86 research outputs found
Learning cognitive maps: Finding useful structure in an uncertain world
In this chapter we will describe the central mechanisms that influence how people learn about large-scale space. We will focus particularly on how these mechanisms enable people to effectively cope with both the uncertainty inherent in a constantly changing world and also with the high information content of natural environments. The major lessons are that humans get by with a less is more approach to building structure, and that they are able to quickly adapt to environmental changes thanks to a range of general purpose mechanisms. By looking at abstract principles, instead of concrete implementation details, it is shown that the study of human learning can provide valuable lessons for robotics. Finally, these issues are discussed in the context of an implementation on a mobile robot. © 2007 Springer-Verlag Berlin Heidelberg
Prototypes, Location, and Associative Networks (PLAN): Towards a Unified Theory of Cognitive Mapping
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98111/1/s15516709cog1901_1.pd
A critical, analytical framework for the digital machine
The Faculty of Digital and Computational Studies (DCS) at Bowdoin College proposes a critical, analytical framework, referred to as the ‘4As,’ as an interdisciplinary means to interpret, evaluate, and create the data, operations, and devices of computing across all domains of knowledge production. Following other disciplines that have developed in symbiotic relationships to one another, DCS puts computation in conversation with fields from across the arts, humanities, physical, and social sciences. Our foundational premise is the bidirectional influence between these disciplines and digital artifacts and computation. The 4As (artifact, architecture, abstraction, and agency) benefit from both the scepticism of the liberal arts in the face of ubiquitous digital processes and the analytical opening for examining questions pertaining to creative and imaginative alternatives to the digital and computational status quo. We provide an ultra-contemporary case study to demonstrate the framework in use
H α Emission and H ii Regions at the Locations of Recent Supernovae in Nearby Galaxies
We present a statistical analysis of the local, ≈50–100 pc scale, Hα emission at the locations of recent (≤125 yr) supernovae (SNe) in nearby star-forming galaxies. Our sample consists of 32 SNe in 10 galaxies that are targets of the PHANGS-MUSE survey. We find that 41% (13/32) of these SNe occur coincident with a previously identified H ii region. For comparison, H ii regions cover 32% of the area within ±1 kpc of any recent SN. Contrasting this local covering fraction with the fraction of SNe coincident with H ii regions, we find a statistical excess of 7.6% ± 8.7% of all SNe to be associated with H ii regions. This increases to an excess of 19.2% ± 10.4% when considering only core-collapse SNe (CCSNe). These estimates appear to be in good agreement with qualitative results from new, higher-resolution Hubble Space Telescope Hα imaging, which also suggests many CCSNe detonate near but not in H ii regions. Our results appear consistent with the expectation that only a modest fraction of stars explode during the first ≲5 Myr of the life of a stellar population when Hα emission is expected to be bright. Of the H ii region associated SNe, 85% (11/13) also have associated detected CO (2–1) emission, indicating the presence of molecular gas. The SNe associated with H ii regions have typical extinctions of A V ∼ 1 mag, consistent with a significant amount of pre-clearing of gas from the region before the SNe explode
A Two-Component Probability Distribution Function Describes the mid-IR Emission from the Disks of Star-Forming Galaxies
High-resolution JWST-MIRI images of nearby spiral galaxies reveal emission
with complex substructures that trace dust heated both by massive young stars
and the diffuse interstellar radiation field. We present high angular (0."85)
and physical resolution (20-80 pc) measurements of the probability distribution
function (PDF) of mid-infrared (mid-IR) emission (7.7-21 m) from 19 nearby
star-forming galaxies from the PHANGS-JWST Cycle-1 Treasury. The PDFs of mid-IR
emission from the disks of all 19 galaxies consistently show two distinct
components: an approximately log-normal distribution at lower intensities and a
high-intensity power-law component. These two components only emerge once
individual star-forming regions are resolved. Comparing with locations of HII
regions identified from VLT/MUSE H-mapping, we infer that the power-law
component arises from star-forming regions and thus primarily traces dust
heated by young stars. In the continuum-dominated 21 m band, the power-law
is more prominent and contains roughly half of the total flux. At 7.7-11.3
m, the power-law is suppressed by the destruction of small grains
(including PAHs) close to HII regions while the log-normal component tracing
the dust column in diffuse regions appears more prominent. The width and shape
of the log-normal diffuse emission PDFs in galactic disks remain consistent
across our sample, implying a log-normal gas column density
(H)cm shaped by supersonic turbulence with typical
(isothermal) turbulent Mach numbers . Finally, we describe how the
PDFs of galactic disks are assembled from dusty HII regions and diffuse gas,
and discuss how the measured PDF parameters correlate with global properties
such as star-formation rate and gas surface density.Comment: 30 pages without appendix, 17 figures, (with appendix images of full
sample: 56 pages, 39 figures), accepted in A
PHANGS-JWST First Results: A Global and Moderately Resolved View of Mid-Infrared and CO Line Emission from Galaxies at the Start of the JWST Era
We explore the relationship between mid-infrared (mid-IR) and CO rotational
line emission from massive star-forming galaxies, which is one of the tightest
scalings in the local universe. We assemble a large set of unresolved and
moderately ( kpc) spatially resolved measurements of CO (1-0) and CO
(2-1) intensity, , and mid-IR intensity, , at 8, 12,
22, and 24m. The vs. relationship is reasonably
described by a power law with slopes and normalization K km s at MJy sr. Both the slopes
and intercepts vary systematically with choice of line and band. The comparison
between the relations measured for CO~(1-0) and CO (2-1) allow us to infer that
, in good agreement with other work. The
m and m bands, with strong PAH features, show steeper CO vs.
mid-IR slopes than the m and m, consistent with PAH emission
arising not just from CO-bright gas but also from atomic or CO-dark gas. The
CO-to-mid-IR ratio correlates with global galaxy stellar mass () and
anti-correlates with SFR/. At kpc resolution, the first four
PHANGS-JWST targets show CO to mid-IR relationships that are quantitatively
similar to our larger literature sample, including showing the steep
CO-to-mid-IR slopes for the JWST PAH-tracing bands, although we caution that
these initial data have a small sample size and span a limited range of
intensities.Comment: 29 pages, 13 figures, key quantitative results in Table 3, Accepted
as part of a PHANGS-JWST Focus Issue to appear in Ap
PDRs4All IV. An embarrassment of riches: Aromatic infrared bands in the Orion Bar
(Abridged) Mid-infrared observations of photodissociation regions (PDRs) are
dominated by strong emission features called aromatic infrared bands (AIBs).
The most prominent AIBs are found at 3.3, 6.2, 7.7, 8.6, and 11.2 m. The
most sensitive, highest-resolution infrared spectral imaging data ever taken of
the prototypical PDR, the Orion Bar, have been captured by JWST. We provide an
inventory of the AIBs found in the Orion Bar, along with mid-IR template
spectra from five distinct regions in the Bar: the molecular PDR, the atomic
PDR, and the HII region. We use JWST NIRSpec IFU and MIRI MRS observations of
the Orion Bar from the JWST Early Release Science Program, PDRs4All (ID: 1288).
