ABSTRACT
We outline theoretical predictions for extended emission from Mg ii, tracing cool ∼104 K gas in the circumgalactic medium (CGM) of star-forming galaxies in the high-resolution TNG50 ...cosmological magnetohydrodynamical simulation. We synthesize surface brightness maps of this strong rest-frame ultraviolet metal emission doublet (λλ2796, 2803), adopting the assumption that the resonant scattering of Mg ii can be neglected and connecting to recent and upcoming observations with the Keck/KCWI, VLT/MUSE, and BlueMUSE optical integral field unit spectrographs. Studying galaxies with stellar masses 7.5 < log (M⋆/M⊙) < 11 at redshifts z = 0.3, 0.7, 1, and 2 we find that extended Mg ii haloes in emission, similar to their Ly α counterparts, are ubiquitous across the galaxy population. Median surface brightness profiles exceed 10−19 erg s−1 cm−2 arcsec−2 in the central $\sim \,$10 s of kpc, and total halo Mg ii luminosity increases with mass for star-forming galaxies, reaching 1040 erg s−1 for M⋆ ∼ 109.5 M⊙. Mg ii halo sizes increase from a few kpc to ≳ 20 kpc at the highest masses, and sizes are larger for haloes in denser environments. Mg ii haloes are highly structured, clumpy, and asymmetric, with isophotal axial ratio increasing with galaxy mass. Similarly, the amount and distribution of Mg ii emission depends on the star formation activity of the central galaxy. Kinematically, inflowing versus outflowing gas dominates the Mg ii luminosity at high and low galaxy masses, respectively, although the majority of Mg ii halo emission at z ∼ 0.7 traces near-equilibrium fountain flows and gas with non-negligible rotational support, rather than rapidly outflowing galactic winds.
We analyze Mg II lambdalambda2796, 2803 and Fe II lambdalambda2586, 2600 absorption profiles in individual spectra of 105 galaxies at 0.3 < z < 1.4. Hubble Space Telescope Advanced Camera for Surveys ...imaging and our spectral analysis indicate that the outflow detection rate depends primarily on galaxy orientation: winds are detected in ~89% of galaxies having inclinations (i) < 30degrees (face-on), while the wind detection rate is ~45% in objects having i > 50 gamma (edge-on). We find that wind velocity is correlated with galaxy M sub(*) at 3.4sigma significance, while outflow equivalent width is correlated with SFR at 3.5sigma significance, suggesting hosts with higher SFR launch more material and/or generate a larger velocity spread for the absorbing clouds. However, the gas carries sufficient energy to reach distances gap50 kpc, and may therefore be a viable source of material for the massive, cool circumgalactic medium around bright galaxies at z ~ 0.
Abstract
We present spatially resolved spectroscopy from the Keck Cosmic Web Imager (KCWI) of a star-forming galaxy at
z
= 0.6942, which shows emission from the Mg
ii
λ
λ
2796, 2803 doublet in the ...circumgalactic medium (CGM) extending ∼37 kpc at 3
σ
significance in individual spaxels (1
σ
detection limit 4.8 × 10
−19
erg s
−1
cm
−2
arcsec
−2
). The target galaxy, selected from a near-UV spectroscopic survey of Mg
ii
line profiles at 0.3 <
z
< 1.4, has a stellar mass log (
M
*
/
M
⊙
) = 9.9, a star formation rate of 50
M
⊙
yr
−1
, and a morphology indicative of a merger. After deconvolution with the seeing, we obtain 5
σ
detections of Mg
ii
line emission extending for ∼31 kpc measured in 7-spaxel (1.1 arcsec
2
) apertures. Spaxels covering the galaxy stellar regions show clear P Cygni−like emission/absorption profiles, with the blueshifted absorption extending to relative velocities of
v
= −800 km s
−1
; however, the P Cygni profiles give way to pure emission at large radii from the central galaxy. We have performed 3D radiative transfer modeling to infer the geometry and velocity and density profiles of the outflowing gas. Our observations are most consistent with an isotropic outflow rather than biconical wind models with half-opening angles
ϕ
≤ 80°. Furthermore, our modeling suggests that a wind velocity profile that decreases with radius is necessary to reproduce the velocity widths and strengths of Mg
ii
line emission profiles at large circumgalactic radii. The extent of the Mg
ii
emission we measure directly is further corroborated by our modeling, where we rule out outflow models with extent <30 kpc.
SN2017egm is the closest (z = 0.03) H-poor superluminous supernova (SLSN-I) detected to date, and a rare example of an SLSN-I in a massive, metal-rich galaxy. We present the HST UV and optical ...spectra covering 1000-5500 , taken at +3 day relative to the peak. Our data reveal two absorption systems at redshifts matching the host galaxy NGC 3191 (z = 0.0307) and its companion galaxy (z = 0.0299) 73″ apart. Weakly damped Ly absorption lines are detected at these two redshifts, with H i column densities of (3.0 0.8) × 1019 and (3.7 0.9) × 1019 cm−2, respectively. This is an order of magnitude smaller than the H i column densities in the disks of nearby galaxies (>1010 M ) and suggests that SN2017egm is on the near side of NGC 3191 and has a low host extinction (E(B − V) ∼ 0.007). Using unsaturated metal absorption lines, we find that the host of SN2017egm probably has a solar or higher metallicity and is unlikely to be a dwarf companion to NGC 3191. Comparison of early-time UV spectra of SN2017egm, Gaia16apd, iPTF13ajg, and PTF12dam finds that the continuum at λ > 2800 is well fit by a blackbody, whereas the continuum at λ < 2800 is considerably below the model. The degree of UV suppression varies from source to source, with the 1400-2800 continuum flux ratio of 1.5 for Gaia16apd and 0.4 for iPTF13ajg. This cannot be explained by the differences in magnetar power or blackbody temperature. Finally, the UV spectra reveal a common set of seven broad absorption features and their equivalent widths are similar (within a factor of 2) among the four events.
We present Keck Cosmic Web Imager spectroscopy of the four putative images of the lensed quasar candidate J014710+463040 recently discovered by Berghea et al. The data verify the source as a ...quadruply lensed, broad absorption-line quasar having . We detect intervening absorption in the Fe ii λλ2586, 2600, Mg ii λλ2796, 2803, and/or C iv λλ1548, 1550 transitions in eight foreground systems, three of which have redshifts consistent with the photometric-redshift estimate reported for the lensing galaxy (zL 0.57). The source images probe these absorbers over transverse physical scales of 0.3-22 kpc, permitting assessment of the variation in metal-line equivalent width as a function of sight-line separation. We measure differences in of <40% across most of the sight-line pairs subtending 8-22 kpc, suggestive of a high degree of spatial coherence for the Mg ii-absorbing material. varies by >50% over the same scales across the majority of sight-line pairs, while C iv absorption exhibits a wide range in differences of 5%-80% within transverse distances of 3 kpc. These spatial variations are consistent with those measured in intervening absorbers detected toward lensed quasars drawn from the literature, in which and vary by ≤20% in 35 7% and 47 6% of sight lines separated by <10 kpc, respectively. J014710+463040 is one of only a handful of z > 2 quadruply lensed systems for which all four source images are very bright (r = 15.4-17.7 mag) and are easily separated in ground-based seeing conditions. As such, it is an ideal candidate for higher-resolution spectroscopy probing the spatial variation in the kinematic structure and physical state of intervening absorbers.
We study the kinematically narrow, low-ionization line emission from a bright, starburst galaxy at z = 0.69 using slit spectroscopy obtained with Keck/LRIS. The spectrum reveals strong absorption in ...Mg II and Fe II resonance transitions with Doppler shifts of --200 to --300 km s-1, indicating a cool gas outflow. Emission in Mg II near and redward of systemic velocity, in concert with the observed absorption, yields a P-Cygni-like line profile similar to those observed in the Ly Delta *a transition in Lyman break galaxies. Further, the Mg II emission is spatially resolved and extends significantly beyond the emission from stars and H II regions within the galaxy. Assuming that the emission has a simple, symmetric surface brightness profile, we find that the gas extends to distances 7 kpc. We also detect several narrow Fe II* fine-structure lines in emission near the systemic velocity, arising from energy levels that are radiatively excited directly from the ground state. We suggest that the Mg II and Fe II* emission is generated by photon scattering in the observed outflow and emphasize that this emission is a generic prediction of outflows. These observations provide the first direct constraints on the minimum spatial extent and morphology of the wind from a distant galaxy. Estimates of these parameters are crucial for understanding the impact of outflows in driving galaxy evolution.
Simulating the carbon footprint of galactic haloes Bird, Simeon; Rubin, Kate H. R; Suresh, Joshua ...
Monthly notices of the Royal Astronomical Society,
10/2016, Letnik:
462, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We compare simulations, including the Illustris simulations, to observations of C iv and C ii absorption at z = 2–4. These are the C iv column density distribution function in the column density ...range 1012–1015 cm−2, the C iv equivalent width distribution at 0.1–2 Å, and the covering fractions and equivalent widths of C iv1548 Å and C ii 1337 Å around damped Lyman α systems (DLAs). In the context of the feedback models that we investigate, all C iv observations favour the use of more energetic wind models, which are better able to enrich the gas surrounding haloes. We propose two ways to achieve this: an increased wind velocity and an increase in wind thermal energy. However, even our most energetic wind models do not produce enough absorbers with C iv equivalent width >0.6 Å, which in our simulations are associated with the most massive haloes. All simulations are in reasonable agreement with the C ii covering fraction and equivalent widths around damped Lyman α absorbers, although there is a moderate deficit in one bin 10–100 kpc from the DLA. Finally, we show that the C iv in our simulations is predominantly photoionized.
The circumgalactic medium (CGM) close to ∼L* star-forming galaxies hosts strong Mg ii λ2796 absorption (with equivalent width W2796 > 0.1 ) with a near-unity covering fraction. To characterize the ...spatial coherence of this absorption, we analyze the W2796 distribution in the CGM of 27 star-forming galaxies detected in deep spectroscopy of bright background (b/g) galaxies first presented in Rubin et al. The sample foreground (f/g) systems have redshifts and stellar masses 9.1 < log M*/M < 11.1, and the b/g galaxies provide spatially extended probes with half-light radii at projected distances < 50 kpc. Our analysis also draws on literature W2796 values measured in b/g QSO spectroscopy probing the halos of f/g galaxies with a similar range in M* at z ∼ 0.25. By making the assumptions that (1) samples of like galaxies exhibit similar circumgalactic W2796 distributions and, (2) within a given halo, the quantity log W2796 has a Gaussian distribution with a dispersion that is constant with M* and , we use this QSO-galaxy pair sample to construct a model for the log W2796 distribution in the CGM of low-redshift galaxies. Adopting this model, we then demonstrate the dependence of the observed log W2796 distribution on the ratio of the surface area of the b/g probe to the projected absorber surface area (xA AG/AA), finding that distributions that assume xA ≥ 15 are statistically inconsistent with that observed toward our b/g galaxy sample at a 95% confidence level. This limit, in combination with the b/g galaxy sizes, requires that the length scale over which W2796 does not vary (i.e., the "coherence scale" of Mg ii absorption) is A > kpc. This novel constraint on the morphology of cool, photoionized structures in the inner CGM suggests that either these structures each extend over kiloparsec scales or the number and velocity dispersion of these structures are spatially correlated over the same scales.
ABSTRACT
We have re-observed $\rm \sim$40 low-inclination, star-forming galaxies from the MaNGA survey (σ ∼ 65 km s−1) at ∼6.5 times higher spectral resolution (σ ∼ 10 km s−1) using the HexPak ...integral field unit on the WIYN 3.5-m telescope. The aim of these observations is to calibrate MaNGA’s instrumental resolution and to characterize turbulence in the warm interstellar medium and ionized galactic outflows. Here we report the results for the Hα region observations as they pertain to the calibration of MaNGA’s spectral resolution. Remarkably, we find that the previously reported MaNGA line-spread-function (LSF) Gaussian width is systematically underestimated by only 1 per cent. The LSF increase modestly reduces the characteristic dispersion of H ii regions-dominated spectra sampled at 1–2 kpc spatial scales from 23 to 20 km s−1 in our sample, or a 25 per cent decrease in the random-motion kinetic energy. This commensurately lowers the dispersion zeropoint in the relation between line-width and star-formation rate surface-density in galaxies sampled on the same spatial scale. This modest zero-point shift does not appear to alter the power-law slope in the relation between line-width and star-formation rate surface-density. We also show that adopting a scheme whereby corrected line-widths are computed as the square root of the median of the difference in the squared measured line width and the squared LSF Gaussian avoids biases and allows for lower signal-to-noise data to be used reliably.
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