Sloan Digital Sky Survey Data Research Articles

Observational Test of f(Q) Gravity with Weak Gravitational Lensing

In this article we confront a class of f(Q) gravity models with observational data of galaxy–galaxy lensing. Specifically, we consider f(Q) gravity models containing a small quadratic correction when compared with general relativity (GR), and quantify this correction by a model parameter, α. To derive the observational constraints, we start by extracting spherically symmetric solutions, which correspond to deviations from the Schwarzschild solution that depends on the model parameters in a twofold way, i.e., a renormalized mass and a new term proportional to r −2. Then, we calculate the effective lensing potential, the deflection angle, the shear component, and the effective excess surface density profile. After that, we employ a group catalog and a shape catalog from the Sloan Digital Sky Survey Data Release 7 for the lens and source samples, respectively. Moreover, we handle the off-center radius as a free parameter and constrain it using a Markov Chain Monte Carlo method. Concerning the deviation parameter from GR we derive α=1.202−0.179+0.277×10−6Mpc−2 at the 1σ confidence level, and then compare the fitting efficiency with the standard Λ cold dark matter paradigm by applying the Akaike information criterion and Bayesian information criterion. Our results indicate that the f(Q) corrections alongside the off-center effect yield a scenario that is slightly favored.

Red Type-1 Quasars after Cosmic Noon and Impact on L UV-related Quasar Statistics

Over the past decades, nearly a million quasars have been explored to shed light on the evolution of supermassive black holes and galaxies. The ultraviolet-to-optical spectra of type-1 quasars particularly offer insights into their black hole activities. Recent findings, however, raise questions about the prevalence of red type-1 quasars of which colors might be due to dust obscuration and their potential influence on luminosity-related properties of quasars. We examine the fraction of red type-1 quasars within the redshift range of 0.68 ≤ z < 2.20, applying a spectral energy distribution (SED) fitting using optical-to-mid-infrared (MIR) photometric data of Sloan Digital Sky Survey Data Release 14 quasars. Approximately 10% of the type-1 quasars exhibit red colors suggestive of dust obscuration. There is an association between the brightness of the MIR luminosity and a higher fraction of red type-1 quasars, albeit with negligible redshift evolution. By employing E(B − V) values from the SED fitting, we obtained dereddened luminosity of the red type-1 quasars and reassess the quasar luminosity function (QLF) and black hole mass (M BH) estimates. Result shows a modest increase in the number density of bright quasars, linking to more flatten bright-end slope of QLFs, while M BH adjustments are minimal. Current SDSS selections with optical colors could miss a significant population of heavily dust-obscured quasars. As future MIR surveys like Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer expand, they may reveal enough obscured quasars to prompt a more profound revision of fundamental quasar properties.

A Comparative Study of Ultraluminous Infrared Galaxies in the IRAS and SDSS Surveys

We present a comprehensive study of ultraluminous infrared galaxies (ULIRGs), leveraging data from the Infrared Astronomical Satellite Faint Source Catalogue and the spectroscopic catalog in the Sloan Digital Sky Survey Data Release 16. Our meticulous crossmatching technique significantly enhances the reliability of ULIRG identification, resulting in the identification of 283 reliable ULIRGs, including 102 new detections, while discarding 120 previously reported false sources. Covering a redshift range of z = 0.018–0.996, with a median redshift of z¯=0.259 , our uniform sample reveals apparent interaction features in approximately 40% of ULIRGs, increasing to 92% for those with z < 0.1. Through optical spectra analysis, it is indicated that over 58% of ULIRGs host an active galactic nucleus (AGN), which is twice as high as detections based solely on infrared colors. Moreover, a pronounced excess of radio emissions associated with AGN activity results in a steeper radio–far-infrared correlation. Notably, Type I ULIRGs exhibit properties similar to those of narrow-line Seyfert 1 galaxies, with an elevated incidence rate of Mg ii broad absorption lines (16.7%), surpassing that of typical optically selected quasars by over tenfold, consistent with current evolutionary models. We anticipate that forthcoming telescopes such as the China Space Station Telescope and Leighton Chajnantor Telescope will provide deeper insights into ULIRG morphology, dust distribution, molecular gas, and AGN activity.

