36 research outputs found
Near-infrared adaptive optics imaging of infrared luminous galaxies: the brightest cluster magnitude - star formation rate relation
We have established a relation between the brightest super star cluster
magnitude in a galaxy and the host star formation rate (SFR) for the first time
in the near infrared (NIR). The data come from a statistical sample of ~ 40
luminous IR galaxies (LIRGs) and starbursts utilizing K-band adaptive optics
imaging. While expanding the observed relation to longer wavelengths, less
affected by extinction effects, it also pushes to higher SFRs. The relation we
find, M_K ~ - 2.6 log SFR, is similar to that derived previously in the optical
and at lower SFRs. It does not, however, fit the optical relation with a single
optical to NIR color conversion, suggesting systematic extinction and/or age
effects. While the relation is broadly consistent with a size-of-sample
explanation, we argue physical reasons for the relation are likely as well. In
particular, the scatter in the relation is smaller than expected from pure
random sampling strongly suggesting physical constraints. We also derive a
quantifiable relation tying together cluster-internal effects and host SFR
properties to possibly explain the observed brightest SSC magnitude vs. SFR
dependency.Comment: 6 pages, 4 figures, accepted for publication in ApJ Letter
Star formation and AGN activity in a sample of local Luminous Infrared Galaxies through multi-wavelength characterization
Nuclear starbursts and AGN activity are the main heating processes in
luminous infrared galaxies (LIRGs) and their relationship is fundamental to
understand galaxy evolution. In this paper, we study the star-formation and AGN
activity of a sample of 11 local LIRGs imaged with subarcsecond angular
resolution at radio (8.4GHz) and near-infrared (m) wavelengths. This
allows us to characterize the central kpc of these galaxies with a spatial
resolution of pc. In general, we find a good spatial correlation
between the radio and the near-IR emission, although radio emission tends to be
more concentrated in the nuclear regions. Additionally, we use an MCMC code to
model their multi-wavelength spectral energy distribution (SED) using template
libraries of starburst, AGN and spheroidal/cirrus models, determining the
luminosity contribution of each component, and finding that all sources in our
sample are starburst-dominated, except for NGC6926 with an AGN contribution of
\%. Our sources show high star formation rates ( to
), supernova rates (0.4 to
), and similar starburst ages (13 to
), except for the young starburst (9Myr) in NGC6926. A
comparison of our derived star-forming parameters with estimates obtained from
different IR and radio tracers shows an overall consistency among the different
star formation tracers. AGN tracers based on mid-IR, high-ionization line
ratios also show an overall agreement with our SED model fit estimates for the
AGN. Finally, we use our wide-band VLA observations to determine pixel-by-pixel
radio spectral indices for all galaxies in our sample, finding a typical median
value () for synchrotron-powered LIRGs.Comment: Accepted for publication in MNRAS. 20 pages, 12 figure
LSQ13ddu: a rapidly evolving stripped-envelope supernova with early circumstellar interaction signatures
This paper describes the rapidly evolving and unusual supernova LSQ13ddu, discovered by the La Silla-QUEST survey. LSQ13ddu displayed a rapid rise of just 4.8 ± 0.9 d to reach a peak brightness of â19.70 ± 0.02 mag in the LSQgr band. Early spectra of LSQ13ddu showed the presence of weak and narrow HeI features arising from interaction with circumstellar material (CSM). These interaction signatures weakened quickly, with broad features consistent with those seen in stripped-envelope SNe becoming dominant around two weeks after maximum. The narrow HeI velocities are consistent with the wind velocities of luminous blue variables but its spectra lack the typically seen hydrogen features. The fast and bright early light curve is inconsistent with radioactive â”â¶Ni powering but can be explained through a combination of CSM interaction and an underlying â”â¶Ni decay component that dominates the later time behaviour of LSQ13ddu. Based on the strength of the underlying broad features, LSQ13ddu appears deficient in He compared to standard SNe Ib
Observations of the low-luminosity Type Iax supernova 2019gsc: a fainter clone of SN 2008ha?
