Constraints on the Star Formation Efficiency of Galaxies During the Epoch of Reionization

Reionization is thought to have occurred in the redshift range of $6 < z < 9$, which is now being probed by both deep galaxy surveys and CMB observations. Using halo abundance matching over the redshift range $5<z<8$ and assuming smooth, continuous gas accretion, we develop a model for the star formation efficiency $f_{\star}$ of dark matter halos at $z>6$ that matches the measured galaxy luminosity functions at these redshifts. We find that $f_{\star}$ peaks at $\sim 30\%$ at halo masses $M \sim 10^{11}$--$10^{12}$~M$_\odot$, in qualitative agreement with its behavior at lower redshifts. We then investigate the cosmic star formation histories and the corresponding models of reionization for a range of extrapolations to small halo masses. We use a variety of observations to further constrain the characteristics of the galaxy populations, including the escape fraction of UV photons. Our approach provides an empirically-calibrated, physically-motivated model for the properties of star-forming galaxies sourcing the epoch of reionization. In the case where star formation in low-mass halos is maximally efficient, an average escape fraction $\sim0.1$ can reproduce the optical depth reported by Planck, whereas inefficient star formation in these halos requires either about twice as many UV photons to escape, or an escape fraction that increases towards higher redshifts. Our models also predict how future observations with JWST can improve our understanding of these galaxy populations.Comment: 19 pages, 12 figures, accepted for publication in MNRAS, minor modification

The Global 21-cm Signal in the Context of the High-z Galaxy Luminosity Function

Motivated by recent progress in studies of the high-$z$ Universe, we build a new model for the global 21-cm signal that is explicitly calibrated to measurements of the galaxy luminosity function (LF) and further tuned to match the Thomson scattering optical depth of the cosmic microwave background, $\tau_e$. Assuming that the $z \lesssim 8$ galaxy population can be smoothly extrapolated to higher redshifts, the recent decline in best-fit values of $\tau_e$ and the inefficient heating induced by X-ray binaries (HMXBs; the presumptive sources of the X-ray background at high-$z$) imply that the entirety of cosmic reionization and reheating occurs at redshifts $z \lesssim 12$. In contrast to past global 21-cm models, whose $z \sim 20$ ($\nu \sim 70$ MHz) absorption features and strong $\sim 25$ mK emission features were driven largely by the assumption of efficient early star-formation and X-ray heating, our new fiducial model peaks in absorption at $\nu \sim 110$ MHz at a depth of $\sim -160$ mK and has a negligible emission component. As a result, a strong emission signal would provide convincing evidence that HMXBs are not the only drivers of cosmic reheating. Shallow absorption troughs should accompany strong heating scenarios, but could also be caused by a low escape fraction of Lyman-Werner photons. Generating signals with troughs at $\nu \lesssim 95$ MHz requires a floor in the star-formation efficiency in halos below $\sim 10^{9} M_{\odot}$, which is equivalent to steepening the faint-end of the galaxy LF. These findings demonstrate that the global 21-cm signal is a powerful complement to current and future galaxy surveys and efforts to better understand the interstellar medium in high-$z$ galaxies.Comment: 17 pages, 9 figures, in pres

An Algebraic-Coding Equivalence to the Maximum Distance Separable Conjecture

We formulate an Algebraic-Coding Equivalence to the Maximum Distance Separable Conjecture. Specifically, we present novel proofs of the following equivalent statements. Let $(q,k)$ be a fixed pair of integers satisfying $q$ is a prime power and $2\leq k \leq q$. We denote by $\mathcal{P}_q$ the vector space of functions from a finite field $\mathbb{F}_q$ to itself, which can be represented as the space $\mathcal{P}_q := \mathbb{F}_q[x]/(x^q-x)$ of polynomial functions. We denote by $\mathcal{O}_n \subset \mathcal{P}_q$ the set of polynomials that are either the zero polynomial, or have at most $n$ distinct roots in $\mathbb{F}_q$. Given two subspaces $Y,Z$ of $\mathcal{P}_q$, we denote by $\langle Y,Z \rangle$ their span. We prove that the following are equivalent. [A] Suppose that either: 1. $q$ is odd 2. $q$ is even and $k \not\in \{3, q-1\}$. Then there do not exist distinct subspaces $Y$ and $Z$ of $\mathcal{P}_q$ such that: 3. $dim(\langle Y, Z \rangle) = k$ 4. $dim(Y) = dim(Z) = k-1$. 5. $\langle Y, Z \rangle \subset \mathcal{O}_{k-1}$ 6. $Y, Z \subset \mathcal{O}_{k-2}$ 7. $Y\cap Z \subset \mathcal{O}_{k-3}$. [B] Suppose $q$ is odd, or, if $q$ is even, $k \not\in \{3, q-1\}$. There is no integer $s$ with $q \geq s > k$ such that the Reed-Solomon code $\mathcal{R}$ over $\mathbb{F}_q$ of dimension $s$ can have $s-k+2$ columns $\mathcal{B} = \{b_1,\ldots,b_{s-k+2}\}$ added to it, such that: 8. Any $s \times s$ submatrix of $\mathcal{R} \cup \mathcal{B}$ containing the first $s-k$ columns of $\mathcal{B}$ is independent. 9. $\mathcal{B} \cup \{[0,0,\ldots,0,1]\}$ is independent. [C] The MDS conjecture is true for the given $(q,k)$.Comment: This is version: 5.6.18. arXiv admin note: substantial text overlap with arXiv:1611.0235

