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Chinese Virtual Observatory. VO 应用 : 用星流研究银河系引力势. 杨阳 国家天文台. Outline. Scientific Background Practice with VO tools VO-DAS TOPCAT VO-DAS Application. Scientific Background. 恒星在银河系内的运动轨道由引力势决定 通过星流的运动轨迹,我们就可以估算出银河 系的引力势. 方法: 1 )在这个轨道上,我们选取 BHB (蓝水平分支

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Presentation Transcript
slide1

Chinese Virtual Observatory

VO应用:

用星流研究银河系引力势

杨阳

国家天文台

outline
Outline
  • Scientific Background
  • Practice with VO tools

VO-DAS

TOPCAT

  • VO-DAS Application

VO Tutorial @ CAS 2007

scientific background
Scientific Background

恒星在银河系内的运动轨道由引力势决定

通过星流的运动轨迹,我们就可以估算出银河

系的引力势

方法:

1)在这个轨道上,我们选取BHB(蓝水平分支

星)恒星

BHB恒星距离更容易确定

VO Tutorial @ CAS 2007

2 bhb
2)在双色图上确定多边形区域来选取BHB星的范围2)在双色图上确定多边形区域来选取BHB星的范围

BS

BHB

VO Tutorial @ CAS 2007

slide6
确定BHB范围:

0.8<=u-g<=1.2; -0.3<=g-r<=0

u-g>=3*(g-r)+1.8

u-g>=g-r+1.3

u-g>=-0.33*(g-r)+1.1

VO Tutorial @ CAS 2007

slide7
3)距离公式:

g0-Mg+5 = 5 ㏒10d

其中 g0:视星等

Mg:绝对星等 (取0.7mag)

d:距离

d=10^((g0-Mg+5)/5)

VO Tutorial @ CAS 2007

slide8
4)球面银道坐标到直角坐标系转换

银经(l),银纬(b),距离(d)

X=d*cos(l*π/180 )cos(b* π /180)-8000

Y=d*sin(l* π /180 )cos(b* π /180)

Z=d*sin(b* π /180)

VO Tutorial @ CAS 2007

slide9
5)可视化

VO Tutorial @ CAS 2007

practice
Practice

1)在VO-DAS中选出A型星

VO-DAS同步方式查出满足条件的银经、银纬、视星等、u波段和r波段数据

ADQL语句:

SELECT s.glon,s.glat,s.g,s.u,s.r

FROM SDSS:Star2 s

WHERE s.g>17.2 and s.g<20.2 and s.g-

s.r>=-0.3 and s.g-s.r<=0 and s.u-

s.g>=0.8 and s.u-s.g<=1.2

VO Tutorial @ CAS 2007

vo das gui
VO-DAS GUI客户端

VO Tutorial @ CAS 2007

vo das
VO-DAS查询数据结果

VO Tutorial @ CAS 2007

2 topcat
2)结果数据传送给TOPCAT

VO Tutorial @ CAS 2007

3 topcat bhb
3)TOPCAT中筛选出BHB星数据

u-4*g+3*r>=1.8 || u-2*g+r>=1.3 || u-0.67*g-0.33*r>=1.1

VO Tutorial @ CAS 2007

slide15
图示BHB
  • 添加g-r,u-g字段
  • 画密度图

VO Tutorial @ CAS 2007

slide16
4)坐标转换可视化

VO Tutorial @ CAS 2007

slide17
球面图

散点图

VO Tutorial @ CAS 2007

vo das application
VO-DAS Application
  • 客户端

GUI、Command Line、Web Browser

  • 查询方式

异步查询、同步查询

VO Tutorial @ CAS 2007

slide20
Thank you!

VO Tutorial @ CAS 2007