Pub Date : 2023-10-27DOI: 10.3847/1538-4365/acf44d
Marcia J. Rieke, Brant Robertson, Sandro Tacchella, Kevin Hainline, Benjamin D. Johnson, Ryan Hausen, Zhiyuan Ji, Christopher N. A. Willmer, Daniel J. Eisenstein, Dávid Puskás, Stacey Alberts, Santiago Arribas, William M. Baker, Stefi Baum, Rachana Bhatawdekar, Nina Bonaventura, Kristan Boyett, Andrew J. Bunker, Alex J. Cameron, Stefano Carniani, Stephane Charlot, Jacopo Chevallard, Zuyi Chen, Mirko Curti, Emma Curtis-Lake, A. Lola Danhaive, Christa DeCoursey, Alan Dressler, Eiichi Egami, Ryan Endsley, Jakob M. Helton, Raphael E. Hviding, Nimisha Kumari, Tobias J. Looser, Jianwei Lyu, Roberto Maiolino, Michael V. Maseda, Erica J. Nelson, George Rieke, Hans-Walter Rix, Lester Sandles, Aayush Saxena, Katherine Sharpe, Irene Shivaei, Maya Skarbinski, Renske Smit, Daniel P. Stark, Meredith Stone, Katherine A. Suess, Fengwu Sun, Michael Topping, Hannah Übler, Natalia C. Villanueva, Imaan E. B. Wallace, Christina C. Williams, Chris Willott, Lily Whitler, Joris Witstok, Charity Woodrum
Abstract JWST has revolutionized the field of extragalactic astronomy with its sensitive and high-resolution infrared view of the distant Universe. Adding to the new legacy of JWST observations, we present the first NIRCam imaging data release from the JWST Advanced Deep Extragalactic Survey (JADES), providing nine filters of infrared imaging of ∼25 arcmin 2 covering the Hubble Ultra Deep Field and portions of Great Observatories Origins Deep Survey South. Utilizing 87 on-sky dual-filter hours of exposure time, these images reveal the deepest ever near-infrared view of this iconic field. We supply carefully constructed nine-band mosaics of the JADES bands, as well as matching reductions of five additional bands from the JWST Extragalactic Medium-band Survey. Combining with existing Hubble Space Telescope imaging, we provide 23-band space-based photometric catalogs and photometric redshifts for ≈47,500 sources. To promote broad engagement with JADES, we have created an interactive FitsMap website to provide an interface for professional researchers and the public to experience these JWST data sets. Combined with the first JADES NIRSpec data release, these public JADES imaging and spectroscopic data sets provide a new foundation for discoveries of the infrared Universe by the worldwide scientific community.
{"title":"JADES Initial Data Release for the Hubble Ultra Deep Field: Revealing the Faint Infrared Sky with Deep JWST NIRCam Imaging","authors":"Marcia J. Rieke, Brant Robertson, Sandro Tacchella, Kevin Hainline, Benjamin D. Johnson, Ryan Hausen, Zhiyuan Ji, Christopher N. A. Willmer, Daniel J. Eisenstein, Dávid Puskás, Stacey Alberts, Santiago Arribas, William M. Baker, Stefi Baum, Rachana Bhatawdekar, Nina Bonaventura, Kristan Boyett, Andrew J. Bunker, Alex J. Cameron, Stefano Carniani, Stephane Charlot, Jacopo Chevallard, Zuyi Chen, Mirko Curti, Emma Curtis-Lake, A. Lola Danhaive, Christa DeCoursey, Alan Dressler, Eiichi Egami, Ryan Endsley, Jakob M. Helton, Raphael E. Hviding, Nimisha Kumari, Tobias J. Looser, Jianwei Lyu, Roberto Maiolino, Michael V. Maseda, Erica J. Nelson, George Rieke, Hans-Walter Rix, Lester Sandles, Aayush Saxena, Katherine Sharpe, Irene Shivaei, Maya Skarbinski, Renske Smit, Daniel P. Stark, Meredith Stone, Katherine A. Suess, Fengwu Sun, Michael Topping, Hannah Übler, Natalia C. Villanueva, Imaan E. B. Wallace, Christina C. Williams, Chris Willott, Lily Whitler, Joris Witstok, Charity Woodrum","doi":"10.3847/1538-4365/acf44d","DOIUrl":"https://doi.org/10.3847/1538-4365/acf44d","url":null,"abstract":"Abstract JWST has revolutionized the field of extragalactic astronomy with its sensitive and high-resolution infrared view of the distant Universe. Adding to the new legacy of JWST observations, we present the first NIRCam imaging data release from the JWST Advanced Deep Extragalactic Survey (JADES), providing nine filters of infrared imaging of ∼25 arcmin 2 covering the Hubble Ultra Deep Field and portions of Great Observatories Origins Deep Survey South. Utilizing 87 on-sky dual-filter hours of exposure time, these images reveal the deepest ever near-infrared view of this iconic field. We supply carefully constructed nine-band mosaics of the JADES bands, as well as matching reductions of five additional bands from the JWST Extragalactic Medium-band Survey. Combining with existing Hubble Space Telescope imaging, we provide 23-band space-based photometric catalogs and photometric redshifts for ≈47,500 sources. To promote broad engagement with JADES, we have created an interactive FitsMap website to provide an interface for professional researchers and the public to experience these JWST data sets. Combined with the first JADES NIRSpec data release, these public JADES imaging and spectroscopic data sets provide a new foundation for discoveries of the infrared Universe by the worldwide scientific community.","PeriodicalId":8588,"journal":{"name":"Astrophysical Journal Supplement Series","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136235564","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}
