J/A+A/671/A105ivo://CDS.VizieR/J/A+A/671/A105doi:10.26093/cds/vizier.36710105CDSAlvarez-Marquez J.Crespo Gomez A.Colina L.Neeleman M.Walter F.,Labiano A.Perez-Gonzalez P.Bik A.Noorgaard-Nielsen H.U.Ostlin G.,Wright G.Alonso-Herrero A.Azollini R.Caputi K.I.Eckart A.,Le Fevre O.Garcia-Marin M.Greve T.R.Hjorth J.Ilbert O.Kendrew S.,Pye J.P.Tikkanen T.Topinka M.van der Werf P.Ward M.,van Dishoeck F.Guedel M.Henning T.Lagage P.O.Ray T.Waelkens C.2023-07-17T15:49:35Z2023-03-14T14:30:12ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frgalaxiesvisible-astronomyinfrared-astronomyLuminous infrared starbursts in the early universe are thought to be the progenitors of massive quiescent galaxies identified at redshifts 2 to 4. Using MIRI on-board JWST we present mid-infrared sub-arcsec imaging (MIRIM) and spectroscopy (MRS) of such a starburst: the slightly lensed hyperluminous infrared system SPT0311-58 at z=6.9. Our observations target the stellar (rest-frame 1.26um emission) structure and ionised (Pa{alpha} and H{alpha}) medium on kpc scales in the system. MIRI observations are compared with existing ALMA far-infrared continuum and [CII]158um imaging at similar angular resolution. Even though the ALMA observations imply very high star formation rates in the eastern (E) and western (W) galaxies of the system, the H{alpha} line is, strikingly, not detected in our MRS observations. This, together with the detection of the ionised gas phase in Pa{alpha}, implies very high internal nebular extinction with lower limits (A_V_) of 4.2 (E) and 3.9 mag (W), and even larger (5.6 (E) and 10.0 (W)) for SED derived values. The extinction-corrected Pa{alpha} lower limits to the star formation rates are 383 and 230M_{sun}_/yr for the E and W galaxies, respectively. This represents 50 of the SFRs derived from the [CII]158um line and infrared light for the E galaxy and as low as 6% for the W galaxy. The specific star formation (sSFR) in the stellar clumps ranges from 25 to 59Gyr^-1^ assuming a star formation with a 50-100Myr constant rate. This sSFR is 3 to 10 times larger than the values measured in galaxies of similar mass at redshifts 6 to 8: SPT0311-58 thus clearly stands out as a starburst system when compared with typical massive star-forming galaxies at similar high redshifts. The MIRI observations reveal a clumpy stellar structure, with each clump having 3 to 5 x10^9^M_{sun}_ mass in stars, leading to a total stellar mass of 2.0 and 1.5 x10^10M_{sun}_ for the E and W galaxies, respectively. The overall gas mass fraction is M_gas_/M*~3, similar to that of z~4.5-6 star-forming galaxies, suggesting a flattening of the gas mass fraction in massive starbursts up to redshift 7. The kinematics of the ionised gas in the E galaxy agrees with the known [CII] gas kinematics, indicating a physical association between the ionised gas and cold dust/gas clumps. The situation in the W galaxy is more complex as it appears to be a velocity offset of about +700km/s in the Pa{alpha} relative to the [CII] emitting gas. The nature of this offset, and its reality, is not fully established and requires further investigation. The observed properties of SPT0311-58 such as the clumpy distribution at sub(kpc) scales and the very high average extinction are similar to those observed in low- and intermediate-z luminous (E galaxy) and ultraluminous (W galaxy) infrared galaxies, even though SPT0311-58 is observed only ~800Myr after the Big Bang. Massive, heavily obscured, clumpy starburst systems like SPT0311-58 likely represent the early phases in the formation of massive high-redshift bulge/spheroids and luminous quasars. MIRI and JWST will be able to explore for the first time the rest-frame near-infrared stellar and ionised gas structure of these galaxies, even during the Epoch of Reionization as demonstrated by this study.2023A&A...671A.105Ahttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/671/A105CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/671/A105https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/671/A105http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/671/A105https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/671/A105https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/671/A105http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/671/A105GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/671/A105/list (List of fits images)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/671/A105/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/671/A105/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/671/A105/list?GETtext/xml+votable180.050000true47.88787-58.392690.005555555555555556Associated datahttps://cdsarc.cds.unistra.fr/assocdata/?obs_collection=J/A+A/671/A1056/33566https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/671/A105?format=asciiOpticalInfrareddefaultJ/A+A/671/A105/listList of fits imagesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension of center (J2000)degpos.eq.ra;meta.mainDEJ2000Declination of center (J2000)degpos.eq.dec;meta.mainscale? Scale of the imagearcsec/pixinstr.scalefloatnullableNxNumber of pixels along X-axismeta.numberintNyNumber of pixels along Y-axismeta.numberintObs.dateObservation datestime.epoch;obsnullablesizeSize of FITS fileKibytephys.size;meta.fitsintTitleTitle of the FITS filemeta.title;meta.fitscharFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitschar