparison of the velocity profiles of the [C II] lines detected with APEX/FLASH and SPIRE FTS (grey filled profiles) and mid-J CO line observedwith ALMA in Cycle 0 (coloured lines; Weiß et al. 2013). The CO lines have been scaled to match the [C II]peak flux. The similarities between the CO and[C II] lines for individual sources suggest that the spatial distributions are similar and differential lensing is not significant.

MNRAS 449, 2883–2900 (2015)

at National A

stronomical O

bservatory of Japan on July 23, 2015http://m

nras.oxfordjournals.org/D

ownloaded from

High-‐‑‒z [NII]

See Ferkinhoff et al. 2015 for [NII] in the Cloverleaf QSO

Nagao et al. (2012)

Redshised [NII] line in LESS J0332 (z=4.76)

Resolution Comparison Angular Resolution survey

From R. Braun’s presenta?on 0.0001-­‐ 0.00001” (0.01mas)

smmVLBI

Galaxy Evolution Probed in

•  HI emission and low J CO •  Possibly HCN/HCO+ •  Radio con?nuum

•  Synchrotron emission (SF and AGN)

•  mid-­‐high J CO and CII emission

•  mm/submm con?nuum •  Cold (T ~ 30-­‐50K) dust emission

ALMA SKA

Achieved at comparable angular resolu?on

Radio-‐‑‒FIR Correlation

Yun et al. 2001 Correla?on holds at ~< 1 kpc scale for galaxies. Basu et al. (2012), Hirashita et al. (2013)

Roughly constant as a func?on of z but may have slight evolu?on (Casey et al. 2012) => Need further inves?ga?on

Radio FIR spectral index as a z indicator for optical/IR dark galaxies

Carilli & Yun (2999)

Need both SKA and ALMA

U/LIRGs at z~∼8 !?

SKA2 300 hr 0.02μJy/beam (5σ)

Norris et al. 2013

SKA1 300 hr, 0.2μJy/beam (5σ)

SKA1 can observe ULIRGs at z = 8. SKA2 can probe LIRGs at z = 8!

ALMA -­‐ NAOJ Geach & Papadopoulos 2012

Jup=1 2 3 4 5 6 7 8 9

Low J CO and HCN/HCO+

ALMA observa?on of a z=0 LIRG VV114 (Saito et al. 2015)

Line Cri?cal Density (cm-­‐3)

HCN(4-­‐3) 8.5 x 106

HCO+(4-­‐3) 1.8 x 106

CO(3-­‐2) 8.4 x 103

CO(1-­‐0) 4.1 x 102

Molecular Excitation

Carilli & Walter (2013)

Molecular Excitation

Carilli & Walter (2013)

Low-‐‑‒J CO at z > 5

Caveat: •  CO(1-­‐0) may be more difficult at higher z because of the higher TCMB •  Metalicity may play a role for metal poor early galaxies •  CO(1-­‐0) may not trace the global mass at high-­‐z

Need both SKA and ALMA to check!

Obreschkow et al. 2009

z=5 z=10

Serendipitous Detections

Geach & Papadopoulos 2012

Freq (obs) FoV (‘) RMS (μJy) Serendipitous (10 hour) Line MeerKAT 10 55.44 38 0.39 Low J CO/

HCN SKA K 18 11.16 1 14.93 ALMA B3 103 0.83 77 0.28 Mid to high J

CO ALMA B4 147 0.40 77 0.24 ALMA B5 163 0.24 86 0.15 ALMA B6 212 0.14 75 0.10 ALMA B7 278 0.08 87 0.05

Assuming 300 km/s line at 5 sigma

ALMA Serendipitous Discoveries

Discovered a bright submm source at z = 2, right next to a z = 0 LIRG VV114

Tamura et al. 2014

Summary•  ALMA is operational and producing great results! •  Galaxy evolution studies with ALMA (star forming

galaxies) •  SKA-ALMA synergy

–  Sub-arcsec resolution matched to ALMA/HST is important –  Better understanding of the Radio-FIR correlation –  (sub)mm/radio flux ratios can be a good indicator of

redshift –  Low-J CO/HCN/HCO+ are important to constrain the

evolution of gas content and the physical condition •  What can ALMA do now, in preparation for the SKA

era?