[en] We present observations at 1.2 mm with Max-Planck Millimetre Bolometer Array (MAMBO-II) of a sample of z ∼> 2 radio-intermediate obscured quasars, as well as CO observations of two sources with the Plateau de Bure Interferometer. The typical rms noise achieved by the MAMBO observations is 0.55 mJy beam^-1 and five out of 21 sources (24%) are detected at a significance of ≥3σ. Stacking all sources leads to a statistical detection of (S_1.2mm) = 0.96 ± 0.11 mJy and stacking only the non-detections also yields a statistical detection, with (S_1.2mm) = 0.51 ± 0.13 mJy. At the typical redshift of the sample, z = 2, 1 mJy corresponds to a far-infrared luminosity L_FIR∼4 x 10¹² L_sun. If the far-infrared luminosity is powered entirely by star formation, and not by active galactic nucleus heated dust, then the characteristic inferred star formation rate is ∼700 M_sun yr^-1. This far-infrared luminosity implies a dust mass of M_d∼3 x 10⁸ M_sun, which is expected to be distributed on ∼kpc scales. We estimate that such large dust masses on kpc scales can plausibly cause the obscuration of the quasars. Combining our observations at 1.2 mm with mid- and far-infrared data, and additional observations for two objects at 350 μm using SHARC-II, we present dust spectral energy distributions (SEDs) for our sample and derive a mean SED for our sample. This mean SED is not well fitted by clumpy torus models, unless additional extinction and far-infrared re-emission due to cool dust are included. This additional extinction can be consistently achieved by the mass of cool dust responsible for the far-infrared emission, provided the bulk of the dust is within a radius ∼2-3 kpc. Comparison of our sample to other samples of z ∼ 2 quasars suggests that obscured quasars have, on average, higher far-infrared luminosities than unobscured quasars. There is a hint that the host galaxies of obscured quasars must have higher cool-dust masses and are therefore often found at an earlier evolutionary phase than those of unobscured quasars. For one source at z = 2.767, we detect the CO(3-2) transition, with S_COΔν = 630 ± 50 mJy km s^-1, corresponding to L_CO(3-2) = 3.2 x10⁷ L_sun, or a brightness-temperature luminosity of L'_CO(3-2) = 2.4 x 10¹⁰ K km s^-1 pc². For another source at z = 4.17, the lack of detection of the CO(4-3) line suggests the line to have a brightness-temperature luminosity L'_CO(4-3) < 1 x 10¹⁰ K km s^-1 pc². Under the assumption that in these objects the high-J transitions are thermalized, we can estimate the molecular gas contents to be M_H2=1.9x10¹⁰ M _sun and <8 x 10⁹ M_sun, respectively. The estimated gas depletion timescales are τ_g = 4 Myr and <16 Myr, and low gas-to-dust mass ratios of M_g/M _d = 19 and <20 are inferred. These values are at the low end but consistent with those of other high-redshift galaxies.

[en] Bright Lyα blobs (LABs)—extended nebulae with sizes of ∼100 kpc and Lyα luminosities of ∼10⁴⁴ erg s⁻¹—often reside in overdensities of compact Lyα emitters (LAEs) that may be galaxy protoclusters. The number density, variance, and internal kinematics of LABs suggest that they themselves trace group-like halos. Here, we test this hierarchical picture, presenting deep, wide-field Lyα narrowband imaging of a 1° × 0.°5 region around a LAB pair at z = 2.3 discovered previously by a blind survey. We find 183 Lyα emitters, including the original LAB pair and three new LABs with Lyα luminosities of $(0.9\text{--}1.3)\times <!--\; ??\; -->{10}^{43}$ erg s⁻¹ and isophotal areas of 16–24 arcsec². Using the LAEs as tracers and a new kernel density estimation method, we discover a large-scale overdensity (Boötes J1430+3522) with a surface density contrast of ${\mathrm{\delta <!--\; ??\; -->}}_{\mathrm{\Sigma <!--\; ??\; -->}}=2.7$, a volume density contrast of δ ∼10.4, and a projected diameter of ≈20 comoving Mpc. Comparing with cosmological simulations, we conclude that this LAE overdensity will evolve into a present-day Coma-like cluster with $\mathrm{l}\mathrm{o}\mathrm{g}(M/M_{\odot <!--\; ???\; -->})$ ∼ 15.1 ± 0.2. In this and three other wide-field LAE surveys re-analyzed here, the extents and peak amplitudes of the largest LAE overdensities are similar, not increasing with survey size, and implying that they were indeed the largest structures then and today evolve into rich clusters. Intriguingly, LABs favor the outskirts of the densest LAE concentrations, i.e., intermediate LAE overdensities of ${\mathrm{\delta <!--\; ??\; -->}}_{\mathrm{\Sigma <!--\; ??\; -->}}=1\text{--}2$. We speculate that these LABs mark infalling protogroups being accreted by the more massive protocluster.

