We report 250 GHz (1.2 mm) observations of a sample of 20 QSOs at redshifts 5.8<z<6.5 from the the Canada-France High-z Quasar Survey (CFHQS), using the Max-Planck Millimeter Bolometer (MAMBO) array at the IRAM 30-metre telescope. A rms sensitivity <
~ 0.6 mJy was achieved for 65% of the sample, and <~ 1.0 mJy for 90%. Only one QSO, CFHQS J142952+544717, was robustly detected with S_250GHz = 3.46 +/-0.52 mJy. This indicates that one of the most powerful known starbursts at z~6 is associated with this radio loud QSO. On average, the other CFHQS QSOs, which have a mean optical magnitude fainter than previously studied SDSS samples of z~6 QSOs, have a mean 1.2 mm flux density <S_250GHz> = 0.41 +/-0.14 mJy; such a 2.9-sigma average detection is hardly meaningful. It would correspond to <L_FIR> ~ 0.94+/-0.32 10^12 Lo, and an average star formation rate of a few 100s Mo/yr, depending on the IMF and a possible AGN contribution to <L_FIR>. This is consistent with previous findings of Wang et al. (2011) on the far-infrared emission of z~6 QSOs and extends them toward optically fainter sources.
Using IRAM PdBI we report the detection of H2O in six new lensed ultra-luminous starburst galaxies at high redshift, discovered in the Herschel H-ATLAS survey. The sources are detected either in the 2_{02}-1_{11} or 2_{11}-2_{02} H_2O emission lines
with integrated line fluxes ranging from 1.8 to 14 Jy.km/s. The corresponding apparent luminosities are mu x L_H2O ~ 3-12 x 10^8 Lo, where mu is the lensing magnification factor (3 < mu < 12). These results confirm that H2O lines are among the strongest molecular lines in such galaxies, with intensities almost comparable to those of the high-J CO lines, and same profiles and line widths (200-900 km/s) as the latter. With the current sensitivity of PdBI, H2O can therefore easily be detected in high-z lensed galaxies (with F(500um) > 100 mJy) discovered in the Herschel surveys. Correcting the luminosities for lensing amplification, L_H2O is found to have a strong dependence on the IR luminosity, varying as ~L_IR^{1.2}. This relation which needs to be confirmed with better statistics, may indicate a role of radiative (IR) excitation of the H2O lines, and implies that high-z galaxies with L_IR >~ 10^13 Lo tend to be very strong emitters in H2O, that have no equivalent in the local universe.
The Herschel survey, H-ATLAS, with its large areal coverage, has recently discovered a number of bright, strongly lensed high-z submillimeter galaxies. The strong magnification makes it possible to study molecular species other than CO, which are oth
erwise difficult to observe in high-z galaxies. Among the lensed galaxies already identified by H-ATLAS, the source J090302.9-014127B (SDP.17b) at z = 2.305 is remarkable due to its excitation conditions and a tentative detection of the H2O 202-111 emission line (Lupu et al. 2010). We report observations of this line in SDP.17b using the IRAM interferometer equipped with its new 277- 371GHz receivers. The H2O line is detected at a redshift of z = 2.3049+/-0.0006, with a flux of 7.8+/-0.5 Jy km s-1 and a FWHM of 250+/-60 km s-1. The new flux is 2.4 times weaker than the previous tentative detection, although both remain marginally consistent within 1.6-sigma. The intrinsic line luminosity and ratio of H2O(202-111)/CO8-7 seem comparable with those of the nearby starburst/enshrouded-AGN Mrk 231, suggesting that SDP.17b could also host a luminous AGN. The detection of a strong H2O 202-111 line in SDP.17b implies an efficient excitation mechanism of the water levels that must occur in very dense and warm interstellar gas.
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.