Pub Date : 2023-10-25DOI: 10.3847/1538-4365/acdd63
Nicholas J. Wright, Jeremy J. Drake, Mario G. Guarcello, Vinay L. Kashyap, Andreas Zezas
Abstract The Chandra Cygnus OB2 Legacy Survey is a wide and deep X-ray survey of the nearby and massive Cygnus OB2 association. The survey has detected ∼8000 X-ray sources, the majority of which are pre-main-sequence X-ray-emitting young stars in the association itself. To facilitate quantitative scientific studies of these sources, as well as the underlying OB association, it is important to understand the sensitivity of the observations and the level of completeness the observations have obtained. Here we describe the use of a hierarchical Monte Carlo simulation to achieve this goal by combining the empirical properties of the observations, analytic estimates of the source verification process, and an extensive set of source detection simulations. We find that our survey reaches a 90% completeness level for a pre-main-sequence population at the distance of Cyg OB2 at an X-ray luminosity of 4 × 10 30 erg s −1 and a stellar mass of 1.3 M ⊙ for a randomly distributed population. For a spatially clustered population such as Cyg OB2 the 90% completeness level is reached at 1.1 M ⊙ instead, as the sources are more concentrated in areas of our survey with a high exposure. These simulations can easily be adapted for use with other X-ray observations and surveys, and we provide X-ray detection efficiency curves for a very wide array of source and background properties to allow these simulations to be easily exploited by other users.
{"title":"Simulating the Sensitivity to Stellar Point Sources of Chandra X-Ray Observations","authors":"Nicholas J. Wright, Jeremy J. Drake, Mario G. Guarcello, Vinay L. Kashyap, Andreas Zezas","doi":"10.3847/1538-4365/acdd63","DOIUrl":"https://doi.org/10.3847/1538-4365/acdd63","url":null,"abstract":"Abstract The Chandra Cygnus OB2 Legacy Survey is a wide and deep X-ray survey of the nearby and massive Cygnus OB2 association. The survey has detected ∼8000 X-ray sources, the majority of which are pre-main-sequence X-ray-emitting young stars in the association itself. To facilitate quantitative scientific studies of these sources, as well as the underlying OB association, it is important to understand the sensitivity of the observations and the level of completeness the observations have obtained. Here we describe the use of a hierarchical Monte Carlo simulation to achieve this goal by combining the empirical properties of the observations, analytic estimates of the source verification process, and an extensive set of source detection simulations. We find that our survey reaches a 90% completeness level for a pre-main-sequence population at the distance of Cyg OB2 at an X-ray luminosity of 4 × 10 30 erg s −1 and a stellar mass of 1.3 M ⊙ for a randomly distributed population. For a spatially clustered population such as Cyg OB2 the 90% completeness level is reached at 1.1 M ⊙ instead, as the sources are more concentrated in areas of our survey with a high exposure. These simulations can easily be adapted for use with other X-ray observations and surveys, and we provide X-ray detection efficiency curves for a very wide array of source and background properties to allow these simulations to be easily exploited by other users.","PeriodicalId":8588,"journal":{"name":"Astrophysical Journal Supplement Series","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134972730","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}
Pub Date : 2023-10-25DOI: 10.3847/1538-4365/acdd62
Nicholas J. Wright, Jeremy J. Drake, Mario G. Guarcello, Tom L. Aldcroft, Vinay L. Kashyap, Francesco Damiani, Joe DePasquale, Antonella Fruscione
Abstract The Cygnus OB2 association is the largest concentration of young and massive stars within 2 kpc of the Sun, including an estimated ∼65 O-type stars and hundreds of OB stars. The Chandra Cygnus OB2 Legacy Survey is a large imaging program undertaken with the Advanced CCD Imaging Spectrometer on board the Chandra X-ray Observatory. The survey has imaged the central 0.5 deg 2 of the Cyg OB2 association with an effective exposure of ∼120 ks and an outer 0.35 deg 2 area with an exposure of ∼60 ks. Here we describe the survey design and observations, discuss the data reduction and source detection, and present a catalog of ∼8000 X-ray point sources. The survey design employs a grid of 36 heavily (∼50%) overlapping pointings, a method that overcomes Chandra's low off-axis sensitivity and produces a highly uniform exposure over the inner 0.5 deg 2 . The full X-ray catalog is described here and is made available online.
