Enhanced [CII] emission in a z=4.76 submillimetre galaxy

We present the detection of bright [CII] emission in the z=4.76 submillimetre galaxy LESS J033229.4-275619 using the Atacama Pathfinder EXperiment. This represents the highest redshift [CII] detection in a submm selected, star-formation dominated system. The AGN contributions to the [CII] and far-infrared (FIR) luminosities are small. We find an atomic mass derived from [CII] comparable to the molecular mass derived from CO. The ratio of the [CII], CO and FIR luminosities imply a radiation field strength G_0~10^3 and a density ~10^4 cm^-3 in a kpc-scale starburst, as seen in local and high redshift starbursts. The high L_[CII]/L_FIR=2.4x10^-3 and the very high L_[CII]/L_CO(1-0) ~ 10^4 are reminiscent of low metallicity dwarf galaxies, suggesting that the highest redshift star-forming galaxies may also be characterised by lower metallicities. We discuss the implications of a reduced metallicity on studies of the gas reservoirs, and conclude that especially at very high redshift, [CII] may be a more powerful and reliable tracer of the interstellar matter than CO.Comment: 5 pages, 2 figures; accepted for publication in Astronomy & Astrophysics Letter

Constraining the Thermal Dust Content of Lyman-Break Galaxies in an Overdense Field at z~5

We have carried out 870 micron observations in the J1040.7-1155 field, known to host an overdensity of Lyman break galaxies at z=5.16 +/- 0.05. We do not detect any individual source at the S(870)=3.0 mJy/beam (2 sigma) level. A stack of nine spectroscopically confirmed z>5 galaxies also yields a non-detection, constraining the submillimeter flux from a typical galaxy at this redshift to S(870)<0.85 mJy, which corresponds to a mass limit M(dust)<1.2x10^8 M_sun (2 sigma). This constrains the mass of thermal dust in distant Lyman break galaxies to less than one tenth of their typical stellar mass. We see no evidence for strong submillimeter galaxies associated with the ultraviolet-selected galaxy overdensity, but cannot rule out the presence of fainter, less massive sources.Comment: 5 pages, 2 figures. MNRAS in pres

The shortwave infrared bands response to stomatal conductance in Conference" Pear Trees (Pyrus communis L.)"

Published: 8 October 201

Limits on dust emission from z~5 LBGs and their local environments

We present 1.2mm MAMBO-2 observations of a field which is over-dense in Lyman Break Galaxies (LBGs) at z~5. The field includes seven spectroscopically-confirmed LBGs contained within a narrow (z=4.95+/-0.08) redshift range and an eighth at z=5.2. We do not detect any individual source to a limit of 1.6 mJy/beam (2*rms). When stacking the flux from the positions of all eight galaxies, we obtain a limit to the average 1.2 mm flux of these sources of 0.6mJy/beam. This limit is consistent with FIR imaging in other fields which are over-dense in UV-bright galaxies at z~5. Independently and combined, these limits constrain the FIR luminosity (8-1000 micron) to a typical z~5 LBG of LFIR<~3x10^11 Lsun, implying a dust mass of Mdust<~10^8 Msun (both assuming a grey body at 30K). This LFIR limit is an order of magnitude fainter than the LFIR of lower redshift sub-mm sources (z~1-3). We see no emission from any other sources within the field at the above level. While this is not unexpected given millimetre source counts, the clustered LBGs trace significantly over-dense large scale structure in the field at z = 4.95. The lack of any such detection in either this or the previous work, implies that massive, obscured star-forming galaxies may not always trace the same structures as over-densities of LBGs, at least on the length scale probed here. We briefly discuss the implications of these results for future observations with ALMA.Comment: 10 pages, 6 figures, MNRAS Accepte

New CO detections of lensed submillimeter galaxies in A2218: Probing molecular gas in the LIRG regime at high redshift

