Astrophysical Journal Letters最新文献

{"title":"LIGO–Virgo–KAGRA's Oldest Black Holes: Probing Star Formation at Cosmic Noon With GWTC-3","authors":"Maya Fishbach, Lieke van Son","doi":"10.3847/2041-8213/ad0560","DOIUrl":"https://doi.org/10.3847/2041-8213/ad0560","url":null,"abstract":"Abstract In their third observing run, the LIGO–Virgo–KAGRA gravitational-wave (GW) observatory was sensitive to binary black hole (BBH) mergers out to redshifts z merge ≈ 1. Because GWs are inefficient at shrinking the binary orbit, some of these BBH systems likely experienced long delay times τ between the formation of their progenitor stars at z form and their GW merger at z merge . In fact, the distribution of delay times predicted by isolated binary evolution resembles a power law <?CDATA $p(tau )propto {tau }^{{alpha }_{tau }}$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:mi>p</mml:mi> <mml:mo stretchy=\"false\">(</mml:mo> <mml:mi>τ</mml:mi> <mml:mo stretchy=\"false\">)</mml:mo> <mml:mo>∝</mml:mo> <mml:msup> <mml:mrow> <mml:mi>τ</mml:mi> </mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>α</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>τ</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:msup> </mml:math> with slope −1 ≲ α τ ≲ −0.35 and a minimum delay time of <?CDATA ${tau }_{min }=10,mathrm{Myr}$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:msub> <mml:mrow> <mml:mi>τ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>min</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>10</mml:mn> <mml:mspace width=\"0.25em\" /> <mml:mi>Myr</mml:mi> </mml:math> . We use these predicted delay time distributions to infer the formation redshifts of the ∼70 BBH events reported in the third GW transient catalog GWTC-3 and the formation rate of BBH progenitors. For our default α τ = –1 delay time distribution, we find that GWTC-3 contains at least one system (with 90% credibility) that formed earlier than z form > 4.4. Comparing our inferred BBH progenitor formation rate to the star formation rate, we find that at z form = 4, the number of BBH progenitor systems formed per stellar mass was <?CDATA ${6.4}_{-5.5}^{+9.4}times {10}^{-6},{M}_{odot }^{-1}$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:msubsup> <mml:mrow> <mml:mn>6.4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>5.5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>9.4</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>6</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width=\"0.25em\" /> <mml:msubsup> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> and this yield dropped to <?CDATA ${0.134}_{-0.127}^{+1.6}times {10}^{-6},{M}_{odot }^{-1}$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:msubsup> <mml:mrow> <mml:mn>0.134</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.127</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>1.6</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10<","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"289 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135566533","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Density Enhancement Streams in The Solar Wind","authors":"F. S. Mozer, O. Agapitov, S. D. Bale, R. Livi, O. Romeo, K. Sauer, I. Y. Vasko, J. Verniero","doi":"10.3847/2041-8213/ad0721","DOIUrl":"https://doi.org/10.3847/2041-8213/ad0721","url":null,"abstract":"Abstract This Letter describes a new phenomenon on the Parker Solar Probe of recurring plasma density enhancements that have Δ n/n ∼ 10% and that occur at a repetition rate of ∼5 Hz. They were observed sporadically for about 5 hr between 14 and 15 solar radii on Parker Solar Probe orbit 12 and they were also seen in the same radial range on both the inbound and outbound orbits 11. Their apparently steady-state existence suggests that their pressure gradient was balanced by the electric field. The X-component of the electric field component produced from this requirement is in good agreement with that measured. This provides strong evidence for the measurement accuracy of the density fluctuations and the X- and Y-components of the electric field (the Z-component was not measured). The electrostatic density waves were accompanied by an electromagnetic low-frequency wave, which occurred with the electrostatic harmonics. The amplitudes of these electrostatic and electromagnetic waves at ≥1 Hz were greater than the amplitude of the Alfvénic turbulence in their vicinity so they can be important for the heating, scattering, and acceleration of the plasma. The existence of this pair of waves is consistent with the observed plasma distributions and is explained as an oscilliton due to the nonlinear coupling between the kinetic Alfvén wave and the ion cyclotron mode, which belongs with the minor population of alpha particles.