252 research outputs found
On the origin of the 40-120 micron emission of galaxy disks: A comparison with H-alpha fluxes
A comparison of 40 to 120 micron Infrared Astronomy Satellite (IRAS) fluxes with published H alpha and UBV photometry shows that the far infrared emission of galaxy disks consists of at least two components: a warm one associated with OB stars in HII-regions and young star-forming complexes, and a cooler one from dust in the diffuse, neutral interstellar medium, heated by the more general interstellar radiation field of the old disk population (a cirrus-like component). Most spiral galaxies are dominated by emission from the cooler component in this model. A significant fraction of the power for the cool component must originate with non-ionizing stars. For a normal spiral disk there is a substantial uncertainty in a star formation rate derived using either the H alpha or the far infrared luminosity
Snake Community Ecology And Conservation In Cusuco National Park, Honduras
The Mesoamerican biodiversity hotspot is threatened with agriculture related deforestation and global climate change, both of which drive widespread changes in forest composition. As the forests change, so too does the community of animals they can support; of which many reptiles have evolved micro-niches specific to these forests. Studying how these anthropogenic pressures affect the assemblages of animals that can persist there, could be vital in understanding how biodiversity will be affected on a global scale. Cusuco National Park (CNP), Honduras, is one of the most important protected sites worldwide for herpetofauna biodiversity, due to having such a high diversity of endemic herpetofauna. Despite its importance, CNP also represents one of the most threatened ecosystems in Honduras; with vast swathes of even the most protected pristine core zone being deforested and its wildlife already showing response to global climate change.
Using an established network of transects throughout CNP, Visual Encounter Surveys were used to monitor the changes in reptile biodiversity over a 13-year study period. A case study was also conducting investigating the spatial ecology and habitat preferences of Bothriechis marchi, the second most detected species, however, one likely that is underrepresented due to its ecology.
Diversity, richness, and evenness were found to decrease with elevation, with higher elevations being dominated by a single species, Cerrophidion wilsoni, whose total encounter numbers were higher than the next two species combined. Species accumulation curves for each of the surveying camps, which span the elevation gradient, have not reached asymptote, suggesting the diversity across CNP has not yet fully been described. Richness and functional guild diversity decreased with deforestation. Snake community assemblages ordinated significantly into lowland, intermediate and higher elevation communities, suggesting elevation is closely linked to snake species assemblage.
Radio telemetered snakes spent most of their time out of visually attainable range. Bothriechis marchi spend most of their time, stationary, in the canopy, at heights over 17 m, in closed canopy, moist broadleaf forests that are associated with rivers. One Atropoides mexicanus spent most of its time out of visually attainable range inside a log, undergoing ecdysis. Temperatures did not differ significantly between the log and surroundings indicating shedding sites perform a protective role for this species during a period of heightened vulnerability, rather than a thermoregulatory one
Color change in the gorgetal scales of an anole, Anolis amplisquamosus (Squamata: Dactyloidae)
Do coaches perceive themselves as influential on physical activity for girls in organised youth sport?
Participation in organised youth sports (OYS) has been recommended as an opportunity to increase young peoplesâ physical activity (PA) levels. While coaches can potentially influence athletesâ PA levels, what has not been explored is the question; do coaches perceive themselves as influential on PA for girls in OYS? Participants were 30 coaches of girls OYS teams aged 9â17 years in the Greater Sydney Metropolitan Area, Australia. Participants took part in a semi-structured interview that lasted approximately 30 minutes. They responded to questions regarding their perceived role as coaches, their perceptions of themselves as role models for PA, their views on their athletesâ current PA levels, their opinions on improving their athletesâ PA levels, and their perceived challenges as coaches in OYS. Many coaches considered themselves role models for PA due to their own involvement in organised sports. Coaches felt that they were conscious of girlsâ PA levels during training and could accurately gauge how active girls were. Coaches perceived their training sessions to provide sufficient PA and thus, did not feel the need to try to increase PA during training. Many coaches were cautious about conducting training sessions where the PA intensity was high for prolonged periods because they believed that it could potentially result in dropout from OYS. Coachesâ perceived time commitment to OYS, variability of skill/experience amongst girls, and poor parental support as major challenges they experienced in OYS. This study provided a unique insight from the perspective of coaches in OYS. Most coaches felt that they had the potential to influence PA for girls in OYS; however, coaches may underestimate or not fully realise the impact they can have on the girls they coach. Future research should focus on educating coaches to capitalise on the opportunity they have to promote PA through OYS
The Infrared Spectral Energy Distribution of Normal Star-Forming Galaxies: Calibration at Far-Infrared and Submillimeter Wavelengths
New far-infrared and submillimeter data are used to solidify and to extend to
long wavelengths the empirical calibration of the infrared spectral energy
distribution (SED) of normal star-forming galaxies. As was found by Dale et al.
