Add Mg II 2800 angstrom doublet absorption feature to the list

[biprateep]

No description provided.

[biprateep]

Its in the Emission list but can also be seen in absorption

[armengau]

Let's use this open issue to summarize mail exchanges on lines.

• Lines are displayed in vaccum; no heliocentric frame correction to my knowledge.

• Suggestion for "major" lines (Tamara):
  Emission: Ly-alpha, CIV, CIII, MgII, OII, Hdelta, Hgamma, Hbeta, OIII, OIII, Halpha, NII, SII, SII
  Absorption: K, H, G, Mg, Na
  Jeff suggests also to add for absorption H beta, gamma, delta, epsilon and zeta

• Lines to add (Alastair): UV absorption lines, Mg II as a doublet, NeV, ArIII at 9076A. Here is Alastair's detailled list (vaccum in principle):
  Missing emission lines
  3346.79 NeV em
  3426.85 NeV em
  9071.1 SIII em
  Missing optical absorption lines
  8500.36 CaII abs
  8544.44 CaII abs triplet
  8664.52 CaII abs
  IS low ionisation in UV
  SiII 1260.4221 abs
  OI 1302.1685 abs
  SiII 1304.3702 abs
  CII 1334.5323 abs
  SiIV 1393.7602 abs
  SiIV 1402.7728 abs
  SV 1501.76 abs
  SiII 1526.7070 abs
  CIV 1548.204 abs
  FeII 1608.4509 abs
  AlII 1670.788 abs
  SiII 1808.0129 abs
  AlIII 1854.7183 abs
  AlIII 1862.7911 abs
  MgI 2026.4768 abs
  FeII 2344.2130 abs
  FeII 2374.4603 abs
  FeII 2382.7642 abs
  FeII 2389 2396 abs
  emission lines in UV
  SiII* 1264.738 em
  SiII* 1309.276 em
  SiII* 1533.431 em
  OIII] 1660.809 em
  OIII] 1666.150 em
  SiIII] 1882.468 em
  SiIII] 1892.030 em
  CIII] 1907.640 em
  CIII] 1908.7346 em
  both absorption and emission
  MgII 2796.3543 abs and em
  MgII 2803.5315 abs and em

• For record here is the current list of lines in prospect:

