303 research outputs found
Social Ecological Climate Resilience Project - 2016
Prepared for: North Central Climate Science Center, Fort Collins, Colorado.February 2017.Includes bibliographical references.Climate change is already having impacts on nature, ecosystem services and people in southwestern Colorado and is likely to further alter our natural landscapes in the coming decades. Understanding the potential changes and developing adaptation strategies can help ensure that natural landscapes and human communities remain healthy in the face of a changing climate. An interdisciplinary team consisting of social, ecological and climate scientists developed an innovative climate planning framework and worked with the SocialâEcological Climate Resilience Project (SECR) and other stakeholders in Coloradoâs San Juan River watershed to develop adaptation strategies for two significant landscapes, pinyon juniper woodlands and seeps, springs, and wetland resources under three climate scenarios between 2035 and 2050. This report summarizes the planning framework and results for the pinyonâjuniper landscape (the seeps, springs and wetlands results will be provided separately). This framework can be utilized to develop strategies for other landscapes at local, state, and national scales. Diagrams, narrative scenarios, and maps that depict climate scenarios and the socialâecological responses help us portray the climate impact in the face of an uncertain future. Interviews and focus group workshops with agency staff and stakeholders who are users of public lands identified several important opportunities to improve the adaptation planning process for developing strategies that meet both social and ecological needs. Planning techniques that include or directly relate to specific resources, such as water and forage, or to activities, such as recreation or grazing, provide avenues for engaging diverse stakeholders into the process. Utilizing the scenarios to understand the impacts to our social and ecological landscapes, three overarching landscapeâscale adaptation strategies were developed. Each of these strategies has a suite of potential actions required to reach a desired future condition. The three key strategies are: 1) identify and protect persistent ecosystems as refugia, 2) proactively manage for resilience, and 3) accept, assist, and allow for transformation in nonâclimate refugia sites. If the framework and strategies from this project are adopted by the local community, including land managers, owners, and users, the climate change impacts can be reduced, allowing for a more sustainable human and natural landscape
Seeps, springs and wetlands: San Juan Basin, Colorado. Social-ecological climate resilience project
Prepared for: North Centeral Climate Adaptation Science Center.Social-Ecological Climate Resilience Project, 2016.Includes bibliographical references
Dynamic Fabry-Perot cavity stabilization technique for atom-cavity experiments
We present a stabilization technique developed to lock and dynamically tune
the resonant frequency of a moderate finesse Fabry-P\'erot (FP) cavity used in
precision atom-cavity quantum electrodynamics (QED) experiments. Most
experimental setups with active stabilization either operate at one fixed
resonant frequency or use transfer cavities to achieve the ability to tune the
resonant frequency of the cavity. In this work, we present a simple and
cost-effective solution to actively stabilize an optical cavity while achieving
a dynamic tuning range of over 100 MHz with a precision under 1 MHz. Our unique
scheme uses a reference laser locked to an electro-optic modulator (EOM)
shifted saturation absorption spectroscopy (SAS) signal. The cavity is locked
to the PDH error signal obtained from the dip in the reflected intensity of
this reference laser. Our setup provides the feature to efficiently tune the
resonant frequency of the cavity by only changing the EOM drive without
unlocking and re-locking either the reference laser or the cavity. We present
measurements of precision control of the resonant cavity frequency and vacuum
Rabi splitting (VRS) to quantify the stability achieved and hence show that
this technique is suitable for a variety of cavity QED experiments
