Haverford College

There is now clear evidence, from a variety of studies, that galactic bars contribute to and/or accelerate processes which quench galaxies. However, bars have a variety of strengths and pattern speeds, and previous work has suggested that slow and strong bars impact their hosts the most. In this paper, we continue to investigate the impact of bar strength and bar speed on host galaxy evolution in a sample of barred galaxies identified via classifications from Galaxy Zoo. We perform a comprehensive assessment of star-formation tracers spanning a variety of timescales, based on spatially resolved spectroscopic information from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. Specifically, we examine the radial distributions of EW[Halpha], HdeltaA, Hbeta, and Dn4000; spectral data that trace star-formation on current, intermediate, and much longer timescales. We investigate how these star-formation tracers vary with respect to each other in diagnostic evolutionary planes for eight categories of barred galaxies (combinations of star forming or quenching; strong and weak; fast and slow). We continue to find that slow-strong bars drive the quenching of their hosts the most by triggering active star-formation throughout the barred region; however, we note some additional complexity: we observe that stronger bars boost star-formation at the bar centre while slower bars have increased star-formation along the bar. This work adds to the growing evidence that galactic bars have both global and local impacts on their host galaxies.

Context. Pulsar rotational glitches are unresolved increments of the rotation rate that sometimes trigger an enhancement of the spin-down rate. On occasion, the augmented spin-down decays gradually over days or months in an exponential manner. This is observed particularly after the largest glitch events. Glitches and their exponential recoveries are attributed to the presence of a neutron superfluid inside pulsars. The young pulsar PSR J0537−6910 exhibits the highest known glitching rate, with 60 events detected over nearly 18 years of monitoring. Aims. Despite most PSR J0537−6910 glitches being large, only one exponential recovery has been reported, following its first discovered glitch. This is puzzling as pulsars of similar age, rotational properties, and glitching behaviour typically present significant exponential recoveries. We wish to understand if this is an intrinsic difference of PSR J0537−6910 or a detectability issue due, for example, to its high glitch frequency. Methods. The full dataset, including recent NICER observations, was systematically searched for evidence of exponential relaxations. Each glitch was first tested for evidence of recovery across a broad range of trial timescales. Good candidates were further investigated by identifying the best recovery models with and without an exponential term, then comparing them using Bayesian evidence. Results. We discovered six new glitches, bringing the total number of glitches in this pulsar to 66. Our search and selection criteria strongly indicate the presence of 11 additional, previously undetected, exponential recoveries. We provide updated glitch and timing solutions. Exponential recoveries were detected only for the largest glitches (Δ ν > 20 μHz), though not for all of them. The inferred exponential timescales vary between 4 and 37 d, with the decaying frequency increment being close to or below 1% of the total in general. We find that the second derivative of the spin frequency ( ν ¨) can remain fairly stable across several glitches, and only some glitches are associated with persistent ν ¨ changes. In particular, ν ¨ tends to take its lowest values after glitches with exponential recoveries, corresponding to inter-glitch braking indices n ig ∼ 6–9. On the other hand, following glitches without exponential recoveries – even large ones – ν ¨ tends to be higher, with varied values that typically lead to braking indices above 9 (inferred n ig mostly clustered between 10 and 35).

Abstract We present new timing models and update our previous ones for the rotational evolution of seven young energetic pulsars, including four of the top five in spin-down luminosity $\dot{E}$ among all known pulsars. For each of the six pulsars that were monitored on a regular basis by NICER, their rotation phase-connected timing model covers the entire period of NICER observations, in many cases from 2017–2025. For PSR J0058−7218, which was only identified in 2021, we extend the baseline of its timing model by 3 years and report detections of its first three glitches. The timing model for PSR J0537−6910 over the entire 8 years of NICER monitoring is presented, including a total of 23 glitches; we also report its spin frequency and pulsed spectrum from a 2016 NuSTAR observation. For PSR B0540−69, its complete timing model from 2015–2025 is provided, including a braking index evolution from near 0 to 1.6 during this period. The 8-year timing model for PSR J1412+7922 (also known as Calvera) is reported, which includes a position that is consistent with that measured from imaging. For PSR J1811−1925, we present its 3.5-year timing model. For PSR J1813−1749, its incoherent timing model is extended through early 2025 using new Chandra observations. For PSR J1849−0001, its 7-year timing model is provided, including a position that is consistent with and more accurate than its imaging position and its first glitch that is one of the largest ever measured. Our timing models of these seven X-ray pulsars enable their study at other energies and in gravitational wave data.

Reading classical Arabic and Chinese sources at once comparatively and intersectionally, this article initiates an investigation of Black labor—specifically Black sailors and slaves—employed in medieval trade networks that connect Africa, Arabia, and Persia to South Asia, Southeast Asia, and China. It does not presume a homogeneous definition of Blackness, nor a generalized notion of slavery. While informed by concepts developed in scholarly studies of transatlantic slavery and Euro-American colonial history, this article strives to expand our understanding of the global articulation of Blackness beyond both the modern period and the Atlantic world. I draw on numerous genres of classical literature—Islamic ḥadīth commentaries, stories of marvels, geographical works, poetry, Buddhist dictionaries, and polemical treatises—and corroborate them with visual evidence from the same or adjacent periods. Rather than aiming for a social history of Black labor, I suggest that we harness the magical qualities of these half-true, half-invented narratives, capitalize on their marvelousness, and instead of laying claim to a definitive account of who the Black sailors were and what they did, create new avenues of research and imagination that may help us regain access to the breathtakingly rich and layered world of a Black subalternity articulated translingually across the medieval Indian Ocean world.

