The Atacama Large Millimeter Array (ALMA) Large Program to INvestigate CII at Early times (ALPINE) targets the CII 158
μ
m line and the far-infrared continuum in 118 spectroscopically confirmed ...star-forming galaxies between
z
= 4.4 and
z
= 5.9. It represents the first large CII statistical sample built in this redshift range. We present details regarding the data processing and the construction of the catalogs. We detected 23 of our targets in the continuum. To derive accurate infrared luminosities and obscured star formation rates (SFRs), we measured the conversion factor from the ALMA 158
μ
m rest-frame dust continuum luminosity to the total infrared luminosity (
L
IR
) after constraining the dust spectral energy distribution by stacking a photometric sample similar to ALPINE in ancillary single-dish far-infrared data. We found that our continuum detections have a median
L
IR
of 4.4 × 10
11
L
⊙
. We also detected 57 additional continuum sources in our ALMA pointings. They are at a lower redshift than the ALPINE targets, with a mean photometric redshift of 2.5 ± 0.2. We measured the 850
μ
m number counts between 0.35 and 3.5 mJy, thus improving the current interferometric constraints in this flux density range. We found a slope break in the number counts around 3 mJy with a shallower slope below this value. More than 40% of the cosmic infrared background is emitted by sources brighter than 0.35 mJy. Finally, we detected the CII line in 75 of our targets. Their median CII luminosity is 4.8 × 10
8
L
⊙
and their median full width at half maximum is 252 km s
−1
. After measuring the mean obscured SFR in various CII luminosity bins by stacking ALPINE continuum data, we find a good agreement between our data and the local and predicted SFR–
L
CII
relations.
We present the ancillary data and basic physical measurements for the galaxies in the ALMA Large Program to Investigate C+ at Early Times (ALPINE) survey-the first large multiwavelength survey that ...aims at characterizing the gas and dust properties of 118 main-sequence galaxies at redshifts 4.4 < z < 5.9 via the measurement of emission at (64% at >3.5 ) and the surrounding far-infrared continuum in conjunction with a wealth of optical and near-infrared data. We outline in detail the spectroscopic data and selection of the galaxies as well as the ground- and space-based imaging products. In addition, we provide several basic measurements including stellar masses, star formation rates (SFR), rest-frame ultra-violet (UV) luminosities, UV continuum slopes (β), and absorption line redshifts, as well as H emission derived from Spitzer colors. We find that the ALPINE sample is representative of the 4 < z < 6 galaxy population selected by photometric methods and only slightly biased toward bluer colors (Δβ ∼ 0.2). Using as tracer of the systemic redshift (confirmed for one galaxy at z = 4.5 out of 118 for which we obtained optical λ3727 emission), we confirm redshifted Ly emission and blueshifted absorption lines similar to findings at lower redshifts. By stacking the rest-frame UV spectra in the rest frame, we find that the absorption lines in galaxies with high specific SFR are more blueshifted, which could be indicative of stronger winds and outflows.
We study the efficiency of galactic feedback in the early Universe by stacking the C II 158
μ
m emission in a large sample of normal star-forming galaxies at 4 <
z
< 6 from the ALMA Large Program ...to INvestigate C II at Early times (ALPINE) survey. Searching for typical signatures of outflows in the high-velocity tails of the stacked C II profile, we observe (i) deviations from a single-component Gaussian model in the combined residuals and (ii) broad emission in the stacked C II spectrum, with velocities of |
v
|≲500 km s
−1
. The significance of these features increases when stacking the subset of galaxies with star formation rates (SFRs) higher than the median (SFR
med
= 25
M
⊙
yr
−1
), thus confirming their star-formation-driven nature. The estimated mass outflow rates are comparable to the SFRs, yielding mass-loading factors of the order of unity (similarly to local star-forming galaxies), suggesting that star-formation-driven feedback may play a lesser role in quenching galaxies at
z
> 4. From the stacking analysis of the datacubes, we find that the combined C II core emission (|
v
|< 200 km s
−1
) of the higher-SFR galaxies is extended on physical sizes of ∼30 kpc (diameter scale), well beyond the analogous C II core emission of lower-SFR galaxies and the stacked far-infrared continuum. The detection of such extended metal-enriched gas, likely tracing circumgalactic gas enriched by past outflows, corroborates previous similar studies, confirming that baryon cycle and gas exchanges with the circumgalactic medium are at work in normal star-forming galaxies already at early epochs.
