665 research outputs found
The Role of Apparent Competition in Facilitating Ecological Release of a Range-expanding Insect
Due to anthropogenic climate change, species are expanding their historical natural ranges. However, interacting species will not shift synchronously and range-expanding species are likely to lose interactions and pick up novel ones in their expanded range. If antagonistic interactions, such as with competitors or enemies are lost, range-expanding species may experience “ecological release” and have impacts in their expanded range. Of the parasitoid wasps that attack phytophagous insects, some are specialists and some are generalists attacking alternative hosts (competitors). Range-expanding species may lose enemies if their specialists fail to follow from their native range and if generalist enemies fail to switch from competitors in the expanded range (“release from apparent competition”). We study a poleward range-expansion of a phytophagous gall-forming insect Neuroterus saltatorius that expanded its range from mainland western North America to Vancouver Island, BC, where it is outbreaking on its plant Querucs garryana. N. saltatorius co-occurs with several other gall-formers on its host, including Andricus opertus, throughout its native and expanded range. Here, we ask if A. opertus acts as an apparent competitor (shares enemies) with N. saltatorius, and if apparent competition is weaker in the expanded range. These two host species were collected from 18 sites that span the range of Q. garryana. We reared parasitoid wasps from them and identified parasitoids to morphospecies using taxonomic keys. We identified 16 parasitoids from N. saltatorius and 39 from A. opertus. Of these, 13 species of parasitoids are shared between the two host species in all regions, and we will calculate the rate of shared overlap to see if there are fewer shared species in the expanded range. This result would suggest that release from apparent competition contributes to ecological release. Understanding how biotic interactions change under range expansions is important to predict species responses to climate change.https://orb.binghamton.edu/research_days_posters_2021/1095/thumbnail.jp
A SCUBA/Spitzer investigation of the far-infrared extragalactic background
We have measured the contribution of submillimetre and mid-infrared sources to the extragalactic background radiation at 70 and 160 μm. Specifically, we have stacked flux in 70- and 160-μm Spitzer Space Telescope (Spitzer) observations of the Canada-United Kingdom Deep Submillimetre Survey 14-h field at the positions of 850-μm sources detected by SCUBA and also 8- and 24-μm sources detected by Spitzer. We find that per source, the SCUBA galaxies are the strongest and the 8-μm sources the weakest contributors to the background flux at both 70 and 160 μm. Our estimate of the contribution of the SCUBA sources is higher than previous estimates. However, expressed as a total contribution, the full 8-μm source catalogue accounts for twice the total 24-μm source contribution and ∼10 times the total SCUBA source contribution. The 8-μm sources account for the majority of the background radiation at 160 μm with a flux of 0.87 ± 0.16 MJy sr−1 and at least a third at 70 μm with a flux of 0.103 ± 0.019 MJy sr−1. These measurements are consistent with current lower limits on the background at 70 and 160 μm. Finally, we have investigated the 70- and 160-μm emission from the 8- and 24-μm sources as a function of redshift. We find that the average 70-μm flux per 24-μm source and the average 160-μm flux per 8- and 24-μm source is constant over all redshifts, up to z∼ 4. In contrast, the low-redshift half (z < 1) of the of 8-μm sample contributes approximately four times the total 70-μm flux of the high-redshift half. These trends can be explained by a single non-evolving SE
A SCUBA/Spitzer Investigation of the Far Infra-Red Extragalactic Background
We have measured the contribution of submillimeter and mid-infrared sources
to the extragalactic background radiation at 70 and 160um. Specifically, we
have stacked flux in 70 and 160um Spitzer Space Telescope (Spitzer)
observations of the Canada-UK Deep Sub-millimeter Survey 14h field at the
positions of 850um sources detected by SCUBA and also 8 and 24um sources
detected by Spitzer. We find that per source, the SCUBA galaxies are the
strongest and the 8um sources the weakest contributors to the background flux
at both 70 and 160um. Our estimate of the contribution of the SCUBA sources is
higher than previous estimates. However, expressed as a total contribution, the
