1,306 research outputs found
The physical properties of S0 galaxy PGC 26218: the origin of starburst and star formation
We present 2D-spectroscopic observations from Centro Astron\'omico Hispano
Alem\'an (CAHA) 3.5 m telescope and the millimetre observation from NOrthern
Extended Millimeter Array (NOEMA) of the nearby S0 galaxy PGC 26218, which
shows central star-formation activity and post-starburst outside in the disk.
We estimate the star formation rate (SFR = ) and molecular gas mass ($M_{\rm H_{2}}=7.60\pm0.15\
M_{\odot}\alpha\rm H_{2}\alpha_{\rm CO}J\alphaJ^{\circ}\alphaJ\sim\rm km\ s^{-1}J5.2\arcsec\sim$ 0.6 kpc) and the latter overlaps with one
of the optical cores. These results support that PGC 26218 may have experienced
a gas-rich minor merger, extending its star formation and locating it in the
SFMS.Comment: accepted for publication in ApJ, 16 page, 12 figure
PGC 38025: A Star-forming Lenticular Galaxy With an Off-nuclear Star-forming Core
Lenticular galaxies (S0s) were considered mainly as passive evolved spirals
due to environmental effects for a long time; however, most S0s in the field
cannot fit into this common scenario. In this work, we study one special case,
SDSS J120237.07+642235.3 (PGC 38025), a star-forming field S0 galaxy with an
off-nuclear blue core. We present optical integral field spectroscopic (IFS)
observation with the 3.5 meter telescope at Calar Alto (CAHA) Observatory, and
high-resolution millimeter observation with the NOrthern Extended Millimeter
Array (NOEMA). We estimated the star formation rate (SFR = 0.446 ) and gaseous metallicity (12 + log(O/H) = 8.42) for PGC 38025, which
follows the star formation main sequence and stellar mass - metallicity
relation. We found that the ionized gas and cold molecular gas in PGC 38025
show the same spatial distribution and kinematics, whilst rotating misaligned
with stellar component. The off-nuclear blue core is locating at the same
redshift as PGC 38025 and its optical spectrum suggest it is \rm H\,{\sc ii}
region. We suggest that the star formation in PGC 38025 is triggered by a
gas-rich minor merger, and the off-nuclear blue core might be a local
star-formation happened during the accretion/merger process.Comment: 16 pages, 13 figures, accepted for publication in Ap
Surface Photometry and Radial Color Gradients of Nearby Luminous Early-type Galaxies in SDSS Stripe 82
We make use of the images from the Sloan Digital Sky Survey Stripe 82 to
present an analysis of r band surface brightness profiles and radial color
gradients (g - r, u - r) in 111 nearby early-type galaxies (ETGs). With Stripe
82 images, we are able to pay special attentions to the low-surface-brightness
areas (LSB areas) of the galaxies. The LSB areas make a difference to the
Sersic fittings and concentration indices, making both the indices less than
the typical values for ETGs. There are about 60% negative color gradients
(red-core) within 1.5Re , much more than the approximately 10% positive ones
(blue-core) within the same radius. However, taking into account of the LSB
areas, we find that the color gradients are not necessarily monotonic: about
one third of the red-core (or blue-core) galaxies have positive (or negative)
color gradients in the outer areas. So LSB areas not only make ETGs' Sersic
profiles deviate from de Vaucouleur ones and shift to the disk end, but also
reveal that quite a number of ETGs have opposite color gradients in inner and
outer areas. These outcomes remind us the necessity of double-Sersic fitting.
These LSB phenomena may be interpreted by mergers and thus different
metallicity in the outer areas. Isophotal parameters are also discussed briefly
in this paper: more disky nearby ETGs are spotted than boxy ones.Comment: 14 pages, 12 figure
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