[en] Analyses of high-redshift ultraluminous infrared (IR) galaxies traditionally use the observed optical to submillimeter spectral energy distribution (SED) and estimates of the dynamical mass as observational constraints to derive the star formation rate (SFR), the stellar mass, and age of these objects. An important observational constraint neglected in the analysis is the mass of dust giving rise to the IR emission. In this paper we add this constraint to the analysis of AzTEC-3. Adopting an upper limit to the mass of stars and a bolometric luminosity for this object, we construct different stellar and chemical evolutionary scenarios, constrained to produce the inferred dust mass and observed luminosity before the associated stellar mass exceeds the observational limit. We use the PEGASE population synthesis code and a chemical evolution model to follow the evolution of the galaxy's SED and its stellar and dust masses as a function of galactic age for seven different stellar initial mass functions (IMFs). We find that the model with a Top Heavy IMF provided the most plausible scenario consistent with the observational constraints. In this scenario the dust formed over a period of ∼200 Myr, with an SFR of ∼500 M_sun yr^-1. These values for the age and SFR in AzTEC-3 are significantly higher and lower, respectively, from those derived without the dust mass constraint. However, this scenario is not unique, and others cannot be completely ruled out because of the prevailing uncertainties in the age of the galaxy, its bolometric luminosity, and its stellar and dust masses. A robust result of our models is that all scenarios require most of the radiating dust mass to have been accreted in molecular clouds. Our new procedure highlights the importance of a multiwavelength approach, and of the use of dust evolution models in constraining the age and the star formation activity and history in galaxies.

[en] We report interferometric measurements of [N ii] 205 μm fine-structure line emission from a representative sample of three galaxies at z = 5–6 using the Atacama Large (sub)Millimeter Array (ALMA). These galaxies were previously detected in [C ii] and far-infrared continuum emission and span almost two orders of magnitude in star formation rate (SFR). Our results show at least two different regimes of ionized interstellar medium properties for galaxies in the first billion years of cosmic time, separated by their $L_{[\mathrm{C}\mathrm{I}\mathrm{I}]}/L_{[\mathrm{N}\mathrm{I}\mathrm{I}]}$ ratio. We find extremely low [N ii] emission compared to [C ii] ($L_{[\mathrm{C}\mathrm{I}\mathrm{I}]}/L_{[\mathrm{N}\mathrm{I}\mathrm{I}]}={68}_{-<!--\; ???\; -->28}^{+200}$) from a “typical” $\sim <!--\; ???\; -->L_{\mathrm{U}\mathrm{V}}^{\ast <!--\; ???\; -->}$ star-forming galaxy, likely directly or indirectly (by its effect on the radiation field) related to low dust abundance and low metallicity. The infrared-luminous modestly star-forming Lyman-break galaxy (LBG) in our sample is characterized by an ionized-gas fraction ($L_{[\mathrm{C}\mathrm{I}\mathrm{I}]}/L_{[\mathrm{N}\mathrm{I}\mathrm{I}]}\lesssim <!--\; ???\; -->20)$ typical of local star-forming galaxies and shows evidence for spatial variations in its ionized-gas fraction across an extended gas reservoir. The extreme SFR, warm and compact dusty starburst AzTEC-3 shows an ionized fraction higher than expected given its SFR surface density ($L_{[\mathrm{C}\mathrm{I}\mathrm{I}]}/L_{[\mathrm{N}\mathrm{I}\mathrm{I}]}=22\pm <!--\; ??\; -->8$) suggesting that [N ii] dominantly traces a diffuse ionized medium rather than star-forming H ii regions in this type of galaxy. This highest redshift sample of [N ii] detections provides some of the first constraints on ionized and neutral gas modeling attempts and on the structure of the interstellar medium at z = 5–6 in “normal” galaxies and starbursts.

