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J/A+A/611/A95     Diffuse ionized gas in the Antennae galaxy (Weilbacher+, 2018)

Lyman-continuum leakage as dominant source of diffuse ionized gas in the Antennae Galaxy. Weilbacher P.M., Monreal-Ibero A., Verhamme A., Sandin C., Steinmetz M., Kollatschny W., Krajnovic D., Kamann S., Roth M.M., Erroz-Ferrer S., Marino R.A., Maseda M.V., Wendt M., Bacon R., Dreizler S., Richard J., Wisotzki L. <Astron. Astrophys. 611, A95 (2018)> =2018A&A...611A..95W (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, optical ; H II regions ; Interstellar medium ; Spectroscopy ; Galaxies, peculiar ; Diffuse clouds ; Balmer lines Keywords: galaxies: interactions - galaxies: individual: NGC 4038, NGC 4039 - galaxies: ISM - ISM: structure - HII regions Abstract: The Antennae galaxy (NGC 4038/39) is the closest major interacting galaxy system and is therefore often studied as a merger prototype. We present the first comprehensive integral field spectroscopic dataset of this system, observed with the MUSE instrument at the ESO VLT. We cover the two regions in this system which exhibit recent star formation: the central galaxy interaction and a region near the tip of the southern tidal tail. In these fields, we detect HII regions and diffuse ionized gas to unprecedented depth. About 15% of the ionized gas was undetected by previous observing campaigns. This newly detected faint ionized gas is visible everywhere around the central merger, and shows filamentary structure. We estimate diffuse gas fractions of about 60% in the central field and 10% in the southern region. We are able to show that the southern region contains a significantly different population of HII regions, showing fainter luminosities. By comparing HII region luminosities with the HST catalog of young star clusters in the central field, we estimate that there is enough Lyman-continuum leakage in the merger to explain the amount of diffuse ionized gas that we detect. We compare the Lyman-continuum escape fraction of each HII region against emission line ratios that are sensitive to the ionization parameter. While we find no systematic trend between these properties, the most extreme line ratios seem to be strong indicators of density bounded ionization. Extrapolating the Lyman-continuum escape fractions to the southern region, we conclude that simply from the comparison of the young stellar populations to the ionized gas there is no need to invoke other ionization mechanisms than Lyman-continuum leaking HII regions for the diffuse ionized gas in the Antennae. Description: We provide two-dimensional maps of two different ways to measure the diffuse ionized gas as traced by the Halpha emission line in the Antennae Galaxy, both for the central field and the field at the end of the southern tidal tail. We provide a velocity map derived from the Halpha emission line, binned to a S/N∼30. Finally, we provide line measurements and derived properties for all HII regions discussed in the paper. Objects: ----------------------------------------------------- RA (2000) DE Designation(s) ----------------------------------------------------- 12 01 53.17 -18 52 37.9 Antennae Galaxy = APG 244 ----------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file list.dat 101 5 List of fits images fits/* 0 5 Individual fits images center.dat 486 551 HII measurements, center south.dat 486 55 HII measurements, south
See also: J/AJ/127/660 : Photometry in southern tail of the Antennae (Saviane+, 2004) J/ApJS/166/211 : Chandra sources in Antennae galaxies (Zezas+, 2006) J/AJ/140/75 : Antennae galaxies (NGC4038/4039) revisited (Whitmore+, 2010) J/ApJ/750/136 : Molecular clouds in the Antennae from CO(2-1) (Wei+, 2012) J/MNRAS/445/1412 : HII regions and GMC in the Antennae (Zaragoza-Cardiel+ 2014) Byte-by-byte Description of file: list.dat
Bytes Format Units Label Explanations
1- 9 F9.5 deg RAdeg Right Ascension of center (J2000) 10- 18 F9.5 deg DEdeg Declination of center (J2000) 20- 22 F3.1 arcsec/pix Scale Scale of the image 24- 26 I3 --- Nx Number of pixels along X-axis 28- 30 I3 --- Ny Number of pixels along Y-axis 32- 35 I4 Kibyte size Size of FITS file 37- 73 A37 --- FileName Name of FITS file, in subdirectory fits 75-101 A27 --- Title Title of the FITS file
