M31核心星團的高分辨率紫外與光學研究
發(fā)布時間：2018-12-21 15:12
【摘要】：我們利用哈勃空間望遠鏡(HST)的紫外與光學波段的圖像與光譜,對M31中心黑洞及其周圍幾個秒差距內(nèi)的恒星(即核心星團)進行研究。M31的核心區(qū)域,存在面亮度的雙峰分布,其中光學更亮的峰值被稱為P1,光學暗一些的峰值被稱為P2;而在紫外波段,P2的亮度超過P1。根據(jù)動力學信息的探測,人們發(fā)現(xiàn)超大質(zhì)量黑洞M31*位于P2的內(nèi)部。為了研究M31*的輻射和周圍核心星團的物理性質(zhì),我們做了以下工作。我們利用HST/COS的近紫外波段的圖像,對M31*進行了相距44天的兩次觀測。我們發(fā)現(xiàn),距離M31*中心0.1角秒的測光孔徑內(nèi),在紫外波段擁有(6.9±3.0)×10-18 erg·s-1·cm-2 A-1的流量差異。我們將M31*在X射線波段的光度外推到紫外波段,得到M31*的平均流量為1.7×10-18 erg·s-1·cm2·A-1。觀測得到的流量差異4倍于該平均流量,因此該差異很可能來自于中心黑洞的光度變化。我們利用HST/WFC3的從近紫外波段到近紅外波段共計10個圖像的數(shù)據(jù),對M31的核心星團進行了測光分析。我們發(fā)現(xiàn)P1內(nèi)部除了存在一個質(zhì)量為1.54-0.05+0.08×106 M& 的接近宇宙年齡、金屬豐度為2.5倍太陽豐度的年老星族成分以外,還有一個質(zhì)量為8.7-2.0+2.1×103M& 、年齡為468-14+57 Myr、金屬豐度接近太陽豐度的年輕星族成分。另外P2內(nèi)部也存在一個質(zhì)量為0.68-0.05+0.07×106M& 的同樣的老年成分,和一個質(zhì)量為5.9-0.9+1.3×103的、年齡為277-18+62 Myr、金屬豐度接近太陽豐度的年輕星族成分。我們通過計算得到,僅靠核區(qū)內(nèi)部的星風損失,恒星形成的時標超過宇宙年齡。因此這些年輕恒星不可能由本地恒星星風損失的氣體堆積形成,我們認為該年輕星族可能起源于外部氣體遷入后坍縮形成,或者在外部形成后遷移進入核區(qū)的。我們研究了 HST/COS獲得的M31核心星團的遠紫外光譜,這也是迄今為止在星系中心pc尺度上獲得的第一個遠紫外光譜。在1320A-1800A的范圍內(nèi),我們得出星族由117Myr和518Myr的兩個成分組成,該結(jié)果與SED測光分析結(jié)果相一致。而且我們發(fā)現(xiàn),光譜中的C Ⅳ吸收線(1548.20A/1550.77A)不是由恒星貢獻,而是由熱星系際介質(zhì)產(chǎn)生,其等值寬度為(2.14±0.12)A,計算出視線方向上CⅣV的柱密度為3.5×1014cm-2,氣體溫度為2×105K,并測算出視線方向上的總氣體柱密度為～1020cm-2。
[Abstract]:Using images and spectra of the ultraviolet and optical wavelengths of the Hubble Space Telescope (HST), we have studied the core region of M31, which is located within a few seconds of the distance between the M31 black hole and its surrounding stars (that is, the core star cluster). There is a bimodal distribution of surface luminance in which the brighter peak is called P1 and the optically darker peak is called P2. In the ultraviolet band, P2 is more luminous than that of P1. Based on the detection of dynamical information, supermassive black hole M 31 * is found to be located inside P2. In order to study the radiation of M 31 * and the physical properties of the surrounding core cluster, we have done the following. We have made two observations of M 31 * by using the near ultraviolet band image of HST/COS. We have found that the flow rate of (6.9 鹵3.0) 脳 10 ~ (-18) erg s ~ (-1) cm-2 A ~ (-1) is different in the ultraviolet band in the measurement aperture of 0.1 angle seconds from the center of M _ (31) *. We extrapolate the luminosity of M31 * in the X-ray band to the ultraviolet band, and obtain the average flux of M31 * is 1.7 脳 10-18 erg s-1 cm2 A-1. The observed flow difference is four times that of the average flow, so it is likely that the difference is due to the luminosity of the central black hole. The core cluster of M31 is analyzed by using the data of 10 images from near ultraviolet band to near infrared band of HST/WFC3. We find that there is an aged star family with a mass of 1.54-0.05 0.08 脳 106M& and a metal abundance of 2.5 times the solar abundance, in addition to a mass of 1.54-0.08 脳 106M-, which is close to the age of the universe. There is also a young star family with a mass of 8.7-2.0 2.1 脳 10 ~ 3M & and a metal abundance of 468-1457 Myr, close to the solar abundance. In addition, within P2 there is the same old age component with a mass of 0.68-0.05 0.07 脳 106M& and a mass of 5.9-0.9 1.3 脳 103, aged 277-18 62 Myr,. A group of young stars with a metallic abundance close to that of the sun. We have calculated that the time scale of star formation exceeds the cosmic age only by the loss of star wind in the nuclear region. Therefore, these young stars can not be formed by the local star wind loss gas accumulation. We