[en] We present deep continuum observations using the GISMO camera at a wavelength of 2 mm centered on the Hubble Deep Field in the GOODS-N field. These are the first deep field observations ever obtained at this wavelength. The 1σ sensitivity in the innermost ∼4' of the 7' diameter map is ∼135 μJy beam^–1, a factor of three higher in flux/beam sensitivity than the deepest available SCUBA 850 μm observations, and almost a factor of four higher in flux/beam sensitivity than the combined MAMBO/AzTEC 1.2 mm observations of this region. Our source extraction algorithm identifies 12 sources directly, and another 3 through correlation with known sources at 1.2 mm and 850 μm. Five of the directly detected GISMO sources have counterparts in the MAMBO/AzTEC catalog, and four of those also have SCUBA counterparts. HDF850.1, one of the first blank-field detected submillimeter galaxies, is now detected at 2 mm. The median redshift of all sources with counterparts of known redshifts is z-tilde =2.91±0.94. Statistically, the detections are most likely real for five of the seven 2 mm sources without shorter wavelength counterparts, while the probability for none of them being real is negligible.

[en] We report interferometric imaging of [C II](² P _3/2→² P _1/2) and OH(²Π_1/2 J = 3/2→1/2) emission toward the center of the galaxy protocluster associated with the z = 5.3 submillimeter galaxy (SMG) AzTEC-3, using the Atacama Large (sub)Millimeter Array (ALMA). We detect strong [C II], OH, and rest-frame 157.7 μm continuum emission toward the SMG. The [C II](² P _3/2→² P _1/2) emission is distributed over a scale of 3.9 kpc, implying a dynamical mass of 9.7 × 10¹⁰ M _☉, and a star formation rate (SFR) surface density of Σ_SFR = 530 M _☉ yr^–1 kpc^–2. This suggests that AzTEC-3 forms stars at Σ_SFR approaching the Eddington limit for radiation pressure supported disks. We find that the OH emission is slightly blueshifted relative to the [C II] line, which may indicate a molecular outflow associated with the peak phase of the starburst. We also detect and dynamically resolve [C II](² P _3/2→² P _1/2) emission over a scale of 7.5 kpc toward a triplet of Lyman-break galaxies with moderate UV-based SFRs in the protocluster at ∼95 kpc projected distance from the SMG. These galaxies are not detected in the continuum, suggesting far-infrared SFRs of <18-54 M _☉ yr^–1, consistent with a UV-based estimate of 22 M _☉ yr^–1. The spectral energy distribution of these galaxies is inconsistent with nearby spiral and starburst galaxies, but resembles those of dwarf galaxies. This is consistent with expectations for young starbursts without significant older stellar populations. This suggests that these galaxies are significantly metal-enriched, but not heavily dust-obscured, 'normal' star-forming galaxies at z > 5, showing that ALMA can detect the interstellar medium in 'typical' galaxies in the very early universe.

