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At least 991 records · Page 55

Photometric Objects Around Cosmic Webs (PAC) Delineated in a Spectroscopic Survey. III. Accurate Measurement of Galaxy Stellar Mass Function with the Aid of Cosmological Redshift Surveys

We present a novel method to accurately measure the galaxy stellar mass function (GSMF) based upon the Photometric objects Around Cosmic webs (PAC) method developed in our first paper (Paper I) of the series. The method allows us to measure the GSMF to a lower-mass end that is not accessible to the spectroscopic sample used in the PAC. Compared with Paper I, the current measurement of GSMF is direct and model independent. We measure the GSMFs in the redshift ranges of z$^{3}_{s}$ < 0.2, 0.2 < z s < 0.4, and 0.5 < z s < 0.7 down to stellar masses of M* = 10 8.2 , 10 10.6 , and 10 10.6 M ⊙ , using the data from the Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys and the spectroscopic samples of Slogan Digital Sky Survey (i.e., Main, LOWZ, and CMASS samples). Our results show that there is no evolution of GSMF from z s = 0.6 to z s = 0.1 for M* > 10 10.6 M ⊙ , and that there is a clear upturn at M* ≈ 10 9.5 M ⊙ toward smaller galaxies in the local GMSF at z s = 0.1. We provide an accurate double Schechter fit to the local GSMF for the entire range of M* and a table of our measurements at the three redshifts, which can be used to test theories of galaxy formation. Our method can achieve an accurate measurement of GSMF to the stellar mass limit where the spectroscopic sample is already highly incomplete (e.g., ~ 10 -3 ) for its target selection.

79 ASTRONOMY AND ASTROPHYSICS↗

Effects of Preionization in Radiative Shocks. II. Application to the Herbig–Haro Objects

In an earlier paper we treated the preionization problem in shocks over the velocity range 20 km s{sup −1 }< v{sub s}<1000 km s{sup −1 }in a fully self-consistent manner. Here we investigate in detail the effect of the upstream UV photon field generated in the radiative zone of shocks in the range in which hydrogen is only partly ionized 20 km s{sup −1 }(< v{sub s}<150 km s{sup −1}). We show that, as a result of superheating in the nonequilibrium preshock plasma, both the magnetic parameter and the Mach number of the shock are strongly affected by the preionization state of the gas, which controls to a large extent the radiative spectrum of the shock. We use these models to provide specific line diagnostics for Herbig–Haro objects, which allow us to solve for both the preshock density and shock velocity, and we present detailed models of the HH 34 jet, which allows us to derive the shock conditions, mass-loss rate, momentum flux, and chemical abundances in the jet. We show that the refractory elements Mg, Ca, Fe, and Ni are enhanced by 0.22 dex over the solar values, which provides interesting clues about the jet-launching mechanism in pre-main-sequence evolution.

79 ASTRONOMY AND ASTROPHYSICS↗

VLA Survey of Dense Gas in Extended Green Objects: Prevalence of 25 GHz Methanol Masers

We present ∼1″–4″ resolution Very Large Array (VLA) observations of four CH{sub 3}OH J{sub 2}--J{sub 1}-E 25 GHz transitions (J = 3, 5, 8, 10) along with the 1.3 cm continuum toward 20 regions of active massive star formation containing Extended Green Objects (EGOs), 14 of which we have previously studied with the VLA in the Class I 44 GHz and Class II 6.7 GHz maser lines. Sixteen regions are detected in at least one 25 GHz line (J = 5), with 13 of 16 exhibiting maser emission. In total, we report 34 new sites of CH{sub 3}OH maser emission and 10 new sites of thermal CH{sub 3}OH emission, significantly increasing the number of 25 GHz Class I CH{sub 3}OH masers observed at high angular resolution. We identify probable or likely maser counterparts at 44 GHz for all 15 of the 25 GHz masers for which we have complementary data, providing further evidence that these masers trace similar physical conditions despite uncorrelated flux densities. The sites of thermal and maser emission of CH{sub 3}OH are both predominantly associated with the 4.5 μm emission from the EGO, and the presence of thermal CH{sub 3}OH emission is accompanied by 1.3 cm continuum emission in 9 out of 10 cases. Of the 19 regions that exhibit 1.3 cm continuum emission, it is associated with the EGO in 16 cases (out of a total of 20 sites), 13 of which are new detections at 1.3 cm. Twelve of the 1.3 cm continuum sources are associated with 6.7 GHz maser emission and likely trace deeply embedded massive protostars.

79 ASTRONOMY AND ASTROPHYSICS↗

The DECam Plane Survey: Optical Photometry of Two Billion Objects in the Southern Galactic Plane

The DECam Plane Survey is a five-band optical and near-infrared survey of the southern Galactic plane with the Dark Energy Camera at Cerro Tololo. The survey is designed to reach past the main-sequence turn-off of old populations at the distance of the Galactic center through a reddening $E(B-V)$ of 1.5 mag. Typical single-exposure depths are 23.7, 22.8, 22.3, 21.9, and 21.0 mag (AB) in the grizY bands, with seeing around $1^{\prime\prime} $. The footprint covers the Galactic plane with $| b| \lesssim 4^\circ $, $5^\circ \gt l\gt -120^\circ $. The survey pipeline simultaneously solves for the positions and fluxes of tens of thousands of sources in each image, delivering positions and fluxes of roughly two billion stars with better than 10 mmag precision. Most of these objects are highly reddened and deep in the Galactic disk, probing the structure and properties of the Milky Way and its interstellar medium. Furthermore, the fully-processed images and derived catalogs are publicly available.

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The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Quasar Survey: Quasar Properties from Data Releases 6 to 9

We report the fourth installment in the series of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) quasar survey, which includes quasars observed between 2017 September and 2021 June. There are in total 13,066 quasars reliably identified, of which 6685 are newly discovered that are not reported in the Sloan Digital Sky Survey (SDSS) DR14 quasar catalog or Million Quasars catalog. Because LAMOST does not provide accurate absolute flux calibration, we recalibrate the spectra with the SDSS/Pan-STARRS1 multiband photometric data. The emission-line properties of Hα, Hβ, Mg II , and C Iv and the continuum luminosities are measured by fitting the recalibrated spectra. We also estimate the single-epoch virial black hole masses (M BH ) using the derived emission-line and continuum parameters. This is the first time that the emission-line and continuum fluxes were estimated based on LAMOST recalibrated quasar spectra. The catalog and spectra for these quasars are available online. After the 9 yr LAMOST quasar survey, there are in total 56,175 identified quasars, of which 24,127 are newly discovered. The LAMOST quasar survey not only discovers a great number of new quasars but also provides a database for investigating the spectral variability of the quasars observed by both LAMOST and SDSS and finding rare quasars, including changing-look quasars and broad absorption line quasars.

79 ASTRONOMY AND ASTROPHYSICS↗

ABSENCE OF SIGNIFICANT COOL DISKS IN YOUNG STELLAR OBJECTS EXHIBITING REPETITIVE OPTICAL OUTBURSTS

We report Submillimeter Array 1.3 mm high angular resolution observations toward the four EXor-type outbursting young stellar objects VY Tau, V1118 Ori, V1143 Ori, and NY Ori. The data mostly show low dust masses M{sub dust} in the associated circumstellar disks. Among the sources, NY Ori possesses a relatively massive disk with M{sub dust} ∼ 9 × 10{sup −4}M{sub ⊙}. V1118 Ori has a marginal detection equivalent to M{sub dust} ∼ 6 × 10{sup −5}M{sub ⊙}. V1143 Ori has a non-detection also equivalent to M{sub dust} < 6 × 10{sup −5}M{sub ⊙}. For the nearest source, VY Tau, we get a surprising non-detection that provides a stringent upper limit M{sub dust} < 6 × 10{sup −6}M{sub ⊙}. We interpret our findings as suggesting that the gas and dust reservoirs that feed the short-duration, repetitive optical outbursts seen in some EXors may be limited to the small-scale, innermost region of their circumstellar disks. This hot dust may have escaped our detection limits. Follow-up, more sensitive millimeter observations are needed to improve our understanding of the triggering mechanisms of EXor-type outbursts.

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First detection in gamma-rays of a young radio galaxy: Fermi -LAT observations of the compact symmetric object PKS 1718−649

We report the γ -ray detection of a young radio galaxy, PKS 1718−649, belonging to the class of compact symmetric objects (CSOs), with the Large Area Telescope (LAT) on board the Fermi satellite. The third Fermi Gamma-ray LAT catalog (3FGL) includes an unassociated γ -ray source, 3FGL J1728.0−6446, located close to PKS 1718−649. Using the latest Pass 8 calibration, we confirm that the best-fit 1 σ position of the γ -ray source is compatible with the radio location of PKS 1718−649. Cross-matching of the γ -ray source position with the positions of blazar sources from several catalogs yields negative results. Thus, we conclude that PKS 1718−649 is the most likely counterpart to the unassociated LAT source. We obtain a detection test statistics TS ∼ 36 (>5 σ ) with a best-fit photon spectral index Γ = 2.9 ± 0.3 and a 0.1–100 GeV photon flux density F {sub 0.1−100} {sub GeV} = (11.5 ± 0.3) × 10{sup −9} ph cm{sup −2} s{sup −1}. We argue that the linear size (∼2 pc), the kinematic age (∼100 years), and the source distance ( z = 0.014) make PKS 1718−649 an ideal candidate for γ -ray detection in the framework of the model proposing that the most compact and the youngest CSOs can efficiently produce GeV radiation via inverse-Compton scattering of the ambient photon fields by the radio lobe non-thermal electrons. Thus, our detection of the source in γ -rays establishes young radio galaxies as a distinct class of extragalactic high-energy emitters and yields a unique insight on the physical conditions in compact radio lobes interacting with the interstellar medium of the host galaxy.

79 ASTRONOMY AND ASTROPHYSICS↗

MAGNETAR-LIKE ACTIVITY FROM THE CENTRAL COMPACT OBJECT IN THE SNR RCW103

The 6.67 hr periodicity and the variable X-ray flux of the central compact object (CCO) at the center of the supernova remnant RCW 103, named 1E 161348–5055, have been always difficult to interpret within the standard scenarios of an isolated neutron star (NS) or a binary system. On 2016 June 22, the Burst Alert Telescope (BAT) on board Swift detected a magnetar-like short X-ray burst from the direction of 1E 161348–5055, also coincident with a large long-term X-ray outburst. Here, we report on Chandra , Nuclear Spectroscopic Telescope Array , and Swift (BAT and XRT) observations of this peculiar source during its 2016 outburst peak. In particular, we study the properties of this magnetar-like burst, we discover a hard X-ray tail in the CCO spectrum during outburst, and we study its long-term outburst history (from 1999 to 2016 July). We find the emission properties of 1E 161348–5055 consistent with it being a magnetar. However, in this scenario, the 6.67 hr periodicity can only be interpreted as the rotation period of this strongly magnetized NS, which therefore represents the slowest pulsar ever detected, by orders of magnitude. We briefly discuss the viable slow-down scenarios, favoring a picture involving a period of fall-back accretion after the supernova explosion, similarly to what is invoked (although in a different regime) to explain the “anti-magnetar” scenario for other CCOs.

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Discovery of a Satellite of the Large Trans-Neptunian Object (225088) 2007 OR{sub 10}

2007 OR{sub 10} is currently the third largest known dwarf planet in the trans-Neptunian region, with an effective radiometric diameter of ∼1535 km. It has a slow rotation period of ∼45 hr that was suspected to be caused by tidal interactions with a satellite undetected at that time. Here, we report on the discovery of a likely moon of 2007 OR{sub 10}, identified on archival Hubble Space Telescope WFC3/UVIS system images. Although the satellite is detected at two epochs, this does not allow an unambiguous determination of the orbit and the orbital period. A feasible 1.5–5.8 · 10{sup 21} kg estimate for the system mass leads to a likely 35–100 day orbital period. The moon is about 4.ͫ2 fainter than 2007 OR{sub 10} in HST images that corresponds to a diameter of 237 km assuming equal albedos with the primary. Due to the relatively small size of the moon, the previous size and albedo estimates for the primary remains unchanged. With this discovery all trans-Neptunian objects larger than 1000 km are now known to harbor satellites, an important constraint for moon formation theories in the young solar system.