believe that the young star family may have originated from the collapse of the external gas migration or migration into the nuclear region after the external formation. We have studied the far ultraviolet spectra of M31 core cluster obtained by HST/COS, which is the first far ultraviolet spectrum obtained so far on the pc scale of the galaxy center. In the range of 1320A-1800A, we obtain that the star family is composed of two components of 117Myr and 518Myr, and the results are in agreement with the results of SED photometry. Furthermore, we find that the absorption line C 鈪，
本文編號：2389081
[Abstract]:Using images and spectra of the ultraviolet and optical wavelengths of the Hubble Space Telescope (HST), we have studied the core region of M31, which is located within a few seconds of the distance between the M31 black hole and its surrounding stars (that is, the core star cluster). There is a bimodal distribution of surface luminance in which the brighter peak is called P1 and the optically darker peak is called P2. In the ultraviolet band, P2 is more luminous than that of P1. Based on the detection of dynamical information, supermassive black hole M 31 * is found to be located inside P2. In order to study the radiation of M 31 * and the physical properties of the surrounding core cluster, we have done the following. We have made two observations of M 31 * by using the near ultraviolet band image of HST/COS. We have found that the flow rate of (6.9 鹵3.0) 脳 10 ~ (-18) erg s ~ (-1) cm-2 A ~ (-1) is different in the ultraviolet band in the measurement aperture of 0.1 angle seconds from the center of M _ (31) *. We extrapolate the luminosity of M31 * in the X-ray band to the ultraviolet band, and obtain the average flux of M31 * is 1.7 脳 10-18 erg s-1 cm2 A-1. The observed flow difference is four times that of the average flow, so it is likely that the difference is due to the luminosity of the central black hole. The core cluster of M31 is analyzed by using the data of 10 images from near ultraviolet band to near infrared band of HST/WFC3. We find that there is an aged star family with a mass of 1.54-0.05 0.08 脳 106M& and a metal abundance of 2.5 times the solar abundance, in addition to a mass of 1.54-0.08 脳 106M-, which is close to the age of the universe. There is also a young star family with a mass of 8.7-2.0 2.1 脳 10 ~ 3M & and a metal abundance of 468-1457 Myr, close to the solar abundance. In addition, within P2 there is the same old age component with a mass of 0.68-0.05 0.07 脳 106M& and a mass of 5.9-0.9 1.3 脳 103, aged 277-18 62 Myr,. A group of young stars with a metallic abundance close to that of the sun. We have calculated that the time scale of star formation exceeds the cosmic age only by the loss of star wind in the nuclear region. Therefore, these young stars can not be formed by the local star wind loss gas accumulation. We believe that the young star family may have originated from the collapse of the external gas migration or migration into the nuclear region after the external formation. We have studied the far ultraviolet spectra of M31 core cluster obtained by HST/COS, which is the first far ultraviolet spectrum obtained so far on the pc scale of the galaxy center. In the range of 1320A-1800A, we obtain that the star family is composed of two components of 117Myr and 518Myr, and the results are in agreement with the results of SED photometry. Furthermore, we find that the absorption line C 鈪，
本文編號：2389081
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