J/AJ/143/98 Spectroscopy of star-forming regions in NGC 4194 (Weistrop+, 2012)
Characteristics of star-forming regions in the advanced minor-merger, luminous
infrared galaxy NGC 4194.
Weistrop D., Nelson C.H., Angione R., Bachilla R., Hancock M., Kaiser M.E.
<Astron. J., 143, 98 (2012)>
=2012AJ....143...98W 2012AJ....143...98W
ADC_Keywords: Galaxies, spectra ; Reddening ; Redshifts ; Abundances
Keywords: galaxies: individual (NGC 4194) - galaxies: starburst -
galaxies: star formation
Abstract:
We report the results of long-slit spectroscopy at position angles
68°, 131°, and 164° for the minor-merger NGC 4194, a
luminous infrared starburst galaxy. The mass within 1.2kpc of the
dynamical center is estimated to be 4.8*109 to 1.7*1010 M☉,
depending on the assumed inclination to the plane of the sky. The star
formation rate (SFR) in the areas sampled is 8 M☉/yr. The
metallicity, log(O/H)+12, ranges from ∼8.8 to >9.0 in regions of
significant star formation, suggesting that the metallicity has been
enhanced by the current star formation. The star-forming regions range
in age from 5 to 9Myr, with the youngest ages occurring in the regions
of high SFR. Electron temperatures and the location of the spectra in
emission line diagnostic diagrams suggest the presence of shock waves,
presumably due to the presence of supernovae, winds from massive
stars, and/or collisions of clouds due to the merger. The presence of
massive stars and supernovae is consistent with the ages determined
for the star-forming regions. The ages of the continua produced by the
stellar population are estimated to range from 10Myr to 5Gyr. Much of
the stellar population represented in the continua was probably formed
before the merger and represents the progenitor galaxies.
Description:
To identify the star-forming regions in NGC 4194, UBVR images were
obtained at the 1m telescope at Mount Laguna Observatory on 1997 May 8
UT using a CCD camera.
The spectra were obtained on the 2.1m telescope at NOAO's Kitt Peak
Observatory on 1999 June 10-12 UT. We used the Gold Camera spectrograph.
Objects:
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RA (2000) DE Designation(s)
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12 14 09.57 +54 31 36.0 NGC 4194 = MEDUSA GALAXY MERGER
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 109 47 Redshift, reddening, and relative fluxes for
individual spectra
table4.dat 82 40 Physical parameters derived from individual spectra
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See also:
VII/239 : History and Accurate Positions for the NGC/IC Objects (Corwin, 2004)
J/ApJ/701/1398 : SFR for starburst galaxies (Sargsyan+, 2009)
J/ApJ/682/1020 : X-ray sources in NGC 4194 and NGC 7541 (Kaaret+, 2008)
J/AJ/127/1360 : Star-forming knots in NGC 4194 center (Weistrop+, 2004)
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 deg PA Position Angle of slit
5- 9 F5.1 arcsec Dist Distance of the spectrum from the center
of the slit
11- 17 F7.5 --- z Redshift
19- 22 F4.2 mag E(B-V) ? Reddening calculated for the extracted
spectra (see Section 4.1 for more details)
24- 28 F5.2 --- F3727 [1.77/10.56]? Flux of [OII]λ3727 (1)
30 A1 --- u_F3727 Uncertainty flag on F3727 (2)
32- 35 F4.2 --- Hb2 [1.0]? Hβ flux (1)
37- 40 F4.2 --- F4959 [0.19/0.96]? Flux of [OIII]λ4959 (1)
42 A1 --- u_F4959 Uncertainty flag on F4959 (2)
44- 47 F4.2 --- F5007 [0.61/1.79]? Flux of [OIII]λ5007 (1)
49 A1 --- u_F5007 Uncertainty flag on F5007 (2)
51- 54 F4.2 --- F5755 [0.03/0.06]? Flux of [NII]λ5755 (1)
56 A1 --- u_F5755 Uncertainty flag on F5755 (2)
58- 61 F4.2 --- F6300 [0.05/0.38]? Flux of [OI]λ6300 (1)
63 A1 --- u_F6300 Uncertainty flag on F6300
65- 68 F4.2 --- F6548 [0.27/0.96]? Flux of [NII]λ6548 (1)
70 A1 --- u_F6548 Uncertainty flag on F6548
72- 75 F4.2 --- Ha ? Hα flux (1)
77- 80 F4.2 --- F6583 [0.94/2.04]? Flux of [NII]λ6583 (1)
82 A1 --- u_F6583 Uncertainty flag on F6583
84- 87 F4.2 --- F6716 [0.31/1.01]? Flux of [SII]λ6716 (1)
89 A1 --- u_F6716 Uncertainty flag on F6716
91- 94 F4.2 --- F6731 [0.27/0.78]? Flux of [SII]λ6731 (1)
96 A1 --- u_F6731 Uncertainty flag on F6731
98-104 E7.2 cW/m2/nm Hb ? Hβ flux (in erg/s/cm2/Å)
106 A1 --- u_Hb Uncertainty flag on Hb
108-109 I2 pix Slit Slit height
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Note (1): Reddening corrected flux relative to the flux of Hβ.
Note (2): Uncertainty greater than 25%.
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 deg PA Position Angle of slit
5- 9 F5.1 arcsec Dist Distance of the spectrum from the center
of the slit
11- 14 F4.2 Msun/yr SFR [0/1.48] Star formation rate from
Hα emission line SFR(Hα)
(see more details in Section 4.2)
16- 19 F4.2 [-] Ab(O)1 ? Oxygen abundance (12+log(O/H)) using method
of Kewley & Dopita (2002ApJS..142...35K 2002ApJS..142...35K)
(see Section 4.3 for more details)
21- 24 F4.2 [-] Ab(O)2 ? Oxygen abundance (12+log(O/H)) using R23
method of Zaritsky et al.(1994ApJ...420...87Z 1994ApJ...420...87Z)
(see Section 4.3 for more details)
26- 29 F4.2 [-] Ab(O)3 ? Oxygen abundance (12+log(O/H)) using R23
method of McGaugh (1991ApJ...380..140M 1991ApJ...380..140M)
(see Section 4.3 for more details)
31- 33 F3.1 Myr Age1 [5.3/8.2] Age of the gas in the star-forming
regions (1)
35- 37 F3.1 10+2cm-3 Ne [0.7/8.2]? Electron density ne
39 A1 --- l_Ne [<] Indicates an upper value only
(no b_Ne value is listed in this case)
41- 44 F4.2 10+2cm-3 b_Ne ? Lower value of the electron density
range (see Section 4.5 for more details)
46- 49 F4.1 10+2cm-3 B_Ne ? Upper value of the electron density
range (see Section 4.5 for more details)
51- 53 F3.1 10+4degC Te ? Electron temperature (in degree Celsius)
(see Section 4.6 for more details)
55- 57 F3.1 10+4degC b_Te ? Lower value of the electron temperature
range (see Section 4.6 for more details)
59- 61 F3.1 10+4degC B_Te ? Upper value of the electron temperature
range (see Section 4.6 for more details)
63- 75 A13 --- Model Starburst99 Star Formation Model (2)
77- 82 E6.2 Myr Age2 Ages derived from the continum
(see Section 5 for more details)
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Note (1): Estimated by comparison of Hα and Hβ equivalent widths
(see Section 4.4 for more details).
Note (2): Indicates whether the best fit was a model assuming "Continuous"
or "Instantaneous" star formation) (see Section 5 for more details).
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History:
From electronic version of the journal
(End) Sylvain Guehenneux [CDS] 31-May-2013