Abstract
The most luminous quasars at
z
> 6 are suspected to be both highly clustered and to reside in the most massive dark matter halos in the early universe, making them prime targets to search ...for galaxy overdensities and/or protoclusters. We search for Lyman-break dropout-selected galaxies using HST WFC3/ACS broadband imaging in the fields of three 6 <
z
< 7 quasars, as well as for their simultaneously observed coordinated parallel fields, and constrain their photometric redshifts using EAZY. One field, J0305-3150, shows a volume density 10× higher than the blank-field UV luminosity function (UVLF) at
M
UV
< −20, with tentative evidence of a 3
σ
overdensity in its parallel field located 15 cMpc away. Another field, J2054–0005, shows an angular overdensity within 500 ckpc from the quasar, but this is still consistent with UVLF predictions within 3
σ
, while the last field, J2348–3054, shows no enhancement. We discuss methods for reducing uncertainty in overdensity measurements when using photometric selection and show that we can robustly select Lyman-break galaxies (LBGs) consistent with being physically associated with the quasar, corroborated by existing JWST/NIRCam WFSS data in the J0305 field. Even accounting for incompleteness, the overdensities in J0305 and J2054 are higher for brighter galaxies at short angular separations, suggesting preferential enhancement of more massive galaxies in the quasar’s immediate vicinity. Finally, we compare the population of LBGs with previously identified C
ii
and millimeter-continuum companions. The LBG overdensities are not accompanied by an enhanced number of dusty galaxies, suggesting that the overdense quasar fields are not in the bursty star-forming phase sometimes seen in high-redshift protoclusters.
Abstract
A complete census of dusty star-forming galaxies (DSFGs) at early epochs is necessary to constrain the obscured contribution to the cosmic star formation rate density (CSFRD); however, DSFGs ...beyond
z
∼ 4 are both rare and hard to identify from photometric data alone due to degeneracies in submillimeter photometry with redshift. Here, we present a pilot study obtaining follow-up Atacama Large Millimeter Array (ALMA) 2 mm observations of a complete sample of 39 850
μ
m-bright dusty galaxies in the SSA22 field. Empirical modeling suggests 2 mm imaging of existing samples of DSFGs selected at 850
μ
m—1 mm can quickly and easily isolate the “needle in a haystack” DSFGs that sit at
z
> 4 or beyond. Combining archival submillimeter imaging with our measured ALMA 2 mm photometry (1
σ
∼ 0.08 mJy beam
−1
rms), we characterize the galaxies’ IR spectral energy distributions (SEDs) and use them to constrain redshifts. With available redshift constraints fit via the combination of six submillimeter bands, we identify 6/39 high-
z
candidates each with >50% likelihood to sit at
z
> 4, and find a positive correlation between redshift and 2 mm flux density. Specifically, our models suggest the addition of 2 mm to a moderately constrained IR SED will improve the accuracy of a millimeter-derived redshift from Δ
z
/(1 +
z
) = 0.3 to Δ
z
/(1 +
z
) = 0.2. Our IR SED characterizations provide evidence for relatively high-emissivity spectral indices (〈
β
〉 = 2.4 ± 0.3) in the sample. We measure that especially bright (
S
850
μ
m
> 5.55 mJy) DSFGs contribute ∼10% to the cosmic-averaged CSFRD from 2 <
z
< 5, confirming findings from previous work with similar samples.
Abstract
Due to their extremely dust-obscured nature, much uncertainty still exists surrounding the stellar mass growth and content in dusty, star-forming galaxies (DSFGs) at
z
> 1. In this work, we ...present a numerical model built using empirical data on DSFGs to estimate their stellar mass contributions across the first ∼10 Gyr of cosmic time. We generate a dust-obscured stellar mass function that extends beyond the mass limit of star-forming stellar mass functions in the literature, and predict that massive DSFGs constitute as much as 50%–100% of all star-forming galaxies with
M
≥10
11
M
⊙
at
z
> 1. We predict the number density of massive DSFGs and find general agreement with observations, although more data is needed to narrow wide observational uncertainties. We forward-model mock massive DSFGs to their quiescent descendants and find remarkable agreement with observations from the literature demonstrating that, to first order, massive DSFGs are a sufficient ancestral population to describe the prevalence of massive quiescent galaxies at
z
> 1. We predict that massive DSFGs and their descendants contribute as much as 25%–60% to the cosmic stellar mass density during the peak of cosmic star formation, and predict an intense epoch of population growth during the ∼1 Gyr from
z
= 6 to 3 during which the majority of the most massive galaxies at high-
z
grow and then quench. Future studies seeking to understand massive galaxy growth and evolution in the early universe should strategize synergies with data from the latest observatories (e.g., JWST and the Atacama Large Millimeter/submillimeter Array) to better include the heavily dust-obscured galaxy population.