The ALPINE-ALMA [CII] survey Khusanova, Y.; Bethermin, M.; Le Fèvre, O. ...
Astronomy and astrophysics (Berlin),
05/2021, Letnik:
649
Journal Article
Recenzirano
Odprti dostop
Star formation rate (SFR) measurements at
z
> 4 have relied mostly on the rest-frame far-ultraviolet (FUV) observations. The corrections for dust attenuation based on the IRX-
β
relation are highly ...uncertain and are still debated in the literature. Hence, rest-frame far-infrared (FIR) observations are necessary to constrain the dust-obscured component of the SFR. In this paper, we exploit the rest-frame FIR continuum observations collected by the ALMA Large Program to INvestigate CII at Early times (ALPINE) to directly constrain the obscured SFR in galaxies at 4.4 <
z
< 5.9. We used stacks of continuum images to measure average infrared luminosities taking both detected and undetected sources into account. Based on these measurements, we measured the position of the main sequence of star-forming galaxies and the specific SFR (sSFR) at
z
∼ 4.5 and
z
∼ 5.5. We find that the main sequence and sSFR do not significantly evolve between
z
∼ 4.5 and
z
∼ 5.5, as opposed to lower redshifts. We developed a method to derive the obscured SFR density (SFRD) using the stellar masses or FUV-magnitudes as a proxy of FIR fluxes measured on the stacks and combining them with the galaxy stellar mass functions and FUV luminosity functions from the literature. We obtain consistent results independent of the chosen proxy. We find that the obscured fraction of SFRD is decreasing with increasing redshift, but even at
z
∼ 5.5 it constitutes around 61% of the total SFRD.
ABSTRACT We report the detection of C ii λ158 $\mu$m emission from a system of three closely separated sources in the Cosmic Evolution Survey (COSMOS) field at z ∼ 4.56 , as part of the Atacama Large ...Millimeter/submillimeter Array (ALMA) Large Program to INvestigate C ii at Early times (ALPINE). The two most luminous sources are closely associated, both spatially (1.6 arcsec ∼ 11 kpc) and in velocity (∼100 km s−1), while the third source is slightly more distant (2.8 arcsec ∼ 18 kpc, ∼300 km s−1). The second most luminous source features a slight velocity gradient, while no significant velocity gradient is seen in the other two sources. Using the observed C ii luminosities, we derive a total log$_{10}(\rm SFR_{C\,{\small II}}\, M_{\odot }\, yr^{-1})=2.8\pm 0.2$, which may be split into contributions of 59, 31, and 10 per cent from the central, east, and west sources, respectively. Comparison of these C ii detections to recent zoom-in cosmological simulations suggests an ongoing major merger. We are thus witnessing a system in a major phase of mass build-up by merging, including an ongoing major merger and an upcoming minor merger, which is expected to end up in a single massive galaxy by z ∼ 2.5.
There are only five radio-loud quasars currently known within 1 Gyr from the Big Bang (
z
> 6) and the properties of their host galaxies have not been explored in detail. We present a NOrthern ...Extended Millimeter Array (NOEMA) survey of CII (158 μm) and underlying continuum emission of four
z
> 6 radio-loud quasars, revealing their diverse properties. J0309+2717 (
z
= 6.10) has a bright CII line and underlying continuum, implying that the host galaxy is a starburst with a star-formation rate SFR = 340–1200
M
⊙
yr
−1
. J1429+5447 (
z
= 6.18) has a SFR = 520 − 870
M
⊙
yr
−1
and its CII profile is consistent with two Gaussians, which could be interpreted as a galaxy merger. J1427+3312 (
z
= 6.12) has a moderate SFR = 30–90
M
⊙
yr
−1
. Notably, this is a broad absorption line quasar and we searched for the presence of high-velocity outflows in the host galaxy. Although the NOEMA data tentatively reveal a broad component of the CII line as wide as ∼1400 km s
−1
, the sensitivity of our current data are not sufficient to confirm it. Finally, P172+18 (
z
= 6.82) is undetected in both CII and the continuum, implying a SFR < 22–40
M
⊙
yr
−1
. The broad range of SFRs is similar to what is observed in radio-quiet quasars at similar redshifts. If radio jets do not significantly contribute to both CII and IR luminosities, this suggests there is no feedback from the jet on the star formation in the host galaxy.
