WISE Catalog Research Articles

Mass density profiles at kiloparsec scales using the sub-millimetre galaxies magnification bias

Context. Gravitational lensing is a powerful tool for studying the distribution of mass in the Universe. Understanding the magnification bias effect in gravitational lensing and its impact on the flux of sub-millimetre galaxies (SMGs) is crucial for accurate interpretations of observational data. Aims. This study aims to investigate the magnification bias effect in the context of gravitational lensing and analyse the mass density profiles of different types of foreground lenses, including quasi-stellar objects (QSOs), galaxies, and galaxy clusters. The specific goals are to compare the lens types, assess the impact of angular resolution on the analysis, and determine the adequacy of theoretical mass density profiles in explaining the observed data. Methods. The magnification bias was estimated using the cross-correlation function between the positions of background SMGs and foreground lens samples. Stacking techniques were employed to enhance the signal at smaller angular separations, and the more precise positions from the WISE catalogue were utilised to improve positional accuracy. Four different theoretical mass density profiles were analysed to extract additional information. Results. The cross-correlation measurements revealed distinctive central excess and outer power-law profiles, with a lack of signal in the intermediate region. The lens types exhibited varying signal strengths, with QSOs producing the strongest signal and galaxy clusters showing weaker signals. The analysis of mass density profiles indicated limitations in the selected profiles’ ability to explain the observed data, highlighting the need for additional considerations. The lack of extended emission in the QSO sample suggested possible influences from close satellites along the line of sight in the other lens types. Conclusions. The study provides valuable insights into the magnification bias effect and mass density profiles in gravitational lensing. The results suggest the presence of isolated galactic halos and the importance of considering environmental factors and close satellites in future investigations. The derived masses and best-fit parameters contribute to our understanding of lensing systems and provide constraints on the nature of central galaxies. Notably, the intriguing lack of signal around 10 arcsec challenges current understanding and calls for further quantitative analysis and confirmation of the observed feature.

A newborn active galactic nucleus in a star-forming galaxy

Aims. We report on the finding of a newborn active galactic nucleus (AGN), based on the observation of current AGN activity in a galaxy previously classified as non-active. We subsequently characterize the AGN’s evolution. Methods. Black hole ignition event candidates were selected from a parent sample of spectrally classified non-active galaxies (2 394 312 objects), which currently show optical flux variability indicative of a type I AGN, according to the ALeRCE light curve classifier. A second epoch spectrum for a sample of candidate newborn AGNs was obtained with the SOAR telescope to search for new AGN features. Results. We present the spectral results for the most convincing case of new AGN activity for a galaxy with a prior star-forming optical classification, where the second epoch spectrum shows the appearance of prominent, broad Balmer lines, without any significant changes seen in the narrow line flux ratios. The long-term optical light curves show a steady increase in luminosity starting 1.5 years after the SDSS spectrum was taken and continuing for at least 7 years. Mid-infrared (MIR) colors from the WISE catalog have also evolved from typical non-active galaxy colors to AGN-like colors. Recent X-ray flux detections confirm its nature as an AGN.

Comparison of [CII] 158µm line widths to luminosities

Acomparison of [CII] 158µm emission line widths to different luminosities is presented to decide if any luminosity relates to velocity dispersion. [CII] 158 µm emission lines are observed with Herschel PACS for 379 galaxies and the archival data for [CII] line widths are taken from http://cassis.sirtf.com/ herschel/. Emission line widths are compared to [CII] luminosities, to near-infrared 1.6µm luminosities and to infrared 22µm luminosities. H magnitudes are taken from 2MASS catalogue, and 22µm fluxes from the WISE catalogue.