{"title":"The Chandra Cygnus OB2 Legacy Survey: Design and X-Ray Point-source Catalog","authors":"Nicholas J. Wright, Jeremy J. Drake, Mario G. Guarcello, Tom L. Aldcroft, Vinay L. Kashyap, Francesco Damiani, Joe DePasquale, Antonella Fruscione","doi":"10.3847/1538-4365/acdd62","DOIUrl":"https://doi.org/10.3847/1538-4365/acdd62","url":null,"abstract":"Abstract The Cygnus OB2 association is the largest concentration of young and massive stars within 2 kpc of the Sun, including an estimated ∼65 O-type stars and hundreds of OB stars. The Chandra Cygnus OB2 Legacy Survey is a large imaging program undertaken with the Advanced CCD Imaging Spectrometer on board the Chandra X-ray Observatory. The survey has imaged the central 0.5 deg 2 of the Cyg OB2 association with an effective exposure of ∼120 ks and an outer 0.35 deg 2 area with an exposure of ∼60 ks. Here we describe the survey design and observations, discuss the data reduction and source detection, and present a catalog of ∼8000 X-ray point sources. The survey design employs a grid of 36 heavily (∼50%) overlapping pointings, a method that overcomes Chandra's low off-axis sensitivity and produces a highly uniform exposure over the inner 0.5 deg 2 . The full X-ray catalog is described here and is made available online.","PeriodicalId":8588,"journal":{"name":"Astrophysical Journal Supplement Series","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134972729","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}
Pub Date : 2023-10-25DOI: 10.3847/1538-4365/acdd69
J. F. Albacete-Colombo, E. Flaccomio, J. J. Drake, N. J. Wright, M. Guarcello, V. Kashyap
Abstract We investigate the uncertainties of fitted X-ray model parameters and fluxes for relatively faint Chandra ACIS-I source spectra. Monte Carlo (MC) simulations are employed to construct a large set of 150,000 fake X-ray spectra in the low photon count statistics regime (from 10 to 350 net counts) using the XSPEC spectral model-fitting package. The simulations employed both absorbed thermal (APEC) and nonthermal (power-law) models, in concert with the Chandra ACIS-I instrument response and interstellar absorption. Simulated X-ray spectra were fit assuming a wide set of different input parameters and C -statistic minimization criteria to avoid numerical artifacts in the accepted solutions. Results provide an error estimate for each parameter (absorption, N H , plasma temperature, kT , or power-law slope, Γ, and flux) and for different background contamination levels. The distributions of these errors are studied as a function of the 1 σ quantiles, and we show how these correlate with different model parameters, net counts in the spectra, and relative background level. Maps of uncertainty in terms of the 1 σ quantiles for parameters and flux are computed as a function of spectrum net counts. We find very good agreement between our estimated X-ray spectral parameter and flux uncertainties and those recovered from spectral fitting for a subset of the X-ray sources detected in the Chandra Cygnus OB2 Legacy Survey diagnosed to be association members and that have between 20 and 350 net counts. Our method can provide uncertainties for spectral parameters whenever formal X-ray spectral fits cannot be well constrained, or are unavailable, and predictions useful for computing Chandra ACIS-I exposure times for observation planning.