Galaxy–Galaxy Lensing Data: f(T) Gravity Challenges General Relativity

We use galaxy–galaxy lensing data to test general relativity and f(T) gravity at galaxy scales. We consider an exact spherically symmetric solution of f(T) theory, which is obtained from an approximate quadratic correction, and thus it is expected to hold for every realistic deviation from general relativity. Quantifying the deviation by a single parameter Q, and following the post-Newtonian approximation, we obtain the corresponding deviation in the gravitational potential, shear component, and effective excess surface density profile. We used five stellar mass samples and divided them into blue and red galaxies to test the model dependence on galaxy color, and we modeled the excess surface density profiles using the Navarro–Frenk–White profiles. Based on the group catalog from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) we finally extract Q=−2.138−0.516+0.952×10−5 Mpc−2 at 1σ confidence. This result indicates that f(T) corrections on top of general relativity are favored. Finally, we apply information criteria, such as the Akaike and Bayesian ones, and although the dependence of f(T) gravity on the off-center effect implies that its optimality needs to be carefully studied, our analysis shows that f(T) gravity is more efficient in fitting the data compared to general relativity and the ΛCDM paradigm, and thus it offers a challenge to the latter.

Ensemble Variability Properties of Active Galactic Nuclei in the SDSS DR17

We present the results from a study of ∼9600 broadline-selected active galactic nuclei (AGNs) with host galaxies detected from the Sloan Digital Sky Survey (SDSS) Data Release 17. We compute ensemble variability statistics based on a comparison of the original SDSS photometric data with spectrophotometric measurements obtained days to decades later in the Sloan g, r, and i bands. Galaxy and AGN templates have been fitted to the SDSS spectra to isolate the AGN component from the host galaxy. The sources have absolute magnitudes in the range −24 < M i < −18 and lie at redshifts less than z ∼ 0.9. A variability analysis reveals that the anticorrelation between luminosity and variability amplitude continues down to log(Lbol [erg s−1]) = 43.5, demonstrating that the relationship extends by 4 orders of magnitude in AGN luminosity. To further explore the connection between AGN luminosity and variability, we determine the black hole mass and the accretion rate through measurement of the Hβ line width and the monochromatic luminosity at rest frame 5100 Å. Our results suggest that the accretion rate is the dominant parameter impacting the amplitude of variability and that the anticorrelation between the accretion rate and amplitude extends to rates as low as 1% Eddington. Moreover, we also identify an anticorrelation between the variability amplitude and black hole mass, with the correlation appearing strongest among the AGNs with low accretion rates.

Study of Double-mode RR Lyrae Stars in the Stripe 82 Region Using SDSS and ZTF

RRd stars are a subclass of RR Lyrae stars that pulsate simultaneously in the fundamental and the first-overtone radial modes. We report the analysis of 10 RRd stars discovered in the Sloan Digital Sky Survey (SDSS) Stripe 82 region of the Galactic halo using SDSS and Zwicky Transient Facility data. By combining the two data sets, we constructed ∼23 yr long lightcurves in gri bands, and conclude that out of 10, 9 were the classical RRd stars and 1 was the anomalous RRd star. We also observed the long-term variation, the Blazhko effect, in 3 classical RRd stars out of 10 stars, giving an incidence rate of 30%. The shortest Blazhko period observed was 226.4 ± 0.8 days and the longest was 2799 ± 75 days.

YOLOX-CS: An Automatic Search Algorithm for Low Surface Brightness Galaxies

The characteristics of Low Surface Brightness Galaxies (LSBGs) are very important for understanding the overall characteristics of galaxies. It is of great significance to search and expand the samples of Low Surface Brightness Galaxies by modern machine learning, especially deep learning algorithm. LSBGs are difficult to discern automatically and accurately with traditional methods because of their obscure features. However, deep learning does have the advantage of automatically identifying complex and effective features. To solve this problem, an algorithm named You Only Look Once version X-CS (YOLOX-CS) is proposed to search LSBG in large sample sky survey. Firstly, five classical target detection algorithms are compared through experiments and the optimal YOLOX algorithm is selected as the basic algorithm. Then, the YOLOX-CS framework is constructed by combining different attention mechanisms and different optimizers. The data set uses images from the Sloan Digital Sky Survey (SDSS), labelled from LSBG in the α.40-SDSS DR7 (the cross coverage area of 40% HI Arecibo Legacy Fast ALFA Survey and SDSS Data Release7) survey. Due to the small number of samples in this data set, Deep Convolutional Generative Adversarial Networks (DCGAN) model is used to expand the experimental test data. After comparing with a series of target detection algorithms, YOLOX-CS has a good test result in searching LSBG recall rate and Average Precision (AP) value in two data sets before and after expansion. The recall rate and AP value in the test set without expansion data set reach 97.75% and 97.83%, respectively. In the expanded data set of DCGAN model, under the same test set, the recall rate reaches 99.10% and the AP value reaches 98.94%, which proves that the algorithm has excellent performance in LSBG search. Finally, the algorithm is applied to SDSS photometric data, and 765 LSBG candidates are obtained.