Unsupervised clustering and analysis of WISE spiral galaxies

ABSTRACT The Wide-Field Infrared Explorer (WISE) survey captured massive amounts of infrared astronomical object data, and different astronomical objects will show different characteristics. Especially spiral galaxies that are richer in colour than other astronomical objects. In addition, the Sloan Digital Sky Survey (SDSS) has obtained a large number of visible light images and their parameter. So this paper mainly explores the colour characteristics of WISE spiral galaxies, and uses SDSS, 2MASS, WISE, and MANGA parameters to analyse the differences between different classes and the commonality of the same class, so that provides help for astronomers to study infrared spiral galaxies. First, the RA and Dec. of the spiral galaxy samples were crossed in GalaxyZoo2. The flux data of w1, w2, and w3 bands in WISE were crossed for image synthesis. The Bootstrap Your Own Latent contrastive learning framework and K-means clustering were used to unsupervised classify the infrared spiral galaxy images. After multiple experiments, five classes of images were selected by referring to the best clustering results. Finally, the parameter of galaxies in SDSS, 2MASS, WISE, and MANGA catalogues were crossed, including redshift, 12 magnitudes that from visible light band to mid-infrared band, stellar formation rate, stellar metallicity, stellar velocity dispersion, etc. These parameters were qualitatively and quantitatively analyzed. The effectiveness of unsupervised clustering algorithms for handling unlabeled data is demonstrated and two special classes of galaxies are found. The analysis result shows that the distribution characteristics of different parameters of different classes of infrared spiral galaxies are different.

Analysis of emission line widhts of [CII]158μm

A study of [CII] 158 μm emission line profiles observed with Herschel PACS for 379 galaxies is presented. Emission line widths are compared to [CII] luminosities, to near-infrared 1.6 μm luminosities and to infrared 22 μm luminosities to decide if any luminosity relates to velocity dispersion. Archival data for [CII] fluxes and line profiles are taken from http://cassis.sirtf.com/ herschel/. Line profiles are classified as Gaussian, flattened and asymmetric. H magnitudes are taken from 2MASS catalogues, and 22 μm fluxes from the WISE catalogue. These luminosities are compared to [CII] line Full Width Half Maximum. Asymmetric profiles are not primarily AGN, which indicates that asymmetries are not produced primarily by outflows from the nuclear region. [CII] line widths do not show a significant correlation with any measure of galaxy luminosity. The correlation having smallest dispersion is with the H band luminosity for which L(H) ~ FWHM0.73, which is a much flatter correlation than the L ~ FWHM4 previously found for optical.

Searching for Galactic H ii Regions from the LAMOST Spectroscopic Database

In this paper, we pioneer a new machine-learning method to search for H ii regions in spectra from The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). H ii regions are emission nebulae created when young and massive stars ionize nearby gas clouds with high-energy ultraviolet radiation. Having more H ii region samples will help us understand the formation and evolution of stars. Machine-learning methods are often applied to search for special celestial bodies such as H ii regions. LAMOST has conducted spectral surveys and provided a wealth of valuable spectra for the research of special and rare celestial bodies. To overcome the problem of sparse positive samples and diversification of negative samples, a novel method called the self-calibrated convolution network is introduced and implemented for spectral processing. A deep network classifier with a structure called a self-calibrated block provides a high precision rate, and the recall rate is improved by adding the strategy of positive-unlabeled bagging. Experimental results show that this method can achieve better performance than other current methods. Eighty-nine spectra are identified as Galactic H ii regions after cross-matching with the WISE Catalog of Galactic H ii Regions, confirming the effectiveness of the method proposed in this paper.

The ROSAT Raster survey in the north ecliptic pole field

The north ecliptic pole (NEP) is an important region for extragalactic surveys. Deep and wide contiguous surveys are being performed by several space observatories, most currently with the eROSITA telescope. Several more are planned for the near future. We analyse all the ROSAT pointed and survey observations in a region of 40 deg2 around the NEP, restricting the ROSAT field of view to the inner 30′ radius. We obtain an X-ray catalogue of 805 sources with 0.5−2 keV fluxes > 2.9 × 10−15 erg cm−2 s−1, about a factor of three deeper than the ROSAT All-Sky Survey in this field. The sensitivity and angular resolution of our data are comparable to the eROSITA All-Sky Survey expectations. The 50% position error radius of the sample of X-ray sources is ∼10″. We use HEROES optical and near-infrared imaging photometry from the Subaru and Canada/France/Hawaii telescopes together with GALEX, SDSS, Pan-STARRS, and WISE catalogues, as well as images from a new deep and wide Spitzer survey in the field to statistically identify the X-ray sources and to calculate photometric redshifts for the candidate counterparts. In particular, we utilize mid-infrared (mid-IR) colours to identify active galactic nucleus (AGN) X-ray counterparts. Despite the relatively large error circles and often faint counterparts, together with confusion issues and systematic errors, we obtain a rather reliable catalogue of 766 high-quality optical counterparts, corresponding redshifts and optical classifications. The quality of the dataset is sufficient to look at ensemble properties of X-ray source classes. In particular we find a new population of luminous absorbed X-ray AGN at large redshifts, identified through their mid-IR colours. This populous group of AGN was not recognized in previous X-ray surveys, but could be identified in our work due to the unique combination of survey solid angle, X-ray sensitivity, and quality of the multi-wavelength photometry. We also use the WISE and Spitzer photometry to identify a sample of 185 AGN selected purely through their mid-IR colours, most of which are not detected by ROSAT. Their redshifts and upper limits to X-ray luminosity and X-ray–to–optical flux ratios are even higher than for the new class of X-ray selected luminous type 2 AGN (AGN2); they are probably a natural extension of this sample. This unique dataset is important as a reference sample for future deep surveys in the NEP region, in particular for eROSITA and also for Euclid and SPHEREX. We predict that most of the absorbed distant AGN should be readily picked up by eROSITA, but they require sensitive mid-IR imaging to be recognized as optical counterparts.

