S. Mahajan, K. Singh, J. Tiwari, Somak Raychaudhury
Abstract We present multi-wavelength data and analysis, including new FUV AstroSat/UVIT observations of the spiral galaxy UGC 10420 ( $z=0.032$ ), a member of the cluster Abell 2199. UGC 10420 is present on the edge of the X-ray emitting region of the cluster at a distance of ${sim} 680$ kpc from the centre. The far-ultraviolet (FUV) data obtained by the AstroSat mission show intense knots of star formation on the leading edge of the galaxy, accompanied by a tail of the same on the diametrically opposite side. Our analysis shows that the images of the galaxy disc in the optical and mid-infrared are much smaller in size than that in the FUV. While the broadband optical colours of UGC 10420 are typical of a post-starburst galaxy, the star formation rate (SFR) derived from a UV-to-IR spectral energy distribution is at least a factor of nine higher than that expected for a star-forming field galaxy of similar mass at its redshift. A careful removal of the contribution of the diffuse intracluster gas shows that the significant diffuse X-ray emission associated with the interstellar medium of UGC 10420 has a temperature, $T_X = 0.24^{+0.09}_{-0.06}$ keV (0.4–2.0 keV) and luminosity, $L_X = 1.8pm{0.9}times 10^{40}$ erg s $^{-1}$ , which are typical of the X-ray emission from late-type spiral galaxies. Two symmetrically placed X-ray hot spots are observed on either sides of an X-ray weak nucleus. Our analysis favours a scenario where the interaction of a galaxy with the hot intracluster medium of the cluster, perturbs the gas in the galaxy causing starburst in the leading edge of the disc. On the other hand, the turbulence thus developed may also push some of the gas out of the disc. Interactions between the gas ejected from the galaxy and the intracluster medium can then locally trigger star formation in the wake of the galaxy experiencing ram-pressure stripping. Our data however does not rule out the possibility of a flyby encounter with a neighbouring galaxy, although no relevant candidates are observed in the vicinity of UGC 10420.
{"title":"Dashing through the cluster: An X-ray to radio view of UGC 10420 undergoing ram-pressure stripping","authors":"S. Mahajan, K. Singh, J. Tiwari, Somak Raychaudhury","doi":"10.1017/pasa.2023.6","DOIUrl":"https://doi.org/10.1017/pasa.2023.6","url":null,"abstract":"Abstract We present multi-wavelength data and analysis, including new FUV AstroSat/UVIT observations of the spiral galaxy UGC 10420 ( \u0000$z=0.032$\u0000 ), a member of the cluster Abell 2199. UGC 10420 is present on the edge of the X-ray emitting region of the cluster at a distance of \u0000${sim} 680$\u0000 kpc from the centre. The far-ultraviolet (FUV) data obtained by the AstroSat mission show intense knots of star formation on the leading edge of the galaxy, accompanied by a tail of the same on the diametrically opposite side. Our analysis shows that the images of the galaxy disc in the optical and mid-infrared are much smaller in size than that in the FUV. While the broadband optical colours of UGC 10420 are typical of a post-starburst galaxy, the star formation rate (SFR) derived from a UV-to-IR spectral energy distribution is at least a factor of nine higher than that expected for a star-forming field galaxy of similar mass at its redshift. A careful removal of the contribution of the diffuse intracluster gas shows that the significant diffuse X-ray emission associated with the interstellar medium of UGC 10420 has a temperature, \u0000$T_X = 0.24^{+0.09}_{-0.06}$\u0000 keV (0.4–2.0 keV) and luminosity, \u0000$L_X = 1.8pm{0.9}times 10^{40}$\u0000 erg s \u0000$^{-1}$\u0000 , which are typical of the X-ray emission from late-type spiral galaxies. Two symmetrically placed X-ray hot spots are observed on either sides of an X-ray weak nucleus. Our analysis favours a scenario where the interaction of a galaxy with the hot intracluster medium of the cluster, perturbs the gas in the galaxy causing starburst in the leading edge of the disc. On the other hand, the turbulence thus developed may also push some of the gas out of the disc. Interactions between the gas ejected from the galaxy and the intracluster medium can then locally trigger star formation in the wake of the galaxy experiencing ram-pressure stripping. Our data however does not rule out the possibility of a flyby encounter with a neighbouring galaxy, although no relevant candidates are observed in the vicinity of UGC 10420.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"32 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2023-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87943312","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
Abstract Pulsar wind nebulae (PWN) are fascinating systems and archetypal sources for high-energy astrophysics in general. Due to their vicinity, brightness, to the fact that they shine at multi-wavelengths, and especially to their long-living emission at gamma rays, modelling their properties is particularly important for the correct interpretation of the visible Galaxy. A complication in this respect is the variety of properties and morphologies they show at different ages. Here, we discuss the differences among the evolutionary phases of PWN, how they have been modeled in the past and what progresses have been recently made. We approach the discussion from a phenomenological, theoretical (especially numerical) and observational point of view, with particular attention to the most recent results and open questions about the physics of such intriguing sources.