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SIMP J013656.5+093347 is likely a planetary-mass object in the carina-near moving group

We report on the discovery that the nearby (∼6 pc) photometrically variable T2.5 dwarf SIMP J013656.5+093347 is a likely member of the ∼200 Myr old Carina-Near moving group with a probability of >99.9% based on its full kinematics. Our vsin i measurement of 50.9 ± 0.8 km s{sup −1} combined with the known rotation period inferred from variability measurements provide a lower limit of 1.01 ± 0.02 R{sub Jup} on the radius of SIMP 0136+0933, an independent verification that it must be younger than ∼950 Myr, according to evolution models. We estimate a field interloper probability of 0.2% based on the density of field T0–T5 dwarfs. At the age of Carina-Near, SIMP 0136+0933 has an estimated mass of 12.7 ± 1.0 M{sub Jup} and is predicted to have burned roughly half of its original deuterium. SIMP 0136+0933 is the closest known young moving group member to the Sun and is one of only a few known young T dwarfs, making it an important benchmark for understanding the atmospheres of young planetary-mass objects.

79 ASTRONOMY AND ASTROPHYSICS↗

Abundant Methanol Ice toward a Massive Young Stellar Object in the Central Molecular Zone

Previous radio observations revealed widespread gas-phase methanol (CH{sub 3}OH) in the Central Molecular Zone (CMZ) at the Galactic center (GC), but its origin remains unclear. Here, we report the discovery of CH{sub 3}OH ice toward a star in the CMZ, based on a Subaru 3.4–4.0 μm spectrum, aided by NASA/IRTF L{sup ′} imaging and 2–4 μm spectra. The star lies ∼8000 au away in projection from a massive young stellar object (MYSO). Its observed high CH{sub 3}OH ice abundance (17%±3% relative to H{sub 2}O ice) suggests that the 3.535 μm CH{sub 3}OH ice absorption likely arises in the MYSO’s extended envelope. However, it is also possible that CH{sub 3}OH ice forms with a higher abundance in dense clouds within the CMZ, compared to within the disk. Either way, our result implies that gas-phase CH{sub 3}OH in the CMZ can be largely produced by desorption from icy grains. The high solid CH{sub 3}OH abundance confirms the prominent 15.4 μm shoulder absorption observed toward GC MYSOs arises from CO{sub 2} ice mixed with CH{sub 3}OH.

79 ASTRONOMY AND ASTROPHYSICS↗

A Statistical Standard Siren Measurement of the Hubble Constant from the LIGO/Virgo Gravitational Wave Compact Object Merger GW190814 and Dark Energy Survey Galaxies

We present a measurement of the Hubble constant H 0 using the gravitational wave (GW) event GW190814, which resulted from the coalescence of a 23 M ⊙ black hole with a 2.6 M ⊙ compact object, as a standard siren. No compelling electromagnetic counterpart has been identified for this event; thus our analysis accounts for thousands of potential host galaxies within a statistical framework. The redshift information is obtained from the photometric redshift (photo- z ) catalog from the Dark Energy Survey. The luminosity distance is provided by the LIGO/Virgo gravitational wave sky map. Since this GW event has the second-smallest localization volume after GW170817, GW190814 is likely to provide the best constraint on cosmology from a single standard siren without identifying an electromagnetic counterpart. Furthermore, our analysis uses photo- z probability distribution functions and corrects for photo- z biases. We also reanalyze the binary black hole GW170814 within this updated framework. We explore how our findings impact the H 0 constraints from GW170817, the only GW merger associated with a unique host galaxy. From a combination of GW190814, GW170814, and GW170817, our analysis yields H 0 =72.0$_{+12}^{–8.2}$ km s -1 Mpc -1 (68% highest-density interval, HDI) for a prior in H 0 uniform between [20 and 140] km s -1 Mpc -1 . The addition of GW190814 and GW170814 to GW170817 improves the 68% HDI from GW170817 alone by ~18%, showing how well-localized mergers without counterparts can provide a significant contribution to standard siren measurements, provided that a complete galaxy catalog is available at the location of the event.