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"113 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135610079","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"First M87 Event Horizon Telescope Results. IX. Detection of Near-horizon Circular Polarization","authors":"Kazunori Akiyama, Antxon Alberdi, Walter Alef, Juan Carlos Algaba, Richard Anantua, Keiichi Asada, Rebecca Azulay, Uwe Bach, Anne-Kathrin Baczko, David Ball, Mislav Baloković, John Barrett, Michi Bauböck, Bradford A. Benson, Dan Bintley, Lindy Blackburn, Raymond Blundell, Katherine L. Bouman, Geoffrey C. Bower, Hope Boyce, Michael Bremer, Christiaan D. Brinkerink, Roger Brissenden, Silke Britzen, Avery E. Broderick, Dominique Broguiere, Thomas Bronzwaer, Sandra Bustamante, Do-Young Byun, John E. Carlstrom, Chiara Ceccobello, Andrew Chael, Chi-kwan Chan, Dominic O. Chang, Koushik Chatterjee, Shami Chatterjee, Ming-Tang Chen, Yongjun 永军 Chen 陈, Xiaopeng Cheng, Ilje Cho, Pierre Christian, Nicholas S. Conroy, John E. Conway, James M. Cordes, Thomas M. Crawford, Geoffrey B. Crew, Alejandro Cruz-Osorio, Yuzhu 玉竹 Cui 崔, Rohan Dahale, Jordy Davelaar, Mariafelicia De Laurentis, Roger Deane, Jessica Dempsey, Gregory Desvignes, Jason Dexter, Vedant Dhruv, Sheperd S. Doeleman, Sean Dougal, Sergio A. Dzib, Ralph P. Eatough, Razieh Emami, Heino Falcke, Joseph Farah, Vincent L. Fish, Ed Fomalont, H. Alyson Ford, Marianna Foschi, Raquel Fraga-Encinas, William T. Freeman, Per Friberg, Christian M. Fromm, Antonio Fuentes, Peter Galison, Charles F. Gammie, Roberto García, Olivier Gentaz, Boris Georgiev, Ciriaco Goddi, Roman Gold, Arturo I. Gómez-Ruiz, José L. Gómez, Minfeng 敏峰 Gu 顾, Mark Gurwell, Kazuhiro Hada, Daryl Haggard, Kari Haworth, Michael H. Hecht, Ronald Hesper, Dirk Heumann, Luis C. 子山 Ho 何, Paul Ho, Mareki Honma, Chih-Wei L. Huang, Lei 磊 Huang 黄, David H. Hughes, Shiro Ikeda, C. M. Violette Impellizzeri, Makoto Inoue, Sara Issaoun, David J. James","doi":"10.3847/2041-8213/acff70","DOIUrl":"https://doi.org/10.3847/2041-8213/acff70","url":null,"abstract":"Abstract Event Horizon Telescope (EHT) observations have revealed a bright ring of emission around the supermassive black hole at the center of the M87 galaxy. EHT images in linear polarization have further identified a coherent spiral pattern around the black hole, produced from ordered magnetic fields threading the emitting plasma. Here we present the first analysis of circular polarization using EHT data, acquired in 2017, which can potentially provide additional insights into the magnetic fields and plasma composition near the black hole. Interferometric closure quantities provide convincing evidence for the presence of circularly polarized emission on event-horizon scales. We produce images of the circular polarization using both traditional and newly developed methods. All methods find a moderate level of resolved circular polarization across the image (〈∣ v ∣〉 < 3.7%), consistent with the low image-integrated circular polarization fraction measured by the Atacama Large Millimeter/submillimeter Array (∣ v int ∣ < 1%). Despite this broad agreement, the methods show substantial variation in the morphology of the circularly polarized emission, indicating that our conclusions are strongly dependent on the imaging assumptions because of the limited baseline coverage, uncertain telescope gain calibration, and weakly polarized signal. We include this upper limit in an updated comparison to general relativistic magnetohydrodynamic simulation models. This analysis reinforces the previously reported preference for magnetically arrested accretion flow models. We find that most simulations naturally produce a low level of circular polarization consistent with our upper limit and that Faraday conversion is likely the dominant production mechanism for circular polarization at 230 GHz in M87*.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"34 10","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136102254","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spatial Extent of Molecular Gas, Dust, and Stars in Massive Galaxies at z ∼ 2.2–2.5 Determined with ALMA and JWST","authors":"Ken-ichi Tadaki, Tadayuki Kodama, Yusei Koyama, Tomoko L. Suzuki, Ikki Mitsuhashi, Ryota Ikeda","doi":"10.3847/2041-8213/ad03f2","DOIUrl":"https://doi.org/10.3847/2041-8213/ad03f2","url":null,"abstract":"Abstract We present the results of 0.″6-resolution observations of CO J = 3 − 2 line emission in 10 massive star-forming galaxies at z ∼ 2.2–2.5 with the Atacama Large Millimeter/submillimeter Array (ALMA). We compare the spatial extent of molecular gas with those of dust and stars, traced by the 870 and 4.4 μ m continuum emissions, respectively. The average effective radius of the CO emission is 1.75 ± 0.34 kpc, which is about 60% larger than that of the 870 μ m emission and is comparable with that of the 4.4 μ m emission. Utilizing the best-fit parametric models, we derive the radial gradients of the specific star formation rate (sSFR), gas depletion timescale, and gas-mass fraction within the observed galaxies. We find a more intense star formation activity with a higher sSFR and a shorter depletion timescale in the inner region than in the outer region. The central starburst may be the primary process for massive galaxies to build up a core. Furthermore, the gas-mass fraction is high, independent of the galactocentric radius in the observed galaxies, suggesting that the galaxies have not begun to quench star formation. Given the shorter gas depletion timescale in the center compared to the outer region, quenching is expected to occur in the center first and then propagate outward. We may be witnessing the observed galaxies in the formation phase of a core prior to the forthcoming phase of star formation propagating outward.