Context.
The star formation rate density (SFRD) evolution presents an area of great interest in the studies of galaxy evolution and reionization. The current constraints of SFRD at
z
> 5 are based ...on the rest-frame UV luminosity functions with the data from photometric surveys. The VIMOS UltraDeep Survey (VUDS) was designed to observe galaxies at redshifts up to ∼6 and opened a window for measuring SFRD at
z
> 5 from a spectroscopic sample with a well-controlled selection function.
Aims.
We establish a robust statistical description of the star-forming galaxy population at the end of cosmic HI reionization (5.0 ≤
z
≤ 6.6) from a large sample of 49 galaxies with spectroscopically confirmed redshifts. We determine the rest-frame UV and Ly
α
luminosity functions and use them to calculate SFRD at the median redshift of our sample
z
= 5.6.
Methods.
We selected a sample of galaxies at 5.0 ≤
z
spec
≤ 6.6 from the VUDS. We cleaned our sample from low redshift interlopers using ancillary photometric data. We identified galaxies with Ly
α
either in absorption or in emission, at variance with most spectroscopic samples in the literature where Ly
α
emitters (LAE) dominate. We determined luminosity functions using the 1/
V
max
method.
Results.
The galaxies in this redshift range exhibit a large range in their properties. A fraction of our sample shows strong Ly
α
emission, while another fraction shows Ly
α
in absorption. UV-continuum slopes vary with luminosity, with a large dispersion. We find that star-forming galaxies at these redshifts are distributed along the main sequence in the stellar mass vs. SFR plane, described with a slope
α
= 0.85 ± 0.05. We report a flat evolution of the specific SFR compared to lower redshift measurements. We find that the UV luminosity function is best reproduced by a double power law, while a fit with a Schechter function is only marginally inferior. The Ly
α
luminosity function is best fitted with a Schechter function. We derive a logSFRD
UV
(
M
⊙
yr
−1
Mpc
−3
) = −1.45
+0.06
−0.08
and logSFRD
Ly
α
(
M
⊙
yr
−1
Mpc
−3
) = −1.40
+0.07
−0.08
. The SFRD derived from the Ly
α
luminosity function is in excellent agreement with the UV-derived SFRD after correcting for IGM absorption.
Conclusions.
Our new SFRD measurements at a mean redshift of
z
= 5.6 are ∼0.2 dex above the mean SFRD reported in Madau & Dickinson (2014, ARA&A, 52, 415), but in excellent agreement with results from Bouwens et al. (2015a, ApJ, 803, 34). These measurements confirm the steep decline of the SFRD at
z
> 2. The bright end of the Ly
α
luminosity function has a high number density, indicating a significant star formation activity concentrated in the brightest LAE at these redshifts. LAE with equivalent width EW > 25 Å contribute to about 75% of the total UV-derived SFRD. While our analysis favors low dust content in 5.0 <
z
< 6.6, uncertainties on the dust extinction correction and associated degeneracy in spectral fitting will remain an issue, when estimating the total SFRD until future surveys extending spectroscopy to the NIR rest-frame spectral domain, such as with JWST.
