Stellar Structure of Dark Stars: a first phase of Stellar Evolution due to Dark Matter Annihilation

Dark Stars are the very first phase of stellar evolution in the history of the universe: the first stars to form (typically at redshifts $z \sim 10-50$) are powered by heating from dark matter (DM) annihilation instead of fusion (if the DM is made of particles which are their own antiparticles). We find equilibrium polytropic configurations for these stars; we start from the time DM heating becomes important ($M \sim 1-10 M_\odot$) and build up the star via accretion up to 1000 M$_\odot$. The dark stars, with an assumed particle mass of 100 GeV, are found to have luminosities of a few times $10^6$ L$_\odot$, surface temperatures of 4000--10,000 K, radii $\sim 10^{14}$ cm, lifetimes of at least $0.5$ Myr, and are predicted to show lines of atomic and molecular hydrogen. Dark stars look quite different from standard metal-free stars without DM heating: they are far more massive (e.g. $\sim 800 M_\odot$ for 100 GeV WIMPs), cooler, and larger, and can be distinguished in future observations, possibly even by JWST or TMT.Comment: 14 pages, 1 figure, 1 table, shortened manuscript for publication, updated mansucript in accordance with referee's repor

Implications of primordial black holes on the first stars and the origin of the super--massive black holes

If the cosmological dark matter has a component made of small primordial black holes, they may have a significant impact on the physics of the first stars and on the subsequent formation of massive black holes. Primordial black holes would be adiabatically contracted into these stars and then would sink to the stellar center by dynamical friction, creating a larger black hole which may quickly swallow the whole star. If these primordial black holes are heavier than $\sim 10^{22} {\rm g}$, the first stars would likely live only for a very short time and would not contribute much to the reionization of the universe. They would instead become $10 - 10^3 M_\odot$ black holes which (depending on subsequent accretion) could serve as seeds for the super--massive black holes seen at high redshifts as well as those inside galaxies today.Comment: 16 pages, 2 figures. v2: refereed versio

Observing supermassive dark stars with James Webb Space Telescope

We study the capability of the James Webb Space Telescope ( JWST ) to detect supermassive dark stars (SMDSs). If the first stars are powered by dark matter (DM) heating in triaxial DM haloes, they may grow to be very large (>10 6  M ⊙ ) and very bright (>10 9  L ⊙ ). These SMDSs would be visible in deep imaging with JWST and even Hubble Space Telescope ( HST ). We use sensitivity limits from previous HST surveys to place bounds on the numbers of SMDSs that may be detected in future JWST imaging surveys. We showed that SMDS in the mass range 10 6 –10 7  M ⊙ are bright enough to be detected in all the wavelength bands of the NIRCam on JWST (but not in the less sensitive MIRI camera at higher wavelengths). If SMDSs exist at z ∼ 10, 12 and 14, they will be detectable as J ‐, H ‐ or K ‐band dropouts, respectively. With a total survey area of 150 arcmin 2 (assuming a multiyear deep parallel survey with JWST ), we find that typically the number of 10 6  M ⊙ SMDSs found as H ‐ or K ‐band dropouts is ∼10 5 f SMDS , where the fraction of early DM haloes hosting DS is likely to be small, f SMDS ≪ 1. If the SMDS survive down to z = 10 where HST bounds apply, then the observable number of SMDSs as H ‐ or K ‐band dropouts with JWST is ∼1–30. While individual SMDS are bright enough to be detected by JWST , standard Population III stars (without DM annihilation) are not, and would only be detected in first galaxies with total stellar masses of 10 6 –10 8  M ⊙ . Differentiating first galaxies at z > 10 from SMDSs would be possible with spectroscopy: the SMDS (which are too cool produce significant nebular emission) will have only absorption lines, while the galaxies are likely to produce emission lines as well. Of particular interest would be the He  ii emission lines at m as well as Hα lines which would be signatures of early galaxies rather than SMDSs. The detection of SMDSs with JWST would not only provide alternative evidence for weakly interacting massive particles, but also provide a possible pathway for the formation of massive (10 4 –10 6  M ⊙ ) seeds for the formation of supermassive black holes that power quasi‐stellar objects at z = 6.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91335/1/j.1365-2966.2012.20760.x.pd

Dark Stars: A New Study of the FIrst Stars in the Universe

We have proposed that the first phase of stellar evolution in the history of the Universe may be Dark Stars (DS), powered by dark matter heating rather than by nuclear fusion. Weakly Interacting Massive Particles, which may be their own antipartners, collect inside the first stars and annihilate to produce a heat source that can power the stars. A new stellar phase results, a Dark Star, powered by dark matter annihilation as long as there is dark matter fuel, with lifetimes from millions to billions of years. We find that the first stars are very bright ($\sim 10^6 L_\odot$) and cool ($T_{surf} < 10,000$K) during the DS phase, and grow to be very massive (500-1000 times as massive as the Sun). These results differ markedly from the standard picture in the absence of DM heating, in which the maximum mass is about 140$M_\odot$ and the temperatures are much hotter ($T_{surf} > 50,000$K); hence DS should be observationally distinct from standard Pop III stars. Once the dark matter fuel is exhausted, the DS becomes a heavy main sequence star; these stars eventually collapse to form massive black holes that may provide seeds for supermassive black holes observed at early times as well as explanations for recent ARCADE data and for intermediate black holes.Comment: article to be published in special issue on Dark Matter and Particle Physics in New Journal of Physic