[en] We present the first spectroscopic confirmation of an ultramassive galaxy at redshift $z><!--\; >\; -->3$ using data from Keck-NIRSPEC, VLT-X-shooter, and GTC-Osiris. We detect strong [O iii] and Lyα emission, and weak [O ii], C iv, and He ii, placing C1-23152 at a spectroscopic redshift of $z_{\mathrm{s}\mathrm{p}\mathrm{e}\mathrm{c}}=3.351$. The modeling of the emission-line-corrected spectral energy distribution (SED) results in a best-fit stellar mass of $M_{\ast <!--\; ???\; -->}={3.1}_{-<!--\; ???\; -->0.7}^{+0.6}\times <!--\; ??\; -->{10}^{11}$ $M_{\odot <!--\; ???\; -->}$, a star formation rate of <7 $M_{\odot <!--\; ???\; -->}$ yr⁻¹, and negligible dust extinction. The stars appear to have formed in a short intense burst ∼300–500 Myr prior to the observation epoch, setting the formation redshift of this galaxy at z ∼ 4.1. From the analysis of the line ratios and widths and the observed flux at 24 μm, we confirm the presence of a luminous hidden active galactic nucleus (AGN), with bolometric luminosity of $\sim <!--\; ???\; -->{10}^{46}$ erg s⁻¹. Potential contamination of the observed SED from the AGN continuum is constrained, placing a lower limit on the stellar mass of $2\times <!--\; ??\; -->{10}^{11}$ $M_{\odot <!--\; ???\; -->}$. HST/WFC3 ${\mathrm{H}}_{160}$ and ACS ${\mathrm{I}}_{814}$ images are modeled, resulting in an effective radius of $r_{\mathrm{e}}\sim <!--\; ???\; -->1$ kpc in the ${\mathrm{H}}_{160}$ band and a Sérsic index $n\sim <!--\; ???\; -->4.4$. This object may be a prototype of the progenitors of local most massive elliptical galaxies in the first 2 Gyr of cosmic history, having formed most of its stars at $z><!--\; >\; -->4$ in a highly dissipative, intense, and short burst of star formation. C1-23152 is completing its transition to a post-starburst phase while hosting a powerful AGN, potentially responsible for the quenching of the star formation activity.

[en] We present the detection of CO (5−4) with signal-to-noise ratio (S/N) > 7–13 and a lower CO transition with S/N > 3 (CO (4−3) for four galaxies, and CO (3−2) for one) with the Atacama Large Millimeter/submillimeter Array in bands 3 and 4 in five main-sequence (MS) star-forming galaxies with stellar masses (3–6) × 10¹⁰ M _⊙ at 3 < z < 3.5. We find a good correlation between the total far-infrared luminosity L _FIR and the luminosity of the CO (5−4) transition $L_{\mathrm{C}\mathrm{O}(5-<!--\; ???\; -->4)}^{\mathrm{\prime <!--\; ???\; -->}}$, where $L_{\mathrm{C}\mathrm{O}(5-<!--\; ???\; -->4)}^{\mathrm{\prime <!--\; ???\; -->}}$ increases with star formation rate (SFR), indicating that CO (5−4) is a good tracer of the obscured SFR in these galaxies. The two galaxies that lie closer to the star-forming MS have CO spectral line energy distribution (SLED) slopes that are comparable to other star-forming populations, such as local submillimeter galaxies and BzK star-forming galaxies; the three objects with higher specific star formation rates have far steeper CO SLEDs, which possibly indicates a more concentrated episode of star formation. By exploiting the CO SLED slopes to extrapolate the luminosity of the CO (1−0) transition and using a classical conversion factor for MS galaxies of ${\mathrm{\alpha <!--\; ??\; -->}}_{\mathrm{C}\mathrm{O}}=3.8M_{\odot <!--\; ???\; -->}{(\mathrm{K}\mathrm{k}\mathrm{m}{\mathrm{s}}^{-<!--\; ???\; -->1}{\mathrm{p}\mathrm{c}}^{-<!--\; ???\; -->2})}^{-<!--\; ???\; -->1}$, we find that these galaxies are very gas-rich, with molecular gas fractions between 60% and 80% and quite long depletion times, between 0.2 and 1 Gyr. Finally, we obtain dynamical masses that are comparable to the sum of stellar and gas mass (at least for four out of five galaxies), allowing us to put a first constraint on the α _CO parameter for MS galaxies at an unprecedented redshift.

