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We report matched resolution imaging spectroscopy of the CO 3-2 line (with the IRAM Plateau de Bure millimeter interferometer) and of the Hα line (with LUCI at the Large Binocular Telescope) in the massive z = 1.53 mainsequence galaxy EGS 13011166, as part of the "Plateau de Bure high-z, blue-sequence survey" (PHIBSS: Tacconi et al.). We combine these data with Hubble Space Telescope V-I-J-H-band maps to derive spatially resolved distributions of stellar surface density, star formation rate, molecular gas surface density, optical extinction, and gas kinematics. The spatial distribution and kinematics of the ionized and molecular gas are remarkably similar and are well modeled by a turbulent, globally Toomre unstable, rotating disk. The stellar surface density distribution is smoother than the clumpy rest-frame UV/optical light distribution and peaks in an obscured, star-forming massive bulge near the dynamical center. The molecular gas surface density and the effective optical screen extinction track each other and are well modeled by a "mixed" extinction model. The inferred slope of the spatially resolved molecular gas to star formation rate relation, N = dlog Σstar form/dlog Σmol gas, depends strongly on the adopted extinction model, and can vary from 0.8 to 1.7. For the preferred mixed dust-gas model, we find N = 1.14 ± 0.1. [ABSTRACT FROM AUTHOR]

We use a combination of new NOrthern Extended Millimeter Array (NOEMA) observations of the pair of [CI] transitions, the CO(7-6) line, and the dust continuum, in addition to ancillary CO(1-0) and CO(3-2) data, to study the molecular gas properties of Q1700-MD94. This is a massive, main-sequence galaxy at z ≈ 2. We find that for a reasonable set of assumptions for a typical massive star-forming galaxy, the CO(1-0), the [CI](1-0) and the dust continuum yield molecular gas masses that are consistent within a factor of ∼2. The global excitation properties of the molecular gas as traced by the [CI] and CO transitions are similar to those observed in other massive star-forming galaxies at z ∼ 2. Our large velocity gradient modeling using RADEX of the CO and [CI] spectral line energy distributions suggests the presence of relatively warm (Tkin = 41 K), dense (nH2 = 8 × 103 cm−3) molecular gas, comparable to the high-excitation molecular gas component observed in main-sequence star-forming galaxies at z ∼ 1. The galaxy size in the CO(1-0) and CO(7-6) line emission is comparable, which suggests that the highly excited molecular gas is distributed throughout the disk, powered by intense star formation activity. A confirmation of this scenario will require spatially resolved observations of the CO and [CI] lines, which can now be obtained with NOEMA upgraded capabilities. [ABSTRACT FROM AUTHOR]

We study the properties of luminous stellar "clumps" identified in deep, high-resolution Hubble Space Telescope NIC2/FI60W imaging at 1.6µm of six z ~ 2 star-forming galaxies with existing near-infrared integral field spectroscopy from SINFONI at the Very Large Telescope. Individual clumps contribute ~0.5%-15% of the galaxy-integrated rest-frame ≈5000Å emission, with median of ≈2%; the total contribution of clump light ranges from 10% to 25%. The median intrinsic clump size and stellar mass are ~ 1 kpc and ~ 109 M⊙, in the ranges for clumps identified in rest-UV or line emission in other studies. The clump sizes and masses in the subset of disks are broadly consistent with expectations for clump formation through gravitational instabilities in gas-rich, turbulent disks given the host galaxies' global properties. By combining the NIC2 data with Advanced Camera for Surveys (ACS)/F814W imaging available for one source, and adaptive-optics-assisted SINFONI Hot data for another, we infer modest color, M/L, and stellar age variations within each galaxy. In these two objects, sets of clumps identified at different wavelengths do not fully overlap; NIC2-identified clumps tend to be redder/older than ACS- or Hα-identified clumps without rest-frame optical counterparts. There is evidence for a systematic trend of older ages at smaller galactocentric radii among the clumps, consistent with scenarios where inward migration of clumps transports material toward the central regions. From constraints on a bulge-like component at radii ≼ 1-3 kpc, none of the five disks in our sample appears to contain a compact massive stellar core, and we do not discern a trend of bulge stellar mass fraction with stellar age of the galaxy. Further observations are necessary to probe the buildup of stellar bulges and the role of clumps in this process. [ABSTRACT FROM AUTHOR]

