Interacting galaxies provide us with an excellent laboratory for studying a number of physical phenomena associated with these processes. In this paper, we present a spectroscopic and kinematic ...analysis of the interacting galaxy NGC 4656 and its companion tidal dwarf galaxy (TDG) candidate, NGC 4656UV. Using Fabry-Perot and GMOS multislit data, we investigated the possible origin of NGC 4656UV. We found that NGC 4656UV has a low metallicity (12 + log(O/H)∼8.2) and it follows the mass-metallicity relation for normal dwarf galaxies. For NGC 4656, we estimated a flat oxygen abundance gradient of β = -0.027 ± 0.029 dex kpc-1, which suggests the presence of gas flows induced by gravitational interactions. By analysing radial velocity profiles and by fitting a kinematic model of the observed velocity field, we confirm the literature result that NGC 4656 consists of one single body instead of two objects. We estimated a dynamical mass of 6.8^{1.8}_{-0.6}× 109 M⊙ and R of 12.1 kpc from the kinematic model of NGC 4656. Although the observed velocity field is dominated by rotation at large scales (Vmax/σ ≳2.8), important non-rotational motions are present at small scales. Based on these new results, and on previously published information, we propose that NGC 4656 and 4656UV are a pair of interacting galaxies. NGC 4656UV is a companion of NGC 4656 and it does not have a tidal origin. The interaction between the two could have triggered the star formation in NGC 4656UV and increased the star formation in the north-east side of NGC 4656.
ABSTRACT
Cool gas (T∼104 K) traced by hydrogen Ly α emission is now routinely detected around z ∼ 3 quasars, but little is known about their molecular gas reservoirs. Here, we present an APEX ...spectroscopic survey of the CO(6-5), CO(7-6), and C i(2-1) emission lines for nine quasars from the QSO MUSEUM survey, which have similar UV luminosities, but very diverse Ly α nebulae. These observations ($\lesssim ngle ~\rm rms~\rangle =2.6$ mJy in 300 km s−1) detected three CO(6-5) lines with 3.4≤ICO(6-5) ≤5.1 Jy km s−1, 620≤FWHM≤707 km s−1, and three C i(2-1) lines with 2.3$\le I_{\rm C{\small I}(2-1)} \le$15.7 Jy km s−1, 329≤FWHM≤943 km s−1. For the CO and C i detected sources, we constrain the molecular gas reservoirs to be $\rm M_{H_{2}} = (0.4-6.9) \times 10^{11}\, M_{\odot }$, while the non-detections imply $\rm M_{H_{2}} \lt 1.1\times 10^{11}\, M_{\odot }$. We compare our observations with the extended Ly α properties to understand the link between the cool and the molecular gas phases. We find large velocity shifts between the bulk of Ly α and the molecular gas systemic redshift in five sources (from ∼−400 to ∼+1200 km s−1). The sources with the largest shifts have the largest Ly α line widths in the sample, suggesting more turbulent gas conditions and/or large-scale inflows/outflows around these quasars. We also find that the brightest ($I_{\rm C{\small I}(2-1)}=15.7\pm 3.7~\rm Jy~km~s^{-1}$) and the widest (FWHM∼900 km s−1) lines are detected for the smallest and dimmest Ly α nebulae. From this, we speculate that host galaxy obscuration can play an important role in reducing the ionizing and Ly α photons able to escape to halo scales, and/or that these systems are hosted by more massive haloes.
ABSTRACT
We present new Gemini imaging and spectroscopic data of the system Arp 314, which consists of a triplet of interacting galaxies. This new imagery exhibits tidal tails and stellar bridges ...between the galaxies' members and confirms the past interactions. Using this data set, we have analysed the physical properties of 22 star-forming regions located in the main disc of these galaxies, as well as in the intergalactic medium. All these regions have emission lines typical of young ages and a couple of them display very high Hα luminosities (LHα ∼ 1040 erg s−1). Using the star-forming regions located in Arp 314-1, we derive its gas-phase oxygen-abundance distribution, which suggests a flatter behaviour than the distribution shown by non-interacting systems. This is in agreement with results obtained for other interacting systems and simulations. The presence of gas flows, as indicated by its complex kinematics, could explain this finding. Most of the star formation in Arp 314-2 is located in a central starburst, where double Hα profiles can be identified, as shown by archival Fabry–Perot data. Additionally, we found that the irregular galaxy Arp 314-3 has a low oxygen abundance. Considering its luminosity, this object has a primordial origin, and it was not formed during the interaction event that this system has experienced.
