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Register a new userThe ALPINE-ALMA [C II] Survey: [C II]158micron Emission Line Luminosity Functions at $z sim 4-6$
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We present the [CII]158$mu$m line luminosity functions (LFs) at $zsim4-6$ using the ALMA observations of 118 sources, which are selected to have UV luminosity $M_{1500A}<-20.2$ and optical spectroscopic redshifts in COSMOS and ECDF-S. Of the 118 targets, 75 have significant [CII] detections and 43 are upper limits. This is by far the largest sample of [CII] detections which allows us to set constraints to the volume density of [CII] emitters at $zsim4-6$. But because this is a UV-selected sample, we are missing [CII]-bright but UV-faint sources making our constraints strict lower limits. Our derived LFs are statistically consistent with the $zsim0$ [CII] LF at $10^{8.25} - 10^{9.75}L_odot$. We compare our results with the upper limits of the [CII] LF derived from serendipitous sources in the ALPINE maps (Loiacono et al. 2020). We also infer the [CII] LFs based on published far-IR and CO LFs at $zsim4-6$. Combining our robust lower limits with these additional estimates, we set further constraints to the true number density of [CII] emitters at $zsim 4 - 6$. These additional LF estimates are largely above our LF at $L_{[CII]}>10^9L_{odot}$, suggesting that UV-faint but [CII]-bright sources likely make a significant contributions to the [CII] emitter volume density. When we include all the LF estimates, we find that available model predictions underestimate the number densities of [CII] emitters at $zsim4-6$. Finally, we set a constraint on the molecular gas mass density at $zsim4-6$, with $rho_{mol} sim (2-7)times10^7M_odot$,Mpc$^{-3}$. This is broadly consistent with previous studies.
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We present the first [CII] 158 $mu$m luminosity function (LF) at $zsim 5$ from a sample of serendipitous lines detected in the ALMA Large Program to INvestigate [CII] at Early times (ALPINE). A search performed over the 118 ALPINE pointings revealed several serendipitous lines. Based on their fidelity, we selected 14 lines for the final catalog. According to the redshift of their counterparts, we identified 8 out of 14 detections as [CII] lines at $zsim 5$, and two as CO transitions at lower redshifts. The remaining 4 lines have an elusive identification in the available catalogs and we considered them as [CII] candidates. We used the 8 confirmed [CII] and the 4 [CII] candidates to build one of the first [CII] LFs at $zsim 5$. We found that 11 out of these 12 sources have a redshift very similar to that of the ALPINE target in the same pointing, suggesting the presence of overdensities around the targets. Therefore, we split the sample in two (a clustered and field sub-sample) according to their redshift separation and built two separate LFs. Our estimates suggest that there could be an evolution of the [CII] LF between $z sim 5$ and $z sim 0$. By converting the [CII] luminosity to star formation rate we evaluated the cosmic star formation rate density (SFRD) at $zsim 5$. The clustered sample results in a SFRD $sim 10$ times higher than previous measurements from UV-selected galaxies. On the other hand, from the field sample (likely representing the average galaxy population) we derived a SFRD $sim 1.6$ higher compared to current estimates from UV surveys but compatible within the errors. Because of the large uncertainties, observations of larger samples are necessary to better constrain the SFRD at $zsim 5$. This study represents one of the first efforts aimed at characterizing the demography of [CII] emitters at $zsim 5$ using a mm-selection of galaxies.
We present the physical extent of [CII] 158um line-emitting gas from 46 star-forming galaxies at z=4-6 from the ALMA Large Program to INvestigate CII at Early Times (ALPINE). Using exponential profile fits, we measure the effective radius of the [CII] line (r_e,[CII]) for individual galaxies and compare them with the rest-frame ultra-violet (UV) continuum (r_e,UV) from Hubble Space Telescope images. The effective radius r_e,[CII] exceeds r_e,UV by factors of ~2-3 and the ratio of r_e,[CII]/r_e,UV increases as a function of M_star. We do not find strong evidence that [CII] line, the rest-frame UV, and FIR continuum are always displaced over ~ 1-kpc scale from each other. We identify 30% of isolated ALPINE sources as having an extended [CII] component over 10-kpc scales detected at 4.1$sigma$-10.9$sigma$ beyond the size of rest-frame UV and far-infrared (FIR) continuum. One object has tentative rotating features up to ~10-kpc, where the 3D model fit shows the rotating [CII]-gas disk spread over 4 times larger than the rest-frame UV-emitting region. Galaxies with the extended [CII] line structure have high star-formation rate (SFR), stellar mass (M_star), low Lya equivalent-width, and more blue-shifted (red-shifted) rest-frame UV metal absorption (Lya line), as compared to galaxies without such extended [CII] structures. Although we cannot rule out the possibility that a selection bias towards luminous objects may be responsible for such trends, the star-formation driven outflow also explains all these trends. Deeper observations are essential to test whether the extended [CII] line structures are ubiquitous to high-z star-forming galaxies.