The Impact of Rurality and Age on Colorectal Cancer Screening Among Michigan Residents

Background: Colorectal cancer (CRC) is a prevalent cause of cancer-related deaths in Michigan, but not all Michigan adults had appropriate CRC screening. Objective: To assess the relationship between rurality and age on CRC screenings to inform how pharmacists could focus their efforts to educate, facilitate, or offer CRC health screenings. Methods: This was a retrospective, cross-sectional study using 2018 Michigan Behavioral Risk Factor Surveillance System (MiBRFSS) survey data. Michigan participants aged ≥ 50 years were included. Outcomes included the utilization of stool-based tests, sigmoidoscopies, colonoscopies, and the most recent CRC screening. Demographic variables included age, sex, income, race/ethnicity, relationship status, education level, employment status, income, rurality, and health insurance. Representative sampling weights were used to adjust for the complex survey design. Descriptive statistics, chi-square, and multivariable logistic regression analyses were conducted. IBM SPSS version 28.0.1.0 was used and an a priori p-value of <0.05 was deemed significant. Results: A weighted total of 3,762,540 participants were included, of which 21.3% (n = 781,907) reported living in a rural area and approximately 70% (n = 2,616,646) were between the ages of 50-69 years old. Most participants reported being White, non-Hispanic (n = 3,104,117, 84.5%), having health insurance (n = 3,619,801, 96.4%), and having a colonoscopy (74.6%, n= 2,620,581). There was no difference based on rurality. Compared to those aged 50-59 years, adults 60-69 years (AOR = 1.97, 95% CI: 1.58,2.45), 70-79 years (AOR = 3.29, 95% CI: 2.40,4.51), and ≥ 80 years (AOR = 2.23, 95% CI: 1.54,3.24) had higher odds of receiving a colonoscopy. Lack of insurance was associated with lower odds of receiving a colonoscopy (AOR = 0.38, 95% CI: 0.23, 0.56). Conclusion: Most participants reported having a CRC screening but efforts to increase CRC screening in Michigan adults aged 50-59 are warranted

Virtual audits of the urban streetscape: comparing the inter-rater reliability of GigaPan® to Google Street View

Abstract Background Although previous research has highlighted the association between the built environment and individual health, methodological challenges in assessing the built environment remain. In particular, many researchers have demonstrated the high inter-rater reliability of assessing large or objective built environment features and the low inter-rater reliability of assessing small or subjective built environment features using Google Street View. New methods for auditing the built environment must be evaluated to understand if there are alternative tools through which researchers can assess all types of built environment features with high agreement. This paper investigates measures of inter-rater reliability of GigaPan®, a tool that assists with capturing high-definition panoramic images, relative to Google Street View. Methods Street segments (n = 614) in Pittsburgh, Pennsylvania in the United States were randomly selected to audit using GigaPan® and Google Street View. Each audit assessed features related to land use, traffic and safety, and public amenities. Inter-rater reliability statistics, including percent agreement, Cohen’s kappa, and the prevalence-adjusted bias-adjusted kappa (PABAK) were calculated for 106 street segments that were coded by two, different, human auditors. Results Most large-scale, objective features (e.g. bus stop presence or stop sign presence) demonstrated at least substantial inter-rater reliability for both methods, but significant differences emerged across finely detailed features (e.g. trash) and features at segment endpoints (e.g. sidewalk continuity). After adjusting for the effects of bias and prevalence, the inter-rater reliability estimates were consistently higher for almost all built environment features across GigaPan® and Google Street View. Conclusion GigaPan® is a reliable, alternative audit tool to Google Street View for studying the built environment. GigaPan® may be particularly well-suited for built environment projects with study settings in areas where Google Street View imagery is nonexistent or updated infrequently. The potential for enhanced, detailed imagery using GigaPan® will be most beneficial in studies in which current, time sensitive data are needed or microscale built environment features would be challenging to see in Google Street View. Furthermore, to better understand the effects of prevalence and bias in future reliability studies, researchers should consider using PABAK to supplement or expand upon Cohen’s kappa findings.http://deepblue.lib.umich.edu/bitstream/2027.42/173713/1/12942_2020_Article_226.pd

A CEERS Discovery of an Accreting Supermassive Black Hole 570 Myr after the Big Bang: Identifying a Progenitor of Massive z > 6 Quasars