{"title":"From young to old: The evolutionary path of Pulsar Wind Nebulae","authors":"B. Olmi, N. Bucciantini","doi":"10.1017/pasa.2023.5","DOIUrl":"https://doi.org/10.1017/pasa.2023.5","url":null,"abstract":"Abstract Pulsar wind nebulae (PWN) are fascinating systems and archetypal sources for high-energy astrophysics in general. Due to their vicinity, brightness, to the fact that they shine at multi-wavelengths, and especially to their long-living emission at gamma rays, modelling their properties is particularly important for the correct interpretation of the visible Galaxy. A complication in this respect is the variety of properties and morphologies they show at different ages. Here, we discuss the differences among the evolutionary phases of PWN, how they have been modeled in the past and what progresses have been recently made. We approach the discussion from a phenomenological, theoretical (especially numerical) and observational point of view, with particular attention to the most recent results and open questions about the physics of such intriguing sources.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"1 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2023-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90550156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
Abstract Pulsars have been studied extensively over the last few decades and have proven instrumental in exploring a wide variety of physics. Discovering more pulsars emitting at low radio frequencies is crucial to further our understanding of spectral properties and emission mechanisms. The Murchison Widefield Array Voltage Capture System (MWA VCS) has been routinely used to study pulsars at low frequencies and discover new pulsars. The MWA VCS offers the unique opportunity of recording complex voltages from all individual antennas (tiles), which can be off-line beamformed or correlated/imaged at millisecond time resolution. Devising imaged-based methods for finding pulsar candidates, which can be verified in beamformed data, can accelerate the complete process and lead to more pulsar detections. Image-based searches for pulsar candidates can reduce the number of tied-array beams required, increasing compute resource efficiency. Despite a factor of $sim$ 4 loss in sensitivity, searching for pulsar candidates in images from the MWA VCS, we can explore a larger parameter space, potentially leading to discoveries of pulsars missed by high-frequency surveys such as steep spectrum pulsars, exotic binary systems, or pulsars obscured in high-time resolution time series data by propagation effects. Image-based searches are also essential to probing parts of parameter space inaccessible to traditional beamformed searches with the MWA (e.g. at high dispersion measures). In this paper we describe the innovative approach and capability of dual-processing MWA VCS data, that is forming 1-s visibilities and sky images, finding pulsar candidates in these images, and verifying by forming tied-array beam. We developed and tested image-based methods of finding pulsar candidates, which are based on pulsar properties such as steep spectral index, polarisation and variability. The efficiency of these methodologies has been verified on known pulsars, and the main limitations explained in terms of sensitivity and low-frequency spectral turnover of some pulsars. No candidates were confirmed to be a new pulsar, but this new capability will now be applied to a larger subset of observations to accelerate pulsar discoveries with the MWA and potentially speed up future searches with the SKA-Low.
{"title":"Image-based searches for pulsar candidates using MWA VCS data","authors":"S. Sett, N. Bhat, M. Sokolowski, E. Lenc","doi":"10.1017/pasa.2022.59","DOIUrl":"https://doi.org/10.1017/pasa.2022.59","url":null,"abstract":"Abstract Pulsars have been studied extensively over the last few decades and have proven instrumental in exploring a wide variety of physics. Discovering more pulsars emitting at low radio frequencies is crucial to further our understanding of spectral properties and emission mechanisms. The Murchison Widefield Array Voltage Capture System (MWA VCS) has been routinely used to study pulsars at low frequencies and discover new pulsars. The MWA VCS offers the unique opportunity of recording complex voltages from all individual antennas (tiles), which can be off-line beamformed or correlated/imaged at millisecond time resolution. Devising imaged-based methods for finding pulsar candidates, which can be verified in beamformed data, can accelerate the complete process and lead to more pulsar detections. Image-based searches for pulsar candidates can reduce the number of tied-array beams required, increasing compute resource efficiency. Despite a factor of \u0000$sim$\u0000 4 loss in sensitivity, searching for pulsar candidates in images from the MWA VCS, we can explore a larger parameter space, potentially leading to discoveries of pulsars missed by high-frequency surveys such as steep spectrum pulsars, exotic binary systems, or pulsars obscured in high-time resolution time series data by propagation effects. Image-based searches are also essential to probing parts of parameter space inaccessible to traditional beamformed searches with the MWA (e.g. at high dispersion measures). In this paper we describe the innovative approach and capability of dual-processing MWA VCS data, that is forming 1-s visibilities and sky images, finding pulsar candidates in these images, and verifying by forming tied-array beam. We developed and tested image-based methods of finding pulsar candidates, which are based on pulsar properties such as steep spectral index, polarisation and variability. The efficiency of these methodologies has been verified on known pulsars, and the main limitations explained in terms of sensitivity and low-frequency spectral turnover of some pulsars. No candidates were confirmed to be a new pulsar, but this new capability will now be applied to a larger subset of observations to accelerate pulsar discoveries with the MWA and potentially speed up future searches with the SKA-Low.