_line_list = [
    #
    # This is the set of emission lines from the spZline files.
    # See $IDLSPEC2D_DIR/etc/emlines.par
    # Wavelengths are in air for lambda > 2000, vacuum for lambda < 2000.
    # TODO: convert to vacuum wavelengths
    #
    {"name" : "Lyα",      "longname" : "Lyman α",        "lambda" : 1215.67,  "emission": True, "major": True  },
    {"name" : "Lyβ",      "longname" : "Lyman β",        "lambda" : 1025.18,  "emission": True, "major": False },
    {"name" : "N V",      "longname" : "N V 1240",       "lambda" : 1240.81,  "emission": True, "major": False },
    {"name" : "Si IV",    "longname" : "Si IV 1394",     "lambda" : 1393.75,  "emission": True, "major": False },
    {"name" : "Si IV",    "longname" : "Si IV 1403",     "lambda" : 1402.77,  "emission": True, "major": False },
    {"name" : "C IV",     "longname" : "C IV 1549",      "lambda" : 1549.48,  "emission": True, "major": True  },
    {"name" : "He II",    "longname" : "He II 1640",     "lambda" : 1640.42,  "emission": True, "major": False },
    {"name" : "C III]",   "longname" : "C III] 1908",    "lambda" : 1908.734, "emission": True, "major": False },
    {"name" : "Mg II",    "longname" : "Mg II 2799",     "lambda" : 2799.49,  "emission": True, "major": False },
    {"name" : "[O II]",   "longname" : "[O II] 3725",    "lambda" : 3726.032, "emission": True, "major": True  },
    {"name" : "[O II]",   "longname" : "[O II] 3727",    "lambda" : 3728.815, "emission": True, "major": True  },
    {"name" : "[Ne III]", "longname" : "[Ne III] 3868",  "lambda" : 3868.76,  "emission": True, "major": False },
    {"name" : "Hζ",       "longname" : "Balmer ζ",       "lambda" : 3889.049, "emission": True, "major": False },
    {"name" : "[Ne III]", "longname" : "[Ne III] 3970",  "lambda" : 3970.00,  "emission": True, "major": False },
    {"name" : "Hε",       "longname" : "Balmer ε",       "lambda" : 3970.072, "emission": True, "major": False },
    {"name" : "Hδ",       "longname" : "Balmer δ",       "lambda" : 4101.734, "emission": True, "major": False },
    {"name" : "Hγ",       "longname" : "Balmer γ",       "lambda" : 4340.464, "emission": True, "major": False },
    {"name" : "[O III]",  "longname" : "[O III] 4363",   "lambda" : 4363.209, "emission": True, "major": False },
    {"name" : "He II",    "longname" : "He II 4685",     "lambda" : 4685.68,  "emission": True, "major": False },
    {"name" : "Hβ",       "longname" : "Balmer β",       "lambda" : 4861.325, "emission": True, "major": False },
    {"name" : "[O III]",  "longname" : "[O III] 4959",   "lambda" : 4958.911, "emission": True, "major": True },
    {"name" : "[O III]",  "longname" : "[O III] 5007",   "lambda" : 5006.843, "emission": True, "major": True  },
    {"name" : "He II",    "longname" : "He II 5411",     "lambda" : 5411.52,  "emission": True, "major": False },
    {"name" : "[O I]",    "longname" : "[O I] 5577",     "lambda" : 5577.339, "emission": True, "major": False },
    {"name" : "[N II]",   "longname" : "[N II] 5755",    "lambda" : 5754.59,  "emission": True, "major": False },
    {"name" : "He I",     "longname" : "He I 5876",      "lambda" : 5875.68,  "emission": True, "major": False },
    {"name" : "[O I]",    "longname" : "[O I] 6300",     "lambda" : 6300.304, "emission": True, "major": False },
    {"name" : "[S III]",  "longname" : "[S III] 6312",   "lambda" : 6312.06,  "emission": True, "major": False },
    {"name" : "[O I]",    "longname" : "[O I] 6363",     "lambda" : 6363.776, "emission": True, "major": False },
    {"name" : "[N II]",   "longname" : "[N II] 6548",    "lambda" : 6548.05,  "emission": True, "major": False },
    {"name" : "Hα",       "longname" : "Balmer α",       "lambda" : 6562.801, "emission": True, "major": True  },
    {"name" : "[N II]",   "longname" : "[N II] 6583",    "lambda" : 6583.45,  "emission": True, "major": False },
    {"name" : "[S II]",   "longname" : "[S II] 6716",    "lambda" : 6716.44,  "emission": True, "major": False },
    {"name" : "[S II]",   "longname" : "[S II] 6730",    "lambda" : 6730.82,  "emission": True, "major": False },
    {"name" : "[Ar III]", "longname" : "[Ar III] 7135",  "lambda" : 7135.790, "emission": True, "major": False },
    #
    # Absorption lines
    #
    {"name" : "Hζ",   "longname" : "Balmer ζ",         "lambda" : 3889.049, "emission": False, "major": False },
    {"name" : "K",    "longname" : "K (Ca II 3933)",   "lambda" : 3933.7,   "emission": False, "major": False },
    {"name" : "H",    "longname" : "H (Ca II 3968)",   "lambda" : 3968.5,   "emission": False, "major": False },
    {"name" : "Hε",   "longname" : "Balmer ε",         "lambda" : 3970.072, "emission": False, "major": True },
    {"name" : "Hδ",   "longname" : "Balmer δ",         "lambda" : 4101.734, "emission": False, "major": False },
    {"name" : "G",    "longname" : "G (Ca I 4307)",    "lambda" : 4307.74,  "emission": False, "major": True },
    {"name" : "Hγ",   "longname" : "Balmer γ",         "lambda" : 4340.464, "emission": False, "major": False },
    {"name" : "Hβ",   "longname" : "Balmer β",         "lambda" : 4861.325, "emission": False, "major": False },
    {"name" : "Mg I", "longname" : "Mg I 5175",        "lambda" : 5175.0,   "emission": False, "major": False },
    {"name" : "D2",   "longname" : "D2 (Na I 5889)",   "lambda" : 5889.95,  "emission": False, "major": True },
    # {"name" : "D",    "longname" : "D (Na I doublet)", "lambda": 5892.9,   "emission": False, "major": False },
    {"name" : "D1",   "longname" : "D1 (Na I 5895)",   "lambda" : 5895.92,  "emission": False, "major": True },
    {"name" : "Hα",   "longname" : "Balmer α",         "lambda" : 6562.801, "emission": False, "major": True },
  ]

The lines are vaccum converted, using:

def _airtovac(w):
    """Convert air wavelengths to vacuum wavelengths. Don't convert less than 2000 Å.
    Parameters
    ----------
    w : :class:`float`
        Wavelength [Å] of the line in air.
    Returns
    -------
    :class:`float`
        Wavelength [Å] of the line in vacuum.
    """
    if w < 2000.0:
        return w;
    vac = w
    for iter in range(2):
        sigma2 = (1.0e4/vac)*(1.0e4/vac)
        fact = 1.0 + 5.792105e-2/(238.0185 - sigma2) + 1.67917e-3/(57.362 - sigma2)
        vac = w*fact
    return vac

[moustakas]

Of possible utility / interest: the line-lists used for some of the spectral sims / templates are here:

• https://github.com/desihub/desisim/blob/master/py/desisim/data/recombination_lines.ecsv
• https://github.com/desihub/desisim/blob/master/py/desisim/data/forbidden_lines.ecsv

[armengau]

The line list was updated (in my current dev branch, disp-models):

• "Major" lines as proposed by Tamara (both emission and absorption).
• Included all of entries in Alastair's list. When an entry already existed in SDSS list, I kept SDSS entry.
• Checked all entries from desisim lists (recombination and forbidden lines): added lines whose quoted line-ratio wrt Hbeta is > 0.1: H8, HeI_3389 ; and ArIII]_7751.

[armengau]

Merged to master