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تسجيل مستخدم جديدكومبوزيت بلجز -- الجزء الثاني. البلجزات الكلاسيكية والقروض النووية في المجرات المشروطة: الحالات المتناقضة لNGC 4608 وNGC 4643
Composite Bulges -- II. Classical Bulges and Nuclear Discs in Barred Galaxies: The Contrasting Cases of NGC 4608 and NGC 4643
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تأليف
Peter Erwin
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نقدم لكم تحليلات مورفولوجية، فوتومترية وكينماتيكية النجومية المفصلة لمناطق المركزية لأجسام باردة نوعها المبكر من الشأن الكبير، والتي تحتويان على باردات كبيرة وقوية مع إضافات داخلية فوتومترية وتشير إلى شكل بوجي/بنت (B/P) للأجسام الشعاعية، والتي تشكل ~ 30٪ من الضوء الشعاعي. داخل أجسامها الشعاعية البوجي/بنت، يحتوي NGC 4608 على بنية مضغوطة، تقريباً مستديرة (نصف نصف الضوء R_e approx. 310 بكسل، Sersic n = 2.2) نحن نعرفها بأنها بنية كلاسيكية، والتي تمثل 12.1٪ من الضوء الكلي، بالإضافة إلى مجموعة نجوم نوكلية (R_e ~ 4 بكسل). وبالمقابل، يحتوي NGC 4643 على قرص نوكلي مع ملف توزيع ضخامة الضوء الظاهري المكسور الأسي (13.2٪ من الضوء)، وبنية صغيرة شعاعية جداً (R_e approx. 35 بكسل، n = 1.6؛ 0.5٪ من الضوء). وتؤيد كينماتيكا النجومية المحددة المحددة هذا الصورة، حيث تتجه بنية كلاسيكية NGC 4608 ببطء وتتمثل في توزيع عالي للسرعة، في حين أن قرص نوكلي NGC 4643 يظهر إنخفاضاً إلى توزيع أقل، تدوير سريع، V-h3 عكس التكافؤ، وh4 مرتفع. يظهر كلا الأجسام على الأقل بعض الأدلة على التكافؤ V-h3 في البار (خارج البنية الكلاسيكية والقرص النوكلي الخاصة بكل منهما)، موافقاً لما يتوقعه النموذج. وتؤدي تقسيمات 2 عنصرية (بنية/قرص) القياسية إلى B/T ~ 0.5-0.7 (وبنية n > 2) لكلا الأجسام. وهذا يفوق الحقيقة لأجسام الشعاعية بمعدلات أربع (NGC 4608) وأكثر من 100 (NGC 4643)، مما يوضح المخاطر المتعلقة بتقسيمات بنية/قرص البسيطة المطبقة على أجسام باردة كبيرة الشأن.
We present detailed morphological, photometric, and stellar-kinematic analyses of the central regions of two massive, early-type barred galaxies with nearly identical large-scale morphologies. Both have large, strong bars with prominent inner photometric excesses that we associate with boxy/peanut-shaped (B/P) bulges; the latter constitute ~ 30% of the galaxy light. Inside its B/P bulge, NGC 4608 has a compact, almost circular structure (half-light radius R_e approx. 310 pc, Sersic n = 2.2) we identify as a classical bulge, amounting to 12.1% of the total light, along with a nuclear star cluster (R_e ~ 4 pc). NGC 4643, in contrast, has a nuclear disc with an unusual broken-exponential surface-brightness profile (13.2% of the light), and a very small spheroidal component (R_e approx. 35 pc, n = 1.6; 0.5% of the light). IFU stellar kinematics support this picture, with NGC 4608s classical bulge slowly rotating and dominated by high velocity dispersion, while NGC 4643s nuclear disc shows a drop to lower dispersion, rapid rotation, V-h3 anticorrelation, and elevated h4. Both galaxies show at least some evidence for V-h3 correlation in the bar (outside the respective classical bulge and nuclear disc), in agreement with model predictions. Standard 2-component (bulge/disc) decompositions yield B/T ~ 0.5-0.7 (and bulge n > 2) for both galaxies. This overestimates the true spheroid components by factors of four (NGC 4608) and over 100 (NGC 4643), illustrating the perils of naive bulge-disc decompositions applied to massive barred galaxies.
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