分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The role of HI content in galaxy interactions is still under debate. To study the HI content of galaxy pairs at different merging stages, we compile a sample of 66 major-merger galaxy pairs and 433 control galaxies from the SDSS-IV MaNGA IFU survey. In this study, we adopt kinematic asymmetry as a new effective indicator to describe the merging stage of galaxy pairs. With archival data from the HI-MaNGA survey and new observations from the Five-hundred-meter Aperture Spherical Radio Telescope (FAST), we investigate the differences in HI gas fraction ($f_{\text{HI}}$), star formation rate (SFR), and HI star formation efficiency ($\rm SFE_{\text{HI}}$) between the pair and control samples. Our results suggest that the HI gas fraction of major-merger pairs on average is marginally decreased by $\sim 15\%$ relative to isolated galaxies, implying mild HI depletion during galaxy interactions. Compared to isolated galaxies, pre-passage paired galaxies have similar $f_{\text{HI}}$, SFR and $\rm SFE_{\text{HI}}$, while pairs during pericentric passage have weakly decreased $f_{\text{HI}}$ ($-0.10\pm0.05$ dex), significantly enhanced SFR ($0.42\pm0.11$ dex) and $\rm SFE_{\text{HI}}$ ($0.48\pm0.12$ dex). When approaching the apocenter, paired galaxies show marginally decreased $f_{\text{HI}}$ ($-0.05\pm0.04$ dex), comparable SFR ($0.04\pm0.06$ dex) and $\rm SFE_{\text{HI}}$ ($0.08\pm0.08$ dex). We propose the marginally detected HI depletion may originate from the gas consumption in fuelling the enhanced $\rm H_2$ reservoir of galaxy pairs. In addition, new FAST observations also reveal an HI absorber ($N_{\text{HI}}\sim 4.7 \times 10^{21} \text{ cm}^{-2}$), which may suggest gas infalling and the triggering of AGN activity.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Tuan Yi
Wei-Min Gu
Zhi-Xiang Zhang
Ling-Lin Zheng
Mouyuan Sun
Junfeng Wang
Zhongrui Bai
Pei Wang
Jianfeng Wu
Yu Bai
Song Wang
Haotong Zhang
Yize Dong
Yong Shao
Xiang-Dong Li
Jia Zhang
Yang Huang
Fan Yang
Qingzheng Yu
Hui-Jun Mu
摘要： Optical time-domain surveys can unveil and characterize exciting but less-explored non-accreting and/or non-beaming neutron stars (NS) in binaries. Here we report the discovery of such a NS candidate using the LAMOST spectroscopic survey. The candidate, designated LAMOST J112306.9+400736 (hereafter J1123), is in a single-lined spectroscopic binary containing an optically visible M star. The star's large radial velocity variation and ellipsoidal variations indicate a relatively massive unseen companion. Utilizing follow-up spectroscopy from the Palomar 200-inch telescope and high-precision photometry from TESS, we measure a companion mass of $1.24_{-0.03}^{+0.03}~M_{\odot}$. Main-sequence stars with this mass are ruled out, leaving a NS or a massive white dwarf (WD). Although a massive WD cannot be ruled out, the lack of UV excess radiation from the companion supports the NS hypothesis. Deep radio observations with FAST yielded no detections of either pulsed or persistent emission. J1123 is not detected in numerous X-ray and gamma-ray surveys. These non-detections suggest that the NS candidate is not presently accreting and pulsing. Our work exemplifies the capability of discovering compact objects in non-accreting close binaries by synergizing the optical time-domain spectroscopy and high-cadence photometry.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Tuan Yi
Wei-Min Gu
Zhi-Xiang Zhang
Ling-Lin Zheng
Mouyuan Sun
Junfeng Wang
Zhongrui Bai
Pei Wang
Jianfeng Wu
Yu Bai
Song Wang
Haotong Zhang
Yize Dong
Yong Shao
Xiang-Dong Li
Jia Zhang
Yang Huang
Fan Yang
Qingzheng Yu
Hui-Jun Mu
摘要： Optical time-domain surveys can unveil and characterize exciting but less-explored non-accreting and/or non-beaming neutron stars (NS) in binaries. Here we report the discovery of such a NS candidate using the LAMOST spectroscopic survey. The candidate, designated LAMOST J112306.9+400736 (hereafter J1123), is in a single-lined spectroscopic binary containing an optically visible M star. The star's large radial velocity variation and ellipsoidal variations indicate a relatively massive unseen companion. Utilizing follow-up spectroscopy from the Palomar 200-inch telescope and high-precision photometry from TESS, we measure a companion mass of $1.24_{-0.03}^{+0.03}~M_{\odot}$. Main-sequence stars with this mass are ruled out, leaving a NS or a massive white dwarf (WD). Although a massive WD cannot be ruled out, the lack of UV excess radiation from the companion supports the NS hypothesis. Deep radio observations with FAST yielded no detections of either pulsed or persistent emission. J1123 is not detected in numerous X-ray and gamma-ray surveys. These non-detections suggest that the NS candidate is not presently accreting and pulsing. Our work exemplifies the capability of discovering compact objects in non-accreting close binaries by synergizing the optical time-domain spectroscopy and high-cadence photometry.
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