J/A+A/602/A97 UV structure of 11 galaxies with Swift-UVOT (Rampazzo+, 2017)
Investigating early-type galaxy evolution with a multiwavelength approach.
II. The UV structure of 11 galaxies with Swift-UVOT.
Rampazzo R., Mazzei P., Marino A., Uslenghi M., Trinchieri G., Wolter A.
<Astron. Astrophys. 602, A97 (2017)>
=2017A&A...602A..97R 2017A&A...602A..97R (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, photometry ; Photometry, ultraviolet ; Photometry, UBV
Keywords: galaxies: elliptical and lenticular, cD -
galaxies: fundamental parameters - ultraviolet: galaxies -
galaxies: evolution
Abstract:
GALEX detected a significant fraction of early-type galaxies, in
particular S0s, showing Far-UV bright structures, sometimes involving
an entire galaxy out to its outskirts. These features suggest the
presence of either recent, ongoing and/or prolonged star formation
episodes, shedding new light on the evolution of these systems.
We aim at understanding the evolutionary path[s] of these early-type
galaxies and the mechanisms at the origin of their UV-bright
structures. We investigate with a multiλ approach the link
between the inner and the outer galaxy regions of a set of eleven
early-type galaxies selected because of their nearly passive stage of
evolution in the nuclear region.
This paper, second of a series, focuses on the information coming from
the comparison between UV features detected by Swift-UVOT, tracing
recent star formation, and the galaxy optical structure mapping older
stellar populations. We performed a surface photometric study of these
early-type galaxies, observed with Swift-UVOT UV filters, W2 2030Å
{lambda_0}, M2 2231Å {lambda_0}, W1 2634Å {lambda_0}, and UBV
bands.
BVRI photometry from other sources in the literature is also used. Our
integrated magnitude measurements have been analyzed and compared with
corresponding values in the literature. We characterize the overall
galaxy structure best fitting the UV and optical luminosity profiles
using a single Sersic law.
NGC 1366, NGC 1426, NGC 3818, NGC 3962 and NGC 7192 show featureless
luminosity profiles. Excluding NGC∼1366 which has a clear edge-on disk
(n∼1-2), and NGC 3818, the remaining three have Sersic's indices n∼3-4
in optical and a lower index in the UV. Bright ring/arm-like
structures are revealed by UV images and luminosity profiles of NGC
1415, NGC 1533, NGC 1543, NGC 2685, NGC 2974 and IC 2006. The
ring/arm-like structures are different from galaxy to galaxy. Sersic
indices of UV profiles for those galaxies are in the range n=1.5-3
both in S0s and in galaxies classified as "bona fide" ellipticals,
such as NGC 2974 and IC 2006.
We notice that in our sample optical Sersic indices are usually larger
than in the UV ones. (M2-V) color profiles are bluer in ring/arm-like
structures with respect to the galaxy body.
The lower values of Sersic's indices in the UV bands with respect to
optical ones, suggesting the presence of a disk, point out that the
role of the dissipation cannot be neglected in recent evolutionary
phases of these early-type galaxies.
Description:
UVOT is a 30cm telescope in the Swift platform operating both in
imaging and spectroscopy modes. We observed our ETGs in imaging in all
six available filters, W2 (λ0 2030), M2 (λ0 2231),
W1 (λ0 2634), U (λ0 3501), B (λ0 4329), V
(λ0 5402). Description of the filters, PSFs (FWHM 2.92" for
W2, 2.45" for M2, 2.37" for W1, 2.37" for U, 2.19" for B, 2.18"
for V), and calibrations are discussed in Breeveld et al.
(2010MNRAS.406.1687B 2010MNRAS.406.1687B, 2011i, in Gamma Ray Bursts 2010, AIP Conf.
Proc., 1358, 373).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
clusters.dat 32 11 Studied clusters
table4.dat 91 488 Luminosity profiles in the NUV and optical UVOT
bands
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Byte-by-byte Description of file: clusters.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Cluster Cluster name
10- 11 I2 h RAh Simbad right ascension (J2000)
13- 14 I2 min RAm Simbad right ascension (J2000)
16- 20 F5.2 s RAs Simbad right ascension (J2000)
22 A1 --- DE- Declination sign (J2000)
23- 24 I2 deg DEd Declination (J2000)
26- 27 I2 arcmin DEm Declination (J2000)
29- 32 F4.1 arcsec DEs Declination (J2000)
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Cluster Cluster name
15- 19 F5.1 arcsec amaj Semi-major axis
21- 25 F5.2 mag/arcsec+2 SuBrW2 ?=- Surface brightness in UVOT W2 band
27- 30 F4.2 mag/arcsec+2 e_SuBrW2 ?=- rms uncertainty on SuBrW2
33- 37 F5.2 mag/arcsec+2 SuBrM2 ?=- Surface brightness in UVOT M2 band
39- 43 F5.3 mag/arcsec+2 e_SuBrM2 ?=- rms uncertainty on SuBrM2
45- 49 F5.2 mag/arcsec+2 SuBrW1 ?=- Surface brightness in UVOT W1 band
51- 54 F4.2 mag/arcsec+2 e_SuBrW1 ?=- rms uncertainty on SuBrW1
57- 61 F5.2 mag/arcsec+2 SuBrU ?=- Surface brightness in UVOT U band (1)
63- 66 F4.2 mag/arcsec+2 e_SuBrU ?=- rms uncertainty on SuBrU
69- 73 F5.2 mag/arcsec+2 SuBrB ?=- Surface brightness in UVOT B band (1)
75- 78 F4.2 mag/arcsec+2 e_SuBrB ?=- rms uncertainty on SuBrB
81- 86 F6.3 mag/arcsec+2 SuBrV ?=- Surface brightness in UVOT V band (1)
88- 91 F4.2 mag/arcsec+2 e_SuBrV ?=- rms uncertainty on SuBrV
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Note (1): The U, B and V bands are not corrected for coincidence loss.
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Acknowledgements:
Roberto Rampazzo, roberto.rampazzo(at)oapd.inaf.it
References:
Trinchieri et al., Paper I 2015MNRAS.449.3021T 2015MNRAS.449.3021T
(End) Patricia Vannier [CDS] 07-Feb-2017