Peculiar Velocity Reconstruction from Simulations and Observations Using Deep Learning Algorithms

In this paper, we introduce a U-Net model of deep learning algorithms for reconstructions of the 3D peculiar velocity field, which simplifies the reconstruction process with enhanced precision. We test the adaptability of the U-Net model with simulation data under more realistic conditions, including the redshift space distortion effect and halo mass threshold. Our results show that the U-Net model outperforms the analytical method that runs under ideal conditions, with a 16% improvement in precision, 13% in residuals, 18% in correlation coefficient, and 27% in average coherence. The deep learning algorithm exhibits exceptional capacities to capture velocity features in nonlinear regions and substantially improve reconstruction precision in boundary regions. We then apply the U-Net model trained under Sloan Digital Sky Survey (SDSS) observational conditions to the SDSS Data Release 7 data for observational 3D peculiar velocity reconstructions.

Sloshing and spiral structures breeding a putative radio mini-halo in the environment of a cool-core cluster, Abell 795

ABSTRACT Spiral structures and cold fronts in X-rays are frequently observed in cool-core galaxy clusters. However, studies on radio mini-haloes associated with such spirals and their physical connections are rare. Here, we present the detection of an extended diffuse radio emission entrained in the X-ray spiral structure in a known cool-core cluster, Abell 795. Though the cool core is a sign of the relaxed nature, our re-analysed 30-ks Chandra X-ray data of Abell 795 confirm the presence of an interesting log spiral structure of an X-ray deficit region complemented by an X-ray excess counter spiral in the residual map, exposing its dynamical activity. Our new analysis of 150- and 325-MHz Giant Metrewave Radio Telescope archival data confirms the detection of a ∼180-kpc ultra-steep (α ∼ −2.7) diffuse radio structure, previously reported as a candidate radio mini-halo from low-sensitive survey maps. This emission spans the entire spiral structure, enclosed by two previously reported cold fronts. Furthermore, optical spectra from the Sloan Digital Sky Survey Data Release 13 and far-ultraviolet data from the Galaxy Evolution Explorer show a considerably low total star formation rate of 2.52 M⊙ yr−1 with no significant variation in metallicity distribution. We argue that the two-phase (hot and cold) plasma at the core with differential velocity has plausibly caused the spiral formation and has redistributed the secondary electrons from the brightest cluster galaxy or the pre-accelerated electrons, which have been (re-)accelerated by the sloshing turbulence to form the observed candidate radio mini-halo structure. This is supported by a few previous studies indicating that spiral formation and sloshing turbulence quenches star formation and facilitates smooth metallicity distribution by mixing the gas in the core.

Stellar Populations of AGN-host Dwarf Galaxies Selected with Different Methods

In this paper we investigate the stellar populations and star formation histories of 235 active galactic nucleus (AGN)-host dwarf galaxies, consisting of four samples identified separately with different methods (i.e., radio, X-ray, mid-IR and variability), utilizing the synthesis code STARLIGHT and spectra from the Sloan Digital Sky Survey Data Release 8. Our results show that the variability sample is the oldest, while the mid-IR sample is the youngest, for which the luminosity at 4020 Å is dominated (>50%) by the young population (t < 108 yr). The light-weighted mean stellar age of the whole sample is in general about 0.7 dex younger than the optical sample studied in Cai et al. We compare the population results between fitting models with and without a power-law (PL) component and find that the neglect of a PL component would lead to an under- and over-estimation by 0.2 and 0.1 dex for the light- and mass-weighted mean stellar age, respectively, for our sample of dwarf galaxies, which has a mean fractional contribution of ∼16% from the AGN. In addition, we obtain further evidence for a possible suppression of star formation in the host galaxy by the central AGN. We also find that there exists an anti-correlation between the extinction-corrected [O iii] luminosity and light-weighted mean stellar age, confirming our previous finding that there is a physical connection between AGN and star-forming activities in AGN-host dwarfs.