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"51 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2023-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91207051","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
M. Thomas, M. Trenti, A. Sanna, R. Campana, G. Ghirlanda, J. Řípa, L. Burderi, F. Fiore, Y. Evangelista, L. Amati, S. Barraclough, K. Auchettl, M. O. del Castillo, A. Chapman, M. Citossi, A. Colagrossi, G. Dilillo, N. Deiosso, E. Demenev, F. Longo, A. Marino, J. McRobbie, R. Mearns, A. Melandri, A. Riggio, T. di Salvo, S. Puccetti, M. Topinka
Abstract Multi-messenger observations of the transient sky to detect cosmic explosions and counterparts of gravitational wave mergers critically rely on orbiting wide-FoV telescopes to cover the wide range of wavelengths where atmospheric absorption and emission limit the use of ground facilities. Thanks to continuing technological improvements, miniaturised space instruments operating as distributed-aperture constellations are offering new capabilities for the study of high-energy transients to complement ageing existing satellites. In this paper we characterise the performance of the upcoming joint SpIRIT and HERMES-TP/SP constellation for the localisation of high-energy transients through triangulation of signal arrival times. SpIRIT is an Australian technology and science demonstrator satellite designed to operate in a low-Earth Sun-synchronous Polar orbit that will augment the science operations for the equatorial HERMES-TP/SP constellation. In this work we simulate the improvement to the localisation capabilities of the HERMES-TP/SP constellation when SpIRIT is included in an orbital plane nearly perpendicular (inclination = 97.6°) to the HERMES-TP/SP orbits. For the fraction of GRBs detected by three of the HERMES satellites plus SpIRIT, we find that the combined constellation is capable of localising 60% of long GRBs to within ${sim}30,textrm{deg}^{2}$ on the sky, and 60% of short GRBs within ${sim}1850,textrm{deg}^{2}$ ( $1sigma$ confidence regions), though it is beyond the scope of this work to characterise or rule out systematic uncertainty of the same order of magnitude. Based purely on statistical GRB localisation capabilities (i.e., excluding systematic uncertainties and sky coverage), these figures for long GRBs are comparable to those reported by the Fermi Gamma Burst Monitor instrument. These localisation statistics represents a reduction of the uncertainty for the burst localisation region for both long and short GRBs by a factor of ${sim}5$ compared to the HERMES-TP/SP alone. Further improvements by an additional factor of 2 (or 4) can be achieved by launching an additional 4 (or 6) SpIRIT-like satellites into a Polar orbit, respectively, which would both increase the fraction of sky covered by multiple satellite elements, and also enable localisation of ${geq} 60%$ of long GRBs to within a radius of ${sim}1.5^{circ}$ (statistical uncertainty) on the sky, clearly demonstrating the value of a distributed all-sky high-energy transient monitor composed of nano-satellites.
瞬态天空的多信使观测，以探测宇宙爆炸和引力波并合，严重依赖于轨道宽视场望远镜，以覆盖大气吸收和发射限制了地面设施的使用的宽波长范围。由于技术的不断改进，作为分布式孔径星座运行的小型化空间仪器为高能瞬变现象的研究提供了新的能力，以补充老化的现有卫星。在本文中，我们描述了即将到来的联合SpIRIT和HERMES-TP/SP星座的性能，通过信号到达时间的三角测量来定位高能瞬态。精神号是澳大利亚的一颗技术和科学演示卫星，设计用于在近地太阳同步极轨道运行，将增强赤道HERMES-TP/SP星座的科学运行。在这项工作中，我们模拟了当SpIRIT被包括在与HERMES-TP/SP轨道几乎垂直(倾角= 97.6°)的轨道平面中时，对HERMES-TP/SP星座定位能力的改进。对于三颗HERMES卫星加上SpIRIT探测到的grb的比例，我们发现合并后的星座能够定位60个% of long GRBs to within ${sim}30,textrm{deg}^{2}$ on the sky, and 60% of short GRBs within ${sim}1850,textrm{deg}^{2}$ ( $1sigma$ confidence regions), though it is beyond the scope of this work to characterise or rule out systematic uncertainty of the same order of magnitude. Based purely on statistical GRB localisation capabilities (i.e., excluding systematic uncertainties and sky coverage), these figures for long GRBs are comparable to those reported by the Fermi Gamma Burst Monitor instrument. These localisation statistics represents a reduction of the uncertainty for the burst localisation region for both long and short GRBs by a factor of ${sim}5$ compared to the HERMES-TP/SP alone. Further improvements by an additional factor of 2 (or 4) can be achieved by launching an additional 4 (or 6) SpIRIT-like satellites into a Polar orbit, respectively, which would both increase the fraction of sky covered by multiple satellite elements, and also enable localisation of ${geq} 60%$ of long GRBs to within a radius of ${sim}1.5^{circ}$ (statistical uncertainty) on the sky, clearly demonstrating the value of a distributed all-sky high-energy transient monitor composed of nano-satellites.