We conducted a systematic survey of the environment of high-redshift quasars at submillimeter wavelengths to unveil and characterize the surrounding distribution of dusty submillimeter galaxies ...(SMGs). We took sensitive observations with the SCUBA-2 instrument on the
James Clerk Maxwell
Telescope for 3 enormous Lyman-alpha nebulae (ELANe) and 17 quasar fields in the redshift range 2 <
z
< 4.2 selected from recent Lyman alpha (Ly
α
) surveys. These observations uncovered 523 and 101 sources at 850 μm and 450 μm, respectively, with signal-to-noise ratios (
S
/
N
) > 4 or detected in both bands at
S
/
N
> 3. We ran self-consistent Monte Carlo simulations to construct 850 μm number counts and unveil an excess of sources in 75% of the targeted fields. Overall, regions around ELANe and quasars are overabundant with respect to blank fields by a factor of 3.4 ± 0.4 and 2.5 ± 0.2, respectively (weighted averages). Therefore, the excess of submillimeter sources is likely part of the megaparsec-scale environment around these systems. By combining all fields and repeating the count analysis in radial apertures, we find (at high significance, ≳5
σ
) a decrease in the overdensity factor from > 3 within ∼2 cMpc to ∼2 in the annulus at the edge of the surveyed field (∼10 cMpc), which suggests that the physical extent of the overdensities is larger than our maps. We computed preferred directions for the overdensities of SMGs from the positions of the sources and used them to orient and create stacked maps of source densities for the quasars’ environment. This stacking unveils an elongated structure reminiscent of a large-scale filament with a scale width of ≈3 cMpc. Finally, the directions of the overdensities are roughly aligned with the major axis of the Ly
α
nebulae, suggesting that the latter trace, on scales of hundreds of kiloparsecs, the central regions of the projected large-scale structure described by the SMGs on megaparsec scales. Confirming member associations of the SMGs is required to further characterize their spatial and kinematic distribution around ELANe and quasars.
ABSTRACT
SN 2017jgh is a type IIb supernova discovered by Pan-STARRS during the C16/C17 campaigns of the Kepler/K2 mission. Here, we present the Kepler/K2 and ground based observations of SN 2017jgh, ...which captured the shock cooling of the progenitor shock breakout with an unprecedented cadence. This event presents a unique opportunity to investigate the progenitors of stripped envelope supernovae. By fitting analytical models to the SN 2017jgh light curve, we find that the progenitor of SN 2017jgh was likely a yellow supergiant with an envelope radius of $\sim 50{\!-\!}290\, {\rm R}_{\odot }$, and an envelope mass of $\sim 0{\!-\!}1.7\, {\rm M}_{\odot }$. SN 2017jgh likely had a shock velocity of ∼7500−10 300 km s−1. Additionally, we use the light curve of SN 2017jgh to investigate how early observations of the rise contribute to constraints on progenitor models. Fitting just the ground based observations, we find an envelope radius of $\sim 50{\!-\!}330\, {\rm R}_{\odot }$, an envelope mass of $\sim 0.3{\!-\!}1.7\, {\rm M}_{\odot }$ and a shock velocity of ∼9000−15 000 km s−1. Without the rise, the explosion time cannot be well constrained that leads to a systematic offset in the velocity parameter and larger uncertainties in the mass and radius. Therefore, it is likely that progenitor property estimates through these models may have larger systematic uncertainties than previously calculated.