{"title":"The Statistical Uncertainties on X-Ray Flux and Spectral Parameters from Chandra ACIS-I Observations of Faint Sources: Application to the Cygnus OB2 Association","authors":"J. F. Albacete-Colombo, E. Flaccomio, J. J. Drake, N. J. Wright, M. Guarcello, V. Kashyap","doi":"10.3847/1538-4365/acdd69","DOIUrl":"https://doi.org/10.3847/1538-4365/acdd69","url":null,"abstract":"Abstract We investigate the uncertainties of fitted X-ray model parameters and fluxes for relatively faint Chandra ACIS-I source spectra. Monte Carlo (MC) simulations are employed to construct a large set of 150,000 fake X-ray spectra in the low photon count statistics regime (from 10 to 350 net counts) using the XSPEC spectral model-fitting package. The simulations employed both absorbed thermal (APEC) and nonthermal (power-law) models, in concert with the Chandra ACIS-I instrument response and interstellar absorption. Simulated X-ray spectra were fit assuming a wide set of different input parameters and C -statistic minimization criteria to avoid numerical artifacts in the accepted solutions. Results provide an error estimate for each parameter (absorption, N H , plasma temperature, kT , or power-law slope, Γ, and flux) and for different background contamination levels. The distributions of these errors are studied as a function of the 1 σ quantiles, and we show how these correlate with different model parameters, net counts in the spectra, and relative background level. Maps of uncertainty in terms of the 1 σ quantiles for parameters and flux are computed as a function of spectrum net counts. We find very good agreement between our estimated X-ray spectral parameter and flux uncertainties and those recovered from spectral fitting for a subset of the X-ray sources detected in the Chandra Cygnus OB2 Legacy Survey diagnosed to be association members and that have between 20 and 350 net counts. Our method can provide uncertainties for spectral parameters whenever formal X-ray spectral fits cannot be well constrained, or are unavailable, and predictions useful for computing Chandra ACIS-I exposure times for observation planning.","PeriodicalId":8588,"journal":{"name":"Astrophysical Journal Supplement Series","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134972573","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}
Pub Date : 2023-10-25DOI: 10.3847/1538-4365/acdd68
Vinay L. Kashyap, Mario G. Guarcello, Nicholas J. Wright, Jeremy J. Drake, Ettore Flaccomio, Tom L. Aldcroft, Juan F. Albacete Colombo, Kevin Briggs, Francesco Damiani, Janet E. Drew, Eduardo L. Martin, Giusi Micela, Tim Naylor, Salvatore Sciortino
Abstract We have devised a predominantly Naive Bayes−based method to classify X-ray sources detected by Chandra in the Cygnus OB2 association into members, foreground objects, and background objects. We employ a variety of X-ray, optical, and infrared characteristics to construct likelihoods using training sets defined by well-measured sources. Combinations of optical photometry from the Sloan Digital Sky Survey ( riz ) and Isaac Newton Telescope Photometric H α Survey ( r I i I H α ), infrared magnitudes from United Kingdom Infrared Telescope Deep Sky Survey and Two-Micron All Sky Survey ( JHK ), X-ray quantiles and hardness ratios, and estimates of extinction A v are used to compute the relative probabilities that a given source belongs to one of the classes. Principal component analysis is used to isolate the best axes for separating the classes for the photometric data, and Gaussian component separation is used for X-ray hardness and extinction. Errors in the measurements are accounted for by modeling as Gaussians and integrating over likelihoods approximated as quartic polynomials. We evaluate the accuracy of the classification by inspection and reclassify a number of sources based on infrared magnitudes, the presence of disks, and spectral hardness induced by flaring. We also consider systematic errors due to extinction. Of the 7924 X-ray detections, 5501 have a total of 5597 optical/infrared matches, including 78 with multiple counterparts. We find that ≈6100 objects are likely association members, ≈1400 are background objects, and ≈500 are foreground objects, with an accuracy of 96%, 93%, and 80%, respectively, with an overall classification accuracy of approximately 95%.
我们设计了一种主要基于朴素贝叶斯的方法，将钱德拉望远镜探测到的天鹅座OB2 x射线源分为成员、前景物体和背景物体。我们使用各种x射线、光学和红外特征来使用由良好测量源定义的训练集构建可能性。结合斯隆数字巡天(riz)和艾萨克牛顿望远镜光度测量H α (r I I I H α)的光学光度测量、英国红外望远镜深空巡天和2微米全天空巡天(JHK)的红外星等、x射线分位数和硬度比以及消光A v的估计，计算出给定光源属于某一类的相对概率。主成分分析用于分离光度数据类别的最佳轴，高斯分量分离用于x射线硬度和消光。测量误差由高斯模型和近似为四次多项式的似然积分来解释。我们通过检查来评估分类的准确性，并根据红外星等、盘的存在和由耀斑引起的光谱硬度对一些源进行重新分类。我们还考虑由于消光引起的系统误差。在7924个x射线探测中，5501个总共有5597个光学/红外匹配，其中78个有多个对应。我们发现，约6100个对象可能是关联成员，约1400个是背景对象，约500个是前景对象，准确率分别为96%、93%和80%，总体分类准确率约为95%。
{"title":"Classification of Chandra X-Ray Sources in Cygnus OB2","authors":"Vinay L. Kashyap, Mario G. Guarcello, Nicholas J. Wright, Jeremy J. Drake, Ettore Flaccomio, Tom L. Aldcroft, Juan F. Albacete Colombo, Kevin Briggs, Francesco Damiani, Janet E. Drew, Eduardo L. Martin, Giusi Micela, Tim Naylor, Salvatore Sciortino","doi":"10.3847/1538-4365/acdd68","DOIUrl":"https://doi.org/10.3847/1538-4365/acdd68","url":null,"abstract":"Abstract We have devised a predominantly Naive Bayes−based method to classify X-ray sources detected by Chandra in the Cygnus OB2 association into members, foreground objects, and background objects. We employ a variety of X-ray, optical, and infrared characteristics to construct likelihoods using training sets defined by well-measured sources. Combinations of optical photometry from the Sloan Digital Sky Survey ( riz ) and Isaac Newton Telescope Photometric H α Survey ( r I i I H α ), infrared