We present a re-reduction and expansion of the Bolocam Galactic Plane Survey (BGPS), first presented by Aguirre et al. and Rosolowsky et al. The BGPS is a 1.1 mm survey of dust emission in the ...Northern galactic plane, covering longitudes ? 10degrees < l < 90degrees and latitudes |b| < 0degrees.5 with a typical 1sigma rms sensitivity of 30-100 mJy in a ~33" beam. Version 2 of the survey includes an additional ~20 deg super(2) of coverage in the third and fourth quadrants and ~2 deg super(2) in the first quadrant. The new data release has improved angular recovery, with complete recovery out to ~80" and partial recovery to ~300", and reduced negative bowls around bright sources resulting from the atmospheric subtraction process. We resolve the factor of 1.5 flux calibration offset between the v1.0 data release and other data sets and determine that there is no offset between v2.0 and other data sets. The v2.0 pointing accuracy is tested against other surveys and is demonstrated to be accurate and an improvement over v1.0. We present simulations and tests of the pipeline and its properties, including measurements of the pipeline's angular transfer function. The Bolocat cataloging tool was used to extract a new catalog, which includes 8594 sources, with 591 in the expanded regions. We have demonstrated that the Bolocat 40" and 80" apertures are accurate even in the presence of strong extended background emission. The number of sources is lower than in v1.0, but the amount of flux and area included in identified sources is larger.
Thalassia testudinum seedling recruitment, survival, and growth were examined within physically disturbed seagrass beds in the Florida Keys. Two separate studies were conducted. In the first, a ...large-scale study, T. testudinum seedlings were surveyed and collected from a large seagrass disturbance (1560 m super(2)), 4.8 yr after the initial impact from a motor-vessel grounding. In the second, a smaller-scale study, T. testudinum seedling recruitment was examined over a 2 yr period within 9 smaller motor-vessel disturbances located within intact T. testudinum beds. In the large-scale study, we reconstructed the age of the seedlings based on shoot production rates from a previous study and from the small-scale study. A total of 79 seedlings were collected that varied in age from young of the year to 4.8 yr old; 6 different seedling cohorts were identified. The average density and rhizome-elongation rate for 1 yr old seedlings were 1 m super(-2) and 6.6 cm yr super(-1), respectively. In the small-scale study, we surveyed and permanently marked all newly recruited seedlings; monitoring was conducted 5 more times over a 2 yr period. The average seedling survival after Year 1 was 42%; after Year 2, average survival dropped to 20%. The average seedling density after Year 1 was 0.071 m super(-2); after Year 2, average density dropped to 0.026 m super(-2). The average rhizome-elongation rate and shoot-production rate of 1 yr old seedlings were 6 cm yr super(-1) and 1.8 shoots yr super(-1), respectively. The results of this study suggest that T. testudinum seedlings are a regular and reliable source of new recruits on seagrass banks in the Florida Keys.
Abstract
A spectral survey of methyl acetylene (CH
3
CCH) was conducted toward the hot molecular core/outflow G331.512-0.103. Our APEX observations allowed the detection of 41 uncontaminated ...rotational lines of CH
3
CCH in the frequency range between 172 and 356 GHz. Through an analysis under the local thermodynamic equilibrium assumption, by means of rotational diagrams, we determined
T
exc
= 50 ± 1 K,
N
(CH
3
CCH) = (7.5 ± 0.4) × 10
15
cm
2
,
X
CH
3
CCH/H
2
≈ (0.8–2.8) × 10
−8
, and
X
CH
3
CCH/CH
3
OH ≈ 0.42 ± 0.05 for an extended emitting region (∼10″). The relative intensities of the
K
= 2 and
K
= 3 lines within a given
K
-ladder are strongly negatively correlated to the transitions’ upper
J
quantum number (
r
= −0.84). Pure rotational spectra of CH
3
CCH were simulated at different temperatures, in order to interpret this observation. The results indicate that the emission is characterized by a nonnegligible temperature gradient with upper and lower limits of ∼45 and ∼60 K, respectively. Moreover, the line widths and peak velocities show an overall strong correlation with their rest frequencies, suggesting that the warmer gas is also associated with stronger turbulence effects. The
K
= 0 transitions present a slightly different kinematic signature than the remaining lines, indicating that they might be tracing a different gas component. We speculate that this component is characterized by lower temperatures and therefore larger sizes. Moreover, we predict and discuss the temporal evolution of the CH
3
CCH abundance using a two-stage zero-dimensional model of the source constructed with the three-phase Nautilus gas-grain code.
