Some formation scenarios that have been put forward to explain multiple populations within globular clusters (GCs) require that the young massive cluster have large reservoirs of cold gas within ...them, which is necessary to form future generations of stars. In this paper, we use deep observations taken with Atacama Large Millimeter/submillimeter Array (ALMA) to assess the amount of molecular gas within three young (50–200 Myr) massive (∼106 M⊙) clusters in the Antennae galaxies. No significant CO(3–2) emission was found associated with any of the three clusters. We place upper limits for the molecular gas within these clusters of ∼1 × 105 M⊙ (or <9 per cent of the current stellar mass). We briefly review different scenarios that propose multiple episodes of star formation and discuss some of their assumptions and implications. Our results are in tension with the predictions of GC formation scenarios that expect large reservoirs of cool gas within young massive clusters at these ages.
We present dynamical models of four interacting systems: NGC 5257/8, The Mice, the Antennae, and NGC 2623. The parameter space of the encounters are constrained using the Identikit model-matching and ...visualization tool. Identikit utilizes hybrid N-body and test particle simulations to enable rapid exploration of the parameter space of galaxy mergers. The Identikit-derived matches of these systems are reproduced with self-consistent collisionless simulations which show very similar results. The models generally reproduce the observed morphology and H I kinematics of the tidal tails in these systems with reasonable properties inferred for the progenitor galaxies. The models presented here are the first to appear in the literature for NGC 5257/8 and NGC 2623, and The Mice and the Antennae are compared with previously published models. Based on the assumed mass model and our derived initial conditions, the models indicate that the four systems are currently being viewed 175-260 Myr after first passage and cover a wide range of merger stages. In some instances there are mismatches between the models and the data (e.g., in the length of a tail); these are likely due to our adoption of a single mass model for all galaxies. Despite the use of a single mass model, these results demonstrate the utility of Identikit in constraining the parameter space for galaxy mergers when applied to real data.
Methyl anthranilate (MA), a compound in maize roots that is repellent to western corn rootworm larvae (Diabrotica virgifera virgifera LeConte) was tested in behavioral bioassays in a soil ...environment. MA prevented larvae from locating roots of a maize seedling, and the repellency strengthened with increasing rates of MA. In a simple push–pull strategy between an MA-treated seedling and an untreated seedling, granules containing 0.1 mg/g MA pushed larvae to the untreated seedling. This push effect increased with dose, with 90% repellency observed for the highest dose tested (100 mg/g). Chemical analysis showed that MA concentrations remained high for 4 wk in dry, sterilized or unsterilized soil, but declined rapidly in moist soil. After 7 d, 50% less MA was recovered in moist, sterilized soil than in dry soil, and only a trace of MA remained in unsterilized moist soil, suggesting that both moisture and microbial activity contributed to the loss of MA. Various (MA) carrier granules were tested in bioassays after aging in moist soil. After 1 d, all of the MA granules were repellent at the 10 mg/g rate and clay granules were also effective at 1 mg/g. After 1 wk, only molecular sieve granules elicited repellency, but that activity disappeared after 2 wk. These results demonstrate that MA is repellent to western corn rootworm larvae in the soil environment and may have potential as a rootworm treatment if formulations can be developed that protect the material from decomposition in the soil.
Methyl anthranilate was identified as the active compound in extracts of maize (Zea mays L.) roots that were shown to be repellent to neonate western corn rootworm (Diabrotica virgifera virgifera ...LeConte) larvae. A bioassay-driven approach was used to isolate the active material from diethyl ether extracts of roots from germinating maize seeds. Separation of the extract on a Florisil column yielded an active fraction of 90:10 hexane:diethyl ether. Analysis with gas chromatography–mass spectrometry identified two compounds in the active fraction: indole (2,3-benzopyrrole) and methyl anthranilate (methyl 2-aminobenzoate). When tested in behavioral bioassays, methyl anthranilate elicited a significant (P < 0.05) repellent response at doses of 1, 10, and 100 µg. In subsequent single-choice bioassays, 1, 10, and 100 µg of methyl anthranilate prevented larvae from approaching 10 mmol/mol concentrations of carbon dioxide, which is normally highly attractive to the larvae. Indole, the other compound identified from the active fraction, did not elicit a behavioral response by the larvae. Methyl anthranilate has potential for development as a management tool for western corn rootworm larvae and may be best suited for use in a push–pull control strategy.
