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Register a new userDynamical Structure of the Molecular Interstellar Medium in an Extremely Bright, Multiply Lensed z~3 Submillimeter Galaxy Discovered with Herschel
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We report the detection of CO 5-4, 3-2, and 1-0 emission in the strongly lensed, Herschel/SPIRE-selected submillimeter galaxy (SMG) HLSW-01 at z=2.9574+/-0.0001, using the Plateau de Bure Interferometer, the Combined Array for Research in Millimeter-wave Astronomy, and the Green Bank Telescope. The observations spatially resolve the molecular gas into four lensed images with a maximum separation of ~9, and reveal the internal gas dynamics in this system. We derive lensing-corrected CO line luminosities of L(CO 1-0) = (4.17+/-0.41), L(CO 3-2) = (3.96+/-0.20) and L(CO 5-4) = (3.45+/-0.20) x 10^10 (mu_L/10.9)^-1 Kkm/s pc^2, corresponding to luminosity ratios of r_31 = 0.95+/-0.10, r_53 = 0.87+/-0.06, and r_51 = 0.83+/-0.09. This suggests a total molecular gas mass of Mgas = 3.3 x 10^10 (alpha_CO/0.8) (mu_L/10.9)^-1 Msun. The gas mass, gas mass fraction, gas depletion timescale, star formation efficiency, and specific star formation rate are typical for an SMG. The velocity structure of the gas reservoir suggests that the brightest two lensed images are dynamically resolved projections of the same dust-obscured region in the galaxy that are kinematically offset from the unresolved fainter images. The resolved kinematics appear consistent with the complex velocity structure observed in major, `wet (i.e., gas-rich) mergers. Major mergers are commonly observed in SMGs, and are likely to be responsible for fueling their intense starbursts at high gas consumption rates. This study demonstrates the level of detail to which galaxies in the early universe can be studied by utilizing the increase in effective spatial resolution and sensitivity provided by gravitational lensing.
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Serendipitously we have discovered a rare, bright submillimeter galaxy (SMG) with a flux density of 30 +/- 2 mJy at lambda=1.2mm, using MAMBO2 at the IRAM 30-meter millimeter telescope. Although no optical counterpart is known for MM18423+5938, we were able to measure the redshift z=3.92960 +/- 0.00013 from the detection of CO lines using the IRAM Eight MIxer Receiver (EMIR). In addition, by collecting all available photometric data in the far-infrared and radio to constrain its spectral energy distribution, we derive the FIR luminosity 4.8 10^14/m Lsol and mass 6.0 10^9/m Msol for its dust, allowing for a magnification factor m caused by a probable gravitational lens. The corresponding star-formation rate is 8.3 10^4/m Msol/yr. The detection of three lines of the CO rotational ladder, and a significant upper limit for a fourth CO line, allow us to estimate an H2 mass of between 1.9 10^11/m Msol and 1.1 10^12/m Msol. The two lines CI(3p1-3p0) and CI(3p2-3p1) were clearly detected and yield a [CI]/[H2] number abundance between 1.4 10^-5 and 8.0 10^-5. Upper limits are presented for emission lines of HCN, HCO^+, HNC, H_2O and other molecules observed. The moderate excitation of the CO lines is indicative of an extended starburst, and excludes the dominance of an AGN in heating this high-redshift SMG.
We report the discovery of a bright ($f(250mum) > 400$ mJy), multiply-lensed submillimeter galaxy obj in {it Herschel}/SPIRE Science Demonstration Phase data from the HerMES project. Interferometric 880mum Submillimeter Array observations resolve at least four images with a large separation of $sim 9arcsec$. A high-resolution adaptive optics $K_p$ image with Keck/NIRC2 clearly shows strong lensing arcs. Follow-up spectroscopy gives a redshift of $z=2.9575$, and the lensing model gives a total magnification of $mu sim 11 pm 1$. The large image separation allows us to study the multi-wavelength spectral energy distribution (SED) of the lensed source unobscured by the central lensing mass. The far-IR/millimeter-wave SED is well described by a modified blackbody fit with an unusually warm dust temperature, $88 pm 3$ K. We derive a lensing-corrected total IR luminosity of $(1.43 pm 0.09) times 10^{13}, mathrm{L}_{odot}$, implying a star formation rate of $sim 2500, mathrm{M}_{odot}, mathrm{yr}^{-1}$. However, models primarily developed from brighter galaxies selected at longer wavelengths are a poor fit to the full optical-to-millimeter SED. A number of other strongly lensed systems have already been discovered in early {it Herschel} data, and many more are expected as additional data are collected.
