• 천문학회보
• /
• 제26권1호
• /
• pp.23.1-23.1
• /
• 2001

• 천문학회보
• /
• 제31권2호
• /
• pp.70.1-70.1
• /
• 2006

• 천문학회지
• /
• 제36권1호
• /
• pp.43-48
• /
• 2003

We introduce and describe performance of the 6-meter telescope of Seoul Radio Astronomy Observatory (SRAO). All the softwares and instruments except the antenna structure and its driving system are developed for ourselves. The SIS mixer type receiver resulted in the receiver noise temperature less than 50 K (DSB) over the whole 3-mm radio window. An autocorrelation spectrometer, developed first in Korea, provides maximum 50 MHz band width over 1024 channels. Antenna surface is measured and adjusted using template method and radio holography which resulted in a superb surface accuracy bet-ter than 30${\mu}m$. Accordingly, the aperture and beam efficiences amount to $70\%$ and $75\%$, respectively, largely independent of frequency in the 85 - 115 GHz range. It is also found that telescope pointing errors are less than 10" in both azimuth and elevation and that antenna gain is almost constant against elevation greater than $20^{\circ}$, without adjusting sub-reflector position. The SRAO 6-meter telescope is now fully operational and all these characteristics verify that observations are carried out with high precision and fidelity.

• 천문학회보
• /
• 제40권1호
• /
• pp.50.3-50.3
• /
• 2015

서울전파천문대(Seoul Radio Astronomy Observatory; SRAO)는 서울대학교 물리 천문학부(천문 전공)이 교내에 설치 운영하고 있는 전파천문대로서, 지름 6미터의 안테나와 밀리미터파 수신기를 갖추고 있다. 전파망원경은 1999년 10월에 설치를 시작한 후 1년 반만인 2001년 3월 8일에 완공되어 '최초의 전파'를 검출하였다. 안테나 조립에서부터 수신기 개발까지 대부분의 일이 대학원생들에 의해 이루어졌다는 점에서 유일무이한 전파망원경이다. 2002년 4월 2일에는 관측소를 완공하고 SRAO의 개관식을 가졌다. 설치 초기에는 85-115GHz 수신용 SIS 수신기와 최대 대역폭 50MHz의 1024채널 자기상관 분광기 등을 갖추었으며, 이후 관련 기술 개발을 지속적으로 추진하여 2002년 홀로그래피 방법을 이용해서 경면 정밀도를 90마이크론 수준으로 향상시켰으며, 2003년에는 230GHz 대역용 수신기 개발에 착수하고 2008년 완성하여 우리나라에서 처음으로 230GHz대역 전파 창을 개척하였다. 운영 초기부터 공동 활용을 도모하여 서울대학교의 학생, 교수뿐만 아니라 국내외의 다른 대학, 연구소의 연구자들에게도 시간을 할애하였다. 지난 10여년간 학술지에 약 25편의 논문을 게재하였고, 관측과 기기개발을 주제로 약 12명의 석박사를 배출하였다. 서울대학교 전파망원경은 국내 대학이 보유한 연구용 장비로는 그동안 가장 경쟁력이 있는 장비로 자리매김을 하였고, 천문기기분야의 후진을 양성하는데 중요한 기여를 하였다.

• 천문학회보
• /
• 제43권2호
• /
• pp.52.1-52.1
• /
• 2018

Orion Molecular Clouds Complex(OMC) 분자운에는 별 생성은 없으면서 은하면 방향으로 누워있는 큰 규모($10^{\circ}{\times}0.5^{\circ}$)의 필라멘트 구조가 있다. 본 연구는 북쪽 필라멘트(이하 NF)를 대상으로 12CO (J = 1-0) 선 관측 데이터를 이용하여 필라멘트의 운동학적 연구를 수행함으로서 은하면과의 상관관계를 알아보고자 하였다. 관측은 공간분해능은 2 arcmin인 SRAO(Seoul Radio Astronomy Observatory)의 6m 밀리미터 망원경이 사용되었고 큰 규모로 인해 은하면으로부터 먼 순서로 NF1, NF2, NF3 세 곳으로 관측 지역이 정해졌다. 연구결과 필라멘트는 매우 낮은 수준의 12CO (J = 2-1)과 티끌 분포에서 자기장을 따라 은하면 방향으로 연계되어 보였다. 밀도 분포에서는 SRAO 12CO (J = 1-0) 적분강도와 Planck 위성의 12CO (J = 2-1)과 티끌 자료를 이용했을 때, 12CO와 성간 티끌은 주로 은하면에 수직인 방향에서 밀도가 높았다. 속도 분포와 위치 속도 분석을 통해 NF는 단일 구조의 분자운 형태이고 NF2 하단에서는 회전 운동의 가능성이 확인되었다. NF3는 자기장에 의해 생성된 나선형 회전을 하고 있으며, NF2와 NF3를 따라 은하면을 향하여 12CO (J = 1-0)를 비롯한 물질이 흐르고 있음도 확인되었다. 하지만 은하면을 향하여 물질이 흐르는 원인을 제공하는 천체가 무엇인지와 NF1과 NF2 상단의 회전 운동은 확인 할 수 없었으며 이들 지역에 대한 상세한 관측이 요구된다.