We have searched for compact stellar structures within 17 tidal tails in 13 different interacting galaxies using F606W- and F814W-band images from the Wide Field Planetary Camera 2 on the Hubble ...Space Telescope. The sample of tidal tails includes a diverse population of optical properties, merging galaxy mass ratios, H I content, and ages. Combining our tail sample with Knierman et al., we find evidence of star clusters formed in situ with M V < --8.5 and V -- I < 2.0 in 10 of 23 tidal tails; we are able to identify cluster candidates to M V = --6.5 in the closest tails. Three tails offer clear examples of 'beads on a string' star formation morphology in V -- I color maps. Two tails present both tidal dwarf galaxy candidates and cluster candidates. Statistical diagnostics indicate that clusters in tidal tails may be drawn from the same power-law luminosity functions (with logarithmic slopes --2 to --2.5) found in quiescent spiral galaxies and interiors of interacting systems. We find that the tail regions with the largest number of observable clusters are relatively young (250 Myr old) and bright (V 24 mag arcsec--2), probably attributed to the strong bursts of star formation in interacting systems soon after periapse. Otherwise, we find no statistical difference between cluster-rich and cluster-poor tails in terms of many observable characteristics, though this analysis suffers from complex, unresolved gas dynamics and projection effects.
We present a sample of 46 galaxy nuclei from 12 nearby (z < 4500 km s super(-1)) Hickson Compact Groups (HCGs) with a complete suite of 1-24 mu m 2MASS + Spitzer nuclear photometry. For all objects ...in the sample, blue emission from stellar photospheres dominates in the near-infrared through the 3.6 mu m IRAC band. Of 46 galaxy nuclei, 25 (54%) show red mid-infrared continua characteristic of hot dust powered by ongoing star formation and/or accretion onto a central black hole. We introduce alpha sub(IRAC), the spectral index of a power-law fit to the 4.5-8.0 mu m IRAC data, and demonstrate that it cleanly separates the mid-infrared-active and nonactive HCG nuclei. This parameter is more powerful for identifying low-to moderate-luminosity mid-infrared activity than other measures, which include data at rest-frame lambda < 3.6 mu m that may be dominated by stellar photospheric emission. While the HCG galaxies clearly have a bimodal distribution in this parameter space, a comparison sample from the Spitzer Nearby Galaxy Survey (SINGS) matched in J-band total galaxy luminosity is continuously distributed. A second diagnostic, the fraction of 24 mu m emission in excess of that expected from quiescent galaxies, f24D, reveals an additional three nuclei to be active at 24 mu m. Comparing these two mid-infrared diagnostics of nuclear activity to optical spectroscopic identifications from the literature reveals some discrepancies, and we discuss the challenges of distinguishing the source of ionizing radiation in these and other lower luminosity systems. We find a significant correlation between the fraction of mid-infrared-active galaxies and the total H I mass in a group and investigate possible interpretations of these results in light of galaxy evolution in the highly interactive system of a compact group environment.
Monogalactosyldiacylglycerol (MGDG) was identified as a host recognition cue for larvae of the western corn rootworm Diabrotica virgifera virgifera LeConte. An active glycolipid fraction obtained ...from an extract of germinating maize roots was isolated with thin layer chromatography using a bioassay-driven approach. When analyzed with LC-MS (positive ion scanning), the assay-active spot was found to contain four different MGDG species: 18:3–18:3 (1,2-dilinolenoyl), 18:2–18:3 (1-linoleoyl, 2-linolenoyl), 18:2–18:2 (1,2-dilinoleoyl), and 18:2–16:0 (1-linoleoyl, 2-palmitoyl). A polar fraction was also needed for activity. When combined with a polar fraction containing a blend of sugars (glucose: fructose:sucrose:myoinositol), the isolated MGDG elicited a unique tight-turning behavior by neonate western corn rootworm larvae that is indicative of host recognition. In behavioral bioassays where disks treated with the active blend were exposed to successive sets of rootworm larvae, the activity of MGDG increased over four exposures, suggesting that larvae may be responding to compounds produced after enzymatic breakdown of MGDG. In subsequent tests with synthetic blends composed of theoretical MGDG-breakdown products, larval responses to four synthetic blends were not significantly different (P<0.5) than the response to isolated MGDG. GC-MS analysis showed modest increases in the amounts of the 16:0, 18:0, and 18:3 free fatty acids released from MGDG after a 30-min exposure to rootworm larvae, which is consistent with the enzymatic breakdown hypothesis.
