Journal of Astrophysics and Astronomy最新文献_第3页

A detailed study of dwarf galaxies in the core of the Coma Cluster 对科马星系团核心矮星系的详细研究

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-07-31 DOI: 10.1007/s12036-024-10010-2

Nagamani Poloji, Priya Hasan, S. N. Hasan

{"title":"A detailed study of dwarf galaxies in the core of the Coma Cluster","authors":"Nagamani Poloji, Priya Hasan, S. N. Hasan","doi":"10.1007/s12036-024-10010-2","DOIUrl":"10.1007/s12036-024-10010-2","url":null,"abstract":"<div>In an earlier paper, we determined the morphological types of galaxies in the Coma Cluster using data from the HST/ACS Coma Cluster treasury survey. Of the 132 members, 51 are non-dwarfs and 81 are dwarfs. We define dwarfs to have an absolute luminosity (M_{textrm{F814W}}ge -18.5) as in Marinova et al. (2012). In this paper, we identify the morphological types of these dwarf galaxies and conduct a detailed study of their properties. Using GALFIT, we determined the structural properties of our sample, and with spectroscopic redshifts, we determined memberships and distances to identify dwarfs. A visual examination of the residual images reveals that our sample of 78 dwarf galaxies comprises dwarf lenticular (dS0) 22%, dwarf elliptical (dE) 69%, dwarf spirals (dSp) 4%, dwarf ring (dring) 1%, dwarf barred spirals (dSBp) 3% and dwarf irregular (dIrr) 1% galaxies. The bulge-disk decomposition (Sérsic (+) exponential) fits are only good for the dS0 galaxies. The remainder of the sample gives good fits only for single Sérsic fits. The color-magnitude relation (CMR) shows that the dEs are redder and fainter than the rest of the sample (except one dIrr galaxy). The Kormendy relation reveals that dE galaxies have lower surface brightness than the rest of the sample. Our research leads us to conclude that dwarf galaxies appear to have a different formation and evolution process than non-dwarf galaxies.\u0000</div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"45 2","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141862888","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

引用次数: 0

Herschel investigation of cores and filamentary structures in L1251 located in the Cepheus flare 赫歇尔对位于仙王座耀斑中的 L1251 的核心和丝状结构的研究

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-06-18 DOI: 10.1007/s12036-024-10004-0

Divyansh Dewan, Archana Soam, Guo-Yin Zhang, Akhil Lasrado, Saikhom Pravash Singh, Chang Won LEE

{"title":"Herschel investigation of cores and filamentary structures in L1251 located in the Cepheus flare","authors":"Divyansh Dewan, Archana Soam, Guo-Yin Zhang, Akhil Lasrado, Saikhom Pravash Singh, Chang Won LEE","doi":"10.1007/s12036-024-10004-0","DOIUrl":"10.1007/s12036-024-10004-0","url":null,"abstract":"<div>Molecular clouds are the prime locations of star formation. These clouds contain filamentary structures and cores which are crucial in the formation of young stars. In this work, we aim to quantify the physical properties of structural characteristics within the molecular cloud L1251 to better understand the initial conditions for star formation. We applied the getsf algorithm to identify cores and filaments within the molecular cloud L1251 using the Herschel multi-band dust continuum image, enabling us to measure their respective physical properties. Additionally, we utilized an enhanced differential term algorithm to produce high-resolution temperature maps and column density maps with a resolution of ({13.5}''). We identified 122 cores in the region. Of those, 23 are protostellar cores, 13 are robust prestellar cores, 32 are candidate prestellar cores (including 13 robust prestellar cores and 19 strictly candidate prestellar cores), and 67 are unbound starless cores. getsf also found 147 filament structures in the region. Statistical analysis of the physical properties (mass (M), temperature (T), size and core brightness (hereafter, we are using the word luminosity (L)) for the core brightness) of obtained cores shows a negative correlation between core mass and temperature and a positive correlation between (M/L) and (M/T). Analysis of the filaments gives a median width of 0.14 pc and no correlation between width and length. Out of those 122 cores, 92 are present in filaments ((sim ) 75.4%) and the remaining were outside them. Out of the cores present in filaments, 57 ((sim ) 62%) cores are present in supercritical filaments ((M_textrm{line}>16 M_{odot }/textrm{pc})).</div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"45 2","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141501905","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

引用次数: 0

A new solution of Einstein’s field equations in isotropic coordinates 各向同性坐标下爱因斯坦场方程的新解

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-06-13 DOI: 10.1007/s12036-024-10006-y

B. S. Ratanpal, BHAVESH Suthar

引用次数: 0

Turbulence and magnetic fields in star formation 恒星形成过程中的湍流和磁场

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-06-04 DOI: 10.1007/s12036-024-10005-z