{"title":"Localisation of gamma-ray bursts from the combined SpIRIT+HERMES-TP/SP nano-satellite constellation","authors":"M. Thomas, M. Trenti, A. Sanna, R. Campana, G. Ghirlanda, J. Řípa, L. Burderi, F. Fiore, Y. Evangelista, L. Amati, S. Barraclough, K. Auchettl, M. O. del Castillo, A. Chapman, M. Citossi, A. Colagrossi, G. Dilillo, N. Deiosso, E. Demenev, F. Longo, A. Marino, J. McRobbie, R. Mearns, A. Melandri, A. Riggio, T. di Salvo, S. Puccetti, M. Topinka","doi":"10.1017/pasa.2023.4","DOIUrl":"https://doi.org/10.1017/pasa.2023.4","url":null,"abstract":"Abstract Multi-messenger observations of the transient sky to detect cosmic explosions and counterparts of gravitational wave mergers critically rely on orbiting wide-FoV telescopes to cover the wide range of wavelengths where atmospheric absorption and emission limit the use of ground facilities. Thanks to continuing technological improvements, miniaturised space instruments operating as distributed-aperture constellations are offering new capabilities for the study of high-energy transients to complement ageing existing satellites. In this paper we characterise the performance of the upcoming joint SpIRIT and HERMES-TP/SP constellation for the localisation of high-energy transients through triangulation of signal arrival times. SpIRIT is an Australian technology and science demonstrator satellite designed to operate in a low-Earth Sun-synchronous Polar orbit that will augment the science operations for the equatorial HERMES-TP/SP constellation. In this work we simulate the improvement to the localisation capabilities of the HERMES-TP/SP constellation when SpIRIT is included in an orbital plane nearly perpendicular (inclination = 97.6°) to the HERMES-TP/SP orbits. For the fraction of GRBs detected by three of the HERMES satellites plus SpIRIT, we find that the combined constellation is capable of localising 60% of long GRBs to within \u0000${sim}30,textrm{deg}^{2}$\u0000 on the sky, and 60% of short GRBs within \u0000${sim}1850,textrm{deg}^{2}$\u0000 ( \u0000$1sigma$\u0000 confidence regions), though it is beyond the scope of this work to characterise or rule out systematic uncertainty of the same order of magnitude. Based purely on statistical GRB localisation capabilities (i.e., excluding systematic uncertainties and sky coverage), these figures for long GRBs are comparable to those reported by the Fermi Gamma Burst Monitor instrument. These localisation statistics represents a reduction of the uncertainty for the burst localisation region for both long and short GRBs by a factor of \u0000${sim}5$\u0000 compared to the HERMES-TP/SP alone. Further improvements by an additional factor of 2 (or 4) can be achieved by launching an additional 4 (or 6) SpIRIT-like satellites into a Polar orbit, respectively, which would both increase the fraction of sky covered by multiple satellite elements, and also enable localisation of \u0000${geq} 60%$\u0000 of long GRBs to within a radius of \u0000${sim}1.5^{circ}$\u0000 (statistical uncertainty) on the sky, clearly demonstrating the value of a distributed all-sky high-energy transient monitor composed of nano-satellites.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"115 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2023-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89177883","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
K. Chand, Gopal-Krishna, A. Omar, H. Chand, P. Bisht
Abstract We examine the long-term stability (on decade-like timescales) of optical ‘high polarisation’ (HP) state with ${p_{opt}}$ ${> 3%}$ , which commonly occurs in flat-spectrum (i.e., beamed) radio quasars (FSRQs) and is a prominent marker of blazar state. Using this clue, roughly a quarter of the FSRQ population has been reported to undergo HP $leftrightarrow$ non-HP state transition on year-like timescales. This work examines the extent to which HP (i.e., blazar) state can endure in a FSRQ, despite these ‘frequent’ state transitions. This is the first attempt to verify, using purely opto-polarimetric data for a much enlarged sample of blazars, the recent curious finding that blazar state in individual quasars persists for at least a few decades, despite its changing/swinging observed fairly commonly on year-like timescales. The present analysis is based on a well-defined sample of 83 radio quasars, extracted from the opto-polarimetric survey RoboPol (2013–2017), for which old opto-polarimetric data taken prior to 1990 could be found in the literature. By a source-wise comparison of these two datasets of the same observable ( $p_{opt}$ ), we find that $sim$ 90% of the 63 quasars found in blazar state in our RoboPol sample, were also observed to be in that state about three decades before. On the other hand, within the RoboPol survey itself, we find that roughly a quarter of the blazars in our sample migrated to the other polarisation state on year-like timescales, by crossing the customary $p_{opt}$ = 3% threshold. Evidently, these relatively frequent transitions (in either direction) do not curtail the propensity of a radio quasar to retain its blazar (i.e., HP) state for at least a few decades. The observed transitions/swings of polarisation state are probably manifestation of transient processes, like ejections of synchrotron plasma blobs (VLBI radio knots) from the active nucleus.