Efficient identification of broad absorption line quasars using dimensionality reduction and machine learning

Efficient identification of broad absorption line quasars using dimensionality reduction and machine learning

Star Formation and Dust in the Cosmic Web

The large-scale environment of the cosmic web is believed to impact galaxy evolution, but there is still no consensus regarding the mechanisms. We use a semi-analytic model (SAM) galaxy catalog to study the star formation and dust content of local galaxies in different cosmic environments of the cosmic web—namely voids, filaments, walls, and nodes. We find a strong impact of the environment only for galaxies with M stars ≲ 1010.8 M ⊙: the less dense the environment, the larger the star formation rate and dust content at fixed stellar mass. This is attributed to the fact that galaxies in less dense environments typically feature younger stellar populations, a slower evolution of their stellar mass, and delayed star formation compared to galaxies in denser environments. As for galaxies with M stars ≳ 1010.8 M ⊙, the differences among environments are milder, due to the disk-instability-driven supermassive black hole (SMBH) growth implemented in the SAM, which makes SMBH growth, and thus galaxy quenching, environment-insensitive. We qualitatively test our predictions against observations by identifying environments in Sloan Digital Sky Survey Data Release 16 using dust masses derived from the GAMA survey. The agreement is encouraging, particularly at logMstars/M⊙≳10.5–11 , where the specific star formation rates and dust masses appear quite environment-insensitive. This result confirms the importance of in situ growth channels of SMBHs.

Optical Photometric Indicators of Galaxy Cluster Relaxation

The most dynamically relaxed clusters of galaxies play a special role in cosmological studies as well as astrophysical studies of the intracluster medium (ICM) and active galactic nucleus feedback. While high-spatial-resolution imaging of the morphology of the ICM has long been the gold standard for establishing a cluster’s dynamical state, such data are not available from current or planned surveys, and thus require separate, pointed follow-up observations. With optical and/or near-IR photometric imaging, and red-sequence cluster finding results from those data, expected to be ubiquitously available for clusters discovered in upcoming optical and millimeter-wavelength surveys, it is worth asking how effectively photometric data alone can identify relaxed cluster candidates, before investing in, e.g., high-resolution X-ray observations. Here we assess the ability of several simple photometric measurements, based on the redMaPPer cluster finder run on Sloan Digital Sky Survey data, to reproduce X-ray classifications of dynamical state for an X-ray selected sample of massive clusters. We find that two simple metrics contrasting the bright central galaxy (BCG) to other cluster members can identify a complete sample of relaxed clusters with a purity of ∼40% in our data set. Including minimal ICM information in the form of a center position increases the purity to ∼60%. However, all three metrics depend critically on correctly identifying the BCG, which is presently a challenge for optical red-sequence cluster finders.

Changing-look Active Galactic Nuclei. I. Tracking the Transition on the Main Sequence of Quasars

This paper is the first in a series of papers that prepare and analyze spectral and other properties for a database of already-discovered changing-look active galactic nuclei (CL AGNs). Here we focus on the spectral fitting and analysis of broad emission lines in a sample of 93 CL AGNs collected from the literature with existing Sloan Digital Sky Survey (SDSS)/Baryon Oscillation Spectroscopic Survey (BOSS)/extended-BOSS spectroscopy where the Hβ emission-line profile does not completely disappear in any epochs. Additionally, we have gathered older/newer spectral epochs from all the available SDSS data releases to make the database more complete. We use PyQSOFit and perform a homogeneous spectral decomposition of all of our SDSS spectra and tabulate the AGN continuum and emission-line properties per epoch per source, chronologically. This further allows us to categorize the sources in our sample as Turn-On or Turn-Off and subsequently check for repeated occurrences of such phases. We then estimate the black hole mass (M BH) and the Eddington ratio (λ Edd) per epoch per source where the required parameters are available and well estimated. We demonstrate the movement of the source in the M BH–λ Edd plane, allowing us to check for systematic changes in the source’s fundamental properties. We then track their transition along the optical plane of the Eigenvector 1 schema and categorize sources that either stay within the same population (A or B) or make an interpopulation movement as a function of spectral epoch. We also test the Balmer decrement (Hα/Hβ) of a subset of our sample of CL AGNs as a function of time and AGN luminosity.