Nuclear and starburst activity are known to often occur concomitantly. Herschel-SPIRE provides sampling of the FIR SEDs of type 1 and type 2 AGN, allowing for the separation between the hot dust (torus) and cold dust (starburst) emission. We study la
rge samples of spectroscopically confirmed type 1 and type 2 AGN lying within the Herschel Multi-tiered Extragalactic Survey (HerMES) fields observed during the science demonstration phase, aiming to understand their FIR colour distributions and constrain their starburst contributions. We find that one third of the spectroscopically confirmed AGN in the HerMES fields have 5-sigma detections at 250um, in agreement with previous (sub)mm AGN studies. Their combined Spitzer-MIPS and Herschel-SPIRE colours - specifically S(250)/S(70) vs. S(70)/S(24) - quite clearly separate them from the non-AGN, star-forming galaxy population, as their 24-um flux is dominated by the hot torus emission. However, their SPIRE colours alone do not differ from those of non-AGN galaxies. SED fitting shows that all those AGN need a starburst component to fully account for their FIR emission. For objects at z > 2, we find a correlation between the infrared luminosity attributed to the starburst component, L(SB), and the AGN accretion luminosity, L(acc), with L(SB) propto L(acc)^0.35. Type 2 AGN detected at 250um show on average higher L(SB) than type 1 objects but their number is still too low to establish whether this trend indicates stronger star-formation activity.
We present millimetre observations of a sample of 12 high redshift ultraluminous infrared galaxies (ULIRGs) in the Extended Growth Strip (EGS). These objects were initially selected on the basis of their observed mid--IR colours (0.0 < [3.6]-[4.5] <
0.4 and -0.7 < [3.6]-[8.0] < 0.5) to lie at high redshift 1.5 < z < 3, and subsequent 20-38 micron mid-IR spectroscopy confirms that they lie in a narrow redshift window centered on z=2. We detect 9/12 of the objects in our sample at high significance (>3 sigma) with a mean 1200micron flux of <F_1200> = 1.6+/-0.1 mJy. Our millimetre photometry, combined with existing far-IR photometry from the Far-IR Deep Extragalactic Legacy (FIDEL) Survey and accurate spectroscopic redshifts, places constraints both sides of the thermal dust peak. This allows us to estimate the dust properties, including the far--IR luminosity, dust temperature, and dust mass. We find that our sample is similar to other high-z and intermediate-z ULIRGs, and local systems, but has a different dust selection function than submillimeter-selected galaxies. Finally, we use existing 20cm radio continuum imaging to test the far-IR/radio correlation at high redshift. We find that our sample is consistent with the local relation, implying little evolution. Furthermore, this suggests that our sample selection method is efficient at identifying ultraluminous, starburst--dominated systems within a very narrow redshift range centered at z~2.
We report the discovery of two sources at z=3.867 and z=3.427 that exhibit powerful starburst and AGN activities. They benefit from data from radio to X rays from the CFHTLS-D1/SWIRE/XMDS surveys. Follow-up optical and near-infrared spectroscopy, and
millimeter IRAM/MAMBO observations are also available. We performed an analysis of their spectral energy distributions to understand the origin of their emission and constrain their luminosities. A comparison with other composite systems at similar redshifts from the literature is also presented. The AGN and starburst bolometric luminosities are ~10^13 Lsun. The AGN emission dominates at X ray, optical, mid-infrared wavelengths, and probably in the radio. The starburst emission dominates in the far-infrared. The estimated star formation rates range from 500 to 3000Msun/yr. The AGN near-infrared and X ray emissions are heavily obscured in both sources with an estimated dust extinction Av>4, and Compton-thick gas column densities. The two sources are the most obscured and most luminous AGNs detected at millimeter wavelengths currently known. The sources presented in this work are heavily obscured QSOs, but their properties are not fully explained by the standard AGN unification model. In one source, the ultraviolet and optical spectra suggest the presence of outflowing gas and shocks, and both sources show emission from hot dust, most likely in the vicinity of the nucleus. Evidence of moderate AGN-driven radio activity is found in both sources. The two sources lie on the local M_BH-M_bulge relation. To remain on this relation, their star formation rate has to decrease. Our results support evolutionary models that invoke radio feedback as star formation quenching mechanism, and suggest that such a mechanism might play a major role also in powerful AGNs.