During our Herschel Lensing Survey (HLS) of massive galaxy clusters, we have discovered an exceptionally bright source behind the z=0.22 cluster Abell 773, which appears to be a strongly lensed submillimeter galaxy (SMG) at z=5.2429. This source is unusual compared to most other lensed sources discovered by Herschel so far, because of its higher submm flux (sim 200mJy at 500micron) and its high redshift. The dominant lens is a foreground z=0.63 galaxy, not the cluster itself. The source has a far-infrared (FIR) luminosity of L_FIR= 1.1 10^{14}/mu Lo, where mu is the magnification factor, likely sim 11. We report here the redshift identification through CO lines with the IRAM-30m, and the analysis of the gas excitation, based on CO(7-6), CO(6-5), CO(5-4) detected at IRAM and the CO(2-1) at the EVLA. All lines decompose into a wide and strong red component, and a narrower and weaker blue component, 540kms apart. Assuming the ultraluminous galaxy (ULIRG) CO-to-H2 conversion ratio, the H2 mass is 5.8 10^{11}/mu Mo, of which one third is in a cool component. From the CI line we derive a CI/H2 number abundance of 6 10^{-5} similar to that in other ULIRGs. The H2O line is strong only in the red velocity component, with an intensity ratio I(H_2O)/I(CO) sim 0.5, suggesting a strong local FIR radiation field, possibly from an active nucleus (AGN) component. We detect the [NII]205mics line for the first time at high-z. It shows comparable blue and red components, with a strikingly broad blue one, suggesting strong ionized gas flows.
We present the observations of the starburst galaxy M82 taken with the Herschel SPIRE Fourier Transform Spectrometer. The spectrum (194-671 {mu}m) shows a prominent CO rotational ladder from J = 4-3 to 13-12 emitted by the central region of M82. The fundamental properties of the gas are well constrained by the high J lines observed for the first time. Radiative transfer modeling of these high-S/N 12CO and 13CO lines strongly indicates a very warm molecular gas component at ~500 K and pressure of ~3x10^6 K cm^-3, in good agreement with the H_2 rotational lines measurements from Spitzer and ISO. We suggest that this warm gas is heated by dissipation of turbulence in the interstellar medium (ISM) rather than X-rays or UV flux from the straburst. This paper illustrates the promise of the SPIRE FTS for the study of the ISM of nearby galaxies.
We report the very bright detection of cold molecular gas with the IRAM NOEMA interferometer of the strongly lensed source WISE J132934.18+224327.3 at z=2.04, the so-called Cosmic Eyebrow. This source has a similar spectral energy distribution from optical-mid/IR to submm/radio but significantly higher fluxes than the well-known lensed SMG SMMJ 2135, the Cosmic Eyelash at z=2.3. The interferometric observations identify unambiguously the location of the molecular line emission in two components, component CO32-A with I_CO(3-2)=52.2+-0.9 Jy km s^-1 and component CO32-B with I_CO(3-2)=15.7+-0.7 Jy km s^-1. Thus, our NOEMA observations of the CO(3-2) transition confirm the SMG-nature of WISE J132934.18+224327.3, resulting in the brightest CO(3-2) detection ever of a SMG. In addition, we present follow-up observations of the brighter component with the Green Bank Telescope (CO(1-0) transition) and IRAM 30m telescope (CO(4-3) and [CI](1-0) transitions). The star-formation efficiency of ~100 L_sun (K km s^-1 pc^2) is at the overlap region between merger-triggered and disk-like star-formation activity and the lowest seen for lensed dusty star-forming galaxies. The determined gas depletion time ~60~Myr, intrinsic infrared star-formation SFR_IR approx. 2000 M_sun yr^-1 and gas fraction M_mol/M_star=0.44 indicates a starburst/merger triggered star-formation. The obtained data of the cold ISM - from CO(1-0) and dust continuum - indicates a gas mass M_mol~15x10^11 M_sun for component CO32-A. Its unseen brightness offers the opportunity to establish the Cosmic Eyebrow as a new reference source at z=2 for galaxy evolution.
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