Short Communication: Effects of temperature and chemical formulation on the acute toxicity of pentachlorophenol to Simocephalus vetulus (Schoedler, 1858) (Crustacea: Cladocera)

The influence of temperature on the acute toxicity of a technical formulation (86%) and pure formulation (99%) of pentachlorophenol (PCP) to less than 24-h-old Simocephalus vetulus neonates was determined with 48-h static toxicity tests. The technical grade PCP was significantly more toxic to S. vetulus than the pure PCP (P < 0.05). Sensitivity of S. vetulus to technical PCP also significantly increased with temperature (P < 0.05), but a significant temperature effect was not found with the pure PCP. The mean 48-h LC50 values for neonates exposed to technical PCP were 140 and 199 ug l⁻¹ at 22deg.C and 16deg.C, respectively, and for those exposed to pure PCP were 262 and 304 ug l⁻¹, respectively

The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds. XI. Lupus Observed With IRAC and MIPS

We present c2d Spitzer/IRAC observations of the Lupus I, III and IV dark clouds and discuss them in combination with optical and near-infrared and c2d MIPS data. With the Spitzer data, the new sample contains 159 stars, 4 times larger than the previous one. It is dominated by low- and very-low mass stars and it is complete down to M $\approx$ 0.1M$_\odot$. We find 30-40 % binaries with separations between 100 to 2000 AU with no apparent effect in the disk properties of the members. A large majority of the objects are Class II or Class III objects, with only 20 (12%) of Class I or Flat spectrum sources. The disk sample is complete down to ``debris''-like systems in stars as small as M $\approx$ 0.2 M$_\odot$ and includes sub-stellar objects with larger IR excesses. The disk fraction in Lupus is 70 -- 80%, consistent with an age of 1 -- 2 Myr. However, the young population contains 20% optically thick accretion disks and 40% relatively less flared disks. A growing variety of inner disk structures is found for larger inner disk clearings for equal disk masses. Lupus III is the most centrally populated and rich, followed by Lupus I with a filamentary structure and by Lupus IV, where a very high density core with little star-formation activity has been found. We estimate star formation rates in Lupus of 2 -- 10 M$_\odot$ Myr$^{-1}$ and star formation efficiencies of a few percent, apparently correlated with the associated cloud masses.Comment: Accepted for publication in the ApJS. Contains 101 pages, 23 figures, and 13 tables. A version with full resolution figures can be found at http://peggysue.as.utexas.edu/SIRTF/PAPERS/pap102.pub.pd

The Spitzer c2d survey of large, nearby, interstellar clouds. X. The Chamaeleon II pre-main-sequence population as observed with IRAC and MIPS

We discuss the results from the combined IRAC and MIPS c2d Spitzer Legacy survey observations and complementary optical and NIR data of the Chamaeleon II (Cha II) dark cloud. We perform a census of the young population in an area of similar to 1.75 deg^(2) and study the spatial distribution and properties of the cloud members and candidate pre-main-sequence (PMS) objects and their circumstellar matter. Our census is complete down to the substellar regime (M approximate to 0.03 M☉). From the analysis of the volume density of the PMS objects and candidates we find two groups of objects with volume densities higher than 25 M☉ pc^(-3) and 5-10 members each. A multiplicity fraction of about 13% +/- 3% is observed for objects with separations 0.8" < θ < 6.0" (142-1065 AU). No evidence for variability between the two epochs of the c2d IRAC data set, Δt ~ 6 hr, is detected. We estimate a star formation efficiency of 1%-4%, consistent with the estimates for Taurus and Lupus, but lower than for Cha I. This might mean that different star formation activities in the Chamaeleon clouds reflect a different history of star formation. We also find that Cha II is turning some 6-7 M☉ into stars every Myr, which is low in comparison with the star formation rate in other c2d clouds. The disk fraction of 70%-80% that we estimate in Cha II is much higher than in other star-forming regions and indicates that the population in this cloud is dominated by objects with active accretion. Finally, the Cha II outflows are discussed; a new Herbig-Haro outflow, HH 939, driven by the classical T Tauri star Sz 50, has been discovered

The Spitzer Survey of Interstellar Clouds in the Gould Belt. VI. The Auriga-California Molecular Cloud observed with IRAC and MIPS