Serendipitous discovery of a dusty disc around WDJ181417.84−735459.83

ABSTRACT Spectroscopic observations of white dwarfs reveal that many of them are polluted by exoplanetary material, whose bulk composition can be uniquely probed this way. We present a spectroscopic and photometric analysis of the DA white dwarf WDJ181417.84−735459.83, an object originally identified to have a strong infrared (IR) excess in the 2MASS and WISE catalogues that we confirmed to be intrinsic to the white dwarf, and likely corresponding to the emission of a dusty disc around the star. The finding of Ca, Fe, and Mg absorption lines in two X-SHOOTER spectra of the white dwarf, taken 8 years apart, is further evidence of accretion from a dusty disc. We do not report variability in the absorption lines between these two spectra. Fitting a blackbody model to the IR excess gives a temperature of 910 ± 50 K. We have estimated a total accretion flux from the spectroscopic metal lines of $|\dot{\rm M}| = 1.784 \times 10^{9}\,$g s−1.

Galactic Rotation Parameters Based on Stars from Active Star-Forming Regions with Data from the Gaia DR2 Catalogue

We have studied a sample of more than 25 000 young stars with proper motions and trigonometric parallaxes from the Gaia DR2 catalogue. The relative errors of their parallaxes do not exceed 10\%. The selection of stars belonging to active star-forming regions was made by Marton et al. based on data from the Gaia DR2 catalogue by invoking infrared measurements from the WISE and Planck catalogues. Low-mass T Tauri stars constitute the majority of sample stars. The following parameters of the angular velocity of Galactic rotation have been found from them: $\Omega_0 =28.40\pm0.11$ km s$^{-1}$ kpc$^{-1}$, $\Omega^{'}_0=-3.933\pm0.033$ km s$^{-1}$ kpc$^{-2}$ and $\Omega^{''}_0=0.804\pm0.040$ km s$^{-1}$ kpc$^{-3}$. The Oort constants are $A=15.73\pm0.32$ km s$^{-1}$ kpc$^{-1}$ and $B=-12.67\pm0.34$ km s$^{-1}$ kpc$^{-1}$, while the circular rotation velocity of the solar neighborhood around the Galactic center is $V_0=227\pm4$ km s$^{-1}$ for the adopted Galactocentric distance of the Sun $R_0=8.0\pm0.15$ kpc.

INFRARED COUNTERPARTS OF X-RAY GALAXIES

Population studies of the extragalactic objects are a major part of the universe large-scale structure study. Apart from radio, infrared, and visible wavelength bands, observations and further identification of extragalactic objects such as galaxies, quasars, blazers, liners, and active star burst regions are also conducted in the X-ray and gamma bands. In this paper we make identification and cross-correlate of the infrared and X-ray observational data, build a distribution of a selected sample sources by types and attempted to analyze types of the extragalactic objects at distances up to z = 0.1 using observational data of relevant space observatories. Data from a leading X-ray space observatory XMM-Newton were used to compile the largest catalog of X-ray sources. Current version of XMM SSC (Serendipitous Source Catalog) contains more than half a million sources. In our previous works we selected and analyzed a sample of 5021 X-ray galaxies observed by XMM-Newton. Identification and classification of these sources is essential next step of the study. In this study we used infrared apparent magnitudes from WISE catalog of AGN candidates. In 2010 space telescope WISE performed full sky survey in four infrared bands and detected 747 million sources. WISE catalog of AGN candidates amounts 4 million of possible extragalactic sources. We built infrared color-color diagram for our sample of X-ray galaxies and assessed their types using WISE telescope data. In this study we also analyzed large scale structure of the universe (distances up to z=0.1). This analysis revealed Coma galaxy cluster and SDSS Sloan Great Wall. In the further studies we are planning to investigate the distribution of different types of X-ray galaxies within the large-scale structures of the Universe.