We use new cosmic microwave background (CMB) primary temperature and polarization anisotropy measurements from the Atacama Cosmology Telescope (ACT) Data Release 6 (DR6) to test foundational assumptions of the standard cosmological model, ΛCDM, and set constraints on extensions to it. We derive constraints from the ACT DR6 power spectra alone, as well as in combination with legacy data from the Planck mission. To break geometric degeneracies, we include ACT and Planck CMB lensing data and baryon acoustic oscillation data from DESI Year-1. To test the dependence of our results on non-ACT data, we also explore combinations replacing Planck with WMAP and DESI with BOSS, and further add supernovae measurements from Pantheon+ for models that affect the late-time expansion history. We verify the near-scale-invariance (running of the spectral index dns /d ln k = 0.0062 ± 0.0052) and adiabaticity of the primordial perturbations. Neutrino properties are consistent with Standard Model predictions: we find no evidence for new light, relativistic species that are free-streaming (N eff = 2.86 ± 0.13, which combined with astrophysical measurements of primordial helium and deuterium abundances becomes N eff = 2.89 ± 0.11), for non-zero neutrino masses (∑mν < 0.089 eV at 95% CL), or for neutrino self-interactions. We also find no evidence for self-interacting dark radiation (N idr < 0.134), or for early-universe variation of fundamental constants, including the fine-structure constant (α EM/α EM,0 = 1.0043 ± 0.0017) and the electron mass (me /me,0 = 1.0063 ± 0.0056). Our data are consistent with standard big bang nucleosynthesis (we find Yp = 0.2312 ± 0.0092), the COBE/FIRAS-inferred CMB temperature (we find T CMB = 2.698 ± 0.016 K), a dark matter component that is collisionless and with only a small fraction allowed as axion-like particles, a cosmological constant (w = -0.986 ± 0.025), and the late-time growth rate predicted by general relativity (γ = 0.663 ± 0.052). We find no statistically significant preference for a departure from the baseline ΛCDM model. In fits to models invoking early dark energy, primordial magnetic fields, or an arbitrary modified recombination history, we find H 0 = 69.9+0.8 -1.5, 69.1 ± 0.5, or 69.6 ± 1.0 km/s/Mpc, respectively; using BOSS instead of DESI BAO data reduces the central values of these constraints by 1–1.5 km/s/Mpc while only slightly increasing the error bars. In general, models introduced to increase the Hubble constant or to decrease the amplitude of density fluctuations inferred from the primary CMB are not favored over ΛCDM by our data.

We present Atacama Cosmology Telescope (ACT) Data Release 6 (DR6) maps of the Cosmic Microwave Background temperature and polarization anisotropy at arcminute resolution over three frequency bands centered on 98, 150 and 220 GHz. The maps are based on data collected with the AdvancedACT camera over the period 2017–2022 and cover 19,000 square degrees with a median combined depth of 10 μK arcmin. We describe the instrument, mapmaking and map properties and illustrate them with a number of figures and tables. The ACT DR6 maps and derived products are available on LAMBDA at https://lambda.gsfc.nasa.gov/product/act/actadv_prod_table.html. We also provide an interactive web atlas at https://phy-act1.princeton.edu/public/snaess/actpol/dr6/atlas and HiPS data sets in Aladin (e.g. https://alasky.cds.unistra.fr/ACT/DR4DR6/color_CMB).

During pregnancy, estrogen levels rise dramatically, but quickly drop to prepartum levels following birth, and remain suppressed until ovulation resumes. This “postpartum estrogen withdrawal” state has been linked to changes in the brain and behavior in humans and rodents. Previous research has demonstrated that following a hormone-simulated pseudopregnancy (HSP), an experimental model of postpartum estrogen withdrawal, female mice show increased anxiety-like behaviors and decreased social motivation. Further, these behavioral changes occur concurrently with an increase in ΔFOSB, a transcription factor associated with stable long-term plasticity, in the nucleus accumbens core. To test whether this increase in ΔFOSB is required for these behavioral changes, we used a viral-mediated gene transfer approach to prevent ΔFOSB-mediated transcription in the NAcC during HSP and found that it reduced the high-anxiety behavioral phenotype in estrogen-withdrawn females. However, preventing ΔFOSB-mediated transcription had little effect on social motivation. Together, these results suggest that postpartum estrogen withdrawal increases ΔFOSB in the NAc core to impact anxiety-like behaviors, but not social motivation, following estrogen withdrawal.

Abstract We measure independent pattern speeds for bar and spiral arms in 98 barred spiral galaxies with Mapping Nearby Galaxies at Apache Point Observatory data. Some galaxies exhibit statistically different pattern speeds (Ω bar ≠ Ω spiral ), while others have statistically equal pattern speeds. We find no trends of ΔΩ with stellar mass or galaxy color. Our results are consistent with a Universe which might have some bar-driven spirals (ΔΩ = 0), but some spirals in barred galaxies must be tidally driven or self-excited (ΔΩ ≠ 0). These results demonstrate the potential for ΔΩ measurements to constrain spiral arm formation mechanisms.