Abstract We report the discovery of 15 exceptionally luminous 10 ≲ z ≲ 14 candidate galaxies discovered in the first 0.28 deg 2 of JWST/NIRCam imaging from the COSMOS-Web survey. These sources span ...rest-frame UV magnitudes of −20.5 > M UV > −22, and thus constitute the most intrinsically luminous z ≳ 10 candidates identified by JWST to date. Selected via NIRCam imaging, deep ground-based observations corroborate their detection and help significantly constrain their photometric redshifts. We analyze their spectral energy distributions using multiple open-source codes and evaluate the probability of low-redshift solutions; we conclude that 12/15 (80%) are likely genuine z ≳ 10 sources and 3/15 (20%) likely low-redshift contaminants. Three of our z ∼ 12 candidates push the limits of early stellar mass assembly: they have estimated stellar masses ∼ 5 × 10 9 M ⊙ , implying an effective stellar baryon fraction of ϵ ⋆ ∼ 0.2−0.5, where ϵ ⋆ ≡ M ⋆ /( f b M halo ). The assembly of such stellar reservoirs is made possible due to rapid, burst-driven star formation on timescales < 100 Myr where the star formation rate may far outpace the growth of the underlying dark matter halos. This is supported by the similar volume densities inferred for M ⋆ ∼ 10 10 M ⊙ galaxies relative to M ⋆ ∼ 10 9 M ⊙ —both about 10 −6 Mpc −3 —implying they live in halos of comparable mass. At such high redshifts, the duty cycle for starbursts would be of order unity, which could cause the observed change in the shape of the UV luminosity function from a double power law to a Schechter function at z ≈ 8. Spectroscopic redshift confirmation and ensuing constraints of their masses will be critical to understand how, and if, such early massive galaxies push the limits of galaxy formation in the Lambda cold dark matter paradigm.
Nonsexual acute genital ulcerations (NAGUs), also known as Lipschütz ulcers, are vulvar ulcers occurring predominantly in adolescent females. Although the pathogenesis is unknown, NAGUs are commonly ...associated with systemic infections. Here, we present a female child with NAGU along with disseminated Lyme disease. We believe this is the first reported pediatric case of this phenomenon.
ABSTRACT
Many inspiraling and merging stellar remnants emit both gravitational and electromagnetic radiation as they orbit or collide. These gravitational wave events together with their associated ...electromagnetic counterparts provide insight about the nature of the merger, allowing us to further constrain properties of the binary. With the future launch of the Laser Interferometer Space Antenna (LISA), follow-up observations and models are needed of ultracompact binary (UCB) systems. Current and upcoming long baseline time domain surveys will observe many of these UCBs. We present a new fast periodic object search tool capable of searching for generic periodic signals based on the conditional entropy algorithm. This new implementation allows for a grid search over both the period (P) and the time derivative of the period ($\dot{P}$). To demonstrate the usage of this tool, we use a small, hand-picked subset of a UCB population generated from the population synthesis code cosmic
, as well as a custom catalogue for varying periods at fixed intrinsic parameters. We simulate light curves as likely to be observed by future time domain surveys by using an existing eclipsing binary light-curve model accounting for the change in orbital period due to gravitational radiation. We find that a search with $\dot{P}$ values is necessary for detecting binaries at orbital periods less than ∼10 min. We also show it is useful in finding and characterizing binaries with longer periods, but at a higher computational cost. Our code is called gce
(GPU-accelerated Conditional Entropy). It is available on Github (https://github.com/mikekatz04/gce).
ABSTRACT
We present a spectroscopic survey of Ly α emitters in the Extended Groth Strip (EGS) field, targeting the regime near the Epoch of Reionization. Using Keck/DEep Imaging Multi-Object ...Spectrograph, we observed 947 high-z candidates with photometric redshifts from 3 < zphot < 7 and down to an H-band (Hubble Space Telescope/Wide Field Camera 3 F160W) magnitude limit of <27.5. Observations were taken over the course of eight nights, with integration times ranging from 4 to 7.8 h. Our survey secured 137 unique redshifts, 126 of which are Ly α emitters at 2.8 < z < 6.3 with a mean redshift of $\overline{z} = 4.3$. We provide a comprehensive redshift catalogue for our targets, as well as the reduced one- and two-dimensional spectra for each object. These observations will provide an important auxiliary data set for the JWST Directors Discretionary Early Release Science programme the Cosmic Evolution Early Release Science Survey, which recently completed near- and mid-infrared imaging and spectroscopy of galaxies in the EGS field.