Byte-by-byte Description of file: center.dat south.dat
Bytes Format Units Label Explanations
1- 4 I4 --- ID ?=999999 MUSE ID of the HII region (ID) 6- 8 I3 pix Xpeak ?=999999 Peak in x pixel coordinate (XPEAK) 10- 12 I3 pix Ypeak ?=999999 Peak in y pixel coordinate (YPEAK) 14- 16 I3 --- Npix ?=999999 Number of MUSE pixels in HII region (NPIX) 18- 27 F10.1 mW/m2 Ha Observed integrated line flux (HALPHA) 29- 38 F10.1 mW/m2 e_Ha Error estimate of Ha (E_HALPHA) 40- 49 F10.1 mW/m2 Hb Observed integrated line flux (HBETA) 51- 60 F10.1 mW/m2 e_Hb Error estimate of Hb (E_HBETA) 62- 71 F10.1 mW/m2 OIII5007 ? OIII5007Å observed integrated line flux (OIII5007) 73- 82 F10.1 mW/m2 e_OIII5007 Error estimate of OIII5007 (E_OIII5007) 84- 93 F10.1 mW/m2 OI6300 OI 6300Å observed integrated line flux (OI6300) 95-104 F10.1 mW/m2 e_OI6300 Error estimate of OI6300 (E_OI6300) 106-115 F10.1 mW/m2 SII6716 SII 6716Å observed integrated line flux (SII6716) 117-126 F10.1 mW/m2 e_SII6716 Error estimate of SII6716 (E_SII6716) 128-137 F10.1 mW/m2 SII6731 SII 6731Å observed integrated line flux (SII6731) 139-148 F10.1 mW/m2 e_SII6731 Error estimate of SIII9068 (E_SII6731) 150-159 F10.1 mW/m2 SIII9068 ?=- SIII 9068Å observed integrated line flux (SIII9068) 161-170 F10.1 mW/m2 e_SIII9068 ?=- Error estimate of SIII9068 (E_SIII9068) 172-177 F6.2 --- Ha/Hb Balmer decrement (HA_HB) 179-185 F7.2 --- e_Ha/Hb Error estimate of Balmer decrement (EHAHB) 187-191 F5.3 --- cHb Logarithmic extinction at Hbeta (C_HBETA) 193-202 F10.1 mW/m2 FH1r6563A H1r 6563Å Extinction-corrected flux (FH1r6563A) 204-213 F10.1 mW/m2 e_FH1r6563A Error estimate of FH1r6563A (EH1r6563A) 215-224 F10.1 mW/m2 FH1r4861A H1r 4861Å extinction-corrected flux (FH1r4861A) 226-235 F10.1 mW/m2 e_FH1r4861A Error estimate of FH1r4861A (EH1r4861A) 237-246 F10.1 mW/m2 FO35007A O3 5007Å extinction-corrected flux (FO35007A) 248-257 F10.1 mW/m2 e_FO35007A Error estimate of FO35007A (EO35007A) 259-269 F11.1 mW/m2 FO16300A O1 6300Å extinction-corrected flux (FO16300A) 271-280 F10.1 mW/m2 e_FO16300A Error estimate of FO16300A (EO16300A) 282-291 F10.1 mW/m2 FS26716A S2 6716Å extinction-corrected flux (FS26716A) 293-302 F10.1 mW/m2 e_FS26716A Error estimate of FS26716A (ES26716A) 304-313 F10.1 mW/m2 FS26731A S2 6731Å extinction-corrected flux (FS26731A) 315-324 F10.1 mW/m2 e_FS26731A Error estimate of FS26731A (ES26731A) 326-335 F10.1 mW/m2 FS39069A S3 9069Å extinction-corrected flux (FS39069A) 337-346 F10.1 mW/m2 e_FS39069A ?=- Error estimate of FS39069A (ES39069A) 348-354 F7.3 --- OIII/SII OIII/SII extinction-corrected emission line ratio (OIII_SII) 356-363 F8.3 --- e_OIII/SII ? Error estimate of OIII/SII (EOIIISII) 365-371 F7.3 --- SIII/SII SIII/SII extinction-corrected emission line ratio (SIII_SII) 373-379 F7.3 --- e_SIII/SII ? Error estimate of SIII/SII (ESIIISII) 381-388 F8.3 --- OIII/OI OIII/OI extinction-corrected emission line ratio (OIII_OI) 390-397 F8.3 --- e_OIII/OI ? Error estimate of OIII/OI (EOIIIOI) 399-408 E10.5 10-7W LHaobs Observed Halpha luminosity (LHa_obs) 410-419 E10.5 10-7W LHacor Extinction-corrected Halpha luminosity (LHa_cor) 421-430 E10.5 s-1 qH0 Halpha-based estimate of LyC photon rate (Q_H0) 432-441 E10.5 s-1 e_qH0 Error estimate of qH0 (EQH0) 443-444 I2 --- NCluster ?=999999 Number of young HST clusters in HII region (NCluster) 446-455 E10.5 s-1 NLyCG ? GALEV-based estimate of LyC photon rate (NLyC_GALEV) 457-460 F4.2 --- fescG ? GALEV-based LyC escape fraction (fesc_GALEV) 462-465 F4.2 --- e_fescG ? Error estimate of fescG (EfescGALEV) 467-476 E10.5 s-1 NLyCSB99 ? SB99-based estimate of LyC photon rate (NLyC_SB99) 478-481 F4.2 --- fescSB99 ? SB99-based LyC escape fraction (fesc_SB99) 483-486 F4.2 --- e_fescSB99 ? Error estimate of fescSB99 (EfescSB99)
Acknowledgements: Peter Weilbacher, pweilbacher(at)aip.de
(End) Peter M. Weilbacher [AIP, Germany], Patricia Vannier [CDS] 14-Dec-2017
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