- ID:
- ivo://CDS.VizieR/J/ApJS/204/14
- Title:
- Deep Chandra observations of NGC 4649. I.
- Short Name:
- J/ApJS/204/14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the X-ray source catalog for the Chandra monitoring observations of the elliptical galaxy, NGC 4649 (M60). The galaxy has been observed with Chandra ACIS-S3 in six separate pointings, reaching a total exposure of 299ks. There are 501 X-ray sources detected in the 0.3-8.0keV band in the merged observation or in one of the six individual observations; 399 sources are located within the D_25_ ellipse. The observed 0.3-8.0keV luminosities of these 501 sources range from 9.3x10^36^erg/s to 5.4x10^39^erg/s. The 90% detection completeness limit within the D_25_ ellipse is 5.5x10^37^erg/s. Based on the surface density of background active galactic nuclei (AGNs) and detection completeness, we expect ~45 background AGNs among the catalog sources (~15 within the D_25_ ellipse). There are nine sources with luminosities greater than 10^39^erg/s, which are candidates for ultraluminous X-ray sources. The nuclear source of NGC 4649 is a low-luminosity AGN, with an intrinsic 2.0-8.0keV X-ray luminosity of 1.5x10^38^erg/s. The X-ray colors suggest that the majority of the catalog sources are low-mass X-ray binaries (LMXBs). We find that 164 of the 501 X-ray sources show long-term variability, indicating that they are accreting compact objects. We discover four transient candidates and another four potential transients. We also identify 173 X-ray sources (141 within the D_25_ ellipse) that are associated with globular clusters (GCs) based on Hubble Space Telescope and ground-based data; these LMXBs tend to be hosted by red GCs. Although NGC 4649 has a much larger population of X-ray sources than the structurally similar early-type galaxies, NGC 3379 and NGC 4278, the X-ray source properties are comparable in all three systems.
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- ID:
- ivo://CDS.VizieR/J/ApJ/862/73
- Title:
- Deep Chandra obs. of X-ray point sources in M87
- Short Name:
- J/ApJ/862/73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of X-ray source populations in M87, the cD galaxy of the Virgo cluster, using 12 archival Chandra observations with a total exposure of ~680ks spanning about a decade. A total of 346 point-like sources are detected down to a limiting 0.5-8keV luminosity of 4x10^37^erg/s and out to a galactocentric radius of ~40kpc. We cross-correlate the X-ray sources with published catalogs of globular clusters (GCs), derived from the ACS Virgo Cluster Survey and the Next Generation Virgo Cluster Survey. This results in 122 matches, making it one of the largest samples of GC-hosting X-ray sources in an external galaxy. These sources, most likely low-mass X-ray binaries (LMXBs), correspond to ~5% of all known GCs within the Chandra field-of-view. Conversely, ~50% of the detected X-ray sources are found in a GC. Moreover, red (metal-rich) GCs are ~2.2 times more likely to host an X-ray source than blue (metal-poor) GCs. We also examine 76 currently known ultra-compact dwarf galaxies around M87 but find no significant X-ray counterparts. After statistically accounting for the cosmic X-ray background, we identify ~110 field-LMXBs. The GC-LMXBs and field-LMXBs differ in their luminosity function and radial distribution, which indicates that the latter cannot be primarily originated from GCs. Using another set of deep Chandra observations toward ~100kpc northwest of the M87 center, we statistically constrain the abundance of field-LMXBs in the stellar halo, which is consistent with that found in the central region. We also identify 40 variable X-ray sources, among which one source is likely a black hole binary residing in a GC.