(2001), a single parameter family, characterized by f_nu(60 microns)/f_nu(100
microns), is adequate to describe the range of normal galaxy spectral energy
distributions observed by IRAS and ISO from 3 to 100 microns. However,
predictions based on the first generation models at longer wavelengths (122 to
850 microns) are increasingly overluminous compared to the data for smaller
f_nu(60 microns)/f_nu(100 microns), or alternatively, for weaker global
interstellar radiation fields. After slightly modifying the
far-infrared/submillimeter dust emissivity in those models as a function of the
radiation field intensity to better match the long wavelength data, a suite of
SEDs from 3 microns to 20 cm in wavelength is presented. Results from relevant
applications are also discussed, including submillimeter-based photometric
redshift indicators, the infrared energy budget and simple formulae for
recovering the bolometric infrared luminosity, and dust mass estimates in
galaxies. Regarding the latter, since galaxy infrared SEDs are not
well-described by single blackbody curves, the usual methods of estimating dust
masses can be grossly inadequate. The improved model presented herein is used
to provide a more accurate relation between infrared luminosity and dust mass.Comment: 25 pages including 9 figures; accepted for publication in the
Astrophysical Journa
Connecting the cosmic infrared background to the X-ray background
We estimate the contribution of AGNs and of their host galaxies to the
infrared background. We use the luminosity function and evolution of AGNs
recently determined by the hard X-ray surveys, and new Spectral Energy
Distributions connecting the X-ray and the infrared emission, divided in
intervals of absorption. These two ingredients allow us to determine the
contribution of AGNs to the infrared background by using mostly observed
quantities, with only minor assumptions. We obtain that AGN emission
contributes little to the infrared background (5% over most of the infrared
bands), implying that the latter is dominated by star formation. However, AGN
host galaxies may contribute significantly to the infrared background, and more
specifically 10--20% in the 1--20m range and 5% at . We also give the contribution of AGNs and of their host galaxies to the
source number counts in various infrared bands, focusing on those which will be
observed with Spitzer. We also report a significant discrepancy between the
expected contribution of AGN hosts to the submm background and bright submm
number counts with the observational constraints. We discuss the causes and
implications of this discrepancy and the possible effects on the Spitzer far-IR
bands.Comment: to appear in MNRAS, replaced with accepted version, paper shortened,
results unchange
Emission Features and Source Counts of Galaxies in Mid-Infrared
In this work we incorporate the newest ISO results on the mid-infrared
spectral-energy-distributions (MIR SEDs) of galaxies into models for the number
counts and redshift distributions of MIR surveys. A three-component model, with
empirically determined MIR SED templates of (1) a cirrus/PDR component (2) a
starburst component and (3) an AGN component, is developed for infrared
(3--120\micron) SEDs of galaxies. The model includes a complete IRAS 25\micron
selected sample of 1406 local galaxies (; Shupe et al. 1998a).
Results based on these 1406 spectra show that the MIR emission features cause
significant effects on the redshift dependence of the K-corrections for fluxes
in the WIRE 25\micron band and ISOCAM 15\micron band. This in turn will affect
deep counts and redshift distributions in these two bands, as shown by the
predictions of two evolution models (a luminosity evolution model with
and a density evolution model with ).