StellarGAN: Classifying Stellar Spectra with Generative Adversarial Networks in SDSS and APOGEE Sky Surveys

Extracting precise stellar labels is crucial for large spectroscopic surveys like the Sloan Digital Sky Survey (SDSS) and APOGEE. In this paper, we report the newest implementation of StellarGAN, a data-driven method based on generative adversarial networks (GANs). Using 1D operators like convolution, the 2D GAN is modified into StellarGAN. This allows it to learn the relevant features of 1D stellar spectra without needing labels for specific stellar types. We test the performance of StellarGAN on different stellar spectra trained on SDSS and APOGEE data sets. Our result reveals that StellarGAN attains the highest overall F1-score on SDSS data sets (F1-score = 0.82, 0.77, 0.74, 0.53, 0.51, 0.61, and 0.55, for O-type, B-type, A-type, F-type, G-type, K-type, and M-type stars) when the signal-to-noise ratio (S/N) is low (90% of the spectra have an S/N < 50), with 1% of labeled spectra used for training. Using 50% of the labeled spectral data for training, StellarGAN consistently demonstrates performance that surpasses or is comparable to that of other data-driven models, as evidenced by the F1-scores of 0.92, 0.77, 0.77, 0.84, 0.84, 0.80, and 0.67. In the case of APOGEE (90% of the spectra have an S/N < 500), our method is also superior regarding its comprehensive performance (F1-score = 0.53, 0.60, 0.56, 0.56, and 0.78 for A-type, F-type, G-type, K-type, and M-type stars) with 1% of labeled spectra for training, manifesting its learning ability out of a limited number of labeled spectra. Our proposed method is also applicable to other types of data that need to be classified (such as gravitational-wave signals, light curves, etc.).

Living with Neighbors. V. Better-aligned Spiral+Spiral Galaxy Pairs Show Stronger Star Formation

Enhanced star formation (SF) with star-forming neighboring galaxies bolsters the hydrodynamical contributions during paired interactions. Although the relative spin orientation between interacting galaxies can influence this effect, it has not been comprehensively explored. In this study, utilizing a meticulously curated sample of nearby (0.02 < z < 0.06) spiral+spiral pairs and an isolated control sample from Sloan Digital Sky Survey Data Release 7, coupled with Galaxy Zoo 2, and an approach to estimate spin–spin alignment (SSA), we systematically compare the impact of relative orientation, cosξ , on interaction-induced SF. We reveal that SSA plays a pivotal role along with the conventionally recognized parameters of projected separation and SF of neighboring galaxies. Our results show an increase in SF augmentation as configurations transition from perpendicular ( cosξ∼0 ) to well aligned ( cosξ>0.7 ). This enhancement is especially pronounced when neighboring galaxies have higher SF, suggesting that hydrodynamical processes drive the effects of relative orientation. The heightened hydrodynamical friction, attributed to increased ram pressure and the propensity for prograde orbits in well-aligned pairs, is consistent with our findings.

The Mass Assembly History for Galaxies with MaNGA

How galaxies assemble masses through their own star formation or interaction with the external environment is still an important topic in the field of galaxy formation and evolution. We use Value Added Catalogs with galaxy features that are spatially and temporally resolved from Sloan Digital Sky Survey Data Release 17 to investigate the mass growth histories of early-type galaxies (ETGs) and late-type galaxies (LTGs). We find that the mass growth of ETGs is earlier than that of LTGs for massive galaxies (M * > 1010 M ⊙), while low-mass (M * ≤ 1010 M ⊙) ETGs have statistically similar mass assembly histories as low-mass LTGs. The stellar metallicity of all massive galaxies shows a negative gradient and basically does not change with time. However, in low-mass galaxies, the stellar metallicity gradient of elliptical galaxies is negative, and the stellar metallicity gradient of lenticular and spiral galaxies evolves from positive to negative. ETGs are not all in a high-density environment, but exhibit mass dependence. As the tidal strength increases, the star formation rate of low-mass ETGs rapidly decreases. These results support a picture where massive galaxies exhibit inside-out quenching mode, while low-mass galaxies show outside-in quenching mode. Environmental effects play an important role in regulating the mass assembly histories of low-mass ETGs.