- ID:
- ivo://CDS.VizieR/J/ApJ/758/135
- Title:
- DEEP2 galaxies with UV spectra in the EGS
- Short Name:
- J/ApJ/758/135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate galactic-scale outflowing winds in 72 star-forming galaxies at z~1 in the Extended Groth Strip. Galaxies were selected from the DEEP2 survey and follow-up LRIS spectroscopy was obtained covering Si II, C IV, Fe II, Mg II, and Mg I lines in the rest-frame ultraviolet. Using Galaxy Evolution Explorer (GALEX), Hubble Space Telescope (HST), and Spitzer imaging available for the Extended Groth Strip, we examine galaxies on a per-object basis in order to better understand both the prevalence of galactic outflows at z~1 and the star-forming and structural properties of objects experiencing outflows. Gas velocities, measured from the centroids of Fe II interstellar absorption lines, are found to span the interval [-217,+155]km/s. We find that ~40% (10%) of the sample exhibits blueshifted Fe II lines at the 1{sigma} (3{sigma}) level. We also measure maximal outflow velocities using the profiles of the Fe II and Mg II lines; we find that Mg II frequently traces higher velocity gas than Fe II. Using quantitative morphological parameters derived from the HST imaging, we find that mergers are not a prerequisite for driving outflows. More face-on galaxies also show stronger winds than highly inclined systems, consistent with the canonical picture of winds emanating perpendicular to galactic disks. In light of clumpy galaxy morphologies, we develop a new physically motivated technique for estimating areas corresponding to star formation. We use these area measurements in tandem with GALEX-derived star formation rates (SFRs) to calculate SFR surface densities. At least 70% of the sample exceeds an SFR surface density of 0.1M_{sun}_/yr/kpc2, the threshold necessary for driving an outflow in local starbursts. At the same time, the outflow detection fraction of only 40% in Fe II absorption provides further evidence for an outflow geometry that is not spherically symmetric. We see a ~3{sigma} trend between outflow velocity and SFR surface density, but no significant trend between outflow velocity and SFR. Higher resolution data are needed in order to test the scaling relations between outflow velocity and both SFR and SFR surface density predicted by theory.
- ID:
- ivo://CDS.VizieR/J/ApJS/193/14
- Title:
- DEEP3 Galaxy Redshift Survey: GOODS-N field
- Short Name:
- J/ApJS/193/14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of spectroscopic observations in the GOODS-N field completed using DEIMOS on the Keck II telescope as part of the DEEP3 Galaxy Redshift Survey (M. C. Cooper et al. 2011, in preparation). Observations of 370 unique targets down to a limiting magnitude of R_AB_=24.4 yielded 156 secure redshifts. In addition to redshift information, we provide sky-subtracted one- and two-dimensional spectra of each target. Observations were conducted following the procedures of the Team Keck Redshift Survey (TKRS, Cat. J/AJ/127/3121), thereby producing spectra that augment the TKRS sample while maintaining the uniformity of its spectral database.
- ID:
- ivo://CDS.VizieR/J/ApJS/159/41
- Title:
- DEEP Groth Strip Survey. I.
- Short Name:
- J/ApJS/159/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Deep Extragalactic Exploratory Probe (DEEP) is a multiphase research program dedicated to the study of the formation and evolution of galaxies and of large-scale structure in the distant universe. This paper describes the first five-year phase, denoted DEEP1. A series of 10 DEEP1 papers will discuss a range of scientific topics (e.g., the study of photometric and spectral properties of a general distant galaxy survey, the evolution observed in galaxy populations of varied morphologies). The observational basis for these studies is the Groth Survey Strip field, a 127arcmin^2^ region that has been observed with the Hubble Space Telescope (HST) in both broad I-band and V-band optical filters and with the Low Resolution Imaging Spectrograph on the Keck Telescopes. Catalogs of photometric and structural parameters have been constructed for 11,547 galaxies and stars at magnitudes brighter than 29, and spectroscopy has been conducted for a magnitude-color weighted subsample of 818 objects.
- ID:
- ivo://CDS.VizieR/J/ApJS/142/1
- Title:
- DEEP Groth Strip Survey. II.
- Short Name:
- J/ApJS/142/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents Hubble Space Telescope WFPC2 F606W and F814W photometric structural parameters for 7450 galaxies in the "Groth Strip". These parameters are based on a two-dimensional bulge + disk surface brightness model and were obtained using an automated reduction and analysis pipeline described in detail here.
- ID:
- ivo://CDS.VizieR/J/ApJ/599/1006
- Title:
- DEEP Groth Strip Survey. VII.
