More Like this

1. Discovery of H α Emission from a Protoplanet Candidate around the Young Star 2MASS J16120668–3010270 with MagAO-X

   https://doi.org/10.3847/2041-8213/adfcbd  

   Li_李, Jialin 嘉霖; Close, Laird M; Long_龙, Feng 凤; Males, Jared R; Haffert, Sebastiaan Y; Weinberger, Alycia; Follette, Katherine; Andrews, Sean; Carpenter, John; Foster, Warren B; et al (September 2025, The Astrophysical Journal Letters)

   Abstract 2MASS J16120668–3010270 (hereafter 2MJ1612) is a young M0 star that hosts a protoplanetary disk in the Upper Scorpius star-forming region. Recent Atacama Large Millimeter/submillimeter Array (ALMA) observations of 2MJ1612 show a mildly inclined disk (i = 37°) with a large dust-depleted gap (R_cav ≈ 0 $\stackrel{\text{″}}{.}$4 or 53 au). We present high-contrast Hαobservations from MagAO-X on the 6.5 m Magellan telescope and new high-resolution submillimeter dust continuum observations with ALMA of 2MJ1612. On both 2025 April 13 and 16, we recovered a point source with Hαexcess with a signal-to-noise ratio ≳5 within the disk gap in our MagAO-X angular and spectral differential images at a separation of 141.96 ± 2.10 mas (23.45 ± 0.29 au deprojected) from the star and a position angle ​​​​​of 159 $\stackrel{\text{°}}{.}$00 ± 0 $\stackrel{\text{°}}{.}$55. Furthermore, this Hαsource is within close proximity to aK-band point source in the SPHERE/IRDIS observation taken on 2023 July 21. The astrometric offset between theKband and Hαsource can be explained by orbital motion of a bound companion. Thus, our observations can be best explained by the discovery of an accreting protoplanet, 2MJ1612 b, with an estimated mass of 4M_Jupand a Hαline flux ranging from (29.7 ± 7.5) × 10⁻¹⁶erg s cm²to (8.2 ± 3.4) × 10⁻¹⁶erg s cm². 2MJ1612 b is likely the third example of an accreting Hαprotoplanet responsible for carving the gap in its host disk, joining PDS 70 b and c. Further study is necessary to confirm and characterize this protoplanet candidate and to identify any additional protoplanets that may also play a role in shaping the gap. 

   more » « less
2. Mapping the Growth of Supermassive Black Holes as a Function of Galaxy Stellar Mass and Redshift

   https://doi.org/10.3847/1538-4357/ad27cc  

   Zou, Fan; Yu, Zhibo; Brandt, W N; Tak, Hyungsuk; Yang, Guang; Ni, Qingling (March 2024, The Astrophysical Journal)

   Abstract The growth of supermassive black holes is strongly linked to their galaxies. It has been shown that the population mean black hole accretion rate ( $\overline{\mathrm{BHAR}}$) primarily correlates with the galaxy stellar mass (M_⋆) and redshift for the general galaxy population. This work aims to provide the best measurements of $\overline{\mathrm{BHAR}}$as a function ofM_⋆and redshift over ranges of 10^9.5<M_⋆< 10¹²M_⊙andz< 4. We compile an unprecedentedly large sample with 8000 active galactic nuclei (AGNs) and 1.3 million normal galaxies from nine high-quality survey fields following a wedding cake design. We further develop a semiparametric Bayesian method that can reasonably estimate $\overline{\mathrm{BHAR}}$and the corresponding uncertainties, even for sparsely populated regions in the parameter space. $\overline{\mathrm{BHAR}}$is constrained by X-ray surveys sampling the AGN accretion power and UV-to-infrared multiwavelength surveys sampling the galaxy population. Our results can independently predict the X-ray luminosity function (XLF) from the galaxy stellar mass function (SMF), and the prediction is consistent with the observed XLF. We also try adding external constraints from the observed SMF and XLF. We further measure $\overline{\mathrm{BHAR}}$for star-forming and quiescent galaxies and show that star-forming $\overline{\mathrm{BHAR}}$is generally larger than or at least comparable to the quiescent $\overline{\mathrm{BHAR}}$. 

   more » « less
3. Active Galactic Nucleus Quenching in Simulated Dwarf Galaxies

   https://doi.org/10.3847/1538-4357/ace046  

   Sharma, Ray S; Brooks, Alyson M; Tremmel, Michael; Bellovary, Jillian; Quinn, Thomas R (October 2023, The Astrophysical Journal)