Context: Submillimeter galaxies (SMGs) are distant, dusty galaxies undergoing star formation at prodigious rates. Recently there has been major progress in understanding the nature of the bright SMGs (i.e. S(850um)>5mJy). The samples for the fainter SMGs are small and are currently in a phase of being built up through identification studies. Aims: We study the molecular gas content in two SMGs, SMMJ163555 and SMMJ163541, at z=1.034 and z=3.187 with unlensed submm fluxes of 0.4mJy and 6.0mJy. Both SMGs are gravitationally lensed by the foreground cluster A2218. Methods: IRAM Plateau de Bure Interferometry observations at 3mm were obtained for the lines CO(2-1) for SMMJ163555 and CO(3-2) for SMMJ163541. Additionally we obtained CO(4-3) for the candidate z=4.048 SMMJ163556 with an unlensed submm flux of 2.7mJy. Results: CO(2-1) was detected for SMMJ163555 at z=1.0313 with an integrated line intensity of 1.2+-0.2Jy km/s and a line width of 410+-120 km/s. From this a gas mass of 1.6x10^9 Msun is derived and a star formation efficiency of 440Lsun/Msun is estimated. CO(3-2) was detected for SMMJ163541 at z=3.1824, possibly with a second component at z=3.1883, with an integrated line intensity of 1.0+-0.1 Jy km/s and a line width of 280+-50 km/s. From this a gas mass of 2.2x10^10 Msun is derived and a star formation efficiency of 1000 Lsun/Msun is estimated. For SMMJ163556 the CO(4-3) is undetected within the redshift range 4.035-4.082 down to a sensitivity of 0.15 Jy km/s. Conclusions: Our CO line observations confirm the optical redshifts for SMMJ163555 and SMMJ163541. The CO line luminosity L'_CO for both galaxies is consistent with the L_FIR-L'_CO relation. SMMJ163555 has the lowest FIR luminosity of all SMGs with a known redshift and is one of the few high redshift LIRGs whose properties can be estimated prior to ALMA.Comment: 7 pages, 4 figures. A&A in pres

ALMA reveals a chemically evolved submillimeter galaxy at z=4.76

The chemical properties of high-z galaxies provide important information to constrain galaxy evolutionary scenarios. However, widely-used metallicity diagnostics based on rest-frame optical emission lines are not usable for heavily dust-enshrouded galaxies (such as Sub-Millimeter Galaxies; SMGs), especially at z>3. Here we focus on the flux ratio of the far-infrared fine-structure emission lines [NII]205um and [CII]158um to assess the metallicity of high-z SMGs. Through ALMA cycle 0 observations, we have detected the [NII]205um emission in a strongly [CII]-emitting SMG, LESS J033229.4-275619 at z=4.76. The velocity-integrated [NII]/[CII] flux ratio is 0.043 +/- 0.008. This is the first measurement of the [NII]/[CII] flux ratio in high-z galaxies, and the inferred flux ratio is similar to the ratio observed in the nearby universe (~0.02-0.07). The velocity-integrated flux ratio and photoionization models suggest that the metallicity in this SMG is consistent with solar, implying the chemical evolution has progressed very rapidly in this system at z=4.76. We also obtain a tight upper limit on the CO(12-11) transition, which translates into CO(12-11)/CO(2-1) <3.8 (3 sigma). This suggests that the molecular gas clouds in LESS J033229.4-275619 are not affected significantly by the radiation field emitted by the AGN in this system.Comment: 5 pages, 3 figures, accepted for publication in Astronomy and Astrophysics Letter

Origins of the extragalactic background at 1mm from a combined analysis of the AzTEC and MAMBO data in GOODS-N

We present a study of the cosmic infrared background, which is a measure of the dust obscured activity in all galaxies in the Universe. We venture to isolate the galaxies responsible for the background at 1mm; with spectroscopic and photometric redshifts we constrain the redshift distribution of these galaxies. We create a deep 1.16mm map (sigma ~ 0.5mJy) by combining the AzTEC 1.1mm and MAMBO 1.2mm datasets in GOODS-N. This combined map contains 41 secure detections, 13 of which are new. By averaging the 1.16mm flux densities of individually undetected galaxies with 24um flux densities > 25uJy, we resolve 31--45 per cent of the 1.16mm background. Repeating our analysis on the SCUBA 850um map, we resolve a higher percentage (40--64 per cent) of the 850um background. A majority of the background resolved (attributed to individual galaxies) at both wavelengths comes from galaxies at z > 1.3. If the ratio of the resolved submillimeter to millimeter background is applied to a reasonable scenario for the origins of the unresolved submillimeter background, 60--88 per cent of the total 1.16mm background comes from galaxies at z > 1.3.Comment: 12 pages, 10 figures. Accepted by MNRAS. The combined map is publicly available at http://www.astro.umass.edu/~pope/goodsn_mm

A continuous isotropic-nematic liquid crystalline transition of F-actin solutions

The phase transition from the isotropic (I) to nematic (N) liquid crystalline suspension of F-actin of average length $3~\mu$m or above was studied by local measurements of optical birefringence and protein concentration. Both parameters were detected to be continuous in the transition region, suggesting that the I-N transition is higher than 1st order. This finding is consistent with a recent theory by Lammert, Rokhsar & Toner (PRL, 1993, 70:1650), predicting that the I-N transition may become continuous due to suppression of disclinations. Indeed, few line defects occur in the aligned phase of F-actin. Individual filaments in solutions of a few mg/ml F-actin undergo fast translational diffusion along the filament axis, whereas both lateral and rotational diffusions are suppressed.Comment: 4 pages with 4 figures. Submitted to Physical Review Letter