IRTS/NIRS Point Source Catalogue  (version 1)

  Tanaka, M.(*), Murakami, H., Freund, M. M., Matsuura, M., Noda, M.,
  Matsumoto, T., Yamamura, I., Le Bertre, T., Cohen, M.

 (*) Email: masa@ir.isas.ac.jp


* Executive summary
--------------------

The NIRS Point Source Catalogue (PSC) contains point source fluxes
observed with the NIRS (Near InfraRed Spectrometer; Noda et al. 1994)
which is one of the four focal-plane instruments of the IRTS (InfraRed
Telescope in Space; Murakami et al. 1994).  The IRTS mission was
performed during the 4-week period in March and April 1995 and surveyed
two strips (called as `north scan' and `south scan', respectively),
which covered about 7% of the sky (Murakami et al. 1996).  The NIRS was
primarily designed to measure the absolute diffuse sky brightness with a
beam of 8'x8' with low dispersion (~0.1 micron).  However, the NIRS
obtained useful data for studies on the stars; it measured spectra of
many point sources in the wavelength range of 1.4-4 micron, where ground
observation is partly prohibited by the atmosphere.  Spectra obtained
with the NIRS clearly show molecular bands such as H2O, CO, C2H2 typical
to late type stars (Matsuura et al. 1999; Le Bertre et al. 2001).

In the NIRS PSC version 1, 14,223 objects confirmed by at least double
detection are catalogued.  Positions, magnitudes in pseudo-H,K,L bands
and associations with IRAS and Tycho catalogued are also presented.
The NIRS PSC may be revised in future due to error correction, improved
processing, addition of objects and so on.  Please find the latest
information from the DARTS WWW site at the ISAS:
http://www.darts.isas.ac.jp/.


* File list
------------

 README.txt         This file
 NIRSPSC.dat        The NIRS PSC in ASCII format

 hist_mag.ps        Histogram of H,K,L magnitude
 hist_mag_2mass.ps  Histogram of difference in H,K magnitude from 2MASS
 hist_pos.ps        Histogram of difference in position from other catalogues


* Descriptions on the NIRS data reduction and processing
---------------------------------------------------------

Flight performance of the NIRS observation is described by Noda et al.
(1996).  Post flight calibration is described by Murakami et al. (2001)
and Matsuura et al. (2001).  An overview of processing the NIRS PSC is
described by Freund et al. (1997).  Detailed description of processing
and characteristics for this catalogue will be appeared in the near
future.


* NIRS Instrument Characteristics
----------------------------------

Beam size: 8'x8'

Characteristics of NIRS spectral channels:

-------------------------------------
c-1   col-2   col-3   col-4   col-5
 ch wavelen bandwid   noise   0-mag
     micron  micron     Jy      Jy
-------------------------------------
 24   1.386   0.108   0.145  1344.  
 23   1.486   0.115   0.151  1212.  
 22   1.588   0.114   0.144  1077.  
 21   1.691   0.117   0.129   990.4 
 20   1.795   0.115   0.119   914.3 
 19   1.898   0.119   0.127   831.8 
 18   2.002   0.115   0.118   764.9 
 17   2.106   0.117   0.124   703.0 
 16   2.209   0.114   0.129   641.9 
 15   2.312   0.113   0.135   597.3 
 14   2.415   0.112   0.214   552.7 
 13   2.518   0.109   0.150   510.8 
 12   2.860   0.108   0.245   409.1 
 11   2.962   0.108   0.303   386.5 
 10   3.065   0.112   0.283   358.9 
  9   3.167   0.111   0.329   343.0 
  8   3.269   0.113   0.520   321.1 
  7   3.370   0.110   0.524   304.5 
  6   3.472   0.115   0.476   289.6 
  5   3.575   0.109   0.546   274.4 
  4   3.675   0.113   0.880   259.5 
  3   3.778   0.110   0.555   243.6 
  2   3.878   0.106   0.597   234.7 
  1   3.977   0.107   0.657   224.1 
-------------------------------------

 Column-1: Channel number (numbered in descending order of wavelength).
 Column-2: Wavelength of band center weighted by system transmittance.
 Column-3: Band width.
 Column-4: Typical RMS noise of output signal for point source extraction.
 Column-5: Flux of zero magnitude in NIRS channel band.

Note: The channel characteristics above are derived assuming that
objects are scanned at the center of the NIRS beam.  The observed
wavelengths shift depending on the cross-scan position.  Multiple
detection of the same object may reduce this uncertainty (see also the
description on `position' below).


* Catalogue Format
-------------------

The NIRS PSC data are stored in `NIRSPSC.dat' file in ASCII format.
Each line of this file contains catalogue data of a object in the format
of the next table.  Length of each line is 754 bytes including newline
code (0x0A).  First line is a header which shows the data format.
Following the header line, catalogue data are listed in the order of
North-scan and South-scan, and then, Right Ascension (J2000).