ABSTRACT
In this paper we present a thorough discussion about the photometric redshift (photo-z) performance of the Southern Photometric Local Universe Survey (S-PLUS). This survey combines a seven ...narrow +5 broad passband filter system, with a typical photometric-depth of r ∼ 21 AB. For this exercise, we utilize the Data Release 1 (DR1), corresponding to 336 deg2 from the Stripe-82 region. We rely on the BPZ2 code to compute our estimates, using a new library of SED models, which includes additional templates for quiescent galaxies. When compared to a spectroscopic redshift control sample of ∼100 k galaxies, we find a precision of σz <0.8 per cent, <2.0 per cent, or <3.0 per cent for galaxies with magnitudes r < 17, <19, and <21, respectively. A precision of 0.6 per cent is attained for galaxies with the highest Odds values. These estimates have a negligible bias and a fraction of catastrophic outliers inferior to 1 per cent. We identify a redshift window (i.e. 0.26 < z < 0.32) where our estimates double their precision, due to the simultaneous detection of two emission lines in two distinct narrow bands; representing a window opportunity to conduct statistical studies such as luminosity functions. We forecast a total of ∼2 M, ∼16 M and ∼32 M galaxies in the S-PLUS survey with a photo-z precision of σz <1.0 per cent, <2.0 per cent, and <2.5 per cent after observing 8000 deg2. We also derive redshift probability density functions, proving their reliability encoding redshift uncertainties and their potential recovering the n(z) of galaxies at z < 0.4, with an unprecedented precision for a photometric survey in the Southern hemisphere.
ABSTRACT
The Southern Photometric Local Universe Survey (S-PLUS) is imaging ∼9300 deg2 of the celestial sphere in 12 optical bands using a dedicated 0.8 m robotic telescope, the T80-South, at the ...Cerro Tololo Inter-american Observatory, Chile. The telescope is equipped with a 9.2k × 9.2k e2v detector with 10 $\rm {\mu m}$ pixels, resulting in a field of view of 2 deg2 with a plate scale of 0.55 arcsec pixel−1. The survey consists of four main subfields, which include two non-contiguous fields at high Galactic latitudes (|b| > 30°, 8000 deg2) and two areas of the Galactic Disc and Bulge (for an additional 1300 deg2). S-PLUS uses the Javalambre 12-band magnitude system, which includes the 5 ugriz broad-band filters and 7 narrow-band filters centred on prominent stellar spectral features: the Balmer jump/OII, Ca H + K, H δ, G band, Mg b triplet, H α, and the Ca triplet. S-PLUS delivers accurate photometric redshifts (δz/(1 + z) = 0.02 or better) for galaxies with r < 19.7 AB mag and z < 0.4, thus producing a 3D map of the local Universe over a volume of more than $1\, (\mathrm{Gpc}/h)^3$. The final S-PLUS catalogue will also enable the study of star formation and stellar populations in and around the Milky Way and nearby galaxies, as well as searches for quasars, variable sources, and low-metallicity stars. In this paper we introduce the main characteristics of the survey, illustrated with science verification data highlighting the unique capabilities of S-PLUS. We also present the first public data release of ∼336 deg2 of the Stripe 82 area, in 12 bands, to a limiting magnitude of r = 21, available at datalab.noao.edu/splus.
Cool gas (T$\sim$10$^{4}$~K) traced by hydrogen Ly$\alpha$ emission is now
routinely detected around $z\sim3$ quasars, but little is known about their
molecular gas reservoirs. Here, we present an ...APEX spectroscopic survey of the
CO(6-5), CO(7-6) and CI(2-1) emission lines for 9 quasars from the QSO MUSEUM
survey which have similar UV luminosities, but very diverse Ly$\alpha$ nebulae.
