A list of the previously discussed papers can be found here .
The structure of stars orbiting close to supermassive black holes (SMBHs) can be dramatically modified by tidal heating, which can in principle dissipate an energy much larger than the stellar binding energy. We use analytic models and MESA to explore the coupled dynamics of tidal heating, stellar structural evolution, orbital decay due to gravitational waves and tides, and mass transfer due to Roche lobe overflow. In contrast to more equal mass stellar binaries, the stable mass transfer rate for stars orbiting SMBHs is typically set by the tidal heating timescale (the timescale for tides to increase the stellar radius), not by the gravitational wave orbital decay timescale. The resulting stable mass transfer rate is sensitive to the tidal heating model but is plausibly ∼10−3−10−5M⊙yr−1 (and perhaps larger), sufficient to produce low-luminosity active galactic nuclei in many galaxies. The stability of mass transfer is sensitive to where in the stellar interior the tidal energy is dissipated. MESA models confirm the expected result that mass transfer is unstable (stable) if tidal heating increases (decreases) the fraction of the star that is convective. More detailed conclusions about the stability of mass-transfer will require self-consistently calculating how the tidal heating of stars changes in response to internal structural changes produced by the tidal heating itself. Stars with tidal heating-induced mass transfer can produce a large population of low-luminosity active galactic nuclei; they may also be the progenitors of some partial tidal disruption candidates (e.g., ASASSN-14ko) as well as short period quasi-periodic eruptions (e.g., eRO-QPE2 and GSN 069). However, many repeating nuclear transients produced by tidal heating-induced mass loss are likely fainter than those detected thus far, and remain to be discovered.
We demonstrate the power of JWST-NIRCam medium-band photometry to measure emission line fluxes and study dust and star formation properties of galaxies at cosmic noon. In this work, we present photometric emission line measurements and spatially-resolved maps of Hα and Paβ for a sample of 14 galaxies at 1.3≤z≤2.4, observed by the MegaScience medium-band survey and the UNCOVER deep spectroscopic survey. We measure line fluxes directly from the medium-band photometry and compare with spectroscopic measurements from UNCOVER. We find reasonable agreement between the photometric and spectroscopic emission line fluxes for both Hα and Paβ, with scatter <0.15 dex down to emission line equivalent widths of 10Å. We also make a nebular dust measurement from the ratio Paβ / Hα, finding an average nebular AV of 1.4. Our photometric AV measurements show a slightly larger scatter of 0.5 magnitudes when compared to spectroscopic measurements; however, this scatter may be partially caused by aperture effects. Finally, we produce spatially resolved maps of Hα emission, Paβ emission, and stellar continuum. We find that offsets in Hα and Paβ emission are common, especially for galaxies with the highest AV, indicating dusty sub-structures. Furthermore, the correlation between Hα and continuum emission decreases with increasing AV, suggesting that the dustiest objects have clumpy dust and star formation distributions. Our study demonstrates the power of medium-band photometry to directly probe emission line strengths, star formation, and dust attenuation for hundreds of galaxies in UNCOVER and thousands of galaxies in upcoming JWST medium-band surveys.
We report an observation of the Rossiter-McLaughlin (RM) effect of the transiting planet HD 93963 Ac, a mini-Neptune planet orbiting a G0-type star with an orbital period of Pc=3.65d, accompanied by an inner super-Earth planet with Pb=1.04d. We observed a full transit of planet c on 2024 May 3rd UT with Keck/KPF. The observed RM effect has an amplitude of ∼1ms−1 and implies a sky-projected obliquity of λ=14+17−19 degrees for HD 93963 Ac. Our dynamical analysis suggests that the two inner planets are likely well aligned with the stellar spin, to within a few degrees, thus allowing both to transit. Along with WASP-47, 55 Cnc, and HD 3167, HD 93963 is the fourth planetary system with an ultra-short-period planet and obliquity measurement(s) of any planet(s) in the system. HD 93963, WASP-47, and 55 Cnc favor largely coplanar orbital architectures, whereas HD 3167 has been reported to have a large mutual inclination (∼100∘) between its transiting planets b and c. In this configuration, the probability that both planets transit is low. Moreover, one planet would quickly evolve to be non-transiting due to nodal precession. Future missions such as ESO/PLATO should detect the resulting transit duration variations. We encourage additional obliquity measurements of the HD 3167 system to better constrain its orbital architecture.
The matter cycle between gas clouds and stars in galaxies plays a crucial role in regulating galaxy evolution through feedback mechanisms. In turn, the local and global galactic environments shape the interstellar medium and provide the initial conditions for star formation, potentially affecting the properties of this small-scale matter cycle. In particular, spiral arms have been proposed to play a pivotal role in the star formation life cycle, by enhancing the gas density and triggering star formation. However, their exact role is still debated. In this paper, we investigate the role of spiral arms in the giant molecular cloud evolutionary life cycle and on the star formation process in a sample of 22 nearby spiral galaxies from the PHANGS survey. We measure the cloud lifetime, the feedback timescale, the typical distance between independent regions and the star formation efficiency in spiral arms and inter-arm regions separately. We find that the distributions of the cloud lifetime as well as the feedback timescale are similar in both environments. This result suggests that spiral arms are unlikely to play a dominant role in triggering star formation. By contrast, the star formation efficiency appears to be slightly higher in inter-arm regions compared to spiral arms.
JWST has revealed a stunning population of bright galaxies at surprisingly early epochs, z>10, where few such sources were expected. Here we present the most distant example of this class yet -- MoM-z14, a luminous (MUV=−20.2) source in the COSMOS legacy field at zspec=14.44+0.02−0.02 that expands the observational frontier to a mere 280 million years after the Big Bang. The redshift is confirmed with NIRSpec/prism spectroscopy through a sharp Lyman-α break and ≈3σ detections of five rest-UV emission lines. The number density of bright zspec≈14−15 sources implied by our "Mirage or Miracle" survey spanning ≈350 arcmin2 is >100× larger (182+329−105×) than pre-JWST consensus models. The high EWs of UV lines (≈15−35 Å) signal a rising star-formation history, with a ≈10× increase in the last 5 Myr (SFR5Myr/SFR50Myr=9.9+3.0−5.8). The source is extremely compact (circularized re=74+15−12 pc), and yet resolved, suggesting an AGN is not the dominant source of light. The steep UV slope (β=−2.5+0.2−0.2) implies negligible dust attenuation and a young stellar population. The absence of a strong damping wing may indicate that the immediate surroundings of MoM-z14 are partially ionized at a redshift where virtually every reionization model predicts a ≈100% neutral fraction. The nitrogen emission and highly super-solar [N/C]>1 hint at an abundance pattern similar to local globular clusters that may have once hosted luminous supermassive stars. Since this abundance pattern is also common among the most ancient stars born in the Milky Way, we may be directly witnessing the formation of such stars in dense clusters, connecting galaxy evolution across the entire sweep of cosmic time.
this http URL @sns.it)
this https URL . This article is identical to v2.5 of the aforementioned collection: DOI this https URL
this http URL is the compiled version with the complete Appendix A.3 table. Please include it as an ancillary file
this https URL , corresponding to preprint: arXiv:2312.08080