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"23 17","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135371437","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Formation Mechanism for “Wrong Way” Radio Relics","authors":"Ludwig M. Böss, Ulrich P. Steinwandel, Klaus Dolag","doi":"10.3847/2041-8213/ad03f7","DOIUrl":"https://doi.org/10.3847/2041-8213/ad03f7","url":null,"abstract":"Abstract Radio relics are typically found to be arc-like regions of synchrotron emission in the outskirts of merging galaxy clusters, bowing out from the cluster center. In most cases they show synchrotron spectra that steepen toward the cluster center, indicating that they are caused by relativistic electrons being accelerated at outward traveling merger shocks. A number of radio relics break with this ideal picture and show morphologies that are bent the opposite way and show spectral index distributions that do not follow expectations from the ideal picture. We propose that these “wrong way” relics can form when an outward traveling shock wave is bent inward by an infalling galaxy cluster or group. We test this in an ultra-high-resolution zoom-in simulation of a massive galaxy cluster with an on-the-fly spectral cosmic-ray model. This allows us to study not only the synchrotron emission at colliding shocks, but also their synchrotron spectra to address the open question of relics with strongly varying spectral indices over the relic surface.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"23 14","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135371438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"VERTICO and IllustrisTNG: The Spatially Resolved Effects of Environment on Galactic Gas","authors":"Adam R. H. Stevens, Toby Brown, Benedikt Diemer, Annalisa Pillepich, Lars Hernquist, Dylan Nelson, Yannick M. Bahé, Alessandro Boselli, Timothy A. Davis, Pascal J. Elahi, Sara L. Ellison, María J. Jiménez-Donaire, Ian D. Roberts, Kristine Spekkens, Vicente Villanueva, Adam B. Watts, Christine D. Wilson, Nikki Zabel","doi":"10.3847/2041-8213/ad014b","DOIUrl":"https://doi.org/10.3847/2041-8213/ad014b","url":null,"abstract":"It has been shown in previous publications that the TNG100 simulation quantitatively reproduces the observed reduction in each of the total atomic and total molecular hydrogen gas for galaxies within massive halos, i.e., dense environments. In this Letter, we study how well TNG50 reproduces the resolved effects of a Virgo-like cluster environment on the gas surface densities of satellite galaxies with m * > 109 M ⊙ and star formation rate > 0.05 M ⊙ yr−1. We select galaxies in the simulation that are analogous to those in the HERACLES and VERTICO surveys and mock-observe them to the common specifications of the data. Although TNG50 does not quantitatively match the observed gas surface densities in the centers of galaxies, the simulation does qualitatively reproduce the trends of gas truncation and central density suppression seen in VERTICO in both H i and H2. This result promises that modern cosmological hydrodynamic simulations can be used to reliably model the post-infall histories of cluster satellite galaxies.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"3 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135411086","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tilted Dark Halos Are Common and Long-lived, and Can Warp Galactic Disks","authors":"Jiwon Jesse Han, Vadim Semenov, Charlie Conroy, Lars Hernquist","doi":"10.3847/2041-8213/ad0641","DOIUrl":"https://doi.org/10.3847/2041-8213/ad0641","url":null,"abstract":"Abstract In the Lambda cold dark matter paradigm, the dark halo governs the gravitational potential within which a galaxy can form and evolve. In this Letter we show that the present-day inner ( r < 50 kpc) dark halo can be significantly misaligned with the stellar disk. To this end, we use the TNG50 run from the cosmological magnetohydrodynamic IllustrisTNG simulation suite. Such “tilted” dark halos can arise from a variety of processes including major mergers, massive flybys, or interactions with satellite companions. Furthermore, we show that tilted dark halos (1) are well traced by tilted stellar halos, (2) can maintain their tilt for >5 Gyr in isolated evolution, and (3) can generate warps in the outer disks that are stable over many Gyr. A tilted dark halo holds clues to important events in the formation history of a galaxy, and could help explain the abundance of warped disks in galaxy observations, including the Milky Way.