ABSTRACT
We study the projected spatial offset between the ultraviolet continuum and Ly α emission for 65 lensed and unlensed galaxies in the Epoch of Reionization (5 ≤ z ≤ 7), the first such study ...at these redshifts, in order to understand the potential for these offsets to confuse estimates of the Ly α properties of galaxies observed in slit spectroscopy. While we find that ∼40 per cent of galaxies in our sample show significant projected spatial offsets ($|\Delta _{\rm {Ly}\alpha -\rm {UV}}|$), we find a relatively modest average projected offset of $|\widetilde{\Delta }_{\rm {Ly}\alpha -\rm {UV}}|$ = 0.61 ± 0.08 proper kpc for the entire sample. A small fraction of our sample, ∼10 per cent, exhibit offsets in excess of 2 proper kpc, with offsets seen up to ∼4 proper kpc, sizes that are considerably larger than the effective radii of typical galaxies at these redshifts. An internal comparison and a comparison to studies at lower redshift yielded no significant evidence of evolution of $|\Delta _{\rm {Ly}\alpha -\rm {UV}}|$ with redshift. In our sample, ultraviolet (UV)-bright galaxies ($\widetilde{L_{\mathrm{ UV}}}/L^{\ast }_{\mathrm{ UV}}=0.67$) showed offsets a factor of three greater than their fainter counterparts ($\widetilde{L_{\mathrm{ UV}}}/L^{\ast }_{\mathrm{ UV}}=0.10$), 0.89 ± 0.18 versus 0.27 ± 0.05 proper kpc, respectively. The presence of companion galaxies and early stage merging activity appeared to be unlikely causes of these offsets. Rather, these offsets appear consistent with a scenario in which internal anisotropic processes resulting from stellar feedback, which is stronger in UV-brighter galaxies, facilitate Ly α fluorescence and/or backscattering from nearby or outflowing gas. The reduction in the Ly α flux due to offsets was quantified. It was found that the differential loss of Ly α photons for galaxies with average offsets is not, if corrected for, a limiting factor for all but the narrowest slit widths (<0.4 arcsec). However, for the largest offsets, if they are mostly perpendicular to the slit major axis, slit losses were found to be extremely severe in cases where slit widths of ≤1 arcsec were employed, such as those planned for James Webb Space Telescope/NIRSpec observations.
Aims.
Our aim is to analyze the variance of the intergalactic medium (IGM) transmission by studying this parameter in the rest-frame UV spectra of a large sample of high-redshift galaxies.
Methods.
...We made use of the VIMOS Ultra Deep Survey and the VANDELS public survey to gain insight into the far UV spectrum of 2.7 <
z
< 6 galaxies. Using the SPARTAN fitting software, we estimated the IGM toward individual galaxies and then divided them into two sub-samples characterized by a transmission above or below the theoretical prescription. We created average spectra of combined VUDS and VANDELS data for each set of galaxies in seven redshift bins.
Results.
The resulting spectra clearly exhibit the variance of the IGM transmission that can be seen directly from high-redshift galaxy observations. Computing the optical depth based on the IGM transmission, we find an excellent agreement with results for quasi-stellar objects. In addition, our measurements appear to suggest that there is a large dispersion of redshift where a complete Gunn-Peterson Trough occurs, depending on the line of sight.
Aims.
Our aim is to estimate the intergalactic medium (IGM) transmission towards UV-selected star-forming galaxies at
z
≳ 4 and study the effect of the dust attenuation on these measurements.
...Methods.
The UV spectrum of high-redshift galaxies is a combination of their intrinsic emission and the effect of the IGM absorption along their line of sight. Using data coming from the unprecedentedly deep spectroscopy from the VANDELS ESO public survey carried out with the VIMOS instrument, we compute both the dust extinction and the mean transmission of the IGM as well as its scatter from a set of 281 galaxies at
z
> 3.87. Because of a degeneracy between the dust content of the galaxy and the IGM, we first estimate the stellar dust extinction parameter
E
(
B
−
V
) and study the result as a function of the dust prescription. Using these measurements as constraint for the spectral fit we estimate the IGM transmission Tr(Ly
α
). Both photometric and spectroscopic spectral energy distribution fits are performed using the SPectroscopy And photometRy fiTting tool for Astronomical aNalysis which is able to fit the spectral continuum of the galaxies as well as photometric data.
Results.
Using the classical Calzetti attenuation law we find that
E
(
B
−
V
) goes from 0.11 at
z
= 3.99 to 0.08 at
z
= 5.15. These results are in very close agreement with published measurements. We estimate the IGM transmission and find that the transmission is decreasing with increasing redshift from Tr(Ly
α
) = 0.53 at
z
= 3.99 to 0.28 at
z
= 5.15. We also find a large standard deviation around the average transmission that is more than 0.1 at every redshift. Our results are in very good agreement with both previous measurements from AGN studies and with theoretical models.
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