J/MNRAS/489/4669 UGC 1378's giant low surface brightness disc (Saburova+, 2019)
UGC 1378 - a Milky Way sized galaxy embedded in a giant low surface brightness
disc.
Saburova A.S., Chilingarian I.V., Kasparova A.V., Katkov I.Y.,
Fabricant D.G., Uklein R.I.
<Mon. Not. R. Astron. Soc., 489, 4669-4678 (2019)>
=2019MNRAS.489.4669S 2019MNRAS.489.4669S (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, spectra ; Galaxies, rotation ; Galaxies, optical ;
Velocity dispersion
Keywords: galaxies: evolution - galaxies: kinematics and dynamics -
galaxies: photometry - galaxies: spiral - galaxies: star formation -
galaxies: structure
Abstract:
The dominant physical processes responsible for the formation and
longevity of giant gaseous and stellar discs in galaxies remain
controversial. Although they are rare (less than 10 confirmed as of
now), giant low-surface brightness (gLSB) discy galaxies provide
interesting insights given their extreme nature. We describe
observations of UGC 1378 including deep spectroscopy with the Russian
6-m telescope and multiband imaging with Binospec at the MMT. Galaxy
UGC 1378 has both high surface brightness and an extended low surface
brightness discs. Our stellar velocity dispersion data for the high
surface brightness, Milky Way sized, disc appears inconsistent with a
recent major merger, a widely discussed formation scenario for the
very extended low surface brightness disc. We estimate the star
formation rates (SFRs) from archival Wide-Field Infrared Survey
Explorer data. The SFR surface density in the LSB disc is low relative
to its gas density, consistent with recent gas accretion. We argue
that the unusually large size of UGC 1378's disc may be the product of
a rich gas reservoir (e.g. a cosmic filament) and an isolated
environment that has preserved the giant disc.
Description:
We observed UGC 1378 with the SCORPIO focal reducer/spectrograph
(Afanasiev & Moiseev 2005AstL...31..194A 2005AstL...31..194A) at the prime focus of the
6-m Russian telescope on 2017 September 20 using a 6-arcmin long and
1-arcsec wide slit, and the VPH G2300G grism. This setup provides
spectral coverage from 4800-5570Å, dispersion of 0.38Å/pixel,
with an instrumental FWHM of 2.2Å. The plate scale along the slit
is 0.36arcsec/pixel. The total on-source exposure time was 7h in
1.4arcsec seeing. The slit was oriented along the major axis of UGC
1378 at PA=181° (Mishra et al. 2017MNRAS.464.2741M 2017MNRAS.464.2741M). We used
spectra of on-board arc and flat-field lamps for calibration.
We reduced the spectral data using our IDL-based pipeline. We then
fitted the reduced spectra of UGC 1378 with intermediate-resolution
(R=10000) PEGASE.HR (Le Borgne et al. 2004A&A...425..881L 2004A&A...425..881L) simple
stellar population models (SSP). The fitting procedure returns the
best-fitting parameters of an SSP model, that is age and metallicity
of stellar population. We parametrized the line-of-sight velocity
distribution (LOSVD) of stars by Gauss-Hermite series (see van der
Marel & Franx 1993ApJ...407..525V 1993ApJ...407..525V). We obtained a luminosity-weighted
stellar age and metallicity, line-of-sight velocity, velocity
dispersion, and Gauss-Hermite moments h3 and h4.
Objects:
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RA (ICRS) DE Designation(s)
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01 56 19.26 +73 16 57.7 UGC1378 = 2MASX J01561923+7316580
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
ugc1378.dat 34 1 UGC 1378 basic information
hbeta.dat 89 17 Results of the analysis of Hβ emission
line of UGC 1378
o3.dat 89 14 Results of the analysis of [OIII] emission line
of UGC 1378
stars.dat 158 53 The properties of stellar population of UGC 1378
obtained from the spectral analysis
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Byte-by-byte Description of file: ugc1378.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Galaxy name (UGC 1378)
10- 11 I2 h RAh Right ascension (J2000)
13- 14 I2 min RAm Right ascension (J2000)
16- 21 F6.3 s RAs Right ascension (J2000)
23 A1 --- DE- Declination sign (J2000)
24- 25 I2 deg DEd Declination (J2000)
27- 28 I2 arcmin DEm Declination (J2000)
30- 34 F5.2 arcsec DEs Declination (J2000)
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Byte-by-byte Description of file: hbeta.dat
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Bytes Format Units Label Explanations
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1- 13 F13.8 arcsec R Radius
15- 23 F9.4 km/s vLOS Line of sight velocity of ionized gas
measured in Hβ line
25- 34 F10.7 km/s e_vLOS Error on vLOS
36- 46 F11.7 km/s vdisp Velocity dispersion
48- 58 F11.8 km/s e_vdisp Error on vdisp
60- 73 E14.9 10-2W/m2/nm FHb Flux of the Hβ line
75- 89 E15.10 10-2W/m2/nm e_FHb Error on FHb
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Byte-by-byte Description of file: o3.dat
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Bytes Format Units Label Explanations
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1- 13 F13.8 arcsec R Radius
15- 23 F9.4 km/s vLOS Line of sight velocity of ionized gas
measured in [OIII] line
25- 34 F10.7 km/s e_vLOS Error on vLOS
36- 46 F11.7 km/s vdisp Velocity dispersion
48- 58 F11.8 km/s e_vdisp Error on vdisp
60- 73 E14.9 10-2W/m2/nm F[OIII] Flux on the [OIII] line
75- 89 E15.10 10-2W/m2/nm e_F[OIII] Error on F[OIII]
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Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 12 F12.8 arcsec R Radius
14- 22 F9.4 km/s vLOS Line of sight velocity of ionized gas
measured in stars
24- 33 F10.8 km/s e_vLOS Error on vLOS
35- 44 F10.6 km/s vdisp Velocity dispersion
46- 54 F9.7 km/s e_vdisp Error on vdisp
56- 68 F13.10 --- h3 Gauss-Hermite moment h3 (1)
70- 81 F12.10 --- e_h3 Error on h3
83- 95 F13.10 --- h4 Gauss-Hermite moment h4 (1)
97-109 F13.10 --- e_h4 Error on h4
111-120 F10.7 Gyr Age Age from simple stellar population (SSP) model
best-fit
122-131 F10.8 Gyr e_Age Error on Age
133-145 F13.10 [-] Z Metallicity from simple stellar population
(SSP) model best-fit
147-158 F12.10 [-] e_Z Error on Z
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Note (1): Gauss-Hermite moments h3 and h4 characterize the deviation of
line-of-sight velocity distribution (LOSVD) from the Gaussian profile
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 18-Jan-2023