[en] We performed a comprehensive stacking analysis on ∼14,200 quiescent galaxy (QG) candidates at z = 0–3 across mid-, far-infrared (MIR and FIR), and radio wavelengths. Identified via their rest-frame NUV − r and r − J colors, the QG candidates ($M_{\star <!--\; ???\; -->}={10}^{9.8\text{--}12.2}{M}_{\odot <!--\; ???\; -->}$) have drastically different IR and radio properties depending on their 24 μm emission strength. The fraction of QG candidates with strong 24 μm emission (equivalent to inferred star formation rates SFR${}_{24}⩾<!--\; ???\; -->100M_{\odot <!--\; ???\; -->}{yr}^{-<!--\; ???\; -->1}$, hereafter “IR-bright”) increases with redshift and peaks at 15%, and their stacked MIPS 24 μm, Herschel (PACS and SPIRE) and VLA emissions are consistent with being star-forming galaxies (SFGs). In contrast, the majority of QG candidates are faint or undetected at 24 μm individually (i.e., SFR₂₄ < 100 M_⊙ yr⁻¹, hereafter “IR-faint”). Their low dust-obscured SFRs derived from Herschel stacking (SFR_H ≲  3, 15, 50 M_⊙ yr⁻¹ out to z ∼ 1, 2, 3) are >2.5–12.5× lower than compared to SFGs. This is consistent with the quiescence, as expected from their low unobscured SFRs, as inferred from modeling their ultraviolet-to-NIR photometry. The discrepancy between the L_IR derived from stacking Herschel and 24 μm indicates that IR-faint QGs have dust SEDs that are different from those of SFGs. For the most massive ($M_{\star <!--\; ???\; -->}⩾<!--\; ???\; -->{10}^{11}{M}_{\odot <!--\; ???\; -->}$) IR-faint QGs at z < 1.5, the stacked 1.4 GHz emission is in excess of that expected from other SFR indicators, suggesting a widespread presence of low-luminosity active galactic nuclei. Our results reaffirm the existence of a significant population of QGs out to z = 3, thus corroborating the need to quench star formation in galaxies at early epochs.

[en] We provide a coherent, uniform measurement of the evolution of the logarithmic star formation rate (SFR)–stellar mass (M _*) relation, called the main sequence (MS) of star-forming galaxies , for star-forming and all galaxies out to $z\sim <!--\; ???\; -->5$. We measure the MS using mean stacks of 3 GHz radio-continuum images to derive average SFRs for ∼ 200,000 mass-selected galaxies at z > 0.3 in the COSMOS field. We describe the MS relation by adopting a new model that incorporates a linear relation at low stellar mass (log(M _*/M _⊙) < 10) and a flattening at high stellar mass that becomes more prominent at low redshift (z < 1.5). We find that the SFR density peaks at 1.5 < z < 2, and at each epoch there is a characteristic stellar mass (M _* = 1–4 × 10¹⁰ M _⊙) that contributes the most to the overall SFR density. This characteristic mass increases with redshift, at least to z ∼ 2.5. We find no significant evidence for variations in the MS relation for galaxies in different environments traced by the galaxy number density at 0.3 < z < 3, nor for galaxies in X-ray groups at z ∼ 0.75. We confirm that massive bulge-dominated galaxies have lower SFRs than disk-dominated galaxies at a fixed stellar mass at z < 1.2. As a consequence, the increase in bulge-dominated galaxies in the local star-forming population leads to a flattening of the MS at high stellar masses. This indicates that “mass quenching” is linked with changes in the morphological composition of galaxies at a fixed stellar mass.