full 8um source catalogue accounts for twice the total 24um source contribution
and ~10 times the total SCUBA source contribution. The 8um sources account for
the majority of the background radiation at 160um with a flux of 0.87+/-0.16
MJy/sr and at least a third at 70um with a flux of 0.103+/-0.019 MJy/sr. These
measurements are consistent with current lower limits on the background at 70
and 160um. Finally, we have investigated the 70 and 160um emission from the 8
and 24um sources as a function of redshift. We find that the average 70um flux
per 24um source and the average 160um flux per 8 and 24um source is constant
over all redshifts, up to z~4. In contrast, the low-redshift half (z<1) of the
of 8um sample contributes approximately four times the total 70um flux of the
high-redshift half. These trends can be explained by a single non-evolving SED.Comment: 15 pages, 5 figures, accepted by MNRAS. This version incorporates
various ammendments suggested by the referee and some new analysi
The Calar Alto Deep Imaging Survey: K-band Galaxy Number Counts
We present K-band number counts for the faint galaxies in the Calar Alto Deep
Imaging Survey (CADIS). We covered 4 CADIS fields, a total area of 0.2deg^2, in
the broad band filters B, R and K. We detect about 4000 galaxies in the K-band
images, with a completeness limit of K=19.75mag, and derive the K-band galaxy
number counts in the range of 14.25 < K < 19.75mag. This is the largest medium
deep K-band survey to date in this magnitude range. The B- and R-band number
counts are also derived, down to completeness limits of B=24.75mag and
R=23.25mag. The K-selected galaxies in this magnitude range are of particular
interest, since some medium deep near-infrared surveys have identified breaks
of both the slope of the K-band number counts and the mean B-K color at
K=17\sim18mag. There is, however, a significant disagreement in the K-band
number counts among the existing surveys. Our large near-infrared selected
galaxy sample allows us to establish the presence of a clear break in the slope
at K=17.0mag from dlogN/dm = 0.64 at brighter magnitudes to dlogN/dm = 0.36 at
the fainter end. We construct no-evolution and passive evolution models, and
find that the passive evolution model can simultaneously fit the B-, R- and
K-band number counts well. The B-K colors show a clear trend to bluer colors
for K > 18mag. We also find that most of the K=18-20mag galaxies have a B-K
color bluer than the prediction of a no-evolution model for an L_* Sbc galaxy,
implying either significant evolution, even for massive galaxies, or the
existence of an extra population of small galaxies.Comment: Accepted for A&A, 10 pages, 7 figure
Testing for a large local void by investigating the Near-Infrared Galaxy Luminosity Function
Recent cosmological modeling efforts have shown that a local underdensity on
scales of a few hundred Mpc (out to z ~ 0.1), could produce the apparent
acceleration of the expansion of the universe observed via type Ia supernovae.
Several studies of galaxy counts in the near-infrared (NIR) have found that the
local universe appears under-dense by ~25-50% compared with regions a few
hundred Mpc distant. Galaxy counts at low redshifts sample primarily L ~ L*
galaxies. Thus, if the local universe is under-dense, then the normalization of
the NIR galaxy luminosity function (LF) at z>0.1 should be higher than that
measured for z 90%) spectroscopic
sample of 1436 galaxies selected in the H-band to study the normalization of
the NIR LF at 0.1<z<0.3 and address the question of whether or not we reside in
a large local underdensity. We find that for the combination of our six fields,
the product phi* L* at 0.1 < z < 0.3 is ~ 30% higher than that measured at
lower redshifts. While our statistical errors in this measurement are on the
~10% level, we find the systematics due to cosmic variance may be larger still.
We investigate the effects of cosmic variance on our measurement using the
COSMOS cone mock catalogs from the Millennium simulation and recent empirical
estimates. We find that our survey is subject to systematic uncertainties due
to cosmic variance at the 15% level ($1 sigma), representing an improvement by
a factor of ~ 2 over previous studies in this redshift range. We conclude that
observations cannot yet rule out the possibility that the local universe is
under-dense at z<0.1.Comment: Accepted for publication in Ap
The mid-IR Luminosity Function at z<0.3 from 5MUSES: Understanding the Star-formation/AGN Balance from a Spectroscopic View
We present rest-frame 15 and 24 um luminosity functions and the corresponding
star-forming luminosity functions at z<0.3 derived from the 5MUSES sample.