ABSTRACT
Isocyanic acid (HNCO) is a simple molecule with a potential to form prebiotic and complex organic species. Using a spectral survey collected with the Atacama Pathfinder EXperiment, in this ...work we report the detection of 42 transitions of HNCO in the hot molecular core/outflow G331.512-0.103 (hereafter G331). The spectral lines were observed in the frequency interval ∼160–355 GHz. By means of Local Thermodynamic Equilibrium analyses, applying the rotational diagram method, we studied the excitation conditions of HNCO. The excitation temperature and column density are estimated to be Tex= 58.8 ± 2.7 K and N = (3.7 ± 0.5) × 1015 cm−2, considering beam dilution effects. The derived relative abundance is between (3.8 ± 0.5) × 10−9 and (1.4 ± 0.2) × 10−8. In comparison with other hot molecular cores, our column densities and abundances are in agreement. An update of the internal partition functions of the four CHNO isomers: HNCO; cyanic acid, HOCN; fulminic acid, HCNO; and isofulminic acid, HONC is provided. We also used the astrochemical code Nautilus to model and discuss HNCO abundances. The simulations could reproduce the abundances with a simple zero-dimensional model at a temperature of 60 K and for a chemical age of ∼105 yr, which is larger than the estimated dynamical age for G331. This result could suggest the need for a more robust model and even the revision of chemical reactions associated with HNCO.
A spectral survey of methyl acetylene (CH3CCH) was conducted toward the hot molecular core/outflow G331.512-0.103. Our APEX observations allowed the detection of 41 uncontaminated rotational lines of ...CH3CCH in the frequency range between 172 and 356 GHz. Through an analysis under the local thermodynamic equilibrium assumption, by means of rotational diagrams, we determined Texc = 50 ± 1 K, N(CH3CCH) = (7.5 ± 0.4) × 1015 cm2, XCH3CCH/H2 ≈ (0.8–2.8) × 10−8, and XCH3CCH/CH3OH ≈ 0.42 ± 0.05 for an extended emitting region (∼10″). The relative intensities of the K = 2 and K = 3 lines within a given K-ladder are strongly negatively correlated to the transitions’ upper J quantum number (r = −0.84). Pure rotational spectra of CH3CCH were simulated at different temperatures, in order to interpret this observation. The results indicate that the emission is characterized by a nonnegligible temperature gradient with upper and lower limits of ∼45 and ∼60 K, respectively. Moreover, the line widths and peak velocities show an overall strong correlation with their rest frequencies, suggesting that the warmer gas is also associated with stronger turbulence effects. The K = 0 transitions present a slightly different kinematic signature than the remaining lines, indicating that they might be tracing a different gas component. We speculate that this component is characterized by lower temperatures and therefore larger sizes. Moreover, we predict and discuss the temporal evolution of the CH3CCH abundance using a two-stage zero-dimensional model of the source constructed with the three-phase Nautilus gas-grain code.
Abstract
A grid of 20 millions 3–1100 μm spectral energy distribution (SED) models is presented for synthetic young clusters embedded in dense clumps. The models depend on four primary parameters: ...the clump mass Mclump and dust temperature Tdust, the fraction of mass fcore locked in dense cores, and the age of the clump tSF. We populate the young stellar object (YSO) clusters using the Kroupa initial mass function and the YSOs SED models grid of Robitaille et al. We conduct extensive testing of SED fitting using a simulated data set and we find that Mclump essentially depends on the submillimetre portion of the SED, while Tdust is mostly determined from the shape of the SED in the 70–350 μm range. Thanks to the large number of models computed, we verify that the combined analysis of L/M, 8–24 and 24–70 colours removes much of the SEDs fcore–tSF degeneracy. The L/M values are particularly useful to diagnose fcore. L/M ≤ 1 identifies protoclusters with fcore ≤ 0.1 and tSF $\,\,\lower.6ex\hbox{${\sim }$}\raise.65ex\hbox{$\lt $}\,\,10^5$ yr, while L/M$\,\,\lower.6ex\hbox{${\sim }$}\raise.65ex\hbox{$\gt $}\,\,$10 excludes fcore ≤ 0.1. We characterize lower limits of L/M where zero-age main sequence (ZAMS) stars are not found in models, and we also find models with L/M ≥10 and no ZAMS stars, in which 8–24$\,\,\lower.6ex\hbox{${\sim }$}\raise.65ex\hbox{$\gt $}\,\,0.8\pm 0.1$ independently from Mclump, temperature, and luminosity. This is the first set of synthesis SED models suited to model for embedded and unresolved clusters of YSOs. A set of new evolutionary tracks in the L/M diagram is also presented.
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•Sub-tropical and tropical climax seagrass species such as Thalassia testudinum recover slowly from physical sediment disturbance, and in some environmental conditions may not recover ...at all without restoration efforts.•The modified “compressed succession” restoration technique (i.e. planting a fast growing seagrass species such as Halodule wrightii) temporarily substitutes for the climax species and facilitates restoration of seagrass ecosystem services.•Experimental results using a novel method of wild bird fertilization and sediment re-grading demonstrate the practical application for accelerating the recovery and restoration of slower growing seagrasses in severely disturbed, phosphorous limited sediment environments.
Shallow water seagrass meadows are frequently damaged by recreational and commercial vessels. Severe injury occurs where propeller scarring, hull groundings and mooring anchors uproot entire plants, excavate sediments, and modify the biophysical properties of the substrate. In climax tropical seagrass communities dominated by Thalassia testudinum (turtlegrass), natural recovery in these disturbances can take several years to decades, and in some environmental conditions may not occur at all. During the recovery period, important ecological services provided by seagrasses are absent or substantially diminished and injured meadows can degrade further in response to natural disturbances, e.g. strong currents and severe storms. To determine if we could accelerate rehabilitation and prevent further degradation of injured turtlegrass meadows, we evaluated a restoration method called “modified compressed succession” using the fast-growing, opportunistic species Halodule wrightii to temporarily substitute ecological services for the slower-growing, climax species T. testudinum. In three experiments we showed statistically significant increases in density and coverage rates of H. wrightii transplants fertilized by wild bird feces as compared to unfertilized treatments. In one experiment, we further demonstrated that regrading excavated injuries with sediment-filled biodegradable tubes in combination with wild bird fertilization and H. wrightii transplants also accelerated seagrass recovery. Specific recommendations are presented for the best practical application of this restoration method in the calcium carbonate-based sediments of south Florida and the wider Caribbean region.
Physical damage by motor vessels is a widespread problem for seagrass meadows, with hull and propeller strikes accounting for thousands of acres of impaired habitat in Florida, United States, alone. ...Because the excavations can become topographically unstable, and because recolonization and succession of seagrasses can require decades to reach climax, Thalassia testudinum‐dominated communities, there has been increasing efforts to regrade and stabilize impacted sediments, and to speed succession. A prior project involving eight vessel groundings in two hydrodynamic settings (high and low energy) examined the relative efficacy of capping injuries with sand‐filled fabric tubes or limestone pea rock, followed by planting of fast‐growing seagrass species and nutrient amendment using bird‐roosting stake deployments. Monitoring after 4 years showed recruitment of fast‐growing, subordinate species: Syringodium filiforme or Halodule wrightii, particularly in low‐energy environments; however, T. testudinum had not yet returned to natural densities. The current study extended monitoring an additional 3 years. At 7 years posteffort, T. testudinum recolonization was still incomplete. Of the eight sites, only three had statistically recovered. In low‐energy areas, H. wrightii cover was greater than in reference meadows, and a strong inverse relationship between H. wrightii and T. testudinum was observed. One explanation is that residual nutrients from bird feces switched the competitive outcome. We demonstrate using seagrass tissue N:P that nutrients delivered via bird stakes remained in the sediments of low‐energy environments, and argue that prolonged fertilization resulted in competitive advantages for H. wrightii, depressing T. testudinum recruitment and delaying recovery of the targeted seagrass community.
We present 107 maps of continuum emission at 350 mu m from Galactic molecular clumps. Observed sources were mainly selected from the Bolocam Galactic Plane Survey (BGPS) catalog, with three ...additional maps covering star-forming regions in the outer Galaxy. The higher resolution of the SHARC-II images (8."5 beam) compared with the 1.1 mm images from BGPS (33" beam) allowed us to identify a large population of smaller substructures within the clumps. A catalog is presented for the 1386 sources extracted from the 350 mu m maps. The color temperature distribution of clumps based on the two wavelengths has a median of 13.3 K and mean of 16.3 + or - 0.4 K, assuming an opacity law index of 1.7. For the structures with good determination of color temperatures, the mean ratio of gas temperature, determined from NH sub(3) observations, to dust color temperature is 0.88 and the median ratio is 0.76. About half the clumps have more than 2 substructures and 22 clumps have more than 10. The fraction of the mass in dense substructures seen at 350 mu m compared to the mass of their parental clump is ~0.19, and the surface densities of these substructures are, on average, 2.2 times those seen in the clumps identified at 1.1 mm. For a well-characterized sample, 88 structures (31%) exceed a surface density of 0.2 g cm super(-2), and 18 (6%) exceed 1.0 g cm super(-2), thresholds for massive star formation suggested by theorists.
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