1,847 research outputs found
The IRX- relation: Insights from simulations
We study the relationship between the UV continuum slope and infrared excess
(IRX) predicted by performing dust radiative
transfer on a suite of hydrodynamical simulations of galaxies. Our suite
includes both isolated disk galaxies and mergers intended to be representative
of galaxies at both and . Our low-redshift isolated
disks and mergers often populate a region around the the locally calibrated
\citet[][M99]{M99} relation but move well above the relation during
merger-induced starbursts. Our high-redshift simulated galaxies are blue and
IR-luminous, which makes them lie above the M99 relation. The value of UV
continuum slope strongly depends on the dust type used in the radiative
transfer calculations: Milky Way-type dust leads to significantly more negative
(bluer) slopes compared with Small Magellanic Cloud-type dust. The effect on
due to variations in the dust composition with galaxy properties or
redshift can dominate over other sources of variations and is the
dominant model uncertainty. The dispersion in is anticorrelated with
specific star formation rate and tends to be higher for the
simulations. In the actively star-forming simulated galaxies, dust
attenuation dominates the dispersion in , whereas in the
simulations, the contributions of SFH variations and dust are similar. For
low-SSFR systems at both redshifts, SFH variations dominate the dispersion.
Finally, the simulated isolated disks and mergers both occupy a
region in the \irxbeta\ plane consistent with observed dusty
star-forming galaxies (DSFGs). Thus, contrary to some claims in the literature,
the blue colors of high-z DSFGs do not imply that they are short-lived
starbursts.Comment: 20 pages+a 4-page appendix, Accepted for publication at Ap
A Simple Non-equilibrium Feedback Model for Galaxy-Scale Star Formation: Delayed Feedback and SFR Scatter
We explore a class of simple non-equilibrium star formation models within the
framework of a feedback-regulated model of the ISM, applicable to
kiloparsec-scale resolved star formation relations (e.g. Kennicutt-Schmidt).
Combining a Toomre-Q-dependent local star formation efficiency per free-fall
time with a model for delayed feedback, we are able to match the normalization
and scatter of resolved star formation scaling relations. In particular, this
simple model suggests that large (dex) variations in star formation rates
(SFRs) on kiloparsec scales may be due to the fact that supernova feedback is
not instantaneous following star formation. The scatter in SFRs at constant gas
surface density in a galaxy then depends on the properties of feedback and when
we observe its star-forming regions at various points throughout their
collapse/star formation "cycles". This has the following important
observational consequences: (1) the scatter and normalization of the
Kennicutt-Schmidt relation are relatively insensitive to the local
(small-scale) star formation efficiency, (2) but gas depletion times and
velocity dispersions are; (3) the scatter in and normalization of the
Kennicutt-Schmidt relation is a sensitive probe of the feedback timescale and
strength; (4) even in a model where deterministically
dictates star formation locally, time evolution, variation in local conditions
(e.g., gas fractions and dynamical times), and variations between galaxies can
destroy much of the observable correlation between SFR and
in resolved galaxy surveys. Additionally, this model exhibits large scatter in
SFRs at low gas surface densities, in agreement with observations of flat outer
HI disk velocity dispersion profiles.Comment: 15 pages, 6 figures, accepted by MNRAS (04/25/2019
An improved thin-film microelectrode array and signal conditioning board for measuring cardiac surface potentials.
The work outlined in this thesis expanded on previous work to improve a thin-film microfabricated electrode array intended for cardiac electrophysiology studies. A thin layer of silver was added in between titanium and platinum electrical trace layers to reduce electrode resistance. A 200 nm layer of silver decreased electrode resistance by an order of magnitude. In addition, a new high quality signal conditioning board was developed using precision operational amplifiers from Texas Instruments. Both new sensor and board design were verified together through in vivo studies using rabbit, goat, and dog hearts
Advertising and Dublin’s Consumer Culture in James Joyce’s Ulysses
This thesis reconsiders James Joyce’s representation of advertising and Dublin’s consumer culture in Ulysses. Against earlier, generalising accounts, it applies a carefully historicising methodology to demonstrate the cultural specificity of Joyce’s engagement. It does so in three ways. To begin with, it establishes that Irish consumerism did not simply follow British advances, but developed in a distinct and inflected fashion. Chapters 2 and 3 show that while Joyce incorporates all of the material characteristics of Dublin’s relatively advanced consumer culture, he downplays its advertising industry, making it appear less developed in 1904 than was historically the case.
Secondly, it analyses the distortions introduced by Joyce’s own historical remove from the consumer culture he depicts. Chapter 4 identifies for the first time the sources of Joyce’s “Advertising” notes from his so-called “Notes on Business and Commerce,” and establishes that his representation of Bloom’s advertising consciousness reflects advances in advertising theory that only got seriously underway in the decade between 1904, when the novel is set, and 1914, when Joyce began to write it.
Finally, having analysed the material and compositional background to Joyce’s portrayal of early-twentieth-century consumerism, this thesis analyses Joyce’s engagement with two of its dominant ideologies. Chapter 5 concentrates on the ‘Lestrygonians’ and ‘Ithaca’ episodes to argue that Joyce lays bare the overdetermined nature of colonial consumption, depicting the naturalisation of British commodities on the Irish market, and contesting the spurious claim to disinterestedness presented by imperial consumerist discourses. Chapter 6 develops intertextual readings of the ‘Nausicaa’ chapter to show that Joyce’s narrative is even more fully comprised of the language of female-oriented advertising than has been recognised. It argues that the chapter responds to a particular ideological complex, in which consumerist imperatives struggled with more conservative patriarchal interests.
Overall, this thesis brings together historical, genetic and intertextual critical approaches to uncover the stylistic and chronological manipulations involved in Joyce’s fictionalisation of early-twentieth-century Irish consumerism. It argues that Ulysses stands as both a reflection of this crucial period of socio-economic change, and a politicised response to its dominant ideological coercions
What shapes the far-infrared spectral energy distributions of galaxies?
To explore the connection between the global physical properties of galaxies
and their far-infrared (FIR) spectral energy distributions (SEDs), we study the
variation in the FIR SEDs of a set of hydrodynamically simulated galaxies that
are generated by performing dust radiative transfer in post-processing. Our
sample includes both isolated and merging systems at various stages of the
merging process and covers infrared (IR) luminosities and dust masses that are
representative of both low- and high-redshift galaxies. We study the FIR SEDs
using principle component analysis (PCA) and find that 97\% of the variance in
the sample can be explained by two principle components (PCs). The first PC
characterizes the wavelength of the peak of the FIR SED, and the second encodes
the breadth of the SED. We find that the coefficients of both PCs can be
predicted well using a double power law in terms of the IR luminosity and dust
mass, which suggests that these two physical properties are the primary
determinants of galaxies' FIR SED shapes. Incorporating galaxy sizes does not
significantly improve our ability to predict the FIR SEDs. Our results suggest
that the observed redshift evolution in the effective dust temperature at fixed
IR luminosity is not driven by geometry: the SEDs of ultraluminous
IR galaxies (ULIRGs) are cooler than those of local ULIRGs not because the
high-redshift galaxies are more extended but rather because they have higher
dust masses at fixed IR luminosity. Finally, based on our simulations, we
introduce a two-parameter set of SED templates that depend on both IR
luminosity and dust mass.Comment: Submitted to ApJ, comments welcom
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