J/ApJ/954/211ivo://CDS.VizieR/J/ApJ/954/211doi:10.26093/cds/vizier/ba-xt-6kCDSTran D.Williams B.Levesque E.Lazzarini M.Dalcanton J.Dolphin A.,Koplitz B.Smercina A.Telford O.G.2026-07-02T12:00:33Z2025-12-05T07:53:21ZCDS support team

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

cds-question@unistra.frgalaxiesphotometryhst-photometryultraviolet-astronomyvisible-astronomyThe nearby face-on star-forming spiral galaxy NGC 6946 is known as the Fireworks Galaxy due to its hosting an unusually large number of supernovae. We analyze its resolved near-ultraviolet stellar photometry measured from images taken with the Hubble Space Telescope's Wide Field Camera 3 with the F275W and F336W filters. We model the color-magnitude diagrams of the UV photometry to derive the spatially resolved star formation history of NGC 6946 over the last 25Myr. From this analysis, we produce maps of the spatial distribution of the young stellar population and measure the total recent star formation rate (SFR) of nearly the entire young stellar disk. We find the global SFR(age<=25Myr)=13.17_-0.79_^+0.91^M_{sun}_/yr. Over this period, the SFR is initially very high (23.39_-2.11_^+2.43^M_{sun}_/yr 16-25Myr ago), then monotonically decreases to 5.31_-0.17_^+0.19^M_{sun}_/yr in the last 10Myr. This decrease in global SFR over the last 25Myr is consistent with measurements made with other SFR indicators. We discuss in detail two of the most active regions of the galaxy, which we find are responsible for 3% and 5% of the total star formation over the past 6.3Myr.2023ApJ...954..211Thttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/954/211CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toB/hst : HST Archived Exposures Catalog (STScI, 2007)I/345 : Gaia DR2 (Gaia Collaboration, 2018)I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)J/AJ/127/1531 : Star formation history of SMC (Harris+, 2004)J/ApJS/173/185 : GALEX UV atlas of nearby galaxies (Gil de Paz+, 2007)J/AJ/138/1243 : The star formation history of the LMC (Harris+, 2009)J/A+A/537/A146 : Stellar models with rot. 0.8<M<120 (Ekstrom+, 2012)J/other/Sci/337.444 : RV curves of Galactic massive O stars (Sana+, 2012)J/A+A/545/A43 : HII regions in NGC 628 and NGC 6946 (Cedres+, 2012)J/A+A/552/A19 : Radio-farIR correlation in NGC 6946 (Tabatabaei+, 2013)J/ApJ/795/170 : Sample SNRs for M31 and M33 (Jennings+, 2014)J/ApJS/215/9 : PHAT X. UV-IR photometry of M31 stars (Williams+, 2014)J/A+A/601/A146 : M33 Mol. Clds & young stellar clusters (Corbelli+, 2017)J/ApJ/915/92 : SOFIA CII and NII obs. of M101 and NGC6946 (Tarantino+, 2021)J/ApJ/916/58 : HST obs. of supernova remnants in NGC6946 (Koplitz+, 2021)J/ApJ/945/108 : Red supergiants from HST, Spitzer and Gaia (Johnson+, 2023)J/A+A/694/A87 : NGC 3627, NGC 4321 & NGC 6946 [CII] mapping (Kovacic+, 2025)http://archive.stsci.edu/hlsp/fuvs/ : The Fireworks Ultraviolet Survey (FUVS)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/954/211https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/954/211http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/954/211https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/954/211https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/954/211http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/954/211GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/954/211/fuvscat (*The Fireworks Ultraviolet Survey (FUVS) photometric catalog)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/954/211/fuvscat?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/954/211/fuvscat?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/954/211/fuvscat?GETtext/xml+votable180.050000true308.790425492493160.21813123978380.0055555555555555566/15592-155935.4699463256110985e-19 7.886974166154988e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/954/211?format=asciiUVOpticaldefaultJ/ApJ/954/211/fuvscat*The Fireworks Ultraviolet Survey (FUVS) photometric catalogrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000[308.48/309] Right ascension (J2000)degpos.eq.ra;meta.mainindexedDEJ2000[60/60.3] Declination (J2000)degpos.eq.dec;meta.mainindexedF275Wmag[17.71/41.4] HST/WFC3 F275W band magnitudemagphot.mag;em.UV.200-300nmfloate_F275Wmag[0.003/9.99] Uncertainty in