摘要:我们用${p_{opt}}$${> 3%}$研究了光学“高偏振”(HP)状态的长期稳定性(在十年时间尺度上)，这种状态通常发生在平光谱(即波束)射电类星体(FSRQs)中，是耀变体状态的重要标志。利用这一线索，据报道，大约四分之一的FSRQ人群在类似年的时间尺度上经历了HP $leftrightarrow$非HP状态转变。这项工作考察了HP(即blazar)状态在FSRQ中可以忍受的程度，尽管存在这些“频繁”的状态转换。这是第一次尝试验证，使用纯粹的光学偏振数据，对一个大大扩大的耀变体样本，最近的奇怪发现，耀变体状态在单个类星体中至少持续了几十年，尽管它的变化/摆动在类似年的时间尺度上相当常见。目前的分析是基于一个定义明确的83个射电类星体样本，这些样本是从RoboPol(2013-2017)的光偏振调查中提取的，其中1990年之前的旧光偏振数据可以在文献中找到。通过对这两个相同可观测数据集($p_{opt}$)的源比较，我们发现$sim$ 90% of the 63 quasars found in blazar state in our RoboPol sample, were also observed to be in that state about three decades before. On the other hand, within the RoboPol survey itself, we find that roughly a quarter of the blazars in our sample migrated to the other polarisation state on year-like timescales, by crossing the customary $p_{opt}$ = 3% threshold. Evidently, these relatively frequent transitions (in either direction) do not curtail the propensity of a radio quasar to retain its blazar (i.e., HP) state for at least a few decades. The observed transitions/swings of polarisation state are probably manifestation of transient processes, like ejections of synchrotron plasma blobs (VLBI radio knots) from the active nucleus.
{"title":"The transience and persistence of high optical polarisation state in beamed radio quasars","authors":"K. Chand, Gopal-Krishna, A. Omar, H. Chand, P. Bisht","doi":"10.1017/pasa.2023.3","DOIUrl":"https://doi.org/10.1017/pasa.2023.3","url":null,"abstract":"Abstract We examine the long-term stability (on decade-like timescales) of optical ‘high polarisation’ (HP) state with \u0000${p_{opt}}$\u0000 \u0000${> 3%}$\u0000 , which commonly occurs in flat-spectrum (i.e., beamed) radio quasars (FSRQs) and is a prominent marker of blazar state. Using this clue, roughly a quarter of the FSRQ population has been reported to undergo HP \u0000$leftrightarrow$\u0000 non-HP state transition on year-like timescales. This work examines the extent to which HP (i.e., blazar) state can endure in a FSRQ, despite these ‘frequent’ state transitions. This is the first attempt to verify, using purely opto-polarimetric data for a much enlarged sample of blazars, the recent curious finding that blazar state in individual quasars persists for at least a few decades, despite its changing/swinging observed fairly commonly on year-like timescales. The present analysis is based on a well-defined sample of 83 radio quasars, extracted from the opto-polarimetric survey RoboPol (2013–2017), for which old opto-polarimetric data taken prior to 1990 could be found in the literature. By a source-wise comparison of these two datasets of the same observable ( \u0000$p_{opt}$\u0000 ), we find that \u0000$sim$\u0000 90% of the 63 quasars found in blazar state in our RoboPol sample, were also observed to be in that state about three decades before. On the other hand, within the RoboPol survey itself, we find that roughly a quarter of the blazars in our sample migrated to the other polarisation state on year-like timescales, by crossing the customary \u0000$p_{opt}$\u0000 = 3% threshold. Evidently, these relatively frequent transitions (in either direction) do not curtail the propensity of a radio quasar to retain its blazar (i.e., HP) state for at least a few decades. The observed transitions/swings of polarisation state are probably manifestation of transient processes, like ejections of synchrotron plasma blobs (VLBI radio knots) from the active nucleus.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"70 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2023-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89379935","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
K. Gab'anyi, S. Belladitta, S. Frey, G. Orosz, L. Gurvits, K. Rozgonyi, T. An, H. Cao, Z. Paragi, K. Perger
Abstract Active galactic nuclei (AGN) have been observed as far as redshift $z sim 7$ . They are crucial in investigating the early Universe as well as the growth of supermassive black holes at their centres. Radio-loud AGN with their jets seen at a small viewing angle are called blazars and show relativistic boosting of their emission. Thus, their apparently brighter jets are easier to detect in the high-redshift Universe. DES J014132.4–542749.9 is a radio-luminous but X-ray weak blazar candidate at $z = 5$ . We conducted high-resolution radio interferometric observations of this source with the Australian Long Baseline Array at $1.7$ and $8.5$ GHz. A single, compact radio-emitting feature was detected at both frequencies with a flat radio spectrum. We derived the milliarcsecond-level accurate position of the object. The frequency dependence of its brightness temperature is similar to that of blazar sources observed at lower redshifts. Based on our observations, we can confirm its blazar nature. We compared its radio properties with those of two other similarly X-ray-weak and radio-bright AGN, and found that they show very different relativistic boosting characteristics.
{"title":"Very long baseline interferometry observations of the high-redshift blazar candidate J0141–5427","authors":"K. Gab'anyi, S. Belladitta, S. Frey, G. Orosz, L. Gurvits, K. Rozgonyi, T. An, H. Cao, Z. Paragi, K. Perger","doi":"10.1017/pasa.2023.2","DOIUrl":"https://doi.org/10.1017/pasa.2023.2","url":null,"abstract":"Abstract Active galactic nuclei (AGN) have been observed as far as redshift \u0000$z sim 7$\u0000 . They are crucial in investigating the early Universe as well as the growth of supermassive black holes at their centres. Radio-loud AGN with their jets seen at a small viewing angle are called blazars and show relativistic boosting of their emission. Thus, their apparently brighter jets are easier to detect in the high-redshift Universe. DES J014132.4–542749.9 is a radio-luminous but X-ray weak blazar candidate at \u0000$z = 5$\u0000 . We conducted high-resolution radio interferometric observations of this source with the Australian Long Baseline Array at \u0000$1.7$\u0000 and \u0000$8.5$\u0000 GHz. A single, compact radio-emitting feature was detected at both frequencies with a flat radio spectrum. We derived the milliarcsecond-level accurate position of the object. The frequency dependence of its brightness temperature is similar to that of blazar sources observed at lower redshifts. Based on our observations, we can confirm its blazar nature. We compared its radio properties with those of two other similarly X-ray-weak and radio-bright AGN, and found that they show very different relativistic boosting characteristics.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"183 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2023-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75530332","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
K. Ross, C. Reynolds, N. Seymour, J. Callingham, N. Hurley-Walker, H. Bignall
Abstract Spectral variability offers a new technique to identify small scale structures from scintillation, as well as determining the absorption mechanism for peaked-spectrum (PS) radio sources. In this paper, we present very long baseline interferometry (VLBI) imaging using the long baseline array (LBA) of two PS sources, MRC 0225–065 and PMN J0322–4820, identified as spectrally variable from observations with the Murchison Widefield Array (MWA). We compare expected milliarcsecond structures based on the detected spectral variability with direct LBA imaging. We find MRC 0225–065 is resolved into three components, a bright core and two fainter lobes, roughly 430 pc projected separation. A comprehensive analysis of the magnetic field, host galaxy properties, and spectral analysis implies that MRC 0225–065 is a young radio source with recent jet activity over the last $10^2$ – $10^3$ yr. We find PMN J0322–4820 is unresolved on milliarcsecond scales. We conclude PMN J0322–4820 is a blazar with flaring activity detected in 2014 with the MWA. We use spectral variability to predict morphology and find these predictions consistent with the structures revealed by our LBA images.
{"title":"Milliarcsecond structures of variable-peaked spectrum sources","authors":"K. Ross, C. Reynolds, N. Seymour, J. Callingham, N. Hurley-Walker, H. Bignall","doi":"10.1017/pasa.2023.1","DOIUrl":"https://doi.org/10.1017/pasa.2023.1","url":null,"abstract":"Abstract Spectral variability offers a new technique to identify small scale structures from scintillation, as well as determining the absorption mechanism for peaked-spectrum (PS) radio sources. In this paper, we present very long baseline interferometry (VLBI) imaging using the long baseline array (LBA) of two PS sources, MRC 0225–065 and PMN J0322–4820, identified as spectrally variable from observations with the Murchison Widefield Array (MWA). We compare expected milliarcsecond structures based on the detected spectral variability with direct LBA imaging. We find MRC 0225–065 is resolved into three components, a bright core and two fainter lobes, roughly 430 pc projected separation. A comprehensive analysis of the magnetic field, host galaxy properties, and spectral analysis implies that MRC 0225–065 is a young radio source with recent jet activity over the last \u0000$10^2$\u0000 – \u0000$10^3$\u0000 yr. We find PMN J0322–4820 is unresolved on milliarcsecond scales. We conclude PMN J0322–4820 is a blazar with flaring activity detected in 2014 with the MWA. We use spectral variability to predict morphology and find these predictions consistent with the structures revealed by our LBA images.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"40 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2023-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82298570","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
K.E. Harborne, A. Serene, E.J.A. Davies, C. Derkenne, S. Vaughan, A.I. Burdon, C. del P Lagos, R. McDermid, S. O’Toole, C. Power, A.S.G. Robotham, G. Santucci, R. Tobar
Abstract In this work, we present a methodology and a corresponding code-base for constructing mock integral field spectrograph (IFS) observations of simulated galaxies in a consistent and reproducible way. Such methods are necessary to improve the collaboration and comparison of observation and theory results, and accelerate our understanding of how the kinematics of galaxies evolve over time. This code, SimSpin , is an open-source package written in R, but also with an API interface such that the code can be interacted with in any coding language. Documentation and individual examples can be found at the open-source website connected to the online repository. SimSpin is already being utilised by international IFS collaborations, including SAMI and MAGPI , for generating comparable data sets from a diverse suite of cosmological hydrodynamical simulations.
{"title":"SimSpin v2.6.0 - Constructing synthetic spectral IFU cubes for comparison with observational surveys","authors":"K.E. Harborne, A. Serene, E.J.A. Davies, C. Derkenne, S. Vaughan, A.I. Burdon, C. del P Lagos, R. McDermid, S. O’Toole, C. Power, A.S.G. Robotham, G. Santucci, R. Tobar","doi":"10.1017/pasa.2023.47","DOIUrl":"https://doi.org/10.1017/pasa.2023.47","url":null,"abstract":"Abstract In this work, we present a methodology and a corresponding code-base for constructing mock integral field spectrograph (IFS) observations of simulated galaxies in a consistent and reproducible way. Such methods are necessary to improve the collaboration and comparison of observation and theory results, and accelerate our understanding of how the kinematics of galaxies evolve over time. This code, SimSpin , is an open-source package written in R, but also with an API interface such that the code can be interacted with in any coding language. Documentation and individual examples can be found at the open-source website connected to the online repository. SimSpin is already being utilised by international IFS collaborations, including SAMI and MAGPI , for generating comparable data sets from a diverse suite of cosmological hydrodynamical simulations.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135358164","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
J. Tian, G. E. Anderson, A. J. Cooper, K. Gourdji, M. Sokolowski, A. Rowlinson, A. Williams, G. Sleap, D. Dobie, D. L. Kaplan, Tara Murphy, S. J. Tingay, F. H. Panther, P. D. Lasky, A. Bahramian, J. C. A. Miller-Jones, C. W. James, B. W. Meyers, S. J. McSweeney, P. J. Hancock
Abstract We present and evaluate the prospects for detecting coherent radio counterparts to gravitational wave (GW) events using Murchison Widefield Array (MWA) triggered observations. The MWA rapid-response system, combined with its buffering mode ( $sim$ 4 min negative latency), enables us to catch any radio signals produced from seconds prior to hours after a binary neutron star (BNS) merger. The large field of view of the MWA ( $sim$ $1,000,textrm{deg}^2$ at 120 MHz) and its location under the high sensitivity sky region of the LIGO-Virgo-KAGRA (LVK) detector network, forecast a high chance of being on-target for a GW event. We consider three observing configurations for the MWA to follow up GW BNS merger events, including a single dipole per tile, the full array, and four sub-arrays. We then perform a population synthesis of BNS systems to predict the radio detectable fraction of GW events using these configurations. We find that the configuration with four sub-arrays is the best compromise between sky coverage and sensitivity as it is capable of placing meaningful constraints on the radio emission from 12.6% of GW BNS detections. Based on the timescales of four BNS merger coherent radio emission models, we propose an observing strategy that involves triggering the buffering mode to target coherent signals emitted prior to, during or shortly following the merger, which is then followed by continued recording for up to three hours to target later time post-merger emission. We expect MWA to trigger on $sim$ $5-22$ BNS merger events during the LVK O4 observing run, which could potentially result in two detections of predicted coherent emission.
{"title":"MWA rapid follow-up of gravitational wave transients: Prospects for detecting prompt radio counterparts","authors":"J. Tian, G. E. Anderson, A. J. Cooper, K. Gourdji, M. Sokolowski, A. Rowlinson, A. Williams, G. Sleap, D. Dobie, D. L. Kaplan, Tara Murphy, S. J. Tingay, F. H. Panther, P. D. Lasky, A. Bahramian, J. C. A. Miller-Jones, C. W. James, B. W. Meyers, S. J. McSweeney, P. J. Hancock","doi":"10.1017/pasa.2023.49","DOIUrl":"https://doi.org/10.1017/pasa.2023.49","url":null,"abstract":"Abstract We present and evaluate the prospects for detecting coherent radio counterparts to gravitational wave (GW) events using Murchison Widefield Array (MWA) triggered observations. The MWA rapid-response system, combined with its buffering mode ( $sim$ 4 min negative latency), enables us to catch any radio signals produced from seconds prior to hours after a binary neutron star (BNS) merger. The large field of view of the MWA ( $sim$ $1,000,textrm{deg}^2$ at 120 MHz) and its location under the high sensitivity sky region of the LIGO-Virgo-KAGRA (LVK) detector network, forecast a high chance of being on-target for a GW event. We consider three observing configurations for the MWA to follow up GW BNS merger events, including a single dipole per tile, the full array, and four sub-arrays. We then perform a population synthesis of BNS systems to predict the radio detectable fraction of GW events using these configurations. We find that the configuration with four sub-arrays is the best compromise between sky coverage and sensitivity as it is capable of placing meaningful constraints on the radio emission from 12.6% of GW BNS detections. Based on the timescales of four BNS merger coherent radio emission models, we propose an observing strategy that involves triggering the buffering mode to target coherent signals emitted prior to, during or shortly following the merger, which is then followed by continued recording for up to three hours to target later time post-merger emission. We expect MWA to trigger on $sim$ $5-22$ BNS merger events during the LVK O4 observing run, which could potentially result in two detections of predicted coherent emission.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134979975","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
Garry Foran, Jeff Cooke, Naveen Reddy, Charles Steidel, Alice Shapley
Abstract High-redshift Lyman break galaxies (LBGs) are efficiently selected in deep images using as few as three broadband filters, and have been shown to have multiple intrinsic and small- to large-scale environmental properties related to Lyman- $alpha$ . In this paper we demonstrate a statistical relationship between net Lyman- $alpha$ equivalent width (net Ly $alpha$ EW) and the optical broadband photometric properties of LBGs at $zsim2$ . We show that LBGs with the strongest net Ly $alpha$ EW in absorption (aLBGs) and strongest net Ly $alpha$ EW in emission (eLBGs) separate into overlapping but discrete distributions in $(U_n-mathcal{R})$ colour and $mathcal{R}$ -band magnitude space, and use this segregation behaviour to determine photometric selection criteria by which sub-samples with a desired Ly $alpha$ spectral type can be selected using data from as few as three broadband optical filters. We propose application of our result to current and future large-area and all-sky photometric surveys that will select hundreds of millions of LBGs across many hundreds to thousands of Mpc, and for which spectroscopic follow-up to obtain Ly $alpha$ spectral information is prohibitive. To this end, we use spectrophotometry of composite spectra derived from a sample of 798 LBGs divided into quartiles on the basis of net Ly $alpha$ EW to calculate selection criteria for the isolation of Ly $alpha$ -absorbing and Ly $alpha$ -emitting populations of $zsim3$ LBGs using ugri broadband photometric data from the Vera Rubin Observatory Legacy Survey of Space and Time (LSST).
{"title":"Lyman-<i>α</i> at Cosmic Noon I: Ly<i>α</i> Spectral Type Selection of <i>z</i> ∼ 2 – 3 Lyman Break Galaxies with Broadband Imaging","authors":"Garry Foran, Jeff Cooke, Naveen Reddy, Charles Steidel, Alice Shapley","doi":"10.1017/pasa.2023.48","DOIUrl":"https://doi.org/10.1017/pasa.2023.48","url":null,"abstract":"Abstract High-redshift Lyman break galaxies (LBGs) are efficiently selected in deep images using as few as three broadband filters, and have been shown to have multiple intrinsic and small- to large-scale environmental properties related to Lyman- $alpha$ . In this paper we demonstrate a statistical relationship between net Lyman- $alpha$ equivalent width (net Ly $alpha$ EW) and the optical broadband photometric properties of LBGs at $zsim2$ . We show that LBGs with the strongest net Ly $alpha$ EW in absorption (aLBGs) and strongest net Ly $alpha$ EW in emission (eLBGs) separate into overlapping but discrete distributions in $(U_n-mathcal{R})$ colour and $mathcal{R}$ -band magnitude space, and use this segregation behaviour to determine photometric selection criteria by which sub-samples with a desired Ly $alpha$ spectral type can be selected using data from as few as three broadband optical filters. We propose application of our result to current and future large-area and all-sky photometric surveys that will select hundreds of millions of LBGs across many hundreds to thousands of Mpc, and for which spectroscopic follow-up to obtain Ly $alpha$ spectral information is prohibitive. To this end, we use spectrophotometry of composite spectra derived from a sample of 798 LBGs divided into quartiles on the basis of net Ly $alpha$ EW to calculate selection criteria for the isolation of Ly $alpha$ -absorbing and Ly $alpha$ -emitting populations of $zsim3$ LBGs using ugri broadband photometric data from the Vera Rubin Observatory Legacy Survey of Space and Time (LSST).","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"152 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135838444","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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