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Cold Dark Matter and Self-interacting Dark Matter Interpretations of the Strong Gravitational Lensing Object JWST-ER1

Abstract van Dokkum et al. reported the discovery of JWST-ER1, a strong lensing object at redshift z ≈ 2, using data from the James Webb Space Telescope. The lens mass within the Einstein ring is 5.9 times higher than the expected stellar mass from a Chabrier initial mass function, indicating a high dark matter density. In this work, we show that a cold dark matter halo, influenced by gas-driven adiabatic contraction, can account for the observed lens mass. We interpret the measurement of JWST-ER1 in the self-interacting dark matter scenario and show that the cross section per particle mass σ / m ≈ 0.1 cm 2 g −1 is generally favored. Intriguingly, σ / m ≈ 0.1 cm 2 g −1 can also be consistent with the strong lensing observations of early-type galaxies at redshift z ≈ 0.2, where adiabatic contraction is not observed overall.

Astronomy & Astrophysics↗

A simple object-oriented and open-source model for scientific and policy analyses of the global climate system – Hector v1.0

Simple climate models play an integral role in the policy and scientific communities. They are used for climate mitigation scenarios within integrated assessment models, complex climate model emulation, and uncertainty analyses. Here we describe Hector v1.0, an open source, object-oriented, simple global climate carbon-cycle model. This model runs essentially instantaneously while still representing the most critical global-scale earth system processes. Hector has a three-part main carbon cycle: a one-pool atmosphere, land, and ocean. The model's terrestrial carbon cycle includes primary production and respiration fluxes, accommodating arbitrary geographic divisions into, e.g., ecological biomes or political units. Hector actively solves the inorganic carbon system in the surface ocean, directly calculating air–sea fluxes of carbon and ocean pH. Hector reproduces the global historical trends of atmospheric [CO 2 ], radiative forcing, and surface temperatures. The model simulates all four Representative Concentration Pathways (RCPs) with equivalent rates of change of key variables over time compared to current observations, MAGICC (a well-known simple climate model), and models from the 5th Coupled Model Intercomparison Project. Hector's flexibility, open-source nature, and modular design will facilitate a broad range of research in various areas.

54 ENVIRONMENTAL SCIENCES↗

Legacy Survey of Space and Time Data Preview 1: object dataset type

The Legacy Survey of Space and Time Data Preview 1 (DP1) is the first release of data from the NSF-DOE Vera C. Rubin Observatory. It consists of raw and calibrated single-epoch images, co-adds, difference images, detection catalogs, and other derived data products. DP1 is based on 1792 science-grade optical/near-infrared exposures acquired over 48 distinct nights by the Rubin Commissioning Camera, LSSTComCam, on the Simonyi Survey Telescope at the Summit Facility on Cerro Pachón, Chile during the first on-sky commissioning campaign in late 2024. DP1 covers a total of approximately 15 sq. deg. over seven roughly equally-sized non-contiguous fields, each independently observed in six broad photometric bands, ugrizy, spanning a range of stellar densities and latitudes and overlapping with external reference datasets. This dataset is a subset of the full data release consisting of the object dataset type. These are detections from deep co-adds. This release contains 29 datasets of this type.

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Legacy Survey of Space and Time Data Preview 1: Object searchable catalog

The Legacy Survey of Space and Time Data Preview 1 (DP1) is the first release of data from the NSF-DOE Vera C. Rubin Observatory. It consists of raw and calibrated single-epoch images, co-adds, difference images, detection catalogs, and other derived data products. DP1 is based on 1792 science-grade optical/near-infrared exposures acquired over 48 distinct nights by the Rubin Commissioning Camera, LSSTComCam, on the Simonyi Survey Telescope at the Summit Facility on Cerro Pachón, Chile during the first on-sky commissioning campaign in late 2024. DP1 covers a total of approximately 15 sq. deg. over seven roughly equally-sized non-contiguous fields, each independently observed in six broad photometric bands, ugrizy, spanning a range of stellar densities and latitudes and overlapping with external reference datasets. This dataset is a subset of the full data release consisting of a searchable catalog named Object. This catalog contains detections from deep co-adds. This catalog contains 2,299,757 rows with 1,296 columns.