F275Wmagmagstat.error;phot.mag;em.UV.200-300nmfloatF336Wmag[16/39.2] HST/WFC3 F336W band magnitudemagphot.mag;em.opt.Ufloate_F336Wmag[0.002/9.99] Uncertainty in F336Wmagmagstat.error;phot.mag;em.opt.UfloatSNR275[-0.1/331] Signal-to-noise ratio in F275Wstat.snr;em.UV.200-300nmfloatSNR336[-0.1/698.6] Signal-to-noise ratio in F336Wstat.snr;em.opt.UfloatCrowd275[0/9.93] Crowding, WFC3_F275Wmagphot.mag;arith.difffloatCrowd336[0/9.98] Crowding, WFC3_F336Wmagphot.mag;arith.difffloatSharp275[-9.999/9.999] Sharpness, WFC3_F275Wstat.fit.paramdoubleSharp336[-9.999/9.999] Sharpness, WFC3_F336Wstat.fit.paramdoubleChi275[0.34/89.9] Chi, WFC3_F275Wstat.fit.chi2floatChi336[0.37/83.5] Chi, WFC3_F336Wstat.fit.chi2floatRound275[-9.999/9.999] Roundness, WFC3_F275Wstat.fit.paramfloatRound336[-9.999/9.999] Roundness, WFC3_F336Wstat.fit.paramfloatqf1[0/1] Quality flag (1=high quality: SNR>4, Crowding<0.7, sharpness^2^<0.2)meta.code.qualintfgd[0/1]? Foreground star flag (1)meta.codeintnullableMatch[0/1] Gaia DR2 flag (1=matched to Gaia source; 237 occurrences)meta.codeintGaia? Gaia DR2 identifiermeta.id.crossnullableBlend[0/1] Blend flag (1=likely blend based on F336W magnitude; 91 occurrences)meta.codeintJ/ApJ/954/211/table3Star formation rates (SFRs) over timerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIndex[0/2637] Grid index numbermeta.idintRA-NE[308.4/309.2] NE component Right Ascension (J2000)degpos.eq.raDE-NE[60/60.4] NE component Declination (J2000)degpos.eq.decRA-NW[308.2/309] NW component Right Ascension (J2000)degpos.eq.raDE-NW[60/60.4] NW component Declination (J2000)degpos.eq.decRA-SW[308.4/309.2] SW component Right Ascension (J2000)degpos.eq.raDE-SW[59.9/60.3] SW component Declination (J2000)degpos.eq.decRA-SE[308.2/309] SE component Right Ascension (J2000)degpos.eq.raAge[4/22]? Mean ageMyrtime.age;stat.meanfloatnullableDE-SE[59.9/60.3] SE component Declination (J2000)degpos.eq.decN[0/200] Number of starsmeta.numberintArea[10/165690] Grid sizearcsec**2phys.angSizedoubleSFR0-6.7[0/0.05] Adjusted 0-6.7 star formation ratesolMass/yrphys.SFR;arith.diffdoublee_SFR0-6.7[0/0.06] Lower uncertainty in SFR0-6.7solMass/yrstat.error;stat.min;phys.SFRdoubleE_SFR0-6.7[0/0.07] Upper uncertainty in SFR0-6.7solMass/yrstat.error;stat.max;phys.SFRdoubleSFR6.7-6.8[0/0.1] 6.7-6.8 star formation ratesolMass/yrphys.SFR;arith.diffdoublee_SFR6.7-6.8[0/0.07] Lower uncertainty in SFR6.7-6.8solMass/yrstat.error;stat.min;phys.SFRdoubleE_SFR6.7-6.8[0/0.05] Upper uncertainty in SFR6.7-6.8solMass/yrstat.error;stat.max;phys.SFRdoubleSFR6.8-6.9[0/0.11] 6.8-6.9 star formation ratesolMass/yrphys.SFR;arith.diffdoublee_SFR6.8-6.9[0/0.1] Lower uncertainty in SFR6.8-6.9solMass/yrstat.error;stat.min;phys.SFRdoubleE_SFR6.8-6.9[0/0.1] Upper uncertainty in SFR6.8-6.9solMass/yrstat.error;stat.max;phys.SFRdoubleSFR6.9-7.0[0/0.1] 6.9-7.0 star formation ratesolMass/yrphys.SFR;arith.diffdoublee_SFR6.9-7.0[0/0.1] Lower uncertainty in SFR6.9-7.0solMass/yrstat.error;stat.min;phys.SFRdoubleE_SFR6.9-7.0[0/0.1] Upper uncertainty in SFR6.9-7.0solMass/yrstat.error;stat.max;phys.SFRdoubleSFR7.0-7.1[0/0.2] 7.0-7.1 star formation ratesolMass/yrphys.SFR;arith.diffdoublee_SFR7.0-7.1[0/0.2] Lower uncertainty in SFR7.0-7.1solMass/yrstat.error;stat.min;phys.SFRdoubleE_SFR7.0-7.1[0/0.1] Upper uncertainty in SFR7.0-7.1solMass/yrstat.error;stat.max;phys.SFRdoubleSFR7.1-7.2[0/0.3] 7.1-7.2 star formation ratesolMass/yrphys.SFR;arith.diffdoublee_SFR7.1-7.2[0/0.2] Lower uncertainty in SFR7.1-7.2solMass/yrstat.error;stat.min;phys.SFRdoubleE_SFR7.1-7.2[0/0.2] Upper uncertainty in SFR7.1-7.2solMass/yrstat.error;stat.max;phys.SFRdoubleSFR7.2-7.3[0/1.6] 7.2-7.3 star formation ratesolMass/yrphys.SFR;arith.diffdoublee_SFR7.2-7.3[0/1.5] Lower uncertainty in SFR7.2-7.3solMass/yrstat.error;stat.min;phys.SFRdoubleE_SFR7.2-7.3[0/0.3] Upper uncertainty in SFR7.2-7.3solMass/yrstat.error;stat.max;phys.SFRdoubleSFR7.3-7.4[0/1] 7.3-7.4 star formation ratesolMass/yrphys.SFR;arith.diffdoublee_SFR7.3-7.4[0/0.9] Lower uncertainty in SFR7.3-7.4solMass/yrstat.error;stat.min;phys.SFRdoubleE_SFR7.3-7.4[0/1] Upper uncertainty in SFR7.3-7.4solMass/yrstat.error;stat.max;phys.SFRdoubleAv[0/1.5] V band extinctionmagphys.absorptionfloatdAv[0/2.5] Differential V band extinctionmagphys.absorption;arith.difffloatRegRegion? (1)meta.codechar