Detection of weak lensing by a cluster of galaxies at z=0.83

We report the detection of weak gravitational lensing of faint, distant background galaxies by the rich, X-ray luminous cluster of galaxies MS1054-03 at z=0.83. This is the first measurement of weak lensing by a bona fide cluster at such a high redshift. We detect tangential shear at the 5% - 10% level over a range of radii 50'' < r < 250'' centered on the optical position of the cluster. Two-dimensional mass reconstruction using galaxies with 21.5 < I < 25.5 shows a strong peak which coincides with the peak of the smoothed cluster light distribution. Splitting this sample by magnitude (at I = 23.5) and color (at R-I = 0.7), we find that the brighter and redder subsamples are only very weakly distorted, indicating that the faint blue galaxies (FBG's), which dominate the shear signal, are relatively more distant. The derived cluster mass is quite sensitive to the N(z) for the FBG's. At one extreme, if all the FBG's are at z_s = 3, then the mass within a $0.5h^{-1}$Mpc aperture is $(5.9 \pm 1.24)\times 10^{14}$\h1 $M_\odot$, and the mass-to-light ratio is $M/L_V = 350 \pm 70 h$ in solar units. For $z_s = 1.5$ the derived mass is $\sim$70\% higher and $M/L \simeq 580 h$. If $N(z)$ follows the no evolution model (in shape) then $M/L \simeq 800h$, and if all the FBG's lie at z_s\la 1 the required $M/L$ exceeds $1600h$. These data provide clear evidence that large, dense mass concentrations existed at early epochs; that they can be weighed efficiently by weak lensing observations; and that most of the FBG's are at high redshift.Comment: Submitted to ApJ, 15 pages (incl 8 figs, 3 of which are plates). Plate images not included, but are available from ftp://hubble.ifa.hawaii.edu/pub/ger/ms1054/ms1054_fig[1,3,5].ps.

Weak Lensing Detection of Cl 1604+4304 at z = 0.90

We present a weak lensing analysis of the high-redshift cluster Cl 1604+4304. At z=0.90, this is the highest-redshift cluster yet detected with weak lensing. It is also one of a sample of high-redshift, optically-selected clusters whose X-ray temperatures are lower than expected based on their velocity dispersions. Both the gas temperature and galaxy velocity dispersion are proxies for its mass, which can be determined more directly by a lensing analysis. Modeling the cluster as a singular isothermal sphere, we find that the mass contained within projected radius R is 3.69+-1.47 * (R/500 kpc) 10^14 M_odot. This corresponds to an inferred velocity dispersion of 1004+-199 km/s, which agrees well with the measured velocity dispersion of 989+98-76 km/s (Gal & Lubin 2004). These numbers are higher than the 575+110-85 km/s inferred from Cl 1604+4304 X-ray temperature, however all three velocity dispersion estimates are consistent within ~ 1.9 sigma.Comment: Revised version accepted for publication in AJ (January 2005). 2 added figures (6 figures total

Comparative study of in vitro antioxidant activity of foliar endophytic fungi and leaves extracts of Peganum harmala of Dayate aiat (Laghouat, Algeria)

Endophytic fungi that reside in plant tissues are a potential source of secondary metabolites with biological activities. In our study, we investigated the detection of the antioxidant activity of the crude fungal extract of the genera Cladosporium, Alternaria, Aspergillus and Penicillium: endophytic fungi isolated from the leaves of Peganum harmala harvested in Laghouat and extract of these same leaves. The extraction of these metabolites was carried out using ethyl acetate. The antioxidant activity of the latter was carried out by the DPPH test. Our tests reveal that the extracts studied have a low antioxidant activity. The inhibitory concentrations show a higher antioxidant effect for the Penicillium extract compared to the other extracts studied. The antioxidant molecules are related to the content of polyphenols. Penicillium extract has the highest polyphenol content. Our results confirm that endophytic fungi are a potential and limited source of natural antioxidant compounds, in the same way as plants.Key words: Leaf extract; Extracts of endophytic fungi; Antioxidant activity; Content ofpolyphenols and Peganum harmala

