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We present LIMFAST, a semi-numerical code for simulating high-redshift galaxy formation and cosmic reionization as revealed by multi-tracer line intensity mapping (LIM) signals. LIMFAST builds upon and extends the 21cmFAST code widely used for 21 cm cosmology by implementing state-of-the-art models of galaxy formation and evolution. The metagalactic radiation background, including the production of various star-formation lines, together with the 21 cm line signal tracing the neutral intergalactic medium (IGM), are self-consistently described by photoionization modeling and stellar population synthesis coupled to the galaxy formation model. We introduce basic structure and functionalities of the code, and demonstrate its validity and capabilities by showing broad agreements between the predicted and observed evolution of cosmic star formation, IGM neutral fraction, and metal enrichment. We also present the LIM signals of 21 cm, Ly\\(\\alpha\\), H\\(\\alpha\\), H\\(\\beta\\), [OII], and [OIII] lines simulated by LIMFAST, and compare them with results from the literature. We elaborate on how several major aspects of our modeling framework, including models of star formation, chemical enrichment, and photoionization, may impact different LIM observables and thus become testable once applied to observational data. LIMFAST aims at being an efficient and resourceful tool for intensity mapping studies in general, exploring a wide range of scenarios of galaxy evolution and reionization and frequencies over which useful cosmological signals can be measured.

The cosmic near-infrared background (NIRB) offers a powerful integral probe of radiative processes at different cosmic epochs, including the pre-reionization era when metal-free, Population III (Pop III) stars first formed. While the radiation from metal-enriched, Population II (Pop II) stars likely dominates the contribution to the observed NIRB from the reionization era, Pop III stars -- if formed efficiently -- might leave characteristic imprints on the NIRB thanks to their strong Ly\\(\\alpha\\) emission. Using a physically-motivated model of first star formation, we provide an analysis of the NIRB mean spectrum and anisotropy contributed by stellar populations at \\(z>5\\). We find that in circumstances where massive Pop III stars persistently form in molecular cooling haloes at a rate of a few times \\(10^{-3}\\,M_\\odot \\ \\mathrm{yr}^{-1}\\), before being suppressed towards the epoch of reionization (EoR) by the accumulated Lyman-Werner background, a unique spectral signature shows up redward of \\(1\\,\\mu\\)m in the observed NIRB spectrum sourced by galaxies at \\(z>5\\). While the detailed shape and amplitude of the spectral signature depend on various factors including the star formation histories, IMF, LyC escape fraction and so forth, the most interesting scenarios with efficient Pop III star formation are within the reach of forthcoming facilities such as the Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer (SPHEREx). As a result, new constraints on the abundance and formation history of Pop III stars at high redshifts will be available through precise measurements of the NIRB in the next few years.

We investigate the effects of Population III (Pop III) stars and their remnants on the cosmological 21-cm global signal. By combining a semi-analytic model of Pop III star formation with a global 21-cm simulation code, we investigate how X-ray and radio emission from accreting Pop III black holes may affect both the timing and depth of the 21-cm absorption feature that follows the initial onset of star formation during the Cosmic Dawn. We compare our results to the findings of the EDGES experiment, which has reported the first detection of a cosmic 21-cm signal. In general, we find that our fiducial Pop III models, which have peak star formation rate densities of \\(\\sim 10^{-4}\\) M\\(_\\odot\\) yr\\(^{-1}\\) Mpc\\(^{-3}\\) between \\(z \\sim 10\\) and \\(z \\sim 15\\), are able to match the timing of the EDGES signal quite well, in contrast to models that ignore Pop III stars. To match the unexpectedly large depth of the EDGES signal without recourse to exotic physics, we vary the parameters of emission from accreting black holes (formed as Pop III remnants) including the intrinsic strength of X-ray and radio emission as well as the local column density of neutral gas. We find that models with strong radio emission and relatively weak X-ray emission can self-consistently match the EDGES signal, though this solution requires fine-tuning. We are only able to produce signals with sharp features similar to the EDGES signal if the Pop~III IMF is peaked narrowly around \\(140 \\, M_\\odot\\).