• 천문학회지
• /
• 제46권2호
• /
• pp.65-74
• /
• 2013

We probe the feasibility of high-frequency radio observations of very rapid flux variations in compact active galactic nuclei (AGN). Our study assumes observations at 230GHz with a small 6-meter class observatory, using the SNU Radio Astronomical Observatory (SRAO) as an example. We find that 33 radio-bright sources are observable with signal-to-noise ratios larger than ten. We derive statistical detection limits via exhaustive Monte Carlo simulations assuming (a) periodic, and (b) episodic flaring flux variations on time-scales as small as tens of minutes. We conclude that a wide range of flux variations is observable. This makes high-frequency radio observations-even with small observatories-a powerful probe of AGN intra-day variability; especially, those which complement observations at lower radio frequencies with larger observatories like the Korean VLBI Network (KVN).

• 천문학회보
• /
• 제38권1호
• /
• pp.51.2-51.2
• /
• 2013

We present observational results of CO outflows towards 24 embedded young stellar objects (YSOs), which are selected from the targets of the Herschel key program, "Dust, Ice, and Gas in Time" (DIGIT). Molecular outflow activity, which is believed to have strong dependence on accretion process, is the most powerful in the early embedded phase of star formation and declines as the central protostars evolve to the main sequence stage. In order to study the relation between the CO outflows observed in low J transitions and the properties of protostars, we mapped the CO outflows of the selected targets in J=1-0 and J=2-1 with the 14-m TRAO telescope and the 6-m SRAO telescope, respectively. We also compare the CO outflow momentum fluxes with the FIR molecular line luminosities of CO, $H_2O$, OH, and OI, which were detected by the Herschel-PACS observations.

• 천문학회보
• /
• 제38권1호
• /
• pp.44.2-44.2
• /
• 2013

We probe the feasibility of high-frequency radio observations of very rapid flux variations in compact active galactic nuclei (AGN). Our study assumes observations at 230 GHz with a small 6-meter class observatory, using the SNU Radio Astronomical Observatory (SRAO) as example. We find that 33 radio-bright sources are observable with signal-to-noise ratios larger than ten. We derive statistical detection limits via exhaustive Monte Carlo simulations assuming (a) periodic, and (b) episodic flaring flux variations on time-scales as small as tens of minutes. We conclude that a wide range of flux variations is observable. This makes high-frequency radio observations - even with small observatories - a powerful probe of AGN intra-day variability; especially, those observations complement observations at lower radio frequencies with larger observatories like the Korean VLBI Network (KVN).

• Journal of Astronomy and Space Sciences
• /
• 제23권3호
• /
• pp.269-288
• /
• 2006

We revised the OTFTOOL which was developed in Five College Radio Astronomy Observatory (FCRAO) for the On-The-Fly (OTF) observation. Besides the improvement of data resampling function of conventional OTFTOOL, we added a new SELF referencing mode and data pre-reduction function. Since OTF observation data have a large redundancy, we can choose and use only good quality samples excluding bad samples. Sorting out the bad samples is based on the floating level, rms level, antenna trajectory, elevation, $T_{sys}$, and number of samples. And, spikes are also removed. Referencing method can be chosen between CLASSICAL mode in which the references are taken from the OFFs observation and ELLIPSOIDAL mode in which the references are taken from the inner source free region (this is named as SELF reference). Baseline is subtracted with the source free channel windows and the baseline order chosen by the user. Passing through these procedures, the raw OTF data will be an FITS datacube. The revised-OTFTOOL maximizes the advantages of OTF observation by sorting out the bad samples in the earliest stage. And the new self-referencing method, the ELLIPSOIDAL mode, is very powerful to reduce the data. Moreover since it is possible to see the datacube at once without moving them into other data reduction programs, it is very useful and convenient to check whether the data resampling works well or not. We expect that the revised-OTFTOOL can be applied to the facilities of the OTF observation like SRAO, NRAO, and FCRAO.

• 천문학회보
• /
• 제35권1호
• /
• pp.60.1-60.1
• /
• 2010

Methanol maser sources are believed to represent the earliest evolutionary stage of massive star formation. Pandian et al. (2007) recently made a very sensitive blind survey of 6.7GHz ClassII methanol maser towards the Galacitic midplane ($35^{\circ}$<1<$55^{\circ}$ & |b|<$0.5^{\circ}$) and found 86 maser sources. We carried out 22GHz $H_2O$ and 44.0 GHz $CH_3OH$ maser line surveys of them with KVN 21m and various (CO (2-1), $^{13}CO$ (2-1), $^{13}CO$ (1-0), $C^{18}O$ (2-1), CS (2-1), $HCO^+$ (3-2) and HCN (3-2)) molecular line surveys with SRAO 6m and TRAO 14m. we will present the preliminary results and discuss the implications for massive star formation.