We extract five template spectra to represent the morphology and environment of
the Orion Bar PDR. The superb sensitivity and the spectral and spatial
resolution of these JWST observations reveal many details of the AIB emission
and enable an improved characterization of their detailed profile shapes and
sub-components. While the spectra are dominated by the well-known AIBs at 3.3,
6.2, 7.7, 8.6, 11.2, and 12.7 m, a wealth of weaker features and
sub-components are present. We report trends in the widths and relative
strengths of AIBs across the five template spectra. These trends yield valuable
insight into the photochemical evolution of PAHs, such as the evolution
responsible for the shift of 11.2 m AIB emission from class B in
the molecular PDR to class A in the PDR surface layers. This
photochemical evolution is driven by the increased importance of FUV processing
in the PDR surface layers, resulting in a "weeding out" of the weakest links of
the PAH family in these layers. For now, these JWST observations are consistent
with a model in which the underlying PAH family is composed of a few species:
the so-called 'grandPAHs'.Comment: 25 pages, 10 figures, to appear in A&
PDRs4All III: JWST's NIR spectroscopic view of the Orion Bar
(Abridged) We investigate the impact of radiative feedback from massive stars
on their natal cloud and focus on the transition from the HII region to the
atomic PDR (crossing the ionisation front (IF)), and the subsequent transition
to the molecular PDR (crossing the dissociation front (DF)). We use
high-resolution near-IR integral field spectroscopic data from NIRSpec on JWST
to observe the Orion Bar PDR as part of the PDRs4All JWST Early Release Science
Program. The NIRSpec data reveal a forest of lines including, but not limited
to, HeI, HI, and CI recombination lines, ionic lines, OI and NI fluorescence
lines, Aromatic Infrared Bands (AIBs including aromatic CH, aliphatic CH, and
their CD counterparts), CO2 ice, pure rotational and ro-vibrational lines from
H2, and ro-vibrational lines HD, CO, and CH+, most of them detected for the
first time towards a PDR. Their spatial distribution resolves the H and He
ionisation structure in the Huygens region, gives insight into the geometry of
the Bar, and confirms the large-scale stratification of PDRs. We observe
numerous smaller scale structures whose typical size decreases with distance
from Ori C and IR lines from CI, if solely arising from radiative recombination
and cascade, reveal very high gas temperatures consistent with the hot
irradiated surface of small-scale dense clumps deep inside the PDR. The H2
lines reveal multiple, prominent filaments which exhibit different
characteristics. This leaves the impression of a "terraced" transition from the
predominantly atomic surface region to the CO-rich molecular zone deeper in.
This study showcases the discovery space created by JWST to further our
understanding of the impact radiation from young stars has on their natal
molecular cloud and proto-planetary disk, which touches on star- and planet
formation as well as galaxy evolution.Comment: 52 pages, 30 figures, submitted to A&
PDRs4All II: JWST's NIR and MIR imaging view of the Orion Nebula
The JWST has captured the most detailed and sharpest infrared images ever
taken of the inner region of the Orion Nebula, the nearest massive star
formation region, and a prototypical highly irradiated dense photo-dissociation
region (PDR). We investigate the fundamental interaction of far-ultraviolet
photons with molecular clouds. The transitions across the ionization front
(IF), dissociation front (DF), and the molecular cloud are studied at
high-angular resolution. These transitions are relevant to understanding the
effects of radiative feedback from massive stars and the dominant physical and
chemical processes that lead to the IR emission that JWST will detect in many
Galactic and extragalactic environments. Due to the proximity of the Orion
Nebula and the unprecedented angular resolution of JWST, these data reveal that
the molecular cloud borders are hyper structured at small angular scales of
0.1-1" (0.0002-0.002 pc or 40-400 au at 414 pc). A diverse set of features are
observed such as ridges, waves, globules and photoevaporated protoplanetary
disks. At the PDR atomic to molecular transition, several bright features are
detected that are associated with the highly irradiated surroundings of the
dense molecular condensations and embedded young star. Toward the Orion Bar
PDR, a highly sculpted interface is detected with sharp edges and density
increases near the IF and DF. This was predicted by previous modeling studies,
but the fronts were unresolved in most tracers. A complex, structured, and
folded DF surface was traced by the H2 lines. This dataset was used to revisit
the commonly adopted 2D PDR structure of the Orion Bar. JWST provides us with a
complete view of the PDR, all the way from the PDR edge to the substructured
dense region, and this allowed us to determine, in detail, where the emission
of the atomic and molecular lines, aromatic bands, and dust originate
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