- Short Name:
- J/ApJ/599/1006
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using spectroscopic data from the Deep Extragalactic Evolutionary Probe Groth Strip Survey (DGSS), we analyze the gas-phase oxygen abundances in the warm ionized medium for 64 emission-line field galaxies in the redshift range 0.26<z<0.82. These galaxies comprise a small subset selected from among 693 objects in the DGSS. They are chosen for chemical analysis by virtue of having the strongest emission lines. Oxygen abundances relative to hydrogen are in the range 8.4<12+log(O/H)<9.0 with typical internal plus systematic measurement uncertainties of 0.17dex. The 64 DGSS galaxies collectively exhibit an increase in metallicity with B-band luminosity, i.e., an L-Z relation like that seen among local galaxies. Using the DGSS sample and local galaxy samples for comparison, we searched for a "second parameter" that might explain some of the dispersion seen in the L-Z relation. Parameters such as galaxy color, emission-line equivalent width, and effective radius were explored but found to be uncorrelated with residuals from the mean L-Z relation.
- ID:
- ivo://CDS.VizieR/J/ApJS/157/175
- Title:
- DEEP Groth Strip Survey. VIII.
- Short Name:
- J/ApJS/157/175
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a candidate sample of luminous bulges (including ellipticals) found within the Groth Strip Survey (GSS), with spectroscopic redshifts of 0.73<z<1.04 from the Keck Telescope. This work is distinguished by its use of two-dimensional two-component decomposition photometry from Hubble Space Telescope (HST) images to separate the bulge from any disk before applying the sample selection and to measure disk-free colors. We define a statistically complete sample of 86 bulges with r^1/4^ profiles and luminosities brighter than I_AB_=24. Although larger samples of distant early-type galaxies exist, this is the largest and most homogeneous sample of bulges at z~1 with spectroscopy. A brighter subset of 52 objects with added structural constraints defines our "quality sample" that is used to explore bulge luminosities and colors.
- ID:
- ivo://CDS.VizieR/J/ApJ/571/136
- Title:
- DEEP Groth Strip survey. X.
- Short Name:
- J/ApJ/571/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the luminosity function and color-redshift relation of a magnitude-limited sample of 145 mostly red field E/S0 galaxies at z<~1 from the DEEP Groth Strip Survey (GSS). Using nearby galaxy images as a training set, we develop a quantitative method to classify E/S0 galaxies based on smoothness, symmetry, and bulge-to-total light ratio. Using this method, we identify 145 E/S0's at 16.5<I<22 within the GSS, for which 44 spectroscopic redshifts (z_spec_) are available. Most of the galaxies with spectroscopic redshifts (86%) form a "red envelope" in the redshift-color diagram, consistent with predictions of spectral synthesis models in which the dominant stellar population is formed at redshifts z>~1.5.
- ID:
- ivo://CDS.VizieR/J/A+A/612/A26
- Title:
- Deep HI observations of Leo T with WSRT
- Short Name:
- J/A+A/612/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Leo T is the lowest mass gas-rich galaxy currently known and studies of its gas content help us understand how such marginal galaxies survive and form stars. We present deep neutral hydrogen (HI) observations from the Westerbork Synthesis Radio Telescope in order to understand its HI distribution and potential for star formation. We find a larger HI line flux than the previously accepted value, resulting in a 50% larger HI mass of 4.1x10^5^M_{sun}_. The additional HI flux is from low surface brightness emission that was previously missed; with careful masking this emission can be recovered even in shallower data.We perform a Gaussian spectral decomposition to find a cool neutral medium component (CNM) with a mass of 3.7x10^4^M_{sun}_, or almost 10% of the total HI mass. Leo T has no HI emission extending from the main HI body, but there is evidence of interaction with the Milky Way circumgalactic medium in both a potential truncation of the HI body and the offset of the peak HI distribution from the optical center. The CNM component of Leo T is large when compared to other dwarf galaxies, even though Leo T is not currently forming stars and has a lower star formation efficiency than other gas-rich dwarf galaxies. However, the HI column density associated with the CNM component in Leo T is low. One possible explanation is the large CNM component is not related to star formation potential but rather a recent, transient phenomenon related to the interaction of Leo T with the Milky Way circumgalactic medium.