Hubble Space Telescope weak lensing study of the z=0.83 cluster MS 1054-03

We have measured the weak gravitational lensing signal of MS 1054-03, a rich and X-ray luminous cluster of galaxies at a redshift of z=0.83, using a two-colour mosaic of deep WFPC2 images. The small corrections for the size of the PSF and the high number density of background galaxies obtained in these observations result in an accurate and well calibrated measurement of the lensing induced distortion. The strength of the lensing signal depends on the redshift distribution of the background galaxies. We used photometric redshift distributions from the Northern and Southern Hubble Deep Fields to relate the lensing signal to the mass. The predicted variations of the signal as a function of apparent source magnitude and colour agrees well with the observed lensing signal. We determine a mass of (1.2+-0.2)x10^15 Msun within an aperture of radius 1 Mpc. Under the assumption of an isothermal mass distribution, the corresponding velocity dispersion is 1311^{+83}_{-89} km/s. For the mass-to-light ratio we find 269+-37 Msun/Lsun. The errors in the mass and mass-to-light ratio include the contribution from the random intrinsic ellipticities of the source galaxies, but not the (systematic) error due to the uncertainty in the redshift distribution. However, the estimates for the mass and mass-to-light ratio of MS 1054-03 agree well with other estimators, suggesting that the mass calibration works well. The reconstruction of the projected mass surface density shows a complex mass distribution, consistent with the light distribution. The results indicate that MS 1054-03 is a young system. The timescale for relaxation is estimated to be at least 1 Gyr. Averaging the tangential shear around the cluster galaxies, we find that the velocity dispersion of an Lstar galaxy is 203+-33 km/s.Comment: 21 pages, Latex, with 27 figures (3 figures bitmapped), ApJ, in press. Version (with non-bitmapped figures) available at http://www.astro.rug.nl/~hoekstra/papers.htm

Counts and Colors of Faint Galaxies in the U and R Bands

Ground-based counts and colors of faint galaxies in the U and R bands in one field at high Galactic latitude are presented. Integrated over flux, a total of 1.2x10^5 sources per square degree are found to U=25.5 mag and 6.3x10^5 sources per square degree to R=27 mag, with d log N/dm ~ 0.5 in the U band and d log N/dm ~ 0.3 in the R band. Consistent with these number-magnitude curves, sources become bluer with increasing magnitude to median U-R=0.6 mag at 24<U<25 mag and U-R=1.2 mag at 25 < R < 26 mag. Because the Lyman break redshifts into the U band at z~3, at least 1.2x10^5 sources per square degree must be at redshifts z<3. Measurable U-band fluxes of 73 percent of the 6.3x10^5 sources per square degree suggest that the majority of these also lie at z < 3. These results require an enormous space density of objects in any cosmological model.Comment: 17 pages, MNRAS in pres

An Investigation of an Academic Vocabulary Intervention for Upper Elementary Students Who Struggle with Reading

The current study is a mixed-methods, action research study in which Word Generation (WG) resources were used with students in a learning support classroom. Word Generation is a cross-curricular vocabulary intervention centered on academic language. The goal of the study was to investigate the vocabulary learning of students and to evaluate the WG resources. Students demonstrated statistically significant positive differences on the pretest/posttest and maintained that learning on a delayed posttest. Important findings related to students’ developing word consciousness indicated that the WG resources positively impacted students’ word awareness and that the WG target vocabulary is representative of high-utility academic language. The findings show promise for incorporating multifaceted vocabulary instruction such as Word Generation into middle school classrooms with students who struggle with reading

Submillimeter galaxies behind the Bullet Cluster (1E 0657-56)

Clusters of galaxies are effective gravitational lenses able to magnify background galaxies and making it possible to probe the fainter part of the galaxy population. Submillimeter galaxies, which are believed to be star-forming galaxies at typical redshifts of 2 to 3, are a major contaminant to the extended Sunyaev-Zeldovich (SZ) signal of galaxy clusters. For a proper quantification of the SZ signal the contribution of submillimeter galaxies needs to be quantified. The aims of this study are to identify submillimeter sources in the field of the Bullet Cluster (1E 0657-56), a massive cluster of galaxies at z~0.3, measure their flux densities at 870 micron, and search for counterparts at other wavelengths to constrain their properties. We carried out deep observations of the submillimeter continuum emission at 870 micron using the Large APEX BOlometer CAmera (LABOCA) on the Atacama Pathfinder EXperiment (APEX) telescope. Several numerical techniques were used to quantify the noise properties of the data and extract sources. In total, seventeen sources were found. Thirteen of them lie in the central 10 arcminutes of the map, which has a pixel sensitivity of 1.2 mJy per 22 arcsec beam. After correction for flux boosting and gravitational lensing, the number counts are consistent with published submm measurements. Nine of the sources have infrared counterparts in Spitzer maps. The strongest submm detection coincides with a source previously reported at other wavelengths, at an estimated redshift z~2.7. If the submm flux arises from two images of a galaxy magnified by a total factor of 75, as models have suggested, its intrinsic flux would be around 0.6 mJy, consistent with an intrinsic luminosity below 10^12 L_sun.Comment: Accepted by A&A, 15 pages, 11 figure

The Vacuole Model: New Terms in the Second Order Deflection of Light

The present paper is an extension of a recent work (Bhattacharya et al. 2010) to the Einstein-Strauss vacuole model with a cosmological constant, where we work out the light deflection by considering perturbations up to order M^3 and confirm the light bending obtained previously in their vacuole model by Ishak et al. (2008). We also obtain another local coupling term -((5{\pi}M^2{\Lambda})/8) related to {\Lambda}, in addition to the one obtained by Sereno (2008, 2009). We argue that the vacuole method for light deflection is exclusively suited to cases where the cosmological constant {\Lambda} disappears from the path equation. However, the original Rindler-Ishak method (2007) still applies even if a certain parameter {\gamma} of Weyl gravity does not disappear. Here, using an alternative prescription, we obtain the known term -(({\gamma}R)/2), as well as another new local term ((3{\pi}{\gamma}M)/2) between M and {\gamma}. Physical implications are compared, where we argue that the repulsive term -(({\gamma}R)/2) can be masked by the Schwarzschild term ((2M)/R) in the halo regime supporting attractive property of the dark matter.Comment: 15 page

First redshift determination of an optically/UV faint submillimeter galaxy using CO emission lines

We report the redshift of a distant, highly obscured submm galaxy (SMG), based entirely on the detection of its CO line emission. We have used the newly commissioned Eight-MIxer Receiver (EMIR) at the IRAM 30m telescope, with its 8 GHz of instantaneous dual-polarization bandwidth, to search the 3-mm atmospheric window for CO emission from SMMJ14009+0252, a bright SMG detected in the SCUBA Lens Survey. A detection of the CO(3--2) line in the 3-mm window was confirmed via observations of CO(5--4) in the 2-mm window. Both lines constrain the redshift of SMMJ14009+0252 to z=2.9344, with high precision (dz=2 10^{-4}). Such observations will become routine in determining redshifts in the era of the Atacama Large Millimeter/submillimeter Array (ALMA).Comment: 5 pages, 3 figures, accepted by ApJ

Radio and X-ray properties of submillimeter galaxies in the A2125 field

We present the radio and X-ray properties of 1.2 mm MAMBO source candidates in a 1600 sq. arcmin field centered on the Abell 2125 galaxy cluster at z=0.247. The brightest, non-synchrotron mm source candidate in the field has a photometric redshift, z = 3.93^+1.11_-0.80, and is not detected in a 31 ks Chandra X-ray exposure. These findings are consistent with this object being an extremely dusty and luminous starburst galaxy at high-redshift, possibly the most luminous yet identified in any blank-field mm survey. The deep 1.4 GHz VLA imaging identifies counterparts for 83% of the 29 mm source candidates identified at >=4-sigma S(1.2mm) = 2.7 - 52.1 mJy, implying that the majority of these objects are likely to lie at z <~ 3.5. The median mm-to-radio wavelength photometric redshift of this radio-detected sample is z~2.2 (first and third quartiles of 1.7 and 3.0), consistent with the median redshift derived from optical spectroscopic surveys of the radio-detected subsample of bright submm galaxies (S(850um) > 5 mJy). Three mm-selected quasars are confirmed to be X-ray luminous in the high resolution Chandra imaging, while another mm source candidate with potential multiple radio counterparts is also detected in the X-ray regime. Both of these radio counterparts are positionally consistent with the mm source candidate. One counterpart is associated with an elliptical galaxy at z = 0.2425, but we believe that a second counterpart associated with a fainter optical source likely gives rise to the mm emission at z~1.Comment: Accepted for publication in Ap