The epoch of reionization (EoR) offers a unique window into the dawn of galaxy formation, through which high-redshift galaxies can be studied by observations of both themselves and their impact on the intergalactic medium. Line intensity mapping (LIM) promises to explore cosmic reionization and its driving sources by measuring intensity fluctuations of emission lines tracing the cosmic gas in varying phases. Using LIMFAST, a novel semi-numerical tool designed to self-consistently simulate LIM signals of multiple EoR probes, we investigate how building blocks of galaxy formation and evolution theory, such as feedback-regulated star formation and chemical enrichment, might be studied with multi-tracer LIM during the EoR. On galaxy scales, we show that the star formation law and the feedback associated with star formation can be indicated by both the shape and redshift evolution of LIM power spectra. For a baseline model of metal production that traces star formation, we find that lines highly sensitive to metallicity are generally better probes of galaxy formation models. On larger scales, we demonstrate that inferring ionized bubble sizes from cross-correlations between tracers of ionized and neutral gas requires a detailed understanding of the astrophysics that shape the line luminosity--halo mass relation. Despite various modeling and observational challenges, wide-area, multi-tracer LIM surveys will provide important high-redshift tests for the fundamentals of galaxy formation theory, especially the interplay between star formation and feedback by accessing statistically the entire low-mass population of galaxies as ideal laboratories, complementary to upcoming surveys of individual sources by new-generation telescopes.

We present a semi-analytic model of star formation in the early universe, beginning with the first metal-free stars. By employing a completely feedback-limited star formation prescription, stars form at maximum efficiency until the self-consistently calculated feedback processes halt formation. We account for a number of feedback processes including a meta-galactic Lyman-Werner background, supernovae, photoionization, and chemical feedback. Halos are evolved combining mass accretion rates found through abundance matching with our feedback-limited star formation prescription, allowing for a variety of Population III (Pop III) initial mass functions (IMFs). We find that, for a number of models, massive Pop III star formation can continue on until at least \\(z \\sim 20\\) and potentially past \\(z \\sim 6\\) at rates of around \\(10^{-4}\\) to \\(10^{-5}\\) M\\(_\\odot\\) yr\\(^{-1}\\) Mpc\\(^{-3}\\), assuming these stars form in isolation. At this point Lyman-Werner feedback pushes the minimum halo mass for star formation above the atomic cooling threshold, cutting off the formation of massive Pop III stars. We find that, in most models, Pop II and Pop III star formation co-exist over cosmological time-scales, with the total star formation rate density and resulting radiation background strongly dominated by the former before Pop III star formation finally ends. These halos form at most \\(\\sim 10^3\\) M\\(_\\odot\\) of massive Pop III stars during this phase and typically have absolute magnitudes in the range of \\(M_\\text{AB} = -5 \\) to \\( -10\\). We also briefly discuss how future observations from telescopes such as JWST or WFIRST and 21-cm experiments may be able to constrain unknown parameters in our model such as the IMF, star formation prescription, or the physics of massive Pop III stars.

We demonstrate the potential of line-intensity mapping to place constraints on the initial mass function (IMF) of Population III stars via measurements of the mean He II 1640A/H\\(\\alpha\\) line-intensity ratio. We extend the 21cmFAST code with modern high-redshift galaxy-formation and photoionization models, and estimate the line emission from Population II and Population III galaxies at redshifts \\(5 \\le z \\le 20\\). In our models, mean ratio values of He II/H\\(\\alpha \\gtrsim 0.1\\) indicate top-heavy Population III IMFs with stars of several hundred solar masses, reached at \\(z \\gtrsim 10\\) when Population III stars dominate star formation. A next-generation space mission with capabilities moderately superior to those of CDIM will be able to probe this scenario by measuring the He II and H\\(\\alpha\\) fluctuation power spectrum signals and their cross-correlation at high significance up to \\(z\\sim 20\\). Moreover, regardless of the IMF, a ratio value of He II/H\\(\\alpha \\lesssim 0.01\\) indicates low Population III star formation and, therefore, it signals the end of the period dominated by this stellar population. However, a detection of the corresponding He II power spectrum may be only possible for top-heavy Population III IMFs or through cross-correlation with the stronger H\\(\\alpha\\) signal. Finally, ratio values of \\(0.01 \\lesssim\\) He II/H\\(\\alpha\\) \\(\\lesssim 0.1\\) are complex to interpret because they can be driven by several competing effects. We discuss how various measurements at different redshifts and the combination of the line-intensity ratio with other probes can assist in constraining the Population III IMF in this case.