A Simple Alternative House Price Index Method

This paper presents the Sale Price Appraisal Ratio (SPAR) method for constructing house price indexes. The method, which uses ratios of transaction prices and previous appraised values to build up an index, has been applied since the early 1960s to produce semi-annual price indexes for regions and cities in New Zealand. We compare the official New Zealand indexes for three urban areas with repeat sales and hedonic indexes created from the same transactions data, and observe that the SPAR method produces an index very much like those produced by hedonic methods. Given the number of advantages and few disadvantages that we find for the SPAR method relative to the more traditional methods, we maintain that it should be considered by government agencies elsewhere when developing house price indexes.house price indexes

What’s in a View?

The impact of views on property values has not been the specific focus of as much research as has the impact of other externalities on property values. When the impact of views is assessed, it is usually done by adding a single dummy variable to a hedonic regression equation. This paper provides a detailed literature review as well as an empirical analysis of the impact of a view on residential property values using a very rich database of nearly 5,000 sales in Auckland, New Zealand. Several dimensions of a view are analyzed: type of view, scope of view, distance to coast, appearance of immediately surrounding improvements, average quality of landscaping in the neighborhood, and average quality of structures in the neighborhood. It is found that wide views of water add an average of 59% to the value of a waterfront property, but that this effect diminishes quite rapidly as the distance from the coast increases. Attractive buildings in a property’s neighborhood on average add 37% to value relative to properties in neighborhoods with only average quality structures. Particularly attractive improvements in the immediate surroundings of a property add another 27% to value on average. On the other hand, properties in neighborhoods with only poor quality landscaping on average experience a -51% impact on price. Our results lead to the conclusion that aesthetic externalities are multi-dimensional and can have a substantial impact on residential property values.

The Effect of Compensation Committee Quality on the Association between CEO Cash Compensation and Accounting Performance

We examine the effect of compensation committee quality on the association between CEO cash compensation and accounting earnings and the moderating effects of growth opportunities and earnings status. Research Findings/Insights: Using a sample of 812 US firms, we find that CEO cash compensation is more positively associated with accounting earnings when firms have high compensation committee quality. We also find that the positive effect of compensation committee quality on the association between CEO cash compensation and accounting earnings is less for high growth firms or loss-making firms.Theoretical Implications: We contribute to the agency-based research on CEO compensation by: 1) directly examining the impact of compensation committee quality on the sensitivity of CEO cash compensation to accounting earnings; 2) examining whether the role of compensation committee quality varies across firms; and 3) developing a broader and richer measure of compensation committee quality. Practical Implications: Our findings imply that shareholders and directors should be concerned about the composition of compensation committees as we find that compensation committee quality varies depending on compensation committee size and other characteristics of the committee members. Our findings also imply that for compensation committee members, there are greater challenges in monitoring CEO compensation contracts for firms with high growth or that incur losses. Further, our findings imply that even when all compensation committees are regulated to be fully independent, there are still quality differences among these independent compensation committees

House Price Changes and Idiosyncratic Risk: The Impact of Property Characteristics

While the average change in house prices is related to changes in fundamentals or perhaps market-wide bubbles, not all houses in a market appreciate at the same rate. The primary focus of our study is to investigate the reasons for these variations in price changes among houses within a market. We draw on two theories for guidance, one related to the optimal search strategy for sellers of atypical dwellings and the other focusing on the bargaining process between a seller and potential buyers. We hypothesize that houses will appreciate at different rates depending on the characteristics of the property and the change in the strength of the housing market. These hypotheses are supported using data from three New Zealand housing markets.Atypicality, Bargaining, Housing Risk, House Price Appreciation, Search Models

Exploring Residents\u27 Attitudes toward Solar Photovoltaic System Adoption in China

As the world’s largest energy consuming country, China is facing environmental deterioration, which results from the overuse of non-renewable conventional energy such as coal. Solar photovoltaic (PV) energy, an unlimited and clean energy with minimal impacts on the environment, is considered a good alternative to alleviate this severe issue. A survey was designed and conducted among residents in some major cities in China: Beijing, Shanghai, Nanchang, and Guangdong. Based on the first-hand data, basic statistical methods were utilized to examine Chinese urban residents’ knowledge, concerns, and attitudes about solar PV adoption. The research aimed to identify the drivers and dynamics that most encourage customers to install solar PV systems in their residential buildings. The data suggest that the factors that could increase solar PV adoption are (a) reduced costs, (b) practical government incentives, (c) desire to reduce fossil fuel usage, and (d) education to increase awareness of solar PV systems. This research empirically assesses the impacts of the adoption of solar PV systems on various socio-economic groups