ivo://\getConfig{ivoa}{authority}/~?\rdId/ 400.0 410.0 420.0 430.0 440.0 450.0 460.0 470.0 480.0 490.0 500.0 510.0 520.0 530.0 540.0 550.0 560.0 570.0 580.0 590.0 600.0 610.0 620.0 630.0 640.0 650.0 660.0 670.0 680.0 690.0 700.0 710.0 720.0 730.0 740.0 750.0 760.0 770.0 780.0 790.0 800.0 Gaia DR3 RP/BP (XP) Monte Carlo sampled spectra This is a re-publication the Gaia DR3 RP/BP spectra in the IVOA Spectral Data Model. It presents the continous spectra in sampled form, using a Monte Carlo scheme to decorrelate errors, elaborated in this resource's reference URL. The underlying tables are also available for querying through TAP, which opens some powerful methods for mass-analysing the data. Demleitner, M.;Andrae, R. Catalog Optical 2022-06-20T10:00:00Z 20 stars surveys spectroscopy 2022arXiv220800211G 10.21938/W:hWbPah3wBabuqewQULTA Gaia Gaia BP/BP Spectrometer This data is derived from public Gaia DR3 data. Please take note of `ESAC's guide`_ on how to acknowledge and cite Gaia results. .. _ESAC's guide: https://gea.esac.esa.int/archive/documentation/GDR3/Miscellaneous/sec_credit_and_citation_instructions/ archival survey @import url(/static/css/math.css);` In Gaia's DR3, most BP/RP spectra come in “continuous” form only, that is, as coefficients of Gauss-Hermite polynomials. These can be turned into a “sampled” representation using GaiaXPy_; however, since the errors are given in the form of covariance matrices for the polynomial coefficients, the errors in the resulting spectra are strongly correleated, which can sometimes result in artefacts in the signal. .. _GaiaXPy: https://github.com/gaia-dpci/GaiaXPy.git To get approximately decorrelated errors and hence sampled spectra usable with less caution, we apply a scheme of Monte Carlo-sampling different realisations from the error model of the coefficients. Specifically, given the covariance matrix :math:`C` defined through the Xp_coefficient_errors and Xp_coefficient_correlations column in the DR3 xp_continuous_mean_spectrum table, and noting that for a unit normal-distributed random variable :math:`u` .. math:: \\langle u.u^T\\rangle = 1 holds (:math:`\\langle x\\rangle` denotes the expectation), we can re-write the covariance matrix using a Cholesky decomposition into :math:`LL^T` as .. math:: C =& L L^T \\\\ =& L \\langle u.u^T\\rangle L^T\\\\ =& \\langle L u . u^T L^T\\rangle \\\\ =& \\langle x.x^T\\rangle Hence, :math:`x=L u` is a realisation of the errors satisfying the covariance matrix. To come up with a sampled spectrum, we now draw (in this case) 10 samples of the coefficients and have GaiaXPy convert them to a sampled spectrum. The source code we used for that is `dr3_to_mcsampled.py`_. .. _dr3_to_mcsampled.py: /gaia/s3/preview/static/dr3_to_mcsampled.py To be on the conservative side of the resolution and the bandwidth, and also to keep storage requirements modest, we have chosen a relatively rough grid over the optical band, that is, bins of 10 nm over the spectral range between 400 and 800 nm. ]]> 2014-07-25 2017-05-28 0/0-11 1.986e-19 4.966e-19 Monte Carlo sampled DR3 XP spectraThis table contains the sampled spectra, their errors (as the standard deviation of the samples between the different realisations), and the Gaia DR3 source_id. Join this table on source_id with gaia.dr3lite to obtain information on the sources. (gavo-spec:spectrum) { spectralAxis: @spectral fluxAxis: @flux } \spectralPoints Monte Carlo Sampled DR3 XP Spectra with Basic Object InformationThis table contains the data from \schema.spectra plus position and photometry from gaia.dr3lite. It is a view, and there is generally no advantage to using it instead of manually performing the join.present source_id ra dec ra_error dec_error phot_g_mean_mag phot_bp_mean_mag phot_rp_mean_mag spectra.flux spectra.flux_error CREATE VIEW \qName AS ( SELECT \colNames FROM ( \schema.spectra JOIN gaia.dr3lite USING (source_id))) phot_g_mean_mag phot_bp_mean_mag phot_rp_mean_mag source_id ra dec SSA Metadata for the Monte Carlo-sampled Gaia DR3 XP spectra //ssap#view Gaia DR3 XP spectrum, Monte Carlo-smoothed GaiaXPy sampling//ssap#sdm-instance SAMPLES = [float(v) for v in """\spectralPoints""".split()] with base.getTableConn() as conn: source_id = self.sourceToken["source_id"] res = list(conn.query( "select flux, flux_error" " from \schema.spectra" " where source_id=%(source_id)s", locals())) if not res: raise UnknownURI(f"No spectrum available for '{source_id}'") for rec in zip(SAMPLES, *res[0]): yield { "spectral": rec[0], "flux": rec[1], "flux_error": rec[2]} sourceId = vars["parser_"].sourceToken["source_id"] targetTable.setMeta("description", base.getMetaText(targetTable, "description") +" for Gaia DR3 object {}".format(sourceId)) targetTable.setMeta("name", str(sourceId)) Gaia DR3 XP spectrum datalink class SpecDescriptor(datalink.DatalinkDescriptorMixin): suppressAutoLinks = True data = None forSemantics = soda.DEFAULT_SEMANTICS def __init__(self, pubDID, metadataRow): self.pubDID, self.metadata = pubDID, metadataRow @classmethod def fromDB(cls, did, conn): ssaTD = rd.getById("ssameta") t = rsc.TableForDef(ssaTD, connection=conn ).getTableForQuery( ssaTD, "source_id=%(source_id)s", {"source_id": did}) if not t.rows: return DatalinkFault.NotFoundFault(did, "No spectrum with this source_id known here") return cls(did, t.rows[0]) with base.getTableConn() as conn: return SpecDescriptor.fromDB(pubDID, conn) yield descriptor.makeLink( descriptor.metadata['preview'], description="Preview image", contentType='image/png') yield descriptor.makeLink( descriptor.metadata['accref'], description="Low-resolution, Monte Carlo-sampled spectrum", contentType='appliation/x-votable+xml', contentQualifier="#spectrum") yield descriptor.makeLink( "https://gaia.ari.uni-heidelberg.de/tap/sync?LANG=ADQL&" "REQUEST=doQuery&QUERY=" +urllib.parse.quote("SELECT * FROM gaiadr3.gaia_source" " WHERE source_id={}".format(descriptor.metadata[ "source_id"])), description="The associated Gaia DR3 object", contentType='appliation/x-votable+xml') descriptor.data = sdm.makeSDMDataForSSARow( descriptor.metadata, rd.getById("build_spectrum")) Gaia DR3 XP spectra preview maker source_id bin with base.getTableConn() as conn: res = list(conn.query("SELECT flux" " FROM \schema.spectra" " WHERE source_id=%(source_id)s", inputTable.args)) if not res: raise svcs.UnknownURI("No data for this id known here") fig = figure.Figure((1, 0.4), 200) ax = fig.add_axes([0,0,1,1], frameon=False) ax.plot(res[0][0]) rendered = io.BytesIO() fig.savefig(rendered, format="png") return ("image/png", rendered.getvalue()) \schema Web return T.a(href=data[0])[ T.img(src=data[1], alt="Sketch of plot", loading="lazy")] date: 2023-11-08 date.role: ExportRequested Gaia DR3 MC sampled XP spectra SSA \schema SSAP full MAXREC=1 try: posKey = inputKeys[0].name sizeKey = inputKeys[1].name except IndexError: raise base.ValidationError("Operator error: the cone condition" " is lacking input keys.", "query") parsedPos = pql.PQLPositionPar.fromLiteral( inPars.get(posKey, None), posKey) size = inputKeys[1]._parse(inPars.get(sizeKey, None)) if parsedPos is not None and size is not None: yield parsedPos.getQ3CSQL("ra", "dec", outPars, size) /tap/sync self.assertHasStrings( 'value="400.0 410.0 420.0 430.0 440.0 450.0', # the spectral param ) row = self.getFirstVOTableRow() self.assertEqual(row["source_id"], 2062598017447447680) self.assertEqual(len(row["flux"]), 41) self.assertEqual(len(row["flux_error"]), 41) self.assertAlmostEqual(row["flux"][0]/1.7412900492695593e-18, 1) self.assertAlmostEqual(row["flux_error"][-1]/1.447246961197112e-19, 1) ssa/ssap.xml res = self.getVOTableRows() self.assertEqual(len(res), 1) self.assertTrue(res[0]["accref"], "/gaia/s3/sdl/dlget?ID=2062598395398892160") self.assertTrue(res[0]["preview"], "/gaia/s3/preview/qp/2062598395398892160") self.assertTrue(res[0]["ssa_dateObs"], 57382.0) preview/qp/2062598395398892160 self.assertHasStrings("PNG", "nNAf" # part of the data -- will probably change with mpl versions ) sdl/dlmeta bySemantics = dict((row["semantics"], row) for row in self.getVOTableRows()) self.assertTrue(bySemantics["#this"]["access_url"] .endswith("/gaia/s3/sdl/dlget?ID=2062598395398892160")) self.assertTrue(bySemantics["#this"]["content_qualifier"], "#spectrum") self.assertTrue(bySemantics["#preview"]["access_url"] .endswith("/gaia/s3/preview/qp/2062598395398892160")) self.assertEqual(bySemantics["#coderived"]["access_url"], 'https://gaia.ari.uni-heidelberg.de/tap/sync?LANG=ADQL&' 'REQUEST=doQuery&QUERY=SELECT%20%2A%20FROM%20gaiadr3.' 'gaia_source%20WHERE%20source_id%3D2062598395398892160') sdl/dlget self.assertHasStrings( "NAXIS2 = 41", "TUNIT2 = 'W.m**-2.nm**-1'", b"\\x40\\x79\\0\\0", # start of FITS binary data ) sdl/dlget self.assertHasStrings( "sampling for Gaia\\nDR3 object 2062598395398892160" ) row = self.getFirstVOTableRow(rejectExtras=False) self.assertEqual(row["spectral"], 400.0) self.assertAlmostEqual(row["flux"], 1.568678e-18) self.assertAlmostEqual(row["flux_error"], 5.658210072955931e-19)