magnitudes from United Kingdom Infrared Telescope Deep Sky Survey and Two-Micron All Sky Survey ( JHK ), X-ray quantiles and hardness ratios, and estimates of extinction A v are used to compute the relative probabilities that a given source belongs to one of the classes. Principal component analysis is used to isolate the best axes for separating the classes for the photometric data, and Gaussian component separation is used for X-ray hardness and extinction. Errors in the measurements are accounted for by modeling as Gaussians and integrating over likelihoods approximated as quartic polynomials. We evaluate the accuracy of the classification by inspection and reclassify a number of sources based on infrared magnitudes, the presence of disks, and spectral hardness induced by flaring. We also consider systematic errors due to extinction. Of the 7924 X-ray detections, 5501 have a total of 5597 optical/infrared matches, including 78 with multiple counterparts. We find that ≈6100 objects are likely association members, ≈1400 are background objects, and ≈500 are foreground objects, with an accuracy of 96%, 93%, and 80%, respectively, with an overall classification accuracy of approximately 95%.","PeriodicalId":8588,"journal":{"name":"Astrophysical Journal Supplement Series","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134972732","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}
Pub Date : 2023-10-25DOI: 10.3847/1538-4365/acdd65
J. F. Albacete-Colombo, J. J. Drake, E. Flaccomio, N. J. Wright, V. Kashyap, M. G. Guarcello, K. Briggs, J. E. Drew, D. M. Fenech, G. Micela, M. McCollough, R. K. Prinja, N. Schneider, S. Sciortino, J. S. Vink
Abstract We present a large-scale study of diffuse X-ray emission in the nearby massive stellar association Cygnus OB2 as part of the Chandra Cygnus OB2 Legacy Program. We used 40 Chandra X-ray ACIS-I observations covering ∼1.0 deg 2 . After removing 7924 point sources detected in our survey and applying adaptive smoothing to the background-corrected X-ray emission, the adaptive smoothing reveals large-scale diffuse X-ray emission. Diffuse emission was detected in the subbands soft (0.5−1.2 keV) and medium (1.2−2.5 keV) and marginally in the hard (2.5−7.0 keV) band. From X-ray spectral analysis of stacked spectra we compute a total (0.5–7.0 keV) diffuse X-ray luminosity of LXdiff≈ 4.2 × 10 34 erg s −1 , characterized by plasma temperature components at kT ≈ 0.11, 0.40, and 1.18 keV, respectively. The H i absorption column density corresponding to these temperatures has a distribution consistent with N H = (0.43, 0.80, 1.39) × 10 22 cm −2 . The extended medium-band energy emission likely arises from O-type stellar winds thermalized by wind−wind collisions in the most populated regions of the association, while the soft-band emission probably arises from less energetic termination shocks against the surrounding interstellar medium. Supersoft and soft diffuse emission appears more widely dispersed and intense than the medium-band emission. The diffuse X-ray emission is generally spatially coincident with low-extinction regions that we attribute to the ubiquitous influence of powerful stellar winds from massive stars and their interaction with the local interstellar medium. Diffuse X-ray emission is volume filling, rather than edge brightened, oppositely to other star-forming regions. We reveal the first observational evidence of X-ray halos around some evolved massive stars.
{"title":"Diffuse X-Ray Emission in the Cygnus OB2 Association","authors":"J. F. Albacete-Colombo, J. J. Drake, E. Flaccomio, N. J. Wright, V. Kashyap, M. G. Guarcello, K. Briggs, J. E. Drew, D. M. Fenech, G. Micela, M. McCollough, R. K. Prinja, N. Schneider, S. Sciortino, J. S. Vink","doi":"10.3847/1538-4365/acdd65","DOIUrl":"https://doi.org/10.3847/1538-4365/acdd65","url":null,"abstract":"Abstract We present a large-scale study of diffuse X-ray emission in the nearby massive stellar association Cygnus OB2 as part of the Chandra Cygnus OB2 Legacy Program. We used 40 Chandra X-ray ACIS-I observations covering ∼1.0 deg 2 . After removing 7924 point sources detected in our survey and applying adaptive smoothing to the background-corrected X-ray emission, the adaptive smoothing reveals large-scale diffuse X-ray emission. Diffuse emission was detected in the subbands soft (0.5−1.2 keV) and medium (1.2−2.5 keV) and marginally in the hard (2.5−7.0 keV) band. From X-ray spectral analysis of stacked spectra we compute a total (0.5–7.0 keV) diffuse X-ray luminosity of <?CDATA ${L}_{{rm{X}}}^{mathrm{diff}}approx $?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:msubsup> <mml:mi>L</mml:mi> <mml:mi mathvariant=\"normal\">X</mml:mi> <mml:mi>diff</mml:mi> </mml:msubsup> <mml:mo>≈</mml:mo> </mml:math> 4.2 × 10 34 erg s −1 , characterized by plasma temperature components at kT ≈ 0.11, 0.40, and 1.18 keV, respectively. The H i absorption column density corresponding to these temperatures has a distribution consistent with N H = (0.43, 0.80, 1.39) × 10 22 cm −2 . The extended medium-band energy emission likely arises from O-type stellar winds thermalized by wind−wind collisions in the most populated regions of the association, while the soft-band emission probably arises from less energetic termination shocks against the surrounding interstellar medium. Supersoft and soft diffuse emission appears more widely dispersed and intense than the medium-band emission. The diffuse X-ray emission is generally spatially coincident with low-extinction regions that we attribute to the ubiquitous influence of powerful stellar winds from massive stars and their interaction with the local interstellar medium. Diffuse X-ray emission is volume filling, rather than edge brightened, oppositely to other star-forming regions. We reveal the first observational evidence of X-ray halos around some evolved massive stars.","PeriodicalId":8588,"journal":{"name":"Astrophysical Journal Supplement Series","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134972586","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}
