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Using the IRAM NOrthern Extended Millimeter Array (NOEMA), we conducted a program to measure redshifts for 13 bright galaxies detected in the Herschel Astrophysical Large Area Survey (H-ATLAS) with $S_{500{mu}rm m}ge$80 mJy. We report reliable spectroscopic redshifts for 12 individual sources, which are derived from scans of the 3 and 2 mm bands, covering up to 31 GHz in each band, and are based on the detection of at least two emission lines. The spectroscopic redshifts are in the range $2.08<z<4.05$ with a median value of $z=2.9pm$0.6. The sources are unresolved or barely resolved on scales of 10 kpc. In one field, two galaxies with different redshifts were detected. In two cases the sources are found to be binary galaxies with projected distances of ~140 kpc. The linewidths of the sources are large, with a mean value for the full width at half maximum of 700$pm$300 km/s and a median of 800 km/s. We analyse the nature of the sources with currently available ancillary data to determine if they are lensed or hyper-luminous $L_{rm FIR} > 10^{13},L_odot$ galaxies. We also present a reanalysis of the spectral energy distributions including the continuum flux densities measured at 3 and 2 mm to derive the overall properties of the sources. Future prospects based on these efficient measurements of redshifts of high-z galaxies using NOEMA are outlined, including a comprehensive survey of all the brightest Herschel galaxies.
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We report spectroscopic redshift measurements for three bright submillimeter galaxies (SMGs) near the GOODS-N field, each with SCUBA-2 850 micron fluxes > 10 mJy, using the Northern Extended Millimeter Array (NOEMA). Our molecular linescan observations of these sources, which occupy a ~7 arcmin$^2$ area outside of the HST coverage of the field, reveal that two lie at $z sim$ 3.14. In the remaining object, we detect line emission consistent with CO(7-6), [C I], and H2O at $z$ = 4.42. The far-infrared spectral energy distributions of these galaxies, constrained by SCUBA-2, NOEMA, and Herschel/SPIRE, indicate instantaneous SFRs $sim4000 ~{rm M_{odot}~yr^{-1}}$ in the $z$ = 4.42 galaxy and $sim 2500~{rm M_{odot}~yr^{-1}}$ in the two $z sim$ 3.14 galaxies. Based on our sources CO line luminosities, we estimate $M_{{rm gas}}sim10^{11} M_{odot}$ and find gas depletion timescales of $tau_{{rm depl}}sim 50$ Myr, consistent with findings in other high-redshift SMGs. Finally, we show that the two $z sim$ 3.14 sources, which alone occupy a volume $sim$10 Mpc$^3$, very likely mark the location of a protocluster of bright SMGs and less dusty optical sources.
We present Herschel-PACS observations of rest-frame mid-infrared and far-infrared spectral line emissions from two lensed, ultra-luminous infrared galaxies at high redshift: MIPS J142824.0+352619 (MIPS J1428), a starburst-dominated system at z = 1.3, and IRAS F10214+4724 (F10214), a source at z = 2.3 hosting both star-formation and a luminous AGN. We have detected [OI]63 micron and [OIII]52 micron in MIPS J1428, and tentatively [OIII]52 micron in F10214. Together with the recent ZEUS-CSO [CII]158 micron detection in MIPS J1428 we can for the first time combine [OI], [CII] and far-IR (FIR) continuum measurements for photo-dissociation (PDR) modeling of an ultra-luminous (L_IR > 10^12 L_sun) star forming galaxy at the peak epoch of cosmic star formation. We find that MIPS J1428, contrary to average local ULIRGs, does not show a deficit in [OI] relative to FIR. The combination of far-UV flux G_0 and gas density n (derived from the PDR models), as well as the star formation efficiency (derived from CO and FIR) is similar to normal or starburst galaxies, despite the high infrared luminosity of this system. In contrast, F10214 has stringent upper limits on [OIV] and [SIII], and an [OIII]/FIR ratio at least an order of magnitude lower than local starbursts or AGN, similar to local ULIRGs.