Sagebrush landscape: Upper Gunnison River Basin, Colorado Social-Ecological Climate Resilience Project
Prepared with: The Gunnison Climate Working Group and Stakeholders in Gunnison, Colorado for: the North Central Climate Science Center, Ft. Collins, Colorado.April 30, 2017.Includes bibliographical references.Utilizing climate stories to understand the social and ecological impacts to the sagebrush landscape, the team worked with stakeholders to develop three overarching landscapeâscale adaptation strategies. Each of the strategies has a suite of potential actions required to reach a desired future condition. The three key strategies are: 1) identify and protect climate refugia sites (persistent areas), 2) maintain or enhance the resilience of the climate refugia sites, and 3) accept, assist and allow for transformation in nonâclimate refugia sites. If adopted by the local community, including land managers and landowners, the framework and strategies resulting from this project can help to reduce the adverse impacts of climate change, allowing for a more sustainable human and natural landscape
Cavity based non-destructive detection of photoassociation in a dark MOT
The photoassociation (PA) of rubidium dimer (Rb2) in a dark magneto-optic
trap (MOT) is studied using atom-cavity collective strong coupling. This allows
non-destructive detection of the molecule formation process as well as rapid
and repeated interrogation of the atom-molecule system. The vacuum Rabi
splitting (VRS) measurements from the bright MOT are carefully calibrated
against equivalent measurements with fluorescence. Further loading rates in
dark MOT are determined using VRS. This method provides a reliable, fast, and
non-destructive detection scheme for ultracold molecules when the atoms are
non-fluorescing using the free atoms coupled to a cavity
Cold and Slow Molecular Beam
Employing a two-stage cryogenic buffer gas cell, we produce a cold,
hydrodynamically extracted beam of calcium monohydride molecules with a near
effusive velocity distribution. Beam dynamics, thermalization and slowing are
studied using laser spectroscopy. The key to this hybrid, effusive-like beam
source is a "slowing cell" placed immediately after a hydrodynamic, cryogenic
source [Patterson et al., J. Chem. Phys., 2007, 126, 154307]. The resulting CaH
beams are created in two regimes. One modestly boosted beam has a forward
velocity of vf = 65 m/s, a narrow velocity spread, and a flux of 10^9 molecules
per pulse. The other has the slowest forward velocity of vf = 40 m/s, a
longitudinal temperature of 3.6 K, and a flux of 5x10^8 molecules per pulse
Alpha Enhancement and the Metallicity Distribution Function of Plaut's Window
We present Fe, Si, and Ca abundances for 61 giants in Plaut's Window
(l=-1,b=-8.5) and Fe abundances for an additional 31 giants in a second, nearby
field (l=0,b=-8) derived from high resolution (R~25,000) spectra obtained with
the Blanco 4m telescope and Hydra multifiber spectrograph. The median
metallicity of red giant branch (RGB) stars in the Plaut field is ~0.4 dex
lower than those in Baade's Window, and confirms the presence of an iron
abundance gradient along the bulge minor axis. The full metallicity range of
our (biased) RGB sample spans -1.5<[Fe/H]<+0.3, which is similar to that found
in other bulge fields. We also derive a photometric metallicity distribution
function for RGB stars in the (l=-1,b=-8.5) field and find very good agreement
with the spectroscopic metallicity distribution. The radial velocity and
dispersion data for the bulge RGB stars are in agreement with previous results
of the BRAVA survey, and we find evidence for a decreasing velocity dispersion
with increasing [Fe/H]. The [alpha/Fe] enhancement in Plaut field stars is
nearly identical to that observed in Baade's window, and suggests that an
[alpha/Fe] gradient does not exist between b=-4 and -8. Additionally, a subset
of our sample (23 stars) appear to be foreground red clump stars that are very
metal--rich, exhibit small metallicity and radial velocity dispersions, and are
enhanced in alpha elements. While these stars likely belong to the Galactic
inner disk population, they exhibit [alpha/Fe] ratios that are enhanced above
the thin and thick disk.Comment: Accepted for publication in ApJ. 38 pages, 11 figures, and 2 tables.