Following the success of the Plateau de Bure high-z Blue Sequence Survey (PHIBSS), we present the PHIBSS2 legacy program, a survey of the molecular gas properties of star-forming galaxies on and around the star-formation main sequence (MS) at different redshifts using IRAM's NOrthern Extended Millimeter Array (NOEMA). This survey significantly extends the existing sample of star-forming galaxies with CO molecular gas measurements, probing the peak epoch of star formation (z = 1 − 1.6) as well as its building-up (z = 2 − 3) and winding-down (z = 0.5 − 0.8) phases. The targets are drawn from the well-studied GOODS, COSMOS, and AEGIS cosmological deep fields and uniformly sample the MS in the stellar mass (M⋆) – star formation rate (SFR) plane with log(M⋆/M⊙) = 10 − 11.8 and SFR = 3.5 − 500 M⊙ yr−1 without morphological selection, thus providing a statistically meaningful census of star-forming galaxies at different epochs. We describe the survey strategy and sample selection before focusing on the results obtained at redshift z = 0.5 − 0.8, where we report 60 CO(2-1) detections out of 61 targets. We determine molecular gas masses between 2 × 109 and 5 × 1010 M⊙ and separately obtain disc sizes and bulge-to-total (B/T) luminosity ratios from HST I-band images. The median molecular gas-to-stellar mass ratio μgas∼ = 0.28 ± 0.04 μ gas ∼ = 0.28 ± 0.04 $ \widetilde{\mu_{\mathrm{gas}}} = 0.28 \pm 0.04 $ , gas fraction fgas∼ = 0.22 ± 0.02 f gas ∼ = 0.22 ± 0.02 $ \widetilde{f_{\mathrm{gas}}} = 0.22 \pm 0.02 $ , and depletion time t depl ∼ = 0.84 ± 0.07 Gyr $ \widetilde{t_{\mathrm{depl}}} = 0.84 \pm 0.07\,\mathrm{Gyr} $ as well as their dependence with stellar mass and offset from the MS follow published scaling relations for a much larger sample of galaxies spanning a significantly wider range of redshifts, the cosmic evolution of the SFR being mainly driven by that of the molecular gas fraction. The galaxy-averaged molecular Kennicutt–Schmidt (KS) relation between molecular gas and SFR surface densities is strikingly linear, pointing towards similar star formation timescales within galaxies at any given epoch. In terms of morphology, the molecular gas content, the SFR, the disc stellar mass, and the disc molecular gas fraction do not seem to correlate with B/T and the stellar surface density, which suggests an ongoing supply of fresh molecular gas to compensate for the build-up of the bulge. Our measurements do not yield any significant variation of the depletion time with B/T and hence no strong evidence for morphological quenching within the scatter of the MS. [ABSTRACT FROM AUTHOR]

We present Herschel PACS observations of the [C II] 158 μm emission line in a sample of 24 intermediate mass (9 < logM*/M☉ < 10) and low metallicity (0.4 < Z/Z☉ < 1.0) galaxies from the xCOLD GASS survey. In combination with IRAM CO(1-0) measurements, we establish scaling relations between integrated and molecular region L[C II]/LCO(1-0) ratios as a function of integrated galaxy properties. A Bayesian analysis reveals that only two parameters, metallicity and offset from the main sequence, Δ(MS), are needed to quantify variations in the luminosity ratio; metallicity describes the total dust content available to shield CO from UV radiation, while Δ(MS) describes the strength of this radiation field. We connect the L[C II]/LCO(1-0) ratio to the CO-to-H2 conversion factor and find a multivariate conversion function, which can be used up to z ~ 2.5. This function depends primarily on metallicity, with a second-order dependence on Δ(MS). We apply this to the full xCOLD GASS and PHIBSS1 surveys and investigate molecular gas scaling relations. We find a flattening of the relation between gas mass fraction and stellar mass at logM* < 10.0. While the molecular gas depletion time varies with sSFR, it is mostly independent of mass, indicating that the low LCO/SFR ratios long observed in low-mass galaxies are entirely due to photodissociation of CO and not to an enhanced star formation efficiency. [ABSTRACT FROM AUTHOR]