The dips-and-bumps on curves of MIR number counts, caused by the emission
features, should be useful indicators of evolution mode. The strong emission
features at --8\micron will help the detections of relatively high
redshift () galaxies in MIR surveys. On the other hand, determinations
of the evolutionary rate based on the slope of source counts, and studies on
the large scale structures using the redshift distribution of MIR sources, will
have to treat the effects of the MIR emission features carefully. We have also
estimated a 15\micron local luminosity function from the predicted 15\micron
fluxes of the 1406 galaxies using the bivariate (15\micron vs. 25\micron
luminosities) method. This luminosity function will improve our understanding
of the ISOCAM 15\micron surveys.Comment: 24 pages, 14 EPS figures. Accepted by Ap
Observations of Arp 220 using Herschel-SPIRE: An Unprecedented View of the Molecular Gas in an Extreme Star Formation Environment
We present Herschel SPIRE-FTS observations of Arp~220, a nearby ULIRG. The
FTS continuously covers 190 -- 670 microns, providing a good measurement of the
continuum and detection of several molecular and atomic species. We detect
luminous CO (J = 4-3 to 13-12) and water ladders with comparable total
luminosity; very high-J HCN absorption; OH+, H2O+, and HF in absorption; and CI
and NII. Modeling of the continuum yields warm dust, with T = 66 K, and an
unusually large optical depth of ~5 at 100 microns. Non-LTE modeling of the CO
shows two temperature components: cold molecular gas at T ~ 50 K and warm
molecular gas at T ~1350 K. The mass of the warm gas is 10% of the cold gas,
but dominates the luminosity of the CO ladder. The temperature of the warm gas
is in excellent agreement with H2 rotational lines. At 1350 K, H2 dominates the
cooling (~20 L_sun/M_sun) in the ISM compared to CO (~0.4 L_sun/M_sun). We
found that only a non-ionizing source such as the mechanical energy from
supernovae and stellar winds can excite the warm gas and satisfy the energy
budget of ~20 L_sun/M_sun. We detect a massive molecular outflow in Arp 220
from the analysis of strong P-Cygni line profiles observed in OH+, H2O+, and
H2O. The outflow has a mass > 10^{7} M_sun and is bound to the nuclei with
velocity < 250 km/s. The large column densities observed for these molecular
ions strongly favor the existence of an X-ray luminous AGN (10^{44} ergs/s) in
Arp 220.Comment: Accepted in ApJ on September 1, 201
First Results from the ISOâIRAS Faint Galaxy Survey
We present the first results from the ISO-IRAS Faint Galaxy Survey (IIFGS), a program designed to obtain ISO observations of the most distant and luminous galaxies in the IRAS Faint Source Survey by filling short gaps in the ISO observing schedule with pairs of 12 ÎŒm ISOCAM and 90 ÎŒm ISOPHOT observations. As of 1997 October, over 500 sources have been observed, with an ISOCAM detection rate over 80%, covering over 1.25 deg^2 of sky to an 11.5 ÎŒm point-source completeness limit of approximately 1.0 mJy (corresponding to a ~10 Ï detection sensitivity). Observations are presented for nine sources detected by ISOPHOT and ISOCAM early in the survey for which we have ground-based G- and I-band images and optical spectroscopy. The ground-based data confirm that the IIFGS strategy efficiently detects moderate-redshift (z = 0.11-0.38 for this small sample) strong emission line galaxies with L_(60 ÎŒm) âł 10^(11) L_â; one of our sample has L_(60 ÎŒm) > 10^(12) L_â (H_0 = 75 km s^(-1) Mpc^(-1), Ω = 1). The infrared-optical spectral energy distributions are comparable to those of nearby luminous infrared galaxies, which span the range from pure starburst (e.g., Arp 220) to infrared QSO (Mrk 231). Two of the systems show signs of strong interaction, and four show active galactic nucleus (AGN)-like excitation; one of the AGNs, F15390+6038, which shows a high excitation Seyfert 2 spectrum, has an unusually warm far- to mid-infrared color and may be an obscured QSO. The IIFGS sample is one of the largest and deepest samples of infrared-luminous galaxies available, promising to be a rich sample for studying infrared-luminous galaxies up to z ~ 1 and for understanding the evolution of infrared galaxies and the star formation rate in the universe
The ISO-IRAS Faint Galaxy Survey
The ISO-IRAS Faint Galaxy Survey will obtain comprehensive
space- and ground-based observations of the most distant and luminous galaxies in the IRAS Faint Source Survey. ISO observations are obtained by filling short gaps in the ISO observing schedule with pairs of 11.5ÎŒm ISOCAM and 90ÎŒm ISOPHOT observations. As of the October 1997 date of this Conference, over 500 sources have been observed by ISO with an ISOCAM detection rate exceeding 803. Ground-based
spectrophotometry confirms that the IIFGS efficiently detects moderateredshift, strong emission line Luminous Infrared Galaxies. Spectrophotometry is currently available for 67 galaxies with 0.07 < z < 0. 7 and
L_(fir) > 10^(11) L_â. The galaxies are comparable to nearby LIGs, showing HII/Liner excitation; about 10% exhibit strong AGN characteristics. As a part of this survey we will cover over 1.25 square degrees of
sky to an 11.5ÎŒm limit of approximately l.0mJy, allowing a sensitive estimate of the 11.5ÎŒm logN-logS Relationship. Preliminary ll.5ÎŒm source counts suggest substantial evolution in the mid-infrared galaxy population
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