Requests for higher resolution figures and electronic versions of tables 1
and/or 2 in advance of publication may be sent to cijohnson[at]astro.ucla.ed
Constraints on the Formation of the Galactic Bulge from Na, Al, and Heavy Element Abundances in Plaut's Field
We report chemical abundances of Na, Al, Zr, La, Nd, and Eu for 39 red giant
branch (RGB) stars and 23 potential inner disk red clump stars located in
Plaut-s low extinction window. We also measure lithium for a super Li-rich RGB
star. The abundances were determined by spectrum synthesis of high resolution
(R~25,000), high signal-to-noise (S/N~50-100 pixel-1) spectra obtained with the
Blanco 4m telescope and Hydra multifiber spectrograph. For the bulge RGB stars,
we find a general increase in the [Na/Fe] and [Na/Al] ratios with increasing
metallicity, and a similar decrease in [La/Fe] and [Nd/Fe]. Additionally, the
[Al/Fe] and [Eu/Fe] abundance trends almost identically follow those of the
{\alpha}-elements, and the [Zr/Fe] ratios exhibit relatively little change with
[Fe/H]. The consistently low [La/Eu] ratios of the RGB stars indicate that at
least a majority of bulge stars formed rapidly (<1 Gyr) and before the main
s-process could become a significant pollution source. In contrast, we find
that the potential inner disk clump stars exhibit abundance patterns more
similar to those of the thin and thick disks. Comparisons between the abundance
trends at different bulge locations suggest that the inner and outer bulge
formed on similar timescales. However, we find evidence of some abundance
differences between the most metal-poor and metal-rich stars in various bulge
fields. The data also indicate that the halo may have had a more significant
impact on the outer bulge initial composition than the inner bulge composition.
The [Na/Fe] and to a lesser extent [La/Fe] abundances further indicate that the
metal-poor bulge, at least at ~1 kpc from the Galactic center, and thick disk
may not share an identical chemistry.Comment: Accepted for publication in ApJ; 66 pages, 17 figures, 3 tables;
prior to publication, data tables in electronic form will be made available
upon reques
On the origin of M81 group extended dust emission
Galactic cirrus emission at far-infrared wavelengths affects many extragalactic observations. Separating this emission from that associated with extragalactic objects is both important and difficult. In this paper we discuss a particular case, the M81 group, and the identification of diffuse structures prominent in the infrared, but also detected at optical wavelengths. The origin of these structures has previously been controversial, ranging from them being the result of a past interaction between M81 and M82 or due to more local Galactic emission. We show that over an order of a few arcmin scales, the far-infrared (Herschel 250 mu m) emission correlates spatially very well with a particular narrow-velocity (2-3 km s(-1)) component of the Galactic HI. We find no evidence that any of the far-infrared emission associated with these features actually originates in the M81 group. Thus we infer that the associated diffuse optical emission must be due to galactic light-back scattered off dust in our galaxy. Ultraviolet observations pick out young stellar associations around M81, but no detectable far-infrared emission. We consider in detail one of the Galactic cirrus features, finding that the far-infrared HI relation breaks down below arcmin scales and that at smaller scales there can be quite large dust-temperature variation
SPIRE imaging of M82: cool dust in the wind and tidal streams
M82 is a unique representative of a whole class of galaxies, starbursts with
superwinds, in the Very Nearby Galaxy Survey with Herschel. In addition, its
interaction with the M81 group has stripped a significant portion of its
interstellar medium from its disk. SPIRE maps now afford better
characterization of the far-infrared emission from cool dust outside the disk,
and sketch a far more complete picture of its mass distribution and energetics
than previously possible. They show emission coincident in projection with the
starburst wind and in a large halo, much more extended than the PAH band
emission seen with Spitzer. Some complex substructures coincide with the
brightest PAH filaments, and others with tidal streams seen in atomic hydrogen.
We subtract the far-infrared emission of the starburst and underlying disk from
the maps, and derive spatially-resolved far-infrared colors for the wind and
halo. We interpret the results in terms of dust mass, dust temperature, and
global physical conditions. In particular, we examine variations in the dust
physical properties as a function of distance from the center and the wind
polar axis, and conclude that more than two thirds of the extraplanar dust has
been removed by tidal interaction, and not entrained by the starburst wind.Comment: accepted in A&A Herschel special issu
- âŠ