Because the 157.74 micron [C II] line is the dominant coolant of star-forming regions, it is often used to infer the global star-formation rates of galaxies. By characterizing the [C II] and far-infrared emission from nearby Galactic star-forming molecular clumps, it is possible to determine whether extragalactic [C II] emission arises from a large ensemble of such clumps, and whether [C II] is indeed a robust indicator of global star formation. We describe [C II] and far-infrared observations using the FIFI-LS instrument on the SOFIA airborne observatory toward four dense, high-mass, Milky Way clumps. Despite similar far-infrared luminosities, the [C II] to far-infrared luminosity ratio, L([C II])/L(FIR) varies by a factor of at least 140 among these four clumps. In particular, for AGAL313.576+0.324, no [C II] line emission is detected despite a FIR luminosity of 24,000 L_sun. AGAL313.576+0.324 lies a factor of more than 100 below the empirical correlation curve between L([C II])/L(FIR) and S_ u (63 micron)/S_ u (158 micron) found for galaxies. AGAL313.576+0.324 may be in an early evolutionary protostellar phase with insufficient ultraviolet flux to ionize carbon, or in a deeply embedded ``hypercompact H II region phase where dust attenuation of UV flux limits the region of ionized carbon to undetectably small volumes. Alternatively, its apparent lack of cii, emission may arise from deep absorption of the cii, line against the 158 micron continuum, or self-absorption of brighter line emission by foreground material, which might cancel or diminish any emission within the FIFI-LS instruments broad spectral resolution element (~250 km/s)
We report the discovery of the first spectroscopically resolved C II /C II* 1334, 1335A doublet in the Lyman-break galaxy J0215-0555 at z = 5.754. The separation of the resonant and fluorescent emission channels was possible thanks to the large redshift of the source and long integration time, as well as the small velocity width of the feature, 0.6 +- 0.2A. We model this emission and find that at least two components are required to reproduce the combination of morphologies of C II* emission, C II absorption and emission, and Lyman-alpha emission from the object. We suggest that the close alignment between the fluorescence and Lyman-alpha emission could indicate an ionisation escape channel within the object. While the faintness of such a C II /C II* doublet makes it prohibitively difficult to pursue for similar systems with current facilities, we suggest it can become a valuable porosity diagnostic in the era of JWST and the upcoming generations of ELTs.
We take advantage of the capability of the OTELO survey to obtain the H$alpha$ luminosity function (LF) at ${rm z}sim0.40$. Because of the deepest coverage of OTELO, we are able to determine the faint end of the LF, and thus better constrain the star formation rate and the number of galaxies at low luminosities. The AGN contribution to this LF is estimated as well. We make use of the multi-wavelength catalogue of objects in the field compiled by the OTELO survey, which is unique in terms of minimum flux and equivalent width. We also take advantage of the pseudo-spectra built for each source, which allow the identification of emission lines and the discrimination of different types of objects. The H$alpha$ luminosity function at $zsim0.40$ is obtained, which extends the current faint end by almost 1 dex, reaching minimal luminosities of $log_{10}L_{rm lim}=38.5$ erg s$^{-1}$ (or $sim0.002, text{M}_odottext{ yr}^{-1})$. The AGN contribution to the total H$alpha$ luminosity is estimated. We find that no AGN should be expected below a luminosity of $log_{10}L=38.6$ erg s$^{-1}$. From the sample of non-AGN (presumably, pure SFG) at $zsim0.40$ we estimated a star formation rate density of $rho_{rm SFR}=0.012pm0.005 {rm text{M}_{odot} yr^{-1} Mpc^{-3}}$.
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