ABSTRACT We present Atacama Large Millimeter/submillimeter Array (ALMA) observations from the 2014 Long Baseline Campaign in dust continuum and spectral line emission from the HL Tau region. The ...continuum images at wavelengths of 2.9, 1.3, and 0.87 mm have unprecedented angular resolutions of 0 075 (10 AU) to 0 025 (3.5 AU), revealing an astonishing level of detail in the circumstellar disk surrounding the young solar analog HL Tau, with a pattern of bright and dark rings observed at all wavelengths. By fitting ellipses to the most distinct rings, we measure precise values for the disk inclination ( ) and position angle We obtain a high-fidelity image of the 1.0 mm spectral index ( ), which ranges from in the optically thick central peak and two brightest rings, increasing to 2.3-3.0 in the dark rings. The dark rings are not devoid of emission, and we estimate a grain emissivity index of 0.8 for the innermost dark ring and lower for subsequent dark rings, consistent with some degree of grain growth and evolution. Additional clues that the rings arise from planet formation include an increase in their central offsets with radius and the presence of numerous orbital resonances. At a resolution of 35 AU, we resolve the molecular component of the disk in HCO+ (1-0) which exhibits a pattern over LSR velocities from 2-12 km s−1 consistent with Keplerian motion around a ∼1.3 star, although complicated by absorption at low blueshifted velocities. We also serendipitously detect and resolve the nearby protostars XZ Tau (A/B) and LkH 358 at 2.9 mm.
Feeding behaviour, feeding intensity and staying behaviour of neonate western corn rootworm (Diabrotica virgifera virgifera LeConte) larvae were evaluated in response to synthetic feeding stimulant ...blends. All of the treatments contained a 3‐sugar blend (glucose : fructose : sucrose, 30 : 4 : 4 mg/ml) and one of twelve free fatty acids. Each free fatty acid was tested in this blend at three different concentrations. The addition of the 12 : 0, 16 : 0, 16 : 1, 18 : 0, 18 : 1, 18 : 2 and 18 : 3 free fatty acids to the sugar blend significantly (P < 0.05) increased the percentage of larvae feeding, but did not increase food consumption per larva. Most of the free fatty acids elicited staying behaviour. At the lowest dose (0.1 mg/ml), all of the free fatty acids except the 18 : 0 and the 20 : 0 elicited staying by significantly more larvae than the sugar blend, and at the highest dose (1.0 mg/ml), eight free fatty acids (8 : 0, 10 : 0, 12 : 0, 14 : 0, 16 : 1, 18 : 1, 18 : 2 and 18 : 3) caused more larvae to stay compared to the sugar blend. Larvae were visibly impaired after exposure to some of the free fatty acids. At the highest dose, the 8 : 0, 10 : 0, 12 : 0, 14 : 0, 16 : 1, 18 : 1 and 18 : 2 free fatty acids were toxic to the larvae. At least 60% of larvae were impaired after exposure to the 12 : 0, 16 : 1 and 18 : 2 free fatty acids and the 8 : 0 and 10 : 0 free fatty acids caused 100% impairment or death. Synthetic blends were compared with liquid from crushed maize roots and with a methanol extract of maize roots. Feeding intensity and staying behaviour on the root liquid and the root extract were significantly greater than on any of the synthetic blends, suggesting the presence of additional compounds in maize roots that serve as feeding cues for western corn rootworm larvae.
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