--------------------------------------------------------------------
Field Bytes Format  Description
--------------------------------------------------------------------
  1   1- 10   a10  NIRS PSC name (IRAS conventions)
  2  12- 12    a1  N-scan (N) or S-scan data (S)
  3  14- 29   a16  RA-Dec (J2000) in format of |00h03.0m +74d04'|
  4  31- 36  f6.2  Right Ascension (J2000) (degrees)
  5  38- 43  f6.2  Declination (J2000) (degrees)
  6  45- 49  f5.1  Position Angle (degrees)
  7  51- 56  f6.2  Galactic Longitude (degrees)
  8  58- 63  f6.2  Galactic Latitude (degrees)
  9  65- 70  f6.2  In-scan position (degrees) in IRTS coordinate
 10  72- 77  f6.2  Cross-scan position (degrees) in IRTS coordinate
 11  79- 82  f4.1  In-scan error (arcmin)
 12  84- 87  f4.1  Xross-scan error (arcmin)
 13  89- 94  f6.3  H_nirs magnitude
 14  96-101  f6.3  K_nirs magnitude
 15 103-108  f6.3  L_nirs magnitude
 16 110-114  f5.3  H_nirs magnitude error
 17 116-120  f5.3  K_nirs magnitude error
 18 122-126  f5.3  L_nirs magnitude error
 19 128-138 e11.4  Flux24     : F_nu (Jy) of ch24 (lambda=1.4 micron)
 20 140-150 e11.4  Flux23
 21 152-162 e11.4  Flux22
 22 164-174 e11.4  Flux21
 23 176-186 e11.4  Flux20
 24 188-198 e11.4  Flux19
 25 200-210 e11.4  Flux18
 26 212-222 e11.4  Flux17
 27 224-234 e11.4  Flux16
 28 236-246 e11.4  Flux15
 29 248-258 e11.4  Flux14
 30 260-270 e11.4  Flux13
 31 272-282 e11.4  Flux12
 32 284-294 e11.4  Flux11
 33 296-306 e11.4  Flux10
 34 308-318 e11.4  Flux9
 35 320-330 e11.4  Flux8
 36 332-342 e11.4  Flux7
 37 344-354 e11.4  Flux6
 38 356-366 e11.4  Flux5
 39 368-378 e11.4  Flux4
 40 380-390 e11.4  Flux3
 41 392-402 e11.4  Flux2
 42 404-414 e11.4  Flux1      : F_nu (Jy) of ch1 (lambda=4.0 micron)
 43 416-423  e8.2  Flux_err24 : Error in Flux F_nu (Jy) of ch24
 44 425-432  e8.2  Flux_err23
 45 434-441  e8.2  Flux_err22
 46 443-450  e8.2  Flux_err21
 47 452-459  e8.2  Flux_err20
 48 461-468  e8.2  Flux_err19
 49 470-477  e8.2  Flux_err18
 50 479-486  e8.2  Flux_err17
 51 488-495  e8.2  Flux_err16
 52 497-504  e8.2  Flux_err15
 53 506-513  e8.2  Flux_err14
 54 515-522  e8.2  Flux_err13
 55 524-531  e8.2  Flux_err12
 56 533-540  e8.2  Flux_err11
 57 542-549  e8.2  Flux_err10
 58 551-558  e8.2  Flux_err9
 59 560-567  e8.2  Flux_err8
 60 569-576  e8.2  Flux_err7
 61 578-585  e8.2  Flux_err6
 62 587-594  e8.2  Flux_err5
 63 596-603  e8.2  Flux_err4
 64 605-612  e8.2  Flux_err3
 65 614-621  e8.2  Flux_err2
 66 623-630  e8.2  Flux_err1
 67 632-633    i2  Ndata24    : Num of Event data for ch24
 68 635-636    i2  Ndata23
 69 638-639    i2  Ndata22
 70 641-642    i2  Ndata21
 71 644-645    i2  Ndata20
 72 647-648    i2  Ndata19
 73 650-651    i2  Ndata18
 74 653-654    i2  Ndata17
 75 656-657    i2  Ndata16
 76 659-660    i2  Ndata15
 77 662-663    i2  Ndata14
 78 665-666    i2  Ndata13
 79 668-669    i2  Ndata12
 80 671-672    i2  Ndata11
 81 674-675    i2  Ndata10
 82 677-678    i2  Ndata9
 83 680-681    i2  Ndata8
 84 683-684    i2  Ndata7
 85 686-687    i2  Ndata6
 86 689-690    i2  Ndata5
 87 692-693    i2  Ndata4
 88 695-696    i2  Ndata3
 89 698-699    i2  Ndata2
 90 701-702    i2  Ndata1
 91 704-705    i2  Num of Events used in this source
 92 707-708    i2  Num of nearby event groups
 93 710-710    i1  Num of association with IRAS PSC
 94 712-712    i1  Num of association with 2MASS cat
 95 714-714    i1  Num of association with Tycho cat
 96 716-716    i1  Num of association with Hipparcos cat
 97 718-727   a10  NIRS name of associated PS in the other scan
 98 729-738   a10  IRAS PSC name
 99 740-751   a12  Tycho Identifier
100 753-753    i1  Reset mode: 1m (0), 1s (1), mix (2)
--------------------------------------------------------------------