We report the discovery of an accreting supermassive black hole at z = 8.679. This galaxy, denoted here as CEERS_1019, was previously discovered as a Lyα-break galaxy by Hubble with a Lyα redshift from Keck. As part of the Cosmic Evolution Early Release Science (CEERS) survey, we have observed this source with JWST/NIRSpec, MIRI, NIRCam, and NIRCam/WFSS and uncovered a plethora of emission lines. The Hβ line is best fit by a narrow plus a broad component, where the latter is measured at 2.5σ with an FWHM ∼1200 km s−1. We conclude this originates in the broadline region of an active galactic nucleus (AGN). This is supported by the presence of weak high-ionization lines (N V, N IV], and C III]), as well as a spatial point-source component. The implied mass of the black hole (BH) is log (M BH/M ⊙) = 6.95 ± 0.37, and we estimate that it is accreting at 1.2 ± 0.5 times the Eddington limit. The 1–8 μm photometric spectral energy distribution shows a continuum dominated by starlight and constrains the host galaxy to be massive (log M/M⊙ ∼9.5) and highly star-forming (star formation rate, or SFR ∼ 30 M⊙ yr−1; log sSFR ∼ − 7.9 yr−1). The line ratios show that the gas is metal-poor (Z/Z ⊙ ∼ 0.1), dense (n e ∼ 103 cm−3), and highly ionized (log U ∼ − 2.1). We use this present highest-redshift AGN discovery to place constraints on BH seeding models and find that a combination of either super-Eddington accretion from stellar seeds or Eddington accretion from very massive BH seeds is required to form this object

A CEERS Discovery of an Accreting Supermassive Black Hole 570 Myr after the Big Bang: Identifying a Progenitor of Massive z > 6 Quasars

We report the discovery of an accreting supermassive black hole at z = 8.679. This galaxy, denoted here as CEERS_1019, was previously discovered as a Ly α -break galaxy by Hubble with a Ly α redshift from Keck. As part of the Cosmic Evolution Early Release Science (CEERS) survey, we have observed this source with JWST/NIRSpec, MIRI, NIRCam, and NIRCam/WFSS and uncovered a plethora of emission lines. The H β line is best fit by a narrow plus a broad component, where the latter is measured at 2.5 σ with an FWHM ∼1200 km s ^−1 . We conclude this originates in the broadline region of an active galactic nucleus (AGN). This is supported by the presence of weak high-ionization lines (N V, N IV], and C III]), as well as a spatial point-source component. The implied mass of the black hole (BH) is log ( M _BH / M _⊙ ) = 6.95 ± 0.37, and we estimate that it is accreting at 1.2 ± 0.5 times the Eddington limit. The 1–8 μ m photometric spectral energy distribution shows a continuum dominated by starlight and constrains the host galaxy to be massive (log M/M _⊙ ∼9.5) and highly star-forming (star formation rate, or SFR ∼ 30 M _⊙ yr ^−1 ; log sSFR ∼ − 7.9 yr ^−1 ). The line ratios show that the gas is metal-poor ( Z / Z _⊙ ∼ 0.1), dense ( n _e ∼ 10 ^3 cm ^−3 ), and highly ionized (log U ∼ − 2.1). We use this present highest-redshift AGN discovery to place constraints on BH seeding models and find that a combination of either super-Eddington accretion from stellar seeds or Eddington accretion from very massive BH seeds is required to form this object

The Complete CEERS Early Universe Galaxy Sample: A Surprisingly Slow Evolution of the Space Density of Bright Galaxies at z ∼ 8.5–14.5

Abstract We present a sample of 88 candidate z ∼ 8.5–14.5 galaxies selected from the completed NIRCam imaging from the Cosmic Evolution Early Release Science survey. These data cover ∼90 arcmin2 (10 NIRCam pointings) in six broadband imaging filters and one medium-band imaging filter. With this sample we confirm at higher confidence early JWST conclusions that bright galaxies in this epoch are more abundant than predicted by most theoretical models. We construct the rest-frame ultraviolet luminosity functions at z ∼ 9, 11, and 14 and show that the space density of bright (M UV = −20) galaxies changes only modestly from z ∼ 14 to z ∼ 9, compared to a steeper increase from z ∼ 8 to z ∼ 4. While our candidates are photometrically selected, spectroscopic follow-up has now confirmed 13 of them, with only one significant interloper, implying that the fidelity of this sample is high. Successfully explaining the evidence for a flatter evolution in the number densities of UV-bright z &gt; 10 galaxies may thus require changes to the dominant physical processes regulating star formation. While our results indicate that significant variations of dust attenuation with redshift are unlikely to be the dominant factor at these high redshifts, they are consistent with predictions from models that naturally have enhanced star formation efficiency and/or stochasticity. An evolving stellar initial mass function could also bring model predictions into better agreement with our results. Deep spectroscopic follow-up of a large sample of early galaxies can distinguish between these competing scenarios.</jats:p