Disk Detective Talk

Creating SEDs: Deriving and extracting flux values from online catalogues

  • PreJhTrg by PreJhTrg

    Hello all,

    I'm currently working on creating SEDs,
    but I'm a little lost in regards to all the measures needed to correct the data. I apologize for the large number of questions this post contains. To better illustrate my problem, below is an example: WISE J163800.84-354209.6.
    Below are the Flux density values (Jy) I obtain for this object.
    In the paranthesis are the associated wavelengths in Microns.

    IRAS (Extracted from Abrahamyan+ 2015)
    3.61e-01 (12)
    8.18e-01 (25)
    7.05e-01 (60)
    5.51e+00 (100)

    WISE (Derived from Vega magnitudes: Cutri et al., 2012: http://wise2.ipac.caltech.edu/docs/release/allsky/expsup/sec4_4h.html#example).
    0.282016058 (3.4)
    0.329291425 (4.6)
    0.397111479 (12)
    0.938523145 (22)

    AKARI (Extracted from Abrahamyan+ 2015)
    8.326e-01 (18)

    2MASS (Derived from Cutri et al., 2003 via: http://ssc.spitzer.caltech.edu/warmmission/propkit/pet/magtojy/)
    0.0425 (1.24)
    0.13 (1.65)
    0.25 (2.16)

    DSS Red (based on GSC2.3 R mag. conversion done via: http://ssc.spitzer.caltech.edu/warmmission/propkit/pet/magtojy/)
    0.000603 (0.64)

    Q1: Would it be right of me to assume that these are reasonable flux values as they are (no corrections needed)?


    Q2: Is deblending necessary here (in the case of WISE and IRAS especially)? If that's the case, are there any tools or formulae available to correct these contaminated flux values?

    Also, I've been working on extracting flux values from SUMSS/MOST images (843 MHz = 355.6 microns), as these also cover this area.
    Each pixel (45"x45") gives a value in Jy/beam. Value: 0.00095 (355.6)

    Q3: Am I correct to consider the SUMSS/MOST the flux density values as they are? Are all the above values technically in Jy/beam?

    I know the beam is dependent on the primary mirror size and wavelength, and seems to define the resolution of the images.
    From what I know:

    Theta(lambda)= 1.22*(lambda*1e6/D).
    Theta is the Beam FWHM, from what I have understood. Lambda is the wavelength in microns. D is the diameter of the primary mirror.
    I multiply lambda by 1e6 for the purpose of homogeneity.

    Beam size in steradians (sr): Phi= Theta² x pi.

    Q4: Do I need to divide the above values by phi, or just the SUMSS/MOST value?

    Q5: However, when doing so, one is left with a value in Jy/sr, not in Jy... I think this would be the intensity rather than the flux?

    Q6: What is the primary mirror size of the SUMSS/MOST telescope: 778 m?

    Thank you in advance for your help! 😃

    Best regards,