These observations ($\langle~\rm rms~\rangle=2.6$~mJy in 300~km~s$^{-1}$)
detected three CO(6-5) lines with 3.4$\leq I_{\rm CO(6-5)}
\leq$5.1~Jy~km~s$^{-1}$, 620$\leq$FWHM$\leq$707~km~s$^{-1}$, and three
CI(2-1) lines with 2.3$\leq I_{\rm CI(2-1)} \leq$15.7~Jy~km~s$^{-1}$,
329$\leq$FWHM$\leq$943~km~s$^{-1}$. For the CO and CI detected sources, we
constrain the molecular gas reservoirs to be $\rm M_{H_{2}} = (0.4-6.9) \times
10^{11} M_{\odot}$, while the non-detections imply $\rm M_{H_{2}} < 1.1\times
10^{11} M_{\odot}$. We compare our observations with the extended Ly$\alpha$
properties to understand the link between the cool and the molecular gas
phases. We find large velocity shifts between the bulk of Ly$\alpha$ and the
molecular gas systemic redshift in five sources (from $\sim$-400 to
$\sim+$1200~km~s$^{-1}$). The sources with the largest shifts have the largest
Ly$\alpha$ line widths in the sample, suggesting more turbulent gas conditions
and/or large-scale inflows/outflows around these quasars. We also find that the
brightest ($I_{\rmCI(2-1)}=15.7\pm3.7~\rm Jy~km~s^{-1}$) and the widest
(FWHM$\sim$900~km~s$^{-1}$) lines are detected for the smallest and dimmest
Ly$\alpha$ nebulae. From this, we speculate that host galaxy obscuration can
play an important role in reducing the ionizing and Ly$\alpha$ photons able to
escape to halo scales, and/or that these systems are hosted by more massive
halos.
We present an ultraviolet-to-infrared search for the electromagnetic (EM) counterpart to GW190425, the second-ever binary neutron star (BNS) merger discovered by the LIGO-Virgo-KAGRA Collaboration ...(LVK). GW190425 was more distant and had a larger localization area than GW170817, therefore we use a new tool teglon to redistribute the GW190425 localization probability in the context of galaxy catalogs within the final localization volume. We derive a 90th percentile area of 6,688 deg\(^{2}\), a \(\sim\)1.5\(\times\) improvement relative to the LIGO/Virgo map, and show how teglon provides an order of magnitude boost to the search efficiency of small (\(\leq\)1 deg\(^{2}\)) field-of-view instruments. We combine our data with all publicly reported imaging data, covering 9,078.59 deg\(^2\) of unique area and 48.13% of the LIGO/Virgo-assigned localization probability, to calculate the most comprehensive kilonova, short gamma-ray burst (sGRB) afterglow, and model-independent constraints on the EM emission from a hypothetical counterpart to GW190425 to date under the assumption that no counterpart was found in these data. If the counterpart were similar to AT 2017gfo, there was a 28.4% chance that it would have been detected in the combined dataset. We are relatively insensitive to an on-axis sGRB, and rule out a generic transient with a similar peak luminosity and decline rate as AT 2017gfo to 30% confidence. Finally, across our new imaging and all publicly-reported data, we find 28 candidate optical counterparts that we cannot rule out as being associated with GW190425, finding that 4 such counterparts discovered within the localization volume and within 5 days of merger exhibit luminosities consistent with a kilonova.
SN 2017jgh is a type IIb supernova discovered by Pan-STARRS during the C16/C17 campaigns of the Kepler/K2 mission. Here we present the Kepler/K2 and ground based observations of SN 2017jgh, which ...captured the shock cooling of the progenitor shock breakout with an unprecedented cadence. This event presents a unique opportunity to investigate the progenitors of stripped envelope supernovae. By fitting analytical models to the SN 2017jgh lightcurve, we find that the progenitor of SN 2017jgh was likely a yellow supergiant with an envelope radius of \(\sim50-290~R_{\odot}\), and an envelope mass of \(\sim0-1.7~M_{\odot}\). SN 2017jgh likely had a shock velocity of \(\sim7500-10300\) km s\(^{-1}\). Additionally, we use the lightcurve of SN 2017jgh to investigate how early observations of the rise contribute to constraints on progenitor models. Fitting just the ground based observations, we find an envelope radius of \(\sim50-330~R_{\odot}\), an envelope mass of \(\sim0.3-1.7~M_{\odot}\) and a shock velocity of \(\sim9,000-15,000\) km s\(^{-1}\). Without the rise, the explosion time can not be well constrained which leads to a systematic offset in the velocity parameter and larger uncertainties in the mass and radius. Therefore, it is likely that progenitor property estimates through these models may have larger systematic uncertainties than previously calculated.
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