We present rest-frame optical spectra from the FMOS-COSMOS survey of twelve $z sim 1.6$ textit{Herschel} starburst galaxies, with Star Formation Rate (SFR) elevated by $times$8, on average, above the star-forming Main Sequence (MS). Comparing the H$alpha$ to IR luminosity ratio and the Balmer Decrement we find that the optically-thin regions of the sources contain on average only $sim 10$ percent of the total SFR whereas $sim90$ percent comes from an extremely obscured component which is revealed only by far-IR observations and is optically-thick even in H$alpha$. We measure the [NII]$_{6583}$/H$alpha$ ratio, suggesting that the less obscured regions have a metal content similar to that of the MS population at the same stellar masses and redshifts. However, our objects appear to be metal-rich outliers from the metallicity-SFR anticorrelation observed at fixed stellar mass for the MS population. The [SII]$_{6732}$/[SII]$_{6717}$ ratio from the average spectrum indicates an electron density $n_{rm e} sim 1,100 mathrm{cm}^{-3}$, larger than what estimated for MS galaxies but only at the 1.5$sigma$ level. Our results provide supporting evidence that high-$z$ MS outliers are the analogous of local ULIRGs, and are consistent with a major merger origin for the starburst event.
We present a survey of the molecular gas in 61 submillimetre galaxies (SMGs) selected from 870$mu$m continuum surveys of the COSMOS, UDS and ECDFS fields, using the Atacama Large Millimeter Array (ALMA) and the Northern Extended Millimeter Array (NOEMA). 46 $^{12}$CO ($J=$2-5) emission lines are detected in 45 of the targets at $z=$1.2-4.8, with redshifts indicating that those which are submillimetre bright and undetected/faint in the optical/near-infrared typically lie at higher redshifts, with a gradient of $Delta z/Delta S_{870}=$0.11$pm$0.04mJy$^{-1}$. We also supplement our data with literature sources to construct a statistical CO spectral line energy distribution and find the $^{12}$CO line luminosities in SMGs peak at $J_{rm up}sim$6, consistent with the Cosmic Eyelash, among similar studies. Our SMGs lie mostly on or just above the main sequence, displaying a decrease in their gas depletion timescales $t_{rm dep} = M_{rm gas}/{rm SFR}$ with redshift in the range $zsim$1-5 and a median of 200$pm$50Myr at $zsim$2.8. This coincides with an increase in molecular gas fraction $mu_{rm gas} = M_{rm gas}/M_ast$ across the same redshift range. Finally we demonstrate that the $M_{rm baryon}$-$sigma$ distribution of our SMGs is consistent with that followed by early-type galaxies in the Coma cluster, providing strong support to the suggestion that SMGs are progenitors of massive local spheroidal galaxies. On the basis of this we suggest that the SMG populations above and below an 870-$mu$m flux limit of $S_{870}sim$5mJy may correspond to the division between slow- and fast-rotators seen in local early-type galaxies.
The extreme infrared (IR) luminosity of local luminous and ultra-luminous IR galaxies (U/LIRGs; 11 < log LIR /Lsun < 12 and log LIR /Lsun > 12, respectively) is mainly powered by star-formation processes triggered by mergers or interactions. While U/LIRGs are rare locally, at z > 1, they become more common, they dominate the star-formation rate (SFR) density, and a fraction of them are found to be normal disk galaxies. Therefore, there must be an evolution of the mechanism triggering these intense starbursts with redshift. To investigate this evolution, we present new optical SWIFT integral field spectroscopic H{alpha}+[NII] observations of a sample of 9 intermediate-z (0.2 < z < 0.4) U/LIRG systems selected from Herschel 250{mu}m observations. The main results are the following: (a) the ratios between the velocity dispersion and the rotation curve amplitude indicate that 10-25% (1-2 out of 8) might be compatible with being isolated disks while the remaining objects are interacting/merging systems; (b) the ratio between un-obscured and obscured SFR traced by H{alpha} and LIR, respectively, is similar in both local and these intermediate-z U/LIRGs; and (c) the ratio between 250{mu}m and the total IR luminosities of these intermediate-z U/LIRGs is higher than that of local U/LIRGs with the same LIR . This indicates a reduced dust temperature in these intermediate-z U/LIRGs. This, together with their already measured enhanced molecular gas content, suggests that the interstellar medium conditions are different in our sample of intermediate-z galaxies when compared to local U/LIRGs.
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