We present observations of the Auriga-California Molecular Cloud (AMC) at 3.6, 4.5, 5.8, 8.0, 24, 70 and 160 micron observed with the IRAC and MIPS detectors as part of the Spitzer Gould Belt Legacy Survey. The total mapped areas are 2.5 sq-deg with IRAC and 10.47 sq-deg with MIPS. This giant molecular cloud is one of two in the nearby Gould Belt of star-forming regions, the other being the Orion A Molecular Cloud (OMC). We compare source counts, colors and magnitudes in our observed region to a subset of the SWIRE data that was processed through our pipeline. Using color-magnitude and color-color diagrams, we find evidence for a substantial population of 166 young stellar objects (YSOs) in the cloud, many of which were previously unknown. Most of this population is concentrated around the LkHalpha 101 cluster and the filament extending from it. We present a quantitative description of the degree of clustering and discuss the fraction of YSOs in the region with disks relative to an estimate of the diskless YSO population. Although the AMC is similar in mass, size and distance to the OMC, it is forming about 15 - 20 times fewer stars.Comment: (30 pages, 17 figures (2 multipage figures), accepted for publication in ApJ

The masses of Local Group dwarf spheroidal galaxies: The death of the universal mass profile

We investigate the claim that all dwarf spheroidal galaxies (dSphs) reside within halos that share a common, universal mass profile as has been derived for dSphs of the Galaxy. By folding in kinematic information for 25 Andromeda dSphs, more than doubling the previous sample size, we find that a singular mass profile can not be found to fit all the observations well. Further, the best-fit dark matter density profile measured for solely the Milky Way dSphs is marginally discrepant (at just beyond the 1 sigma level) with that of the Andromeda dSphs, where a profile with lower maximum circular velocity, and hence mass, is preferred. The agreement is significantly better when three extreme Andromeda outliers, And XIX, XXI and XXV, all of which have large half-light radii (>600pc) and low velocity dispersions (sigma_v < 5km/s) are omitted from the sample. We argue that the unusual properties of these outliers are likely caused by tidal interactions with the host galaxy.Comment: ApJ in press, 16 pages, 7 figures. Updated to address referee comment

A kinematic study of the Andromeda dwarf spheroidal system

We present a homogeneous kinematic analysis of red giant branch stars within 18 of the 28 Andromeda dwarf spheroidal (dSph) galaxies, obtained using the Keck I LRIS and Keck II DEIMOS spectrographs. Based on their g-i colors (taken with the CFHT MegaCam imager), physical positions on the sky, and radial velocities, we assign probabilities of dSph membership to each observed star. Using this information, the velocity dispersions, central masses and central densities of the dark matter halos are calculated for these objects, and compared with the properties of the Milky Way dSph population. We also measure the average metallicity ([Fe/H]) from the co-added spectra of member stars for each M31 dSph and find that they are consistent with the trend of decreasing [Fe/H] with luminosity observed in the Milky Way population. We find that three of our studied M31 dSphs appear as significant outliers in terms of their central velocity dispersion, And XIX, XXI and XXV, all of which have large half-light radii (>700 pc) and low velocity dispersions (sigma_v<5 km/s). In addition, And XXV has a mass-to-light ratio within its half-light radius of just [M/L]_{half}=10.3^{+7.0}_{-6.7}, making it consistent with a simple stellar system with no appreciable dark matter component within its 1 sigma uncertainties. We suggest that the structure of the dark matter halos of these outliers have been significantly altered by tides.Comment: 41 pages, 23 figures. Accepted for publication in Ap

The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds. IX. The Serpens YSO Population as Observed with IRAC and MIPS

We discuss the combined IRAC/MIPS c2d Spitzer Legacy observations of the Serpens star-forming region. We describe criteria for isolating bona fide YSOs from the extensive background of extragalactic objects. We then discuss the properties of the resulting high-confidence set of 235 YSOs. An additional 51 lower confidence YSOs outside this area are identified from the MIPS data and 2MASS photometry. We present color-color diagrams to compare our observed source properties with those of theoretical models for star/disk/envelope systems and our own modeling of the objects that are well represented by a stellar photosphere plus circumstellar disk. These objects exhibit a wide range of disk properties, from many with actively accreting disks to some with both passive disks and even possibly debris disks. The YSO luminosity function extends down to at least a few times 10^(-3) L_☉ or lower. The lower limit may be set more by our inability to distinguish YSOs from extragalactic sources than by the lack of YSOs at very low luminosities. We find no evidence for variability in the shorter IRAC bands between the two epochs of our data set, Δt ~ 6 hr. A spatial clustering analysis shows that the nominally less evolved YSOs are more highly clustered than the later stages. The background extragalactic population can be fitted by the same two-point correlation function as seen in other extragalactic studies. We present a table of matches between several previous infrared and X-ray studies of the Serpens YSO population and our Spitzer data set. The clusters in Serpens have a very high surface density of YSOs, primarily with SEDs suggesting extreme youth. The total number of YSOs, mostly Class II, is greater outside the clusters