We present optical photometric and spectroscopic observations of the faint-and-fast evolving Type Iax supernova (SN) 2019gsc, extending from the time of g-band maximum until about 50 d post-maximum, when the object faded to an apparent r-band magnitude m(r )= 22.48 +/- 0.11 mag. SN 2019gsc reached a peak luminosity of only M-g = -13.58 +/- 0.15 mag, and is characterized with a post-maximum decline rate Delta m(15)(g) = 1.08 +/- 0.14 mag. These light curve parameters are comparable to those measured for SN 2008ha of M-g = -13.89 +/- 0.14 mag at peak and Delta m(15)(g) =1.80 +/- 0.03 mag. The spectral features of SN 2019gsc also resemble those of SN 2008ha at similar phases. This includes both the extremely low ejecta velocity at maximum, similar to 3000 km s(-1) and at late-time (phase +54 d) strong forbidden iron and cobalt lines as well as both forbidden and permitted calcium features. Furthermore, akin to SN 2008ha, the bolometric light curve of SN 2019gsc is consistent with the production of approximate to 0.003 +/- 0.001 M-circle dot of Ni-56. The explosion parameters, M-ej approximate to 0.13 M-circle dot and E-k approximate to 12 x 10(48) erg, are also similar to those inferred for SN 2008ha. We estimate a subsolar oxygen abundance for the host galaxy of SN 2019gsc (12 + log(10)(O/H) =8.10 +/- 0.18 dex), consistent with the equally metal-poor environment of SN 2008ha. Altogether, our data set for SN 2019gsc indicates that this is a member of a small but growing group of extreme SN Iax that includes SN 2008ha and SN 2010ae
The Massive Progenitor of the Possible Type II-Linear Supernova 2009hd in Messier 66
We present observations of SN2009hd in the nearby galaxy M66. This SN is one
of the closest to us in recent years but heavily obscured by dust, rendering it
unusually faint in the optical, given its proximity. We find that the observed
properties of SN2009hd support its classification as a possible Type II-L SN, a
relatively rare subclass of CC-SNe. High-precision relative astrometry has been
employed to attempt to identify a SN progenitor candidate, based on a
pixel-by-pixel comparison between HST F555W and F814W images of the SN site
prior to explosion and at late times. A progenitor candidate is identified in
the F814W images only; this object is undetected in F555W. Significant
uncertainty exists in the astrometry, such that we cannot definitively identify
this object as the SN progenitor. Via insertion of artificial stars into the
pre-SN HST images, we are able to constrain the progenitor's properties to
those of a possible supergiant, with M(F555W)0>-7.6 mag and (V-I) 0>0.99 mag.
The magnitude and color limits are consistent with a luminous RSG; however,
they also allow for the possibility that the star could have been more yellow
than red. From a comparison with theoretical massive-star evolutionary tracks,
which include rotation and pulsationally enhanced mass loss, we can place a
conservative upper limit on the initial mass for the progenitor of <20 M_sun.
If the actual mass of the progenitor is near the upper range allowed by our
derived mass limit, then it would be consistent with that for the identified
progenitors of the SNII-L 2009kr and the high-luminosity SNII-P 2008cn. The
progenitors of these three SNe may possibly bridge the gap between lower-mass
RSG that explode as SNeII-P and LBV, or more extreme RSG, from which the more
exotic SNeII-n may arise. Very late-time imaging of the SN2009hd site may
provide us with more clues regarding the true nature of its progenitor.Comment: 19 pages, 9 figures, 3 tables, accepted for publication in Ap
The Extended Hubble Space Telescope Supernova Survey: The Rate of Core Collapse Supernovae to z~1
We use a sample of 45 core collapse supernovae detected with the Advanced
Camera for Surveys on-board the Hubble Space Telescope to derive the core
collapse supernova rate in the redshift range 0.1<z<1.3. In redshift bins
centered on =0.39, =0.73, and =1.11, we find rates 3.00
{+1.28}{-0.94}{+1.04}{-0.57}, 7.39 {+1.86}{-1.52}{+3.20}{-1.60}, and 9.57
{+3.76}{-2.80}{+4.96}{-2.80}, respectively, given in units yr^{-1} Mpc^{-3}
10^{-4} h_{70}^3. The rates have been corrected for host galaxy extinction,
including supernovae missed in highly dust enshrouded environments in infrared
bright galaxies. The first errors represent statistical while the second are
the estimated systematic errors. We perform a detailed discussion of possible
sources of systematic errors and note that these start to dominate over
statistical errors at z>0.5, emphasizing the need to better control the
systematic effects. For example, a better understanding of the amount of dust
extinction in the host galaxies and knowledge of the supernova luminosity
function, in particular the fraction of faint M > -15 supernovae, is needed to
better constrain the rates. When comparing our results with the core collapse
supernova rate based on the star formation rate, we find a good agreement,
consistent with the supernova rate following the star formation rate, as
expected.Comment: 12 pages, 4 figures, ApJ, replaced to match version in pres