We report on--off pointed MAMBO observations at 1.2 mm of 61 Spitzer-selected star-forming galaxies from the SWIRE survey. The sources are selected on the basis of bright 24um fluxes (f_24um>0.4mJy) and of stellar dominated near-infrared spectral ene
rgy distributions in order to favor z~2 starburst galaxies. The average 1.2mm flux for the whole sample is 1.5+/-0.2 mJy. Our analysis focuses on 29 sources in the Lockman Hole field where the average 1.2mm flux (1.9+/-0.3 mJy) is higher than in other fields (1.1+/-0.2 mJy). The analysis of the sources multi-wavelength spectral energy distributions indicates that they are starburst galaxies with far-infrared luminosities ~10^12-10^13.3 Lsun, and stellar masses of ~0.2-6 x10^11 M_sun. Compared to sub-millimeter selected galaxies (SMGs), the SWIRE-MAMBO sources are among those with the largest 24um/millimeter flux ratios. The origin of such large ratios is investigated by comparing the average mid-infrared spectra and the stacked far-infrared spectral energy distributions of the SWIRE-MAMBO sources and of SMGs. The mid-infrared spectra exhibit strong PAH features, and a warm dust continuum. The warm dust continuum contributes to ~34% of the mid-infrared emission, and is likely associated with an AGN component. This constribution is consistent with what is found in SMGs. The large 24um/1.2mm flux ratios are thus not due to AGN emission, but rather to enhanced PAH emission compared to SMGs. The analysis of the stacked far-infrared fluxes yields warmer dust temperatures than typically observed in SMGs. Our selection favors warm ultra-luminous infrared sources at high-z, a class of objects that is rarely found in SMG samples. Our sample is the largest Spitzer-selected sample detected at millimeter wavelengths currently available.
We aim to identify the stellar populations (mostly red giants and young stars) detected in the ISOGAL survey at 7 and 15micron towards a field (LN45) in the direction l=-45, b=0.0. The sources detected in the survey of the Galactic plane by the Infra
red Space Observatory are characterized based on colour-colour and colour-magnitude diagrams. We combine the ISOGAL catalog with the data from surveys such as 2MASS and GLIMPSE. Interstellar extinction and distance are estimated using the red clump stars detected by 2MASS in combination with the isochrones for the AGB/RGB branch. Absolute magnitudes are thus derived and the stellar populations are identified based on their absolute magnitudes and their infrared excess. A standard approach to the analysis of ISOGAL disk observations has been established. We identify several hundred RGB/AGB stars and 22 candidate young stellar objects in the direction of this field in an area of 0.16 deg^2. An over-density of stellar sources is found at distances corresponding to the distance of the Scutum-Crux spiral arm. In addition, we determine mass-loss rates of AGB-stars using dust radiative transfer models from the literature.
We present observations aimed at exploring both the nature of Lya emitting nebulae (Lya blobs) at z=2.38 and the way they trace large scale structure (LSS), by exploring their proximity to maximum starbursts through submillimeter emission. Our most i
mportant objectives are to make a census of associated submillimeter galaxies (SMGs), check their properties, and look for a possible overdensity in the protocluster J2142-4426 at z=2.38. We used the newly commissioned Large APEX Bolometer Camera (LABoCa) on the Atacama Pathfinder EXperiment (APEX) telescope, in its Science Verification phase, to carry out a deep 10x10 map at 870 micron, and we performed multiple checks of the quality of data processing and source extraction. Our map, the first published deep image, confirms the capabilities of APEX/LABoCa as the most efficient current equipment for wide and deep submm mapping. Twenty-two sources were securely extracted with 870 micron flux densities in the range 3-21 mJy, rms noise 0.8-2.4 mJy, and far-IR luminosities probably in the range ~5-20 x 10(12) Lo. Only one of the four 50 kpc-extended Lya blobs has a secure 870 micron counterpart. The 870 micron source counts in the whole area are marginally higher than in the SHADES SCUBA survey, with a possible over-density around this blob. The majority of the 3.6-24 micron SEDs of the submillimeter sources indicate they are starburst dominated, with redshifts mostly >2. However, there is evidence of a high-z AGN in ~30% of the sources.