79 ASTRONOMY AND ASTROPHYSICS↗

Legacy Survey of Space and Time Data Preview 2: object dataset type

We present Rubin Data Preview 2 (DP2), the second data preview from the NDF-DOE Vera C. Rubin Observatory. Data Preview 2 (DP2) comprises coadds, detection catalogs, and ancillary data products; and when fully released will also include single-epoch images and difference images. DP2 is derived from observations acquired by the LSST Science Camera (LSSTCam) on the Simonyi Survey Telescope at the Summit Facility on Cerro Pachón, Chile, primarily during the on-sky commissioning campaign between 2025-04-16 and 2025-09-21, supplemented by observations taken between 2025-10-25 and 2026-01-06 that overlap the commissioning footprint. The DP2 footprint comprises the Science Validation wide-area survey, five Deep Drilling Fields, and a number of targeted small-field regions, including Trifid and Lagoon, Prawn, M49, and New Horizons, all observed as part of the Rubin First Look campaign. Each field was imaged in up to six broad photometric bands, ugrizy, and coadded to produce deep imaging covering an estimated 3,000 deg2. The addition of single-visit-only areas expands the total DP2 footprint to an estimated 15,000 deg2, with coverage in at least one filter. The median per-visit PSF FWHM across the wide-area survey ranges from 1.17 arcsec in the z band to 1.26 arcsec in g and r bands. The deepest field, reaches estimated coadded 5σ depths of u=26 mag, g=26.8 mag, r=26.3 mag, i=26.1 mag, z=25.3 mag, y=23.9 mag. Based on a roughly five-month primary observing baseline and covering only part of the eventual LSST footprint, DP2's area, depth, and multiband coverage nonetheless support a broad range of early science investigations ahead of LSST Data Release This dataset is a subset of the full data release consisting of the object dataset type. These are detections from deep co-adds. This release contains 2,174 datasets of this type.

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Legacy Survey of Space and Time Data Preview 2: Object searchable catalog

We present Rubin Data Preview 2 (DP2), the second data preview from the NDF-DOE Vera C. Rubin Observatory. Data Preview 2 (DP2) comprises coadds, detection catalogs, and ancillary data products; and when fully released will also include single-epoch images and difference images. DP2 is derived from observations acquired by the LSST Science Camera (LSSTCam) on the Simonyi Survey Telescope at the Summit Facility on Cerro Pachón, Chile, primarily during the on-sky commissioning campaign between 2025-04-16 and 2025-09-21, supplemented by observations taken between 2025-10-25 and 2026-01-06 that overlap the commissioning footprint. The DP2 footprint comprises the Science Validation wide-area survey, five Deep Drilling Fields, and a number of targeted small-field regions, including Trifid and Lagoon, Prawn, M49, and New Horizons, all observed as part of the Rubin First Look campaign. Each field was imaged in up to six broad photometric bands, ugrizy, and coadded to produce deep imaging covering an estimated 3,000 deg2. The addition of single-visit-only areas expands the total DP2 footprint to an estimated 15,000 deg2, with coverage in at least one filter. The median per-visit PSF FWHM across the wide-area survey ranges from 1.17 arcsec in the z band to 1.26 arcsec in g and r bands. The deepest field, reaches estimated coadded 5σ depths of u=26 mag, g=26.8 mag, r=26.3 mag, i=26.1 mag, z=25.3 mag, y=23.9 mag. Based on a roughly five-month primary observing baseline and covering only part of the eventual LSST footprint, DP2's area, depth, and multiband coverage nonetheless support a broad range of early science investigations ahead of LSST Data Release This dataset is a subset of the full data release consisting of a searchable catalog named Object. This catalog contains detections from deep co-adds. This catalog contains 786,420,720 rows with 1,248 columns.

79 ASTRONOMY AND ASTROPHYSICS↗