Spectroscopic redshifts have been obtained for ~98% of the objects and the
median redshift is ~0.12. The 5-35 um IRS spectra allow us to estimate
accurately the luminosities and build the luminosity functions. Using a
combination of starburst and quasar templates, we quantify the star-formation
and AGN contributions in the mid-IR SED. We then compute the star-formation
luminosity functions at 15 um and 24 um, and compare with the total 15 um and
24 um luminosity functions. When we remove the contribution of AGN, the bright
end of the luminosity function exhibits a strong decline, consistent with the
exponential cutoff of a Schechter function. Integrating the differential
luminosity function, we find that the fractional contribution by star formation
to the energy density is 58% at 15 um and 78% at 24 um, while it goes up to
~86% when we extrapolate our mid-IR results to the total IR luminosity density.
We confirm that the active galactic nuclei play more important roles
energetically at high luminosities. Finally, we compare our results with work
at z~0.7 and confirm that evolution on both luminosity and density is required
to explain the difference in the LFs at different redshifts.Comment: 31 pages, 12 figures, accepted for Ap
The COSMOS-WIRCam near-infrared imaging survey: I: BzK selected passive and star forming galaxy candidates at z>1.4
(abridged) We present a new near-infrared survey covering the 2 deg sq COSMOS
field. Combining our survey with Subaru B and z images we construct a deep,
wide-field optical-infrared catalogue. At Ks<23 (AB magnitudes) our survey
completeness is greater than 90% and 70% for stars and galaxies respectively
and contains 143,466 galaxies and 13,254 stars. At z~2 our catalogues contain
3931 quiescent and 25,757 star-forming BzK-selected galaxies representing the
largest and most secure sample of these objects to date. Our counts of
quiescent galaxies turns over at Ks~22 an effect which we demonstrate cannot be
due to sample incompleteness. In our survey both the number of faint and bright
quiescent objects exceeds the predictions of a semi-analytic galaxy formation
model, indicating potentially the need for further refinements in the amount of
merging and AGN feedback at z~2 in these models. We measure the angular
correlation function for each sample and find that at small scales the
correlation function for passive BzK galaxies exceeds the clustering of dark
matter. We use 30-band photometric redshifts to derive the spatial correlation
length and the redshift distributions for each object class. At Ks<22 we find
r_0^{\gamma/1.8}=7.0 +/-0.5h^{-1} Mpc for the passive BzK candidates and
4.7+/-0.8h^{-1} Mpc for the star-forming BzK galaxies. Our pBzK galaxies have
an average photometric redshift of z_p~1.4, in approximate agreement with the
limited spectroscopic information currently available. The stacked Ks image
will be made publicly available from IRSA.Comment: Accepted for publication in Astrophysical Journal. 17 pages, 17
figures, minor revisions to match published version available at
http://adsabs.harvard.edu/abs/2010ApJ...708..202
Using the 1.6um Bump to Study Rest-frame NIR Selected Galaxies at Redshift 2
We explore the feasibility and limitations of using the 1.6um bump as a
photometric redshift indicator and selection technique and use it to study the
rest-frame H-band galaxy luminosity and stellar mass functions at redshift z~2.
We use publicly available Spitzer/IRAC images in the GOODS fields and find that
color selection in the IRAC bandpasses alone is comparable in completeness and
contamination to BzK selection. We find that the shape of the 1.6um bump is
robust, and photometric redshifts are not greatly affected by choice of model
parameters. Comparison with spectroscopic redshifts shows photometric redshifts
to be reliable. We create a rest-frame NIR selected catalog of galaxies at z~2
and construct a galaxy stellar mass function (SMF). Comparisons with other SMFs
at approximately the same redshift but determined using shorter wavelengths
show good agreement. This agreement suggests that selection at bluer
wavelengths does not miss a significant amount of stellar mass in passive
galaxies. Comparison with SMFs at other redshifts shows evidence for the
downsizing scenario of galaxy evolution. We conclude by pointing out the
potential for using the 1.6um technique to select high-redshift galaxies with
the JWST, whose lambda > 0.6 um coverage will not be well suited to selecting
galaxies using techniques that require imaging at shorter wavelengths.Comment: Accepted for publication in Ap
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