NAME

Astro::Misc - Miscellaneous astronomical routines

SYNOPSIS

use Astro::Misc;

$U = calc_U($flux, $dist, $freq);
($dist1, $dist2)= kindist($ra, $dec, $vel, $epoch, $model);

DESCRIPTION

Astro::Misc contains an assorted set Perl routines for doing various astronomical calculations.

AUTHOR

Chris Phillips Chris.Phillips@csiro.au

FUNCTIONS

read_possm

Read_possm interprets the output file from the AIPS POSSM task.
the task may be called repeatably if there is more than one POSSM
output in the file. The file must be open before calling
read_possm, using the FileHandle module. The data from the possm
plot is returned in a hash. Some of the header values are returned
as scalar values while the actual plot values are returned as
references to arrays. The scalar values returned are:
  SOURCE, DATE, TIME, BANDWIDTH, TYPE (='A&P'||'R&I')
The array references are: CHANNEL,
  VELOCITY, FREQUENCY, AMPLITUDE, PHASE, ANTENNA
The global variable $Astro::Misc:oldpossm (default=0) controls whether
old or new style possm plots are read.  For oldpossm=1, one of
VELOCITY or FREQUENCY will be a reference to an empty list (but the
hash value IS defined).

Usage:    use FileHandle
          my $fh = FileHandle->new();
          my %ahash = ();
          open($fh, 'possmfile');
          read_possm($fh, %ahash);

Returns:  0 on success (but not hit eof)
          1 on success (and hit eof)
          2 on premature eof

Examples of hash usage:
     $hash{SOURCE}         # Source name
     @{$hash{VELOCITY}}    # Array of velocity values
     ${$hash{PHASE}}[4]    # The fifth phase value

read_lovas

Read_lovas read the Lovas "Recommended Rest Frequencies for Observed
Interstellar Molecular Microwave Transitions - 1991 Revision"
(J. Phys. Chem. Ref. Data, 21, 181-272, 1992). Alpha quality!!

  my @lovas = read_lovas($fname);
  my @lovas = read_lovas($fname, $minfreq, $maxfreq);

calc_U

 $U = calc_U($flux, $dist, $freq);

Calculate U (Excitation Parameter) for an UCHII region
Based on Eqn 8 in Schraml and Mezger, 1969
  $flux        Integrated Source Flux Density (Jy)
  $dist        Distance to source (kpc)
  $freq        Frequency of observation (GHz)
Note:
 Uses the global variable $Astro::Misc::Temp for electron temperature
 Default is 10000K

calc_Nl

 $Nl = calc_Nl($U);

Calculate the Lyman continuum photon flux given U, the Excitation
Parameter for an UCHII region
  $U is the Excitation Parameter (from calc_U)
 Ref: Kurtz 1994 ApJS 91 p659 Eq (1) (Original Origin unknown)

lum2spectral

 $spectral_type = lum2spectral($luminosity);

Calculate the spectral type of a ZAMS star from its luminosity
Based on Thompson 1984 ApJ 283 165 Table 1
  $luminosity   Star luminosity (normalised to Lsun)

Nl2spectral

 $spectral = Nl2spectral($Nl);

Calculate the spectral type of a ZAMS star from its flux of
Lyman Continuum Photons (Nl)
Based on Panagia, 1973, ApJ, 78, 929
   $Nl     Flux of Lyman Continuum Photons

kindist

 ($dist1, $dist2)= kindist($ra, $dec, $vel, $epoch, $model);

Calculate the kinematic distance to an object
  $dist1, $dist2  Near/Far distance (kpc)
  $ra             RA of object (turns)
  $dec            Dec of object (turns)
  $vel            LSR Velocity (km/s)
  $epoch          Epoch of coords (J2000/J/B1950/B)
  $model          Model to use (1 or 2)

Note:
 Model 1 is based on Brand and Blitz, 1993, A&A, 275, 67-90.
 Model 2 has unknown origin.