Value-added Catalogs of M-type Stars in LAMOST DR5

In this work, we present new catalogs of M giant and M dwarf stars from the LAMOST DR5. In total, 39,796 M giants and 501,152 M dwarfs are identified from the classification pipeline. The template-fitting results contain M giants with 7 temperature subtypes from M0 to M6, M dwarfs with 18 temperature subtypes from K7.0 to M8.5 and 12 metallicity subclasses from dMr to usdMp. We cross-matched our M-type catalog with the 2MASS and WISE catalog to obtain infrared magnitude and colors. Adopting the distances derived from the parallaxes in \gaia{} DR2, the M_G vs. (G_bp-G_rp)_0 diagram shows that there are also early-type stars and white dwarf-M dwarf binaries included in our M type stars sample, with a contamination rate of about 4.6% for M giants and 0.48% for M dwarfs. We found that CaH spectral indices are an efficient selection criteria for carbon stars. A total of 289 carbon stars were identified from the M giants sample, and further confirmed by LAMOST spectra.

Positional Offsets between SiO Masers in Evolved Stars and their Cross-matched Counterparts

Observations of dust-enshrouded evolved stars selected from infrared catalogs requiring high positional accuracy, like infrared spectroscopy or long baseline radio interferometric observations, often require preparational observational steps determining a position with an accuracy much better than 1". Using phase-referencing observations with the Very Large Array at its highest resolution, we have compared the positions of SiO 43 GHz masers in evolved stars, assumed to originate in their infrared detected circumstellar shells, with the positions listed in the MSX, WISE, 2MASS, and Gaia catalogs. Starting from an MSX position it is, in general, simple to match 2MASS and WISE counterparts. However, in order to obtain a Gaia match to the MSX source it is required to use a two-step approach due to the large number of nearby candidates and low initial positional accuracy of the MSX data. We show that the closest comparable position to the SiO maser in our limited sample never is the MSX position. When a plausible source with a characteristic signature of an evolved star with a circumstellar shell can be found in the area, the best indicator of the maser position is provided by the Gaia position, with the 2MASS position being second-best. Typical positional offsets from all catalogs to the SiO masers are reported.

Why do many early-type galaxies lack emission lines? I. Fossil clues

Early-type retired galaxies (RGs, i.e. galaxies which no longer form stars) can be divided into two classes: those with no emission lines, here dubbed lineless RGs, and those with emission lines, dubbed liny RGs. Both types of galaxies contain hot low-mass evolved stars (HOLMES) which emit ionizing photons. The difference must thus lie in the presence or absence of a reservoir of ionizable gas. From a volume-limited sample of 38\,038 elliptical galaxies, we explore differences in physical properties between liny and lineless using data from the SDSS, WISE and GALEX catalogues. To avoid biases in the comparison, we pair-match liny and lineless in stellar-mass, redshift and half-light Petrosian radius. We detect marginal differences in their optical stellar ages and NUV luminosities, indicating that liny RGs have an excess of intermediate-age (0.1--5 Gyr) stellar populations. Liny RGs show higher dust attenuation and $W3$ luminosities than their lineless counterparts. We also find that the amount of warm gas needed to explain the observed \Ha luminosity in liny RGs is $10^5$--$10^8$\msun, and that their \nii/\oii emission-line ratios are typical of those of the most massive star-forming galaxies. Taken together, these results rules out the following sources for the warm gas in liny RGs: mass-loss from intermediate-mass stars, mergers with metal-poor galaxies and intergalactic streams. They imply instead an inflow of enriched gas previously expelled from the galaxy or a merger with a metal-rich galaxy. The ionization source and the origin of the gas producing the emission lines are thus disconnected.