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"20 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135509515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hadronic Processes at Work in 5BZB J0630−2406","authors":"Gaëtan Fichet de Clairfontaine, Sara Buson, Leonard Pfeiffer, Stefano Marchesi, Alessandra Azzollini, Vardan Baghmanyan, Andrea Tramacere, Eleonora Barbano, Lenz Oswald","doi":"10.3847/2041-8213/ad0644","DOIUrl":"https://doi.org/10.3847/2041-8213/ad0644","url":null,"abstract":"Abstract Recent observations are shedding light on the important role that active galactic nuclei play in the production of high-energy neutrinos. In this study, we focus on one object, 5BZB J0630−2406, which is among the blazars recently proposed as associated with neutrino emission during the first 7 yr of IceCube observations. Modeling the quasi-simultaneous, broadband spectral energy distribution, we explore various scenarios from purely leptonic to leptohadronic models, testing the inclusion of external photon fields. This theoretical study provides a complementary testing ground for the proposed neutrino–blazar association. Despite being historically classified as a BL Lac, our study shows that 5BZB J0630−2406 belongs to the relatively rare subclass of high-power flat-spectrum radio quasars. Our results indicate that interactions between protons and external radiation fields can produce a neutrino flux that is within the reach of the IceCube detector. Furthermore, the spectral shape of the X-ray emission suggests the imprint of hadronic processes related to very energetic protons.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"53 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135764033","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Betatron Acceleration of Suprathermal Electrons within a Small-scale Flux Rope in the Solar Wind","authors":"Weiduo Meng, Jianpeng Guo, Haibo Lin, Huishan Fu, Meng Zhou, Dan Zhao, Yan Chen, Linxia He, Xianghan Wang, Zelin Wang","doi":"10.3847/2041-8213/ad00ad","DOIUrl":"https://doi.org/10.3847/2041-8213/ad00ad","url":null,"abstract":"Abstract A growing body of evidence from observations, theories, and simulations indicates that particles can be effectively accelerated in solar wind regions filled with dynamic small-scale flux ropes (FRs). The main acceleration mechanisms identified in simulations include parallel electric field acceleration, first-order Fermi acceleration, and generalized betatron acceleration in contracting or merging small-scale FRs. However, direct identification of these acceleration mechanisms from in situ measurements remains a challenge. Here we present a distinct event of local betatron acceleration within a contracting small-scale FR in the solar wind, due to a local compression. In this event, the lower-energy halo electrons were effectively accelerated through the betatron mechanism, whereas the higher-energy suprathermal electrons predominated by the superhalo component were almost not energized. The halo electron energization processes via the betatron mechanism are reproduced using an analytical model. Further examination of small-scale FRs in the vicinity of the heliospheric current sheet over the period 1995–2020 indicates that in situ signatures of the betatron acceleration process are essentially elusive.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"23 18","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135371436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Little Red Dots or Brown Dwarfs? NIRSpec Discovery of Three Distant Brown Dwarfs Masquerading as NIRCam-selected Highly Reddened Active Galactic Nuclei","authors":"Danial Langeroodi, Jens Hjorth","doi":"10.3847/2041-8213/acfeec","DOIUrl":"https://doi.org/10.3847/2041-8213/acfeec","url":null,"abstract":"Abstract Cold, substellar objects such as brown dwarfs have long been recognized as contaminants in color-selected samples of active galactic nuclei (AGNs). In particular, their near- to mid-infrared colors (1–5 μ m) can closely resemble the V-shaped ( f λ ) spectra of highly reddened accreting supermassive black holes (“little red dots”), especially at 6 < z < 7. Recently, a NIRCam-selected sample of little red dots over 45 arcmin 2 has been followed up with deep NIRSpec multiobject prism spectroscopy through the UNCOVER program. By investigating the acquired spectra, we identify 3 of the 14 followed-up objects as T/Y dwarfs with temperatures between 650 and 1300 K and distances between 0.8 and 4.8 kpc. At <?CDATA ${4.8}_{-0.1}^{+0.6}$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:msubsup> <mml:mrow> <mml:mn>4.8</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.6</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> kpc, A2744-BD1 is the most distant brown dwarf discovered to date. We identify the remaining 11 objects as extragalactic sources at z spec ≳ 5. Given that three of these sources are strongly lensed images of the same AGN (A2744-QSO1), we derive a brown dwarf contamination fraction of 25% in this NIRCam selection of little red dots. We find that in the near-infrared filters, brown dwarfs appear much bluer than the highly reddened AGN, providing an avenue for distinguishing the two and compiling cleaner samples of photometrically selected highly reddened AGN.","PeriodicalId":55567,"journal":{"name":"Astrophysical Journal Letters","volume":"24 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135515866","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}