Black Hole Mass and Eddington-ratio Distributions of Less-luminous Quasars at z ∼ 4 in the Subaru Hyper Suprime-Cam Wide Field

We investigate the black hole mass function (BHMF) and Eddington-ratio distribution function (ERDF) of broad-line active galactic nuclei (AGNs) at z = 4, based on a sample of 52 quasars with i < 23.2 at 3.50 ≤ z ≤ 4.25 from the Hyper Suprime-Cam Subaru Strategic Program S16A-Wide2 data set, and 1462 quasars with i < 20.2 in the same redshift range from the Sloan Digital Sky Survey data release 7 quasar catalog. Virial black hole (BH) masses of quasars are estimated using the width of the CIV 1549 Å line and the continuum luminosity at 1350 Å. To obtain the intrinsic broad-line AGN BHMF and ERDF, we correct for the incompleteness in the low-mass and/or low-Eddington-ratio ranges caused by the flux-limited selection. The resulting BHMF is constrained down to logMBH/M⊙∼7.5 . In comparison with broad-line AGN BHMFs at z ∼ 2 in the literature, we find that the number density of massive SMBHs peaks at higher redshifts, consistent with the downsizing evolutionary scenario. Additionally, the resulting ERDF shows a negative dependence on BH mass, suggesting more massive SMBHs tend to accrete at lower-Eddington ratios at z = 4. With the derived intrinsic broad-line AGN BHMF, we also evaluate the active fraction of broad-line AGNs among the entire SMBH population at z = 4. The resulting active fraction may suggest a positive dependence on BH mass. Finally, we examine the time evolution of broad-line AGN BHMF between z = 4 and 6 through solving the continuity equation. The results suggest that the broad-line AGN BHMFs at z = 4–6 only show evolution in their normalization, but with no significant changes in their shape.

Outflow-related radio emission in radio-quiet quasars

ABSTRACT In this work, we revisit the relationship between [O iii] line width w90 (as the indicator of active galactic nucleus outflow velocity) and the radio emission in radio-quiet quasars (RQQs) by employing a large sample of Type I quasars (∼37 000) selected from the Sloan Digital Sky Survey (SDSS) Data Release 16. By median stacking the radio images (to include the dominant fraction of individually radio non-detected RQQs) of Karl G. Jansky Very Large Array Sky Survey for subsamples of RQQs with different w90, our study demonstrates that the correlation between w90 and radio emission in our SDSS RQQs is significant, and remains solid after controlling the effects of black hole mass, quasar luminosity, Eddington ratio, and redshift. This intrinsic link supports that the [O iii] outflows in quasars, most likely resulting from wide-angled sub-relativistic quasar winds launched from the accretion disc, could make a dominant contribution to radio emission in the general RQQs. Alternatively, the correlation may be attributed to low-power jets in RQQs if they are ubiquitous and could efficiently enhance the [O iii] width through interacting with the interstellar medium. Meanwhile, the star formation rates traced by the flux ratio of [Ne v]/[O ii] emission lines display no dependence on w90 after controlling the effects of black hole mass, quasar luminosity, Eddington ratio, and redshift. This suggests that the stronger radio emission in RQQs with larger w90 could not be attributed to outflow-enhanced (positive feedback) star formation in the hosts. However, this also indicates that the outflows, though exhibiting robust correlation with radio power, produce neither positive nor negative feedback to the star formation in their hosts.

A Markedly Expanded Sample of Candidate X-Ray-emitting Isolated Neutron Stars

The current sample of 12 radio-quiet isolated neutron stars that emit strongly in X-rays (XINSs) is both small and heterogeneous, limiting its usefulness for understanding the physics of neutron star atmospheres and cooling rates and for constraining the equation of state of neutron degenerate matter. Utilizing the ROSAT 1RXS and 2RXS data sets, in conjunction with the Sloan Digital Sky Survey Data Release 17 and other companion multiwavelength surveys, we have extended previous searches for blank-field X-ray source candidate XINSs, ultimately recovering two known XINSs while identifying 46 new, unstudied candidate fields devoid of likely multiwavelength counterparts. In this publication, we describe our selection approach and provide detailed information regarding our sample of new candidate XINSs. Future opportunities to verify or to refute these X-ray sources as isolated neutron stars by obtaining more accurate X-ray source positions, quality X-ray spectra, or deeper optical imaging are also discussed.