Far-infrared dust properties of highly dust-obscured active galactic nuclei from the AKARI and WISE all-sky surveys

Abstract The combination of the AKARI and WISE infrared all-sky surveys provides a unique opportunity to identify and characterize the most highly dust-obscured active galactic nuclei (AGNs) in the universe. Dust-obscured AGNs are not easily detectable and are potentially underrepresented in extragalactic surveys due to their high optical extinction, but are readily found in the WISE catalog due to their extremely red mid-infrared (IR) colors. Combining these surveys with photometry from Pan-STARRS and Herschel, we use spectral energy distribution (SED) modeling to characterize the extinction and dust properties of these AGNs. From mid-IR WISE colors we are able to compute bolometric corrections to AGN luminosities. Using AKARI’s far-IR wavelength photometry and broadband AGN/galaxy spectral templates we estimate AGN dust mass and temperature using simple analytic models with three or four parameters. Even without spectroscopic data we can determine a number of AGN dust properties only using SED analysis. These methods, combined with the abundance of archival photometric data publicly available, will be valuable for large-scale studies of dusty, IR-luminous AGNs.

Stellar populations of HII galaxies

Aims. We present a UV to mid-IR spectral energy distribution (SED) study of a large sample of SDSS DR13 HII galaxies. These galaxies are selected as starbursts (EW(Hα) > 50Å) and for their high-excitation locus in the upper left region of the BPT diagram. Their photometry was derived from the cross-matched GALEX, SDSS, UKDISS, and WISE catalogs. Methods. We used CIGALE modeling and a SED fitting routine with the parametrization of a three-burst star formation history, and a comprehensive analysis of all other model parameters. We were able to estimate the contribution of the underlying old stellar population to the observed equivalent width of Hβ, and allow for more accurate burst age determination. Results. We found that the star formation histories of HII Galaxies can be reproduced remarkably well by three major eras of star formation. In addition, the SED fitting results indicate that in all cases the current burst produces a small percent of the total stellar mass, i.e., the bulk of stellar mass in HII galaxies has been produced by the past episodes of star formation, and also indicate that at a given age the Hβ luminosity depends only on the mass of young stars favoring a universal IMF for massive stars. Most importantly, the current star formation episodes are maximum starbursts that produce stars at the highest possible rate.

WG021416.37-210535.3, A Quadruply Lensed Quasar in Three Public Surveys

The Southern Hemisphere has just recently begun to be charted by wide-field surveys, with a sufficient depth and image quality to enable the discovery of strongly lensed quasars. The quadruply imaged quasar WG0214-2105 (r.a.=02:14:16.37, dec.=-21:05:35.3) is a previously unknown lens, with `blue' mid-IR colors and high UV deficit, found in the intersection of three survey footprints: the Dark Energy Survey public DR1 (DES, Abbott et al. 2018), The VST-ATLAS (Shanks et al. 2015) and Pan-STARRS (Chambers et al. 2016). Its discovery relied on high spatial resolution from the Gaia mission (Lindegren et al. 2016) and mid-IR color preselection in the WISE catalog (Wright et al. 2010).

A Green Bank Telescope Survey of Large Galactic H ii Regions

As part of our ongoing HII Region Discovery Survey (HRDS), we report the Green Bank Telescope detection of 148 new angularly-large Galactic HII regions in radio recombination line (RRL) emission. Our targets are located at a declination greater than -45deg., which corresponds to 266deg. > l > -20deg. at b = 0deg. All sources were selected from the WISE Catalog of Galactic HII Regions, and have infrared angular diameters >260''. The Galactic distribution of these "large" HII regions is similar to that of the previously-known sample of Galactic HII regions. The large HII region RRL line width and peak line intensity distributions are skewed toward lower values compared with that of previous HRDS surveys. We discover 7 sources with extremely narrow RRLs <10 km/s. If half the line width is due to turbulence, these 7 sources have thermal plasma temperatures <1100 K. These temperatures are lower than any measured for Galactic HII regions, and the narrow line components may arise instead from partially ionized zones in the HII region photo-dissociation regions. We discover G039.515+00.511, one of the most luminous HII regions in the Galaxy. We also detect the RRL emission from three HII regions with diameters >100 pc, making them some of the physically largest known HII regions in the Galaxy. This survey completes the HRDS HII region census in the Northern sky, where we have discovered 887 HII regions and more than doubled the previously-known census of Galactic HII regions.

Carbon Monoxide Observations toward Star-forming Regions in the Outer Scutum–Centaurus Spiral Arm

Abstract The Outer Scutum–Centaurus arm (OSC) is the most distant molecular spiral arm known in the Milky Way. The OSC may be the very distant end of the well-known Scutum–Centaurus arm, which stretches from the end of the Galactic bar to the outer Galaxy. At this distance the OSC is seen in the first Galactic quadrant. The population of star formation tracers in the OSC remains largely uncharacterized. Extragalactic studies show a strong correlation between molecular gas and star formation, and carbon monoxide (CO) emission was recently discovered in the OSC. Here we use the Arizona Radio Observatory (ARO) 12 telescope to observe the 12CO J = 1–0 and 13CO J = 1–0 transitions toward 78 H ii region candidates chosen from the WISE Catalog of Galactic H ii Regions. These targets are spatially coincident with the Galactic longitude–latitude ( ) OSC locus as defined by H i emission. We detect CO emission in ∼80% of our targets. In total, we detect 117 12CO and 40 13CO emission lines. About two-thirds of our targets have at least one emission line originating beyond the solar orbit. Most of the detections beyond the solar orbit are associated with the outer arm, but there are 17 12CO emission lines and 8 13CO emission lines with LSR velocities that are consistent with the velocities of the OSC. There is no apparent difference between the physical properties (e.g., molecular column density) of these OSC molecular clouds and non-OSC molecular clouds within our sample.

Identification of Stellar Sequences in Various Stellar Systems: ESO65-SC03, Teutsch 106, Turner 6

The spatial morphological study of studied clusters is carried out through the identified probable members within them. The field stars decontamination is performed by the statistical cleaning approach (depends on the magnitude and colour of stars within the field and cluster regions). The CMRD (colour magnitude ratio diagram) approach is used to separate stellar sequences of the cluster systems. The age, distance and reddening of each cluster are estimated through the visual inspection of best fitted isochrone in colour magnitude diagrams(CMDs). The mean proper motion values of clusters are obtained through the extracted data from PPMXL and UCAC4 catalogs. Moreover, these values are varying according to the extracted data-set from these catalogues. This variation is occurred due to their different estimation efficiency of proper motions. The TCR (two colour ratio) and TCMR (two colour magnitude ratio) values of each cluster are determined by utilizing the WISE and PPMXL catalogues, these values are found abnormal for TEUTSCH 106. In addition, the TCMR values are similar to TCR values at longer wavelength, whereas both values are far away to each other at shorter wavelength. The fraction of young stellar objects (YSOs) is also computed for each cluster.

Galactic supernova remnant candidates discovered by THOR

There is a considerable deficiency in the number of known supernova remnants (SNRs) in the Galaxy compared to that expected. Searches for extended low-surface brightness radio sources may find new Galactic SNRs, but confusion with the much larger population of HII regions makes identifying such features challenging. SNRs can, however, be separated from HII regions using their significantly lower mid-infrared (MIR) to radio continuum intensity ratios. We use the combination of high-resolution 1-2 GHz continuum data from The HI, OH, Recombination line survey of the Milky Way (THOR) and lower-resolution VLA 1.4 GHz Galactic Plane Survey (VGPS) continuum data, together with MIR data from the Spitzer GLIMPSE, Spitzer MIPSGAL, and WISE surveys to identify SNR candidates. To ensure that the candidates are not being confused with HII regions, we exclude radio continuum sources from the WISE Catalog of Galactic HII Regions, which contains all known and candidate H II regions in the Galaxy. We locate 76 new Galactic SNR candidates in the THOR and VGPS combined survey area of 67.4deg>l>17.5deg, |b|<1.25deg and measure the radio flux density for 52 previously-known SNRs. The candidate SNRs have a similar spatial distribution to the known SNRs, although we note a large number of new candidates near l=30deg, the tangent point of the Scutum spiral arm. The candidates are on average smaller in angle compared to the known regions, 6.4'+/-4.7' versus 11.0'+/-7.8', and have lower integrated flux densities. If the 76 candidates are confirmed as true SNRs, for example using radio polarization measurements or by deriving radio spectral indices, this would more than double the number of known Galactic SNRs in the survey area. This large increase would still, however, leave a discrepancy between the known and expected SNR populations of about a factor of two.