Note: The flux errors here come from the signal noise and the
fluctuation of baseline.  In addition to this, there are two kinds of
uncertainty.  One is calibration errors.  Another is uncertainty in the
cross-scan position in the NIRS aperture (see below).  Both
uncertainties are estimated to be about +/- 10%, respectively.


* Position
-----------

We define the `IRTS coordinate' for the north- and south-scan
respectively, so that IRTS scan paths are close to its equator.
In-scan and the cross-scan positions correspond to longitude and
latitude of the IRTS coordinate, respectively.

To convert B1950 coordinate to the IRTS coordinate, you rotate
around the Z axis by A and then rotate by D around the Y axis.
The values of A and D are:

        A (degree)  D (degree)
 N scan   2.25        106.25
 S scan   25.0         64.0

(RA,Dec)=(182.25,-73.75) and (25.0,-64.0) (degrees) are converted to
(lon,lat)=(0,0) in the IRTS north-scan and south-scan coordinate,
respectively.

The IRTS pointing reconstruction is performed using data of the star
sensor on the focal plane, by collaborating with the IPAC.  Thus defined
positions have errors of ~1' in in-scan direction and ~2' in cross-scan
direction.  The systematic offset of the NIRS position is corrected
using cross-identified objects with other catalogues; Hipparcos, Tycho,
2MASS, IRAS PSC.  Cross-scan position of single detection has additional
uncertainty up to the NIRS aperture size, +/- 4', since we do not know
the exact position where the objects passed in the field of view.
However, multiple detection of the same object alleviates this
uncertainty.  Errors in cross-scan position are reduced for objects
detected with wide range in cross-scan direction.


* NIRS H,K,L band
------------------

The magnitudes of NIRS H,K,L bands are calculated from summation of
fluxes (in lambda*F_lambda) of the following NIRS channels:

  H_NIRS:  ch20-ch23  (1.486, 1.588, 1.691, 1.795 micron)
  K_NIRS:  ch14-ch18  (2.002, 2.106, 2.209, 2.312, 2.415 micron)
  L_NIRS:   ch3- ch8  (3.269, 3.371, 3.472, 3.575, 3.676, 3.778 micron)

Invalid data (due to under detection limit or data lost) have magnitude
 = 99.0 and magnitude error = 9.0.


* Cross ID statistics
----------------------

 scan=N+S
 ----------------------
    Hipparcos :   3165
        Tycho :   9433
        2MASS :   4736
     IRAS PSC :   5665
 ----------------------
      Entries :  14294
 ----------------------
  dupl.in N&S :  72(N), 71(S) (*)
   Total obj. :  14223

(*) 18487+2940 and 18491+2940 in N-scan are both associated with
    18489+2938 in S-scan.

 scan=N
 ----------------------
    Hipparcos :    704
        Tycho :   3050
        2MASS :   1334
     IRAS PSC :   2605
    No assoc. :    996
 ----------------------
      Entries :   5735

 scan=S
 ----------------------
    Hipparcos :   2461
        Tycho :   6383
        2MASS :   3402
     IRAS PSC :   3060
    No assoc. :    579
 ----------------------
      Entries :   8559


* Reference
------------

Murakami, H. et al. 1994 ApJ. 428, 354
Noda, M. et al. 1994 ApJ. 428, 363
Murakami, H. et al. 1996 PASJ 48L, 41
Noda, M. et al. 1996 SPIE 2817, 248
Freund, M.M. et al. 1997
 `Diffuse Infrared Radiation and the IRTS' ASP Conf. Series Vol. 124,
  Ed. H. Okuda; T. Matsumoto; and T. Rollig, p.67
Matsuura, M. et al. 1999 A&A 348, 579
Le Bertre, T. et al. 2001 A&A 376, 997
Murakami, H. et al. 2001
 `The calibration legacy of the ISO Mission' ESA Special Publ. Series
  Vol. 481, Ed. L. Metcalfe and M. F. K. Kessler
Matsuura, M. et al. 2001
 `The calibration legacy of the ISO Mission' ESA Special Publ. Series
  Vol. 481, Ed. L. Metcalfe and M. F. K. Kessler