In this work we analyse the physical properties of a sample of 56 spectroscopically selected star-forming (SF) Lyα emitting galaxies at 2.0 ≲ z ≲ 3.5 using both a spectral energy distribution (SED) fitting procedure from rest-frame UV to mid-IR and direct 160 μm FIR observations taken with the Photodetector Array Camera and Spectrometer (PACS) instrument onboard the Herschel Space Observatory. We define LAEs as those Lyα-emitting galaxies whose rest-frame Lyα equivalent widths (LyαEWrest-frame) are above 20Å, the typical threshold in narrow-band searches. Lyα-emitting galaxies with LyαEWrest-frame < 20Å are called non-LAEs. As a result of an individual SED fit for each object, we find that the studied sample of LAEs contains galaxies with ages mostly below 100 Myr and a wide variety of dust attenuations, SFRs, and stellar masses. The heterogeneity of the physical properties is also seen in the morphology, ranging from bulge-like galaxies to highly clumpy systems. In this way, we find that LAEs at 2.0 ≲ z ≲ 3.5 are very diverse, and do not have a bimodal nature, as suggested in previous studies. Furthermore, the main difference between LAEs and non-LAEs is their dust attenuation, because LAEs are not as dusty as non-LAEs. On the FIR side, four galaxies of the sample (two LAEs and two non-LAEs) have PACS detections. Their total IR luminosities place all of them in the ULIRG regime, and all are dusty objects, with A1200 ≳ 4mag. This is an indication from direct FIR measurements that dust and Lyα emission are not mutually exclusive. This population of red and dusty LAEs is not seen at z ∼ 0.3, which suggests an evolution with redshift of the IR nature of galaxies selected via their Lyα emission. [ABSTRACT FROM AUTHOR]

We present high spatial resolution (0.4 arcsec, kpc) Plateau de Bure Interferometer interferometric data on three ultraluminous infrared galaxies (ULIRGs) at : two submillimetre galaxies (SMGs) and one submillimetre faint star-forming radio galaxy. The three galaxies have been robustly detected in CO rotational transitions, either CO ( = 4 3) or CO ( = 3 2), allowing their sizes and gas masses to be accurately constrained. These are the highest spatial resolution observations observed to date (by a factor of 2) for intermediate-excitation CO emission in ULIRGs. The galaxies appear extended over several resolution elements, having a mean radius of 3.7 kpc. High-resolution (0.3 arcsec) combined Multi-Element Radio-Linked Interferometer Network-Very Large Array observations of their radio continua allow an analysis of the star formation behaviour of these galaxies, on comparable spatial scales to those of the CO observations. This ‘matched beam’ approach sheds light on the spatial distribution of both molecular gas and star formation, and we can therefore calculate accurate star formation rates and gas surface densities: this allows us to place the three systems in the context of a Kennicutt–Schmidt (KS)-style star formation law. We find a difference in size between the CO and radio emission regions, and as such we suggest that using the spatial extent of the CO emission region to estimate the surface density of star formation may lead to error. This size difference also causes the star formation efficiencies within systems to vary by up to a factor of 5. We also find, with our new accurate sizes, that SMGs lie significantly above the KS relation, indicating that stars are formed more efficiently in these extreme systems than in other high- star-forming galaxies. [ABSTRACT FROM AUTHOR]

Using the IRAM Plateau de Bure Interferometer (PdBI) we have searched for the upper fine structure line of neutral carbon [ ] and towards the submillimetre galaxies (SMGs) GN 20 (SMM J123711.9+622212, ) and GN 20.2 (SMM J123708.8+622202, ). The far-infrared continuum is detected at 8σ significance in GN 20, with a flux density of , while no continuum is detected in GN 20.2. Both sources are statistically undetected in both and lines; we derive line luminosity limits for both C i and CO of . Assuming carbon excitation temperatures of (the galaxies' measured dust temperatures), we infer C i mass limits of (GN 20) and . The derived C i abundance limits are for GN 20 and for GN 20.2, implying that the systems have Milky Way level carbon enrichment ( X[C i]/ X[H2]) or lower, similar to high-redshift carbon-detected systems (at ) but about 50 times less than the carbon enrichment of local starburst galaxies. Observations of GN 20 and GN 20.2 in high-resolution MERLIN+VLA (Multi-Element Radio Linked Interferometer Network+Very Large Array) radio maps of GOODS-N (Great Observatories Origin Deep Survey-North) are used to further constrain the sizes and locations of active regions. We conclude that the physical gas properties of young rapidly evolving systems like GN 20 and GN 20.2 are likely significantly different than starburst/ULIRG (ultraluminous infrared galaxy) environments in the local Universe yet similar to SMGs. Unless gravitationally amplified examples can be found, observations of galaxies like GN 20 will require the order of magnitude increase in sensitivity of the Atacama Large Millimetre Array (ALMA) to constrain their C i and high- J CO content, despite the fact that they are the brightest systems at . [ABSTRACT FROM AUTHOR]