   Abstract We examine the quenching characteristics of 328 isolated dwarf galaxies $\left({10}^8<M_{\mathrm{star}}/M_{\odot }<{10}^{10}\right)$within theRomulus25cosmological hydrodynamic simulation. Using mock-observation methods, we identify isolated dwarf galaxies with quenched star formation and make direct comparisons to the quenched fraction in the NASA Sloan Atlas (NSA). Similar to other cosmological simulations, we find a population of quenched, isolated dwarf galaxies belowM_star< 10⁹M_⊙not detected within the NSA. We find that the presence of massive black holes (MBHs) inRomulus25is largely responsible for the quenched, isolated dwarfs, while isolated dwarfs without an MBH are consistent with quiescent fractions observed in the field. Quenching occurs betweenz= 0.5–1, during which the available supply of star-forming gas is heated or evacuated by MBH feedback. Mergers or interactions seem to play little to no role in triggering the MBH feedback. At low stellar masses,M_star≲ 10^9.3M_⊙, quenching proceeds across several Gyr as the MBH slowly heats up gas in the central regions. At higher stellar masses,M_star≳ 10^9.3M_⊙, quenching occurs rapidly within 1 Gyr, with the MBH evacuating gas from the central few kpc of the galaxy and driving it to the outskirts of the halo. Our results indicate the possibility of substantial star formation suppression via MBH feedback within dwarf galaxies in the field. On the other hand, the apparent overquenching of dwarf galaxies due to MBH suggests that higher-resolution and/or better modeling is required for MBHs in dwarfs, and quenched fractions offer the opportunity to constrain current models. 

   more » « less
4. A Rare Eddington-limited, Heavily Obscured Low-mass Active Galactic Nucleus Likely Triggered by a Galaxy Merger

   https://doi.org/10.3847/1538-4357/ae6779  

   Wang, Shouyi; Zou, Fan; Chen, Chang-Hao; Brandt, W N; Gallo, Elena; Luo, Bin; Wu, Xue-Bing; Fu, Yuming; Nguyen, Dieu D; Sun, Shengxiu (May 2026, The Astrophysical Journal)

   Abstract We report a detailed analysis of GAMA 376183, a powerful, heavily obscured active galactic nucleus (AGN) hosted by a low-mass galaxy (M_⋆ ≈ 10¹⁰M_⊙) likely experiencing a galaxy merger. The source was initially identified due to its remarkably strong [Nev]λ3426 emission, exhibiting a rest-frame equivalent width of ≈48 Å. We present ∼100 ks Nuclear Spectroscopic Telescope Array (or NuSTAR) follow-up observations, confirming its heavily obscured nature with a column density (in cm⁻²) of $\log N_{\mathrm{H}}=23.3_{-1.2}^{+0.4}$and an intrinsic 2–10 keV luminosity (in erg s⁻¹) of $\log L_{\mathrm{X},\mathrm{int}}=42.92_{-0.20}^{+0.24}$. GAMA 376183 thus represents one of the few known heavily obscured AGNs in low-mass galaxies. Its estimated Eddington ratio isλ_Edd ≈ 0.8, indicative of rapid black hole growth. High-resolution optical images reveal a disturbed, likely merging morphology, while its multiwavelength spectral energy distribution indicates a recent starburst in its host galaxy. These pieces of evidence suggest that the ongoing merger has triggered both the heavily obscured, Eddington-limited accretion and the starburst, making GAMA 376183 a rare observed case in low-mass galaxies. Overall, this unique source demonstrates that (i) [Nev] can help identify heavily obscured low-mass AGNs, and (ii) the merger-driven coevolution framework established for massive galaxies may also extend to low-mass galaxies. 

   more » « less
5. The True Stellar Obliquity of a Sub-Saturn Planet from the Tierras Observatory and the Keck Planet Finder

   https://doi.org/10.3847/1538-3881/add530  

   Tamburo, Patrick; Yee, Samuel W; García-Mejía, Juliana; Stefánsson, Gudmundur; Charbonneau, David; Bieryla, Allyson; Howard, Andrew W; Isaacson, Howard; Fulton, Benjamin J; Householder, Aaron (June 2025, The Astronomical Journal)

   Abstract We measure the true obliquity of TOI-2364, a K dwarf with a sub-Saturn-mass (M_p = 0.18M_J) transiting planet on the upper edge of the hot-Neptune desert. We used new Rossiter–McLaughlin observations gathered with the Keck Planet Finder to measure the sky-projected obliquityλ = 7° + 10°–11°. Combined with a stellar rotation period of 23.47 ± 0.29 days measured with photometry from theTierrasObservatory, this yields a stellar inclination of 90° ± 13° and a true obliquityψ = 15 $\stackrel{\text{°}}{.}$6 + 7 $\stackrel{\text{°}}{.}$7–7 $\stackrel{\text{°}}{.}$3, indicating that the planet’s orbit is well aligned with the rotation axis of its host star. The determination ofψis important for investigating a potential bimodality in the orbits of short-period sub-Saturns around cool stars, which tend to be either aligned with or perpendicular to their host stars’ spin axes. 

   more » « less