Abstract
Selecting the first galaxies at
z
> 7 − 10 from JWST surveys is complicated by
z
< 6 contaminants with degenerate photometry. For example, strong optical nebular emission lines at
z
< 6 may ...mimic JWST/NIRCam photometry of
z
> 7–10 Lyman-break galaxies (LBGs). Dust-obscured 3 <
z
< 6 galaxies in particular are potentially important contaminants, and their faint rest-optical spectra have been historically difficult to observe. A lack of optical emission line and continuum measures for 3 <
z
< 6 dusty galaxies now makes it difficult to test their expected JWST/NIRCam photometry for degenerate solutions with NIRCam dropouts. Toward this end, we quantify the contribution by strong emission lines to NIRCam photometry in a physically motivated manner by stacking 21 Keck II/NIRES spectra of hot, dust-obscured, massive (
log
M
*
/
M
⊙
≳
10
–
11
) and infrared (IR) luminous galaxies at
z
∼ 1–4. We derive an average spectrum and measure strong narrow (broad) O
iii
5007
and H
α
features with equivalent widths of 130 ± 20 Å (150 ± 50 Å) and 220 ± 30 Å (540 ± 80 Å), respectively. These features can increase broadband NIRCam fluxes by factors of 1.2 − 1.7 (0.2–0.6 mag). Due to significant dust attenuation (
A
V
∼ 6), we find H
α
+N
ii
to be significantly brighter than O
iii
+H
β
and therefore find that emission-line dominated contaminants of high −
z
galaxy searches can only reproduce moderately blue perceived UV continua of
S
λ
∝
λ
β
with
β
> − 1.5 and
z
> 4. While there are some redshifts (
z
∼ 3.75) where our stack is more degenerate with the photometry of
z
> 10 LBGs at
λ
rest
∼ 0.3–0.8
μ
m , redder filter coverage beyond
λ
obs
> 3.5
μ
m and far-IR/submillimeter follow-up may be useful for breaking the degeneracy and making a crucial separation between two fairly unconstrained populations, dust-obscured galaxies at
z
∼ 3–6 and LBGs at
z
> 10.
Abstract
The PASSAGES (Planck All-Sky Survey to Analyze Gravitationally-lensed Extreme Starbursts) collaboration has recently defined a sample of 30 gravitationally lensed dusty star-forming galaxies ...(DSFGs). These rare, submillimeter-selected objects enable high-resolution views of the most extreme sites of star formation in galaxies at cosmic noon. Here, we present the first major compilation of strong lensing analyses using
lenstool
for PASSAGES, including 15 objects spanning
z
= 1.1–3.3, using complementary information from 0.″6-resolution 1.1 mm Atacama Large Millimeter/submillimeter Array and 0.″4 5 cm Jansky Very Large Array continuum imaging, in tandem with 1.6
μ
m Hubble and optical imaging with Gemini-S. Magnifications range from
μ
= 2 to 28 (median
μ
= 7), yielding intrinsic infrared luminosities of
L
IR
= 0.2–5.9 × 10
13
L
⊙
(median 1.4 × 10
13
L
⊙
) and inferred star formation rates of 170–6300
M
⊙
yr
−1
(median 1500
M
⊙
yr
−1
). These results suggest that the PASSAGES objects comprise some of the most extreme known starbursts, rivaling the luminosities of even the brightest unlensed objects, further amplified by lensing. The intrinsic sizes of far-infrared continuum regions are large (
R
e
= 1.7–4.3 kpc; median 3.0 kpc) but consistent with
L
IR
–
R
e
scaling relations for
z
> 1 DSFGs, suggesting a widespread spatial distribution of star formation. With modestly high angular resolution, we explore if these objects might be maximal starbursts. Instead of approaching Eddington-limited surface densities, above which radiation pressure will disrupt further star formation, they are safely sub-Eddington—at least on global, galaxy-integrated scales.
The increased reliance on interorganizational collaborations (ICs) has created new challenges for leaders. They must attempt to apply leadership theories and behaviors developed primarily for leading ...within one organization or group to leading collaborations of multiple organizations and stakeholders. To provide insight into this issue, this study examines leadership behavior in an IC developing a strategic plan to promote changes to address public health and safety concerns related to substance abuse. Combining observations and interviews, we followed a statewide interagency taskforce in a southwestern state of the United States from its inception through completion of its strategic plan within a 10-month deadline. Findings show different leadership behaviors were integrated and evolved over time to strike a balance between decision-making effectiveness and efficiency. In particular, the findings support recent research on examining leadership behavior holistically to develop a ‘fuller full-range’ leadership perspective (Antonakis and House, 2014), especially in terms of how collectivistic and instrumental leadership should complement transformational leadership, and by demonstrating that the combinations of leadership change over time and occur at multiple levels. These findings provide guidance for future practice and research on ICs promoting change.
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