Pub Date : 2023-10-25DOI: 10.3847/1538-4365/acdd64
M. G. Guarcello, J. J. Drake, N. J. Wright, T. Naylor, E. Flaccomio, V. L. Kashyap, D. García-Alvarez
Abstract The young massive OB association Cygnus OB2, in the Cygnus X complex, is the closest (∼1400 pc) star-forming region to the Sun hosting thousands of young low-mass stars and up to 1000 OB stars, among which are some of the most massive stars known in our Galaxy. This region holds great importance for several fields of modern astrophysics, such as the study of the physical properties of massive and young low-mass stars and the feedback provided by massive stars on star and planet formation processes. Cyg OB2 has been recently observed with Chandra/ACIS-I as part of the 1.08 Ms Chandra Cygnus OB2 Legacy Project. This survey detected 7924 X-ray sources in a square degree area centered on Cyg OB2. Since a proper classification and study of the observed X-ray sources also requires the analysis of their optical and infrared counterparts, we combined a large and deep set of optical and infrared catalogs available for this region with our new X-ray catalog. In this paper we describe the matching procedure and present the combined catalog containing 5703 sources. We also briefly discuss the nature of the X-ray sources with optical and infrared counterparts using their position in the color–magnitude and color–color diagrams.
{"title":"Optical and Infrared Counterparts of the X-Ray Sources Detected in the Chandra Cygnus OB2 Legacy Survey","authors":"M. G. Guarcello, J. J. Drake, N. J. Wright, T. Naylor, E. Flaccomio, V. L. Kashyap, D. García-Alvarez","doi":"10.3847/1538-4365/acdd64","DOIUrl":"https://doi.org/10.3847/1538-4365/acdd64","url":null,"abstract":"Abstract The young massive OB association Cygnus OB2, in the Cygnus X complex, is the closest (∼1400 pc) star-forming region to the Sun hosting thousands of young low-mass stars and up to 1000 OB stars, among which are some of the most massive stars known in our Galaxy. This region holds great importance for several fields of modern astrophysics, such as the study of the physical properties of massive and young low-mass stars and the feedback provided by massive stars on star and planet formation processes. Cyg OB2 has been recently observed with Chandra/ACIS-I as part of the 1.08 Ms Chandra Cygnus OB2 Legacy Project. This survey detected 7924 X-ray sources in a square degree area centered on Cyg OB2. Since a proper classification and study of the observed X-ray sources also requires the analysis of their optical and infrared counterparts, we combined a large and deep set of optical and infrared catalogs available for this region with our new X-ray catalog. In this paper we describe the matching procedure and present the combined catalog containing 5703 sources. We also briefly discuss the nature of the X-ray sources with optical and infrared counterparts using their position in the color–magnitude and color–color diagrams.","PeriodicalId":8588,"journal":{"name":"Astrophysical Journal Supplement Series","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134972731","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}
Pub Date : 2023-10-25DOI: 10.3847/1538-4365/acdd67
M. G. Guarcello, J. J. Drake, N. J. Wright, J. F. Albacete-Colombo, C. Clarke, B. Ercolano, E. Flaccomio, V. Kashyap, G. Micela, T. Naylor, N. Schneider, S. Sciortino, J. S. Vink
Abstract In our Galaxy, star formation occurs in a variety of environments, with a large fraction of stars formed in clusters hosting massive stars. OB stars have an important feedback on the evolution of protoplanetary disks orbiting around nearby young stars and likely on the process of planet formation occurring in them. The nearby massive association Cyg OB2 is an outstanding laboratory to study this feedback. It is the closest massive association to our Sun and hosts hundreds of massive stars and thousands of low-mass members, both with and without disks. In this paper, we analyze the spatial variation of the disk fraction (i.e., the fraction of cluster members bearing a disk) in Cyg OB2 and study its correlation with the local values of far-ultraviolet (FUV) and extreme-ultraviolet (EUV) radiation fields and the local stellar surface density. We present definitive evidence that disks are more rapidly dissipated in the regions of the association characterized by intense local UV fields and large stellar density. In particular, the FUV radiation dominates disk dissipation timescales in the proximity (i.e., within 0.5 pc) of the O stars. In the rest of the association, EUV photons potentially induce a significant mass loss from the irradiated disks across the entire association, but the efficiency of this process is reduced at increasing distances from the massive stars owing to absorption by the intervening intracluster material. We find that disk dissipation due to close stellar encounters is negligible in Cyg OB2 and likely to have affected 1% or fewer of the stellar population. Disk dissipation is instead dominated by photoevaporation. We also compare our results to what has been found in other young clusters with different massive populations, concluding that massive associations like Cyg OB2 are potentially hostile to protoplanetary disks but that the environments where disks can safely evolve in planetary systems are likely quite common in our Galaxy.
