This is a help page specific to using Colden online. For more information, please consult the CIAO colden help page here.

Input Coordinates

The user may enter the input coordinates or resolve a Target Name using the Resolve Name button.

Coordinate System

Select the coordinate system for specifying the column direction. Colden supports the following choices:

• Equatorial (B1950) - Equatorial w/ Besselian epoch B1950
• Equatorial (J2000) - Equatorial w/ Julian epoch J2000
• Equatorial (Xxxxx) - Equatorial w/ specified Besselian epoch or Julian epoch
• Galactic - Galactic
• Ecliptic (B1950) - Ecliptic w/ Besselian epoch B1950
• Ecliptic (Bxxxx) - Ecliptic w/ specified Besselian epoch

Equinox

Specify the epoch. This is enabled only if the selected Coordinate System is Equatorial(Xxxxx) or Ecliptic(Bxxxx).

Coordinates

Input a set of coordinates in the format of the selected coordinate system or resolve a target name which will set the RA/Dec coordinates in J2000. The supported coordinate ranges are listed below.

• EQUATORIAL - RA - Right Ascension, given in either sexagesimal or decimal format. Sexagesimal values are specified as "hh mm [ss[.ss]]" (that is, hours and minutes are required, seconds and fractions of seconds are optional). The range for RA is:
  Sexagesimal 00 00 00.00 to 24 00 00.00
  Decimal 00.00 to 360.00
  
• EQUATORIAL - Dec - Declination, given in either sexagesimal or decimal format. Sexagesimal values are specified as "sdd mm [ss[.ss]]". The range for Dec is:
  Sexagesimal -90 00 00.00 to 90 00 00.00
  Decimal -90.00 to 90.00
  
• GALACTIC - L2 - Longitude, given in either sexagesimal or decimal format. Sexagesimal values are specified as "hh mm [ss[.ss]]". The range for L2 is:
  Sexagesimal 00 00 00.00 to 24 00 00.00
  Decimal 00.00 to 360.00
  
• GALACTIC - B2 - Latitude, given in either sexagesimal or decimal format. Sexagesimal values are specified as "sdd mm [ss[.ss]]". The range for B2 is:
  Sexagesimal -90 00 00.00 to 90 00 00.00
  Decimal -90.00 to 90.00
  
• ECLIPTIC - EL - Ecliptic Longitude, given in either sexagesimal or decimal format. Sexagesimal values are specified as "hh mm [ss[.ss]]". The range for EL is:
  Sexagesimal 00 00 00.00 to 24 00 00.00
  Decimal 00.00 to 360.00
  
• ECLIPTIC - EB - Ecliptic Latitude, given in either sexagesimal or decimal format. Sexagesimal values are specified as "sdd mm [ss[.ss]]". The range for EB is:
  Sexagesimal -90 00 00.00 to 90 00 00.00
  Decimal -90.00 to 90.00
  

Target Name

Enter a valid target name and click the Resolve Name button. This will query the catalog[s] specified in the Name Resolver field. If one, and only one entry is found, the coordinates will be displayed in J2000. If no entry is found or more than one entry is retrieved, the user will be asked to modify the Target Name and try again.

Name Resolver

Name of the service or services that will be used to resolve the target name when the Resolve Name button is pressed. The services will be chosen in the specified order. For example, "NED/SIMBAD" will first search for the target name in NED and then, if the name was not found, in SIMBAD.

Dataset

Select the neutral hydrogen data set. Colden supports the following choices:

• NRAO - compilation by Dickey & Lockman; combines Bell data with other surveys for all sky coverage; not velocity- resolved, so does not support restricted velocity range (full range is -550 to 550 km/s)

  From the header of the NRAO data set:
  
  ORIGIN  = 'Dickey and Lockman, 1990, Annu. Rev. Astron. Astrophys., 28, 215'
  HISTORY --------------------------------------------------------------------
  HISTORY The data is from the CD-ROM "Images from the Radio Universe"
  HISTORY produced by NRAO in 1992.
  HISTORY The following surveys were merged and averaged over 1 X 1 degrees bins
  HISTORY Burton, W. B., te Lintel Hekkert, P. 1986, Astron. Astrophys. Suppl. 65:
  HISTORY 427-63
  HISTORY Cleary, M. N., Heiles, C., Haslam, C. G. T. 1979, Astron. Astrophys.
  HISTORY Suppl. 36: 95-127
  HISTORY Jahoda, K., Lockman, F. J., McCammon, D. 1990, Ap. J. 354: In Press
  HISTORY Kerr, F. J., Bowers, P. F., Jackson, P. D., Kerr, M. 1986, Astron.
  HISTORY Astrophys. Suppl. 66:373-504
  HISTORY Stark, A. A., Bally, J., Linke, R. A., Heiles, C. 1990:In Press
  HISTORY Weaver, R. Williams, D. R. W. 1973, Astron. Astrophys. Suppl. 8:1-503
  HISTORY --------------------------------------------------------------------
  

• Bell - Bell Labs H1 Survey (Tony Stark et al.); northern sky (to 40 degrees south) only; velocity-resolved spectra

  The Bell dataset is a privately distributed (by Tony Stark) dataset made
  available to the Einstein team in 1984; it is an earlier reduction of the 
  data published in Stark et al 1992 ApJS 79. 77
  

Velocity Range

The Bell data set supports integrating over the full range of velocities (-550. to 550. km/s) or over a restricted range. The Bell data have a velocity resolution of about 5 km/s. Specify the range of velocities.

Results

Galactic L2

Longitude in Galactic coordinate system, in decimal degrees (ddd.dddd).

B2

Latitude in Galactic coordinate system, in decimal degrees (sdd.dddd)

NH

The neutral hydrogen column density, in units of 1e+20 per cm**2.

Comments

Auxiliary explanatory comments about the computation are provided.

• (Interpolated) - Value interpolated from four nearest measurement directions
• (At target) - Measurement in exactly the specified column direction
• (At closest point) - Measurement in observed direction closest to the specified column direction; the specified direction does not have four nearest measurement directions suitable for interpolation
• (Gain uncertain) - Specified column direction is less than 0.2 deg from the equator (B1950); measurements near the equator in the Stark et al. ("Bell") survey (ApJ Suppl. 79, p77, 1992) may suffer from large gain fluctuations
• (Too far south) - No value computed -- Specified column direction is at least 40.0 deg south of the equator (B1950); the Stark et al. ("Bell") survey (ApJ Suppl. 79, p77, 1992) used a Northern Hemisphere telescope