Cancer immunotherapy trials have had variable success, prompting a search for biomarkers of response. Tertiary lymphoid structures (TLS) have emerged as prognostic for multiple tumor types. These ectopic immunological bodies resemble secondary lymphoid organs with segregated B and T cell zones, but they are heterogeneous in their organization and cellular composition. These features have consequences in terms of prognostication and disease clearance, so there is interest in what drives TLS heterogeneity and corresponding immunological responses. We applied single RNA molecule resolution imaging to study biopsies from triple negative breast tumors harboring TLS where the biopsies were taken longitudinally, prior to therapy, after pembrolizumab and after pembrolizumab with radiation therapy. We developed a computational framework to identify TLS and tumor beds and to align spatial trajectories between the immune and malignant structures for systematic analyses. We identified two tumor types based on immune infiltration profiles in the tumor bed. Immune “infiltrated” tumors were eliminated after pembrolizumab, while “non-infiltrated” tumors saw gains in effector T cells and myeloid cells after pembrolizumab and were cleared after pembrolizumab with RT. TLS from infiltrated tumors had better separation of B and T cell zones and had higher expression of immunoreactivity gene pathways in most cell types. Further, malignant cell MHC expression was higher in the tumor beds of infiltrated tumors, providing one plausible mechanism for the groupings. In non-infiltrated tumors, classical dendritic cells enter the tumor bed from TLS proximal zones after pembrolizumab and bring transcription of the CXCL9 chemokine, which can recruit T cells and promote T cell effector phenotypes and was higher in infiltrated tumors at baseline.

We investigate the effects of Population III stars on the sky-averaged 21-cm background radiation, which traces the collective emission from all sources of ultraviolet and X-ray photons before reionization is complete. While UV photons from PopIII stars can in principle shift the onset of radiative coupling of the 21-cm transition -- and potentially reionization -- to early times, we find that the remnants of PopIII stars are likely to have a more discernible impact on the 21-cm signal than PopIII stars themselves. The X-rays from such sources preferentially heat the IGM at early times, which elongates the epoch of reheating and results in a more gradual transition from an absorption signal to emission. This gradual heating gives rise to broad, asymmetric wings in the absorption signal, which stand in contrast to the relatively sharp, symmetric signals that arise in models treating PopII sources only. A stronger signature of PopIII, in which the position of the absorption minimum becomes inconsistent with PopII-only models, requires extreme star-forming events that may not be physically plausible, lending further credence to predictions of relatively high frequency absorption troughs, \\(\\nu_{\\min} \\sim 100\\) MHz. As a result, though the trough location alone may not be enough to indicate the presence of PopIII, the asymmetric wings should arise even if only a few PopIII stars form in each halo before the transition to PopII star formation occurs, provided that the PopIII IMF is sufficiently top-heavy and at least some PopIII stars form in binaries.

The American presidential election of 2000 was perhaps the most remarkable, and in many ways the most unsettling, that the country has yet experienced. The millennial election raised fundamental questions not only about American democracy, but also about the nation's constitution and about the legitimate role of American courts, state and federal, and in particular about the United States Supreme Court.The Longest Nightpresents a lively and informed reaction to the legal aftermath of the election by the most prominent experts on the subject. With a balance of opposing views-including those of some of the most distinguished foreign commentators writing on the subject today-the contributors present an unusual breadth of perspectives in addressing the judicial, institutional, and political questions involved in the disputed election. Their commentaries bring the confusion and frenzy of the event into clear focus and lay the groundwork for an essential public debate that is sure to continue well into the future.The Longest Nightcontains a thorough chronology of the events in Florida, a detailed account of the institutional structure of American presidential elections, a series of analyses both criticizing and defending the decisions inBush v. Gore,American perspectives on the Florida struggle and America's electoral system, and a debate on maintaining or reforming the electoral college. The authors include participants in the legal and political battles surrounding the Florida election, foreigners charged with monitoring and supervising elections, and scholars from many disciplines specializing in constitutionalism, democracy, and American election law.Contributors

Franklin First Financial Corp. (NASDAQ:FFFC), parent company of Franklin First Savings Bank, Wednesday announced that net income for the three months ended March 3l, l992, rose 30.2 percent to $2.4 million, or $.59 per share, up from $l.9 million, or $.42 per share, reported for the comparable period one year ago. For the first quarter of l992, earnings per share increased 40.5 percent compared to the first quarter of l99l as a result of the company's increased earnings and stock repurchase program. (excerpt)