Archana Soam, Chakali Eswaraiah, Amit Seta, Lokesh Dewangan, G. Maheswar

{"title":"Turbulence and magnetic fields in star formation","authors":"Archana Soam, Chakali Eswaraiah, Amit Seta, Lokesh Dewangan, G. Maheswar","doi":"10.1007/s12036-024-10005-z","DOIUrl":"10.1007/s12036-024-10005-z","url":null,"abstract":"<div>Molecular clouds are prime locations to study the process of star formation. These clouds contain filamentary structures and cores, which are crucial sites for the formation of young stars. The star-formation process has been investigated using various techniques, including polarimetry, for tracing magnetic fields. In this small review-cum-short report, we put together the efforts (mainly from the Indian community) to understand the roles of turbulence and magnetic fields in star formation. These are two components of the ISM competing against gravity, which is primarily responsible for the collapse of gas to form stars. We also include attempts made using simulations of molecular clouds to study this competition. Studies on feedback and magnetic fields are combined and listed to understand the importance of the interaction between two energies in setting the current observed star formation efficiency. We have listed available and upcoming facilities with the polarization capabilities needed to trace magnetic fields. We have also stated the importance of ongoing and desired collaborations between Indian communities and facilities abroad to shed more light on the roles of turbulence and magnetic fields in the process of star formation.</div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"45 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141253844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

引用次数: 0

SolarAccel: FPGA accelerated 2D cross-correlation of digital images: Application to solar adaptive optics SolarAccel：FPGA 加速数字图像的二维交叉相关：应用于太阳能自适应光学

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-05-23 DOI: 10.1007/s12036-024-10003-1

Soham Das, Nanditha Rao, D. V. S. Phanindra, Sridharan Rengaswamy

{"title":"SolarAccel: FPGA accelerated 2D cross-correlation of digital images: Application to solar adaptive optics","authors":"Soham Das, Nanditha Rao, D. V. S. Phanindra, Sridharan Rengaswamy","doi":"10.1007/s12036-024-10003-1","DOIUrl":"10.1007/s12036-024-10003-1","url":null,"abstract":"<div>The cross-correlation of two-dimensional digital images is fundamental to solar adaptive optics computations. It can be used in a simple tip-tilt correction system to identify the relative shift between consecutive images and correlating sub-aperture images of a Shack–Hartmann wave-front sensor. The typical frequency of computation is about 1 kHz. While the software-based optimized cross-correlations may be sufficient when a small number of sub-apertures are used in a wave-front sensor, hardware-accelerated (FPGA), correlations may be required when a large number of sub-aperture images are involved, e.g., in the case of the proposed National Large Solar Telescope in India. This paper presents SolarAccel: An FPGA-based acceleration of a basic two-dimensional cross-correlation of two images. We accelerate the FPGA-based design by pipelining the individual components of the cross-correlation process. We implemented our RTL logic on a few sets of (128times 128) pixel images and (32times 32) pixel images on a Xilinx Zynq Ultrascale(+) MPSoC on the ZCU104 FPGA evaluation platform. SolarAccel performs a 2D FFT on a (128times 128) image faster than existing work. The cross-correlation on a (32times 32) image is also faster than the existing work. This demonstrates that FPGA acceleration is beneficial in solar adaptive optics applications.</div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"45 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141106711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

引用次数: 0

Searching for wide binary stars with non-coeval components in the northern sky 在北部天空寻找具有非同步成分的宽双星

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-05-13 DOI: 10.1007/s12036-024-10002-2

Oleg Malkov, Alexey Kniazev, Stanislav Gorda

引用次数: 0

Extreme value theory applied to long-term sunspot areas 应用于长期太阳黑子区域的极值理论

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-05-03 DOI: 10.1007/s12036-024-09999-3

Rui Zhang, Yan-Qing Chen, Shu-Guang Zeng, Sheng Zheng, Yan-Shan Xiao, Lin-Hua Deng, Xiang-Yun Zeng, Yao Huang

{"title":"Extreme value theory applied to long-term sunspot areas","authors":"Rui Zhang, Yan-Qing Chen, Shu-Guang Zeng, Sheng Zheng, Yan-Shan Xiao, Lin-Hua Deng, Xiang-Yun Zeng, Yao Huang","doi":"10.1007/s12036-024-09999-3","DOIUrl":"10.1007/s12036-024-09999-3","url":null,"abstract":"<div>Solar activity, such as sunspots and flares, has a great impact on humans, living beings, and technologies in the whole world. Changes in sunspots will influence high-frequency and space-navigation radio communications. Based on the full-disk, southern and northern hemispheres sunspot areas (SAs) data in 1874–2023 from the Royal Observatory, Greenwich (RGO) USAF/NOAA, extreme value theory (EVT) is applied to predict the trend of the 25th and 26th solar cycles (SCs) in this work. Two methods with EVT, the block maxima (BM) approach and the peaks-over-threshold (POT) approach, are employed to research solar extreme events. The former method focuses on each block’s maximum sunspot areas value and is applied for the generalized extreme value (GEV) distribution. The latter method aims to select the extreme values exceeding a threshold value and is used to obtain the generalized Pareto (GP) distribution. It is the first time that the EVT is applied on the sunspot areas data from the Royal Observatory, Greenwich (RGO) USAF/NOAA. The analysis indicates that the estimated 8-year return levels for sunspot areas are 5701 and 6258 using the two methods, while the estimated 19-year return levels are all 7165. This suggests that the trends of the 25th and 26th solar cycles will be stronger than that of the 24th solar cycle.</div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"45 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140883753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

引用次数: 0

Study of magnetic field evolution by Weibel instability in counter-streaming electron–positron plasma flows 逆流电子-正电子等离子体流中魏伯尔不稳定性引起的磁场演化研究

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-04-02 DOI: 10.1007/s12036-024-10001-3

Rakesh Kumar, Hitendra K. Malik, Sandeep Kumar

{"title":"Study of magnetic field evolution by Weibel instability in counter-streaming electron–positron plasma flows","authors":"Rakesh Kumar, Hitendra K. Malik, Sandeep Kumar","doi":"10.1007/s12036-024-10001-3","DOIUrl":"10.1007/s12036-024-10001-3","url":null,"abstract":"<div>Collisionless shocks are generated via the magnetic field mediated by Weibel instability in astrophysical systems. In this work, by performing particle-in-cell (PIC) simulations, Weibel instability-mediated magnetic field amplification is investigated for initially unmagnetized, spatially uniform, counter-streaming electron–positron (e−/e+) plasma flows and compared with the magnetic amplification for nonuniform counter-streaming e−/e+ plasma flows by considering their drift velocity of (0.5 c). Our simulation results show that initially, the magnetic field grows exponentially in the linear regime and then decays further after saturation for homogeneous e−/e+ plasma flows. However, in the case of inhomogeneous counter-streaming e−/e+ plasma flow, the magnetic field re-amplifies in the post-saturation region after the first saturation. It is found that the amplification magnitude of magnetic field energy in the post-saturation region is related to the density fluctuations for upstream plasma. Our calculations show that temperature anisotropy is the reason behind the second saturation of the magnetic field energy in the case of inhomogeneous plasma distribution. Such inhomogeneous media in astrophysical systems like Gamma-ray bursts are common. Therefore, this study will be useful for understanding collisionless shocks' formation and their effects.</div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"45 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140580620","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

引用次数: 0

In-situ acceleration of radio-emitting particles in the lobes of radio galaxies: Evolving observational perspective and recent clues 射电星系裂片中射电发射粒子的原位加速：不断发展的观测视角和最新线索

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-04-01 DOI: 10.1007/s12036-024-10000-4

Gopal-Krishna, Paul J. Wiita

引用次数: 0

Long-term spectroscopic monitoring of comet 46P/Wirtanen 对 46P/Wirtanen 彗星的长期光谱监测

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-03-16 DOI: 10.1007/s12036-024-09996-6

K. Aravind, Kumar Venkataramani, Shashikiran Ganesh, Emmanuel Jehin, Youssef Moulane

{"title":"Long-term spectroscopic monitoring of comet 46P/Wirtanen","authors":"K. Aravind, Kumar Venkataramani, Shashikiran Ganesh, Emmanuel Jehin, Youssef Moulane","doi":"10.1007/s12036-024-09996-6","DOIUrl":"10.1007/s12036-024-09996-6","url":null,"abstract":"<div>Jupiter family comets, having an orbital period <20 years, allow us to observe their activity and analyze the homogeneity in their coma composition over multiple apparitions. Comet 46P/Wirtanen, with its exceptionally close approach to Earth during its 2018 apparition, offered the possibility for long-term spectroscopic observations. We used a 1.2 m telescope equipped with a low-resolution spectrograph to monitor the comet’s activity and compute the relative abundances in the coma as a function of heliocentric distance. We report the production rates of four molecules CN, C(_2), C(_3) and NH(_2,) and Af(rho ) parameter, a proxy to the dust production, before and after perihelion. We found that 46P has a typical coma composition with almost constant abundance ratios with respect to CN across the epochs of observation. Comparing the coma composition of comet 46P during the current and previous apparitions, we conclude the comet has a highly homogeneous chemical composition in the nucleus with an enhancement in ammonia abundance compared to the average abundance in comets.</div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"45 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140151399","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}

引用次数: 0