{"title":"Photoevaporation and Close Encounters: How the Environment around Cygnus OB2 Affects the Evolution of Protoplanetary Disks","authors":"M. G. Guarcello, J. J. Drake, N. J. Wright, J. F. Albacete-Colombo, C. Clarke, B. Ercolano, E. Flaccomio, V. Kashyap, G. Micela, T. Naylor, N. Schneider, S. Sciortino, J. S. Vink","doi":"10.3847/1538-4365/acdd67","DOIUrl":"https://doi.org/10.3847/1538-4365/acdd67","url":null,"abstract":"Abstract In our Galaxy, star formation occurs in a variety of environments, with a large fraction of stars formed in clusters hosting massive stars. OB stars have an important feedback on the evolution of protoplanetary disks orbiting around nearby young stars and likely on the process of planet formation occurring in them. The nearby massive association Cyg OB2 is an outstanding laboratory to study this feedback. It is the closest massive association to our Sun and hosts hundreds of massive stars and thousands of low-mass members, both with and without disks. In this paper, we analyze the spatial variation of the disk fraction (i.e., the fraction of cluster members bearing a disk) in Cyg OB2 and study its correlation with the local values of far-ultraviolet (FUV) and extreme-ultraviolet (EUV) radiation fields and the local stellar surface density. We present definitive evidence that disks are more rapidly dissipated in the regions of the association characterized by intense local UV fields and large stellar density. In particular, the FUV radiation dominates disk dissipation timescales in the proximity (i.e., within 0.5 pc) of the O stars. In the rest of the association, EUV photons potentially induce a significant mass loss from the irradiated disks across the entire association, but the efficiency of this process is reduced at increasing distances from the massive stars owing to absorption by the intervening intracluster material. We find that disk dissipation due to close stellar encounters is negligible in Cyg OB2 and likely to have affected 1% or fewer of the stellar population. Disk dissipation is instead dominated by photoevaporation. We also compare our results to what has been found in other young clusters with different massive populations, concluding that massive associations like Cyg OB2 are potentially hostile to protoplanetary disks but that the environments where disks can safely evolve in planetary systems are likely quite common in our Galaxy.","PeriodicalId":8588,"journal":{"name":"Astrophysical Journal Supplement Series","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134972735","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}
Pub Date : 2023-10-25DOI: 10.3847/1538-4365/acdd66
E. Flaccomio, J. F. Albacete-Colombo, J. J. Drake, M. G. Guarcello, V. Kashyap, N. J. Wright, K. Briggs, B. Ercolano, M. McCollough, S. Sciortino
Abstract We analyze the X-ray spectra of the ∼8000 sources detected in the Cygnus OB2 Chandra Legacy Survey (this focus issue), with the goals of characterizing the coronal plasma of the young low-mass stars in the region and estimating their intrinsic X-ray luminosities. We adopt two different strategies for X-ray sources for which more or less than 20 photons were detected. For the brighter sample we fit the spectra with absorbed isothermal models. In order to limit uncertainties, for most of the fainter Cygnus OB2 members in this sample we constrain the spectral parameters to characteristic ranges defined from the brightest stars. For X-ray sources with <20 net photons we adopt a conversion factor from detected photon flux to intrinsic flux. This was defined, building on the results for the previous sample, as a function of the 20% quantile of the detected photon energy distributions, which we prove to also correlate well with extinction. We then use the X-ray extinction from the spectral fits to constrain the ratio between optical and X-ray extinction toward Cyg OB2, finding it consistent with standard “Galactic” values, when properly accounting for systematics. Finally, we exploit the large number of sources to constrain the average coronal abundances of several elements, through two different ensemble analyses of the X-ray spectra of low-mass Cyg OB2 members. We find the pattern of abundances to be largely consistent with that derived for the young stellar coronae in the Orion Nebula Cluster.
{"title":"X-Ray Spectral Characterization of the Young Cygnus OB2 Population","authors":"E. Flaccomio, J. F. Albacete-Colombo, J. J. Drake, M. G. Guarcello, V. Kashyap, N. J. Wright, K. Briggs, B. Ercolano, M. McCollough, S. Sciortino","doi":"10.3847/1538-4365/acdd66","DOIUrl":"https://doi.org/10.3847/1538-4365/acdd66","url":null,"abstract":"Abstract We analyze the X-ray spectra of the ∼8000 sources detected in the Cygnus OB2 Chandra Legacy Survey (this focus issue), with the goals of characterizing the coronal plasma of the young low-mass stars in the region and estimating their intrinsic X-ray luminosities. We adopt two different strategies for X-ray sources for which more or less than 20 photons were detected. For the brighter sample we fit the spectra with absorbed isothermal models. In order to limit uncertainties, for most of the fainter Cygnus OB2 members in this sample we constrain the spectral parameters to characteristic ranges defined from the brightest stars. For X-ray sources with <20 net photons we adopt a conversion factor from detected photon flux to intrinsic flux. This was defined, building on the results for the previous sample, as a function of the 20% quantile of the detected photon energy distributions, which we prove to also correlate well with extinction. We then use the X-ray extinction from the spectral fits to constrain the ratio between optical and X-ray extinction toward Cyg OB2, finding it consistent with standard “Galactic” values, when properly accounting for systematics. Finally, we exploit the large number of sources to constrain the average coronal abundances of several elements, through two different ensemble analyses of the X-ray spectra of low-mass Cyg OB2 members. We find the pattern of abundances to be largely consistent with that derived for the young stellar coronae in the Orion Nebula Cluster.","PeriodicalId":8588,"journal":{"name":"Astrophysical Journal Supplement Series","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134972733","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}
Pub Date : 2023-10-23DOI: 10.3847/1538-4365/acf764
Ruoyi Zhang, Haibo Yuan, Bingqiu Chen
Abstract The total-to-selective extinction ratio, R V , is a key parameter for tracing the properties of interstellar dust, as it directly determines the variation of the extinction curve with wavelength. By utilizing accurate color excess measurements from the optical to the mid-infrared range, we have derived R V values for approximately three million stars from LAMOST data release 7 using a forward-modeling technique. This extensive data set enables us to construct a comprehensive 2D R V map of the Milky Way within the LAMOST footprint at a spatial resolution of ∼27.′5. Based on reliable sight lines of E ( B − V ) > 0.1, we find that R V exhibits a Gaussian distribution centered around 3.25 with a standard deviation of 0.25. The spatial variability of R V in the Galactic disk exhibits a wide range, spanning from small scales within individual molecular clouds to large scales up to kiloparsecs. A striking correlation is observed between the distribution of R V and molecular clouds. Notably, we observe lower R V values within the regions of nearby molecular clouds compared to their surrounding areas. Furthermore, we have investigated the relationships between R V and various parameters, including dust temperature, dust emissivity spectral index, column densities and ratios of atomic and molecular hydrogen, as well as the gas-to-dust ratio. We find that these relationships vary with the level of extinction. These analyses provide new insights into the properties and evolution of dust grains in diverse interstellar environments and also hold significant importance for achieving accurate extinction corrections.
{"title":"An R <sub>V</sub> Map of the Milky Way Revealed by LAMOST","authors":"Ruoyi Zhang, Haibo Yuan, Bingqiu Chen","doi":"10.3847/1538-4365/acf764","DOIUrl":"https://doi.org/10.3847/1538-4365/acf764","url":null,"abstract":"Abstract The total-to-selective extinction ratio, R V , is a key parameter for tracing the properties of interstellar dust, as it directly determines the variation of the extinction curve with wavelength. By utilizing accurate color excess measurements from the optical to the mid-infrared range, we have derived R V values for approximately three million stars from LAMOST data release 7 using a forward-modeling technique. This extensive data set enables us to construct a comprehensive 2D R V map of the Milky Way within the LAMOST footprint at a spatial resolution of ∼27.′5. Based on reliable sight lines of E ( B − V ) > 0.1, we find that R V exhibits a Gaussian distribution centered around 3.25 with a standard deviation of 0.25. The spatial variability of R V in the Galactic disk exhibits a wide range, spanning from small scales within individual molecular clouds to large scales up to kiloparsecs. A striking correlation is observed between the distribution of R V and molecular clouds. Notably, we observe lower R V values within the regions of nearby molecular clouds compared to their surrounding areas. Furthermore, we have investigated the relationships between R V and various parameters, including dust temperature, dust emissivity spectral index, column densities and ratios of atomic and molecular hydrogen, as well as the gas-to-dust ratio. We find that these relationships vary with the level of extinction. These analyses provide new insights into the properties and evolution of dust grains in diverse interstellar environments and also hold significant importance for achieving accurate extinction corrections.","PeriodicalId":